McQuay RAH 407C Installation Manual

Installation and Maintenance Manual IM 487-5

RoofPak™ Applied Rooftop Systems
Air Handler

RAH 407C - 077C, 12000 to 50000 cfm

RDS 800C - 802C, 4000 to 20000 cfm

Group: Applied Systems

Part Number: IM 487

Date: June 2006

US

© 2006 McQuay International

Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Gas Burner Nameplate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Hazard Identification Information . . . . . . . . . . . . . . . . . . . . . . . 3

Typical Component Locations . . . . . . . . . . . . . . . . . . . . . . . . . 4

Control Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Control Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Controls, Settings, and Functions . . . . . . . . . . . . . . . . . . . . . 12

Mechanical Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Unit Clearances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Ventilation Clearance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Overhead Clearance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

IBC Seismic Compliant Units . . . . . . . . . . . . . . . . . . . . . . . . 20

Roof Curb Arrangement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Post and Rail Arrangement . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Post and Rail Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Rigging and Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Split Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Unit Piping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Steam Coil Piping (All Units) . . . . . . . . . . . . . . . . . . . . . . . . . 33

Steam Piping Recommendations . . . . . . . . . . . . . . . . . . . . . 33

Steam Trap Recommendations . . . . . . . . . . . . . . . . . . . . . . . 34

Vestibule Assembly Instructions . . . . . . . . . . . . . . . . . . . . . . 38

Damper Assemblies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Cabinet Weather Protection . . . . . . . . . . . . . . . . . . . . . . . . . 45

Installing Ductwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Installing Duct Static Pressure Sensor Taps . . . . . . . . . . . . . 46

Installing Building Static Pressure Sensor Taps . . . . . . . . . . 47

Electrical Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Field Power Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Field Control Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

Preparing Unit for Operation . . . . . . . . . . . . . . . . . . . . . 52

Spring Isolated Fans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Relief Damper Tie-Down . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Adjusting Scroll Dampers . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Adjusting Supply Fan Thrust Restraints . . . . . . . . . . . . . . . . 53

Adjusting Seismic Restraints . . . . . . . . . . . . . . . . . . . . . . . . . 54

Sequences of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Power-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Fan Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Economizer Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

Wiring Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Unit Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

Enthalpy Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

External Time Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

Smoke and Fire Protection . . . . . . . . . . . . . . . . . . . . . . . . . . 86

Smoke Detectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

Freeze Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

Entering Fan Temperature Sensor . . . . . . . . . . . . . . . . . . . . 87

Duct High Pressure Limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

MicroTech II™ Remote User Interface (UI) . . . . . . . . . . . . . . 87

Variable Frequency Drive Operation . . . . . . . . . . . . . . . . . . . 89

Convenience Receptacle/Section Lights . . . . . . . . . . . . . . . . 89

DesignFlow™ Outdoor Air Damper Option . . . . . . . . . . . . . . 89

Propeller Exhaust Fan Option . . . . . . . . . . . . . . . . . . . . . . . . 92

Exhaust Fan On/Off Control . . . . . . . . . . . . . . . . . . . . . . . . . . 94

Ultraviolet Lights Option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

Ultraviolet Light Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

Check, Test, and Start Procedures . . . . . . . . . . . . . . . 97

Servicing Control Panel Components . . . . . . . . . . . . . . . . . . 97

Before Start-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

Power Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

Fan Start-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

Economizer Start-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

Heating System Start-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

Air Balancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

Sheave Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

Drive Belt Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

Mounting and Adjusting Motor Sheaves . . . . . . . . . . . . . . . 101

Final Control Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

Servicing Control Panel Components . . . . . . . . . . . . . . . . . 108

Planned Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

Unit Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

Gas Furnace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

Bearing Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

Setscrews . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

Supply Fan Wheel-to-Funnel Alignment . . . . . . . . . . . . . . . 112

Winterizing Water Coils . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

Control Panel Components . . . . . . . . . . . . . . . . . . . . . . . . . 113

Replacement Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . 117

Service and Warranty Procedure . . . . . . . . . . . . . . . . 119

Limited Product Warranty (North America) . . . . . . 120

Exceptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

Assistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

Sole Remedy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

Rooftop Equipment Warranty Regist. Form . . . . . 121

Introduction

Introduction

This manual provides general information about the “C”
vintage McQuay RoofPak applied rooftop unit, models RDS
and RAH. In addition to an overall description of the unit, it
includes mechanical and electrical installation procedures,
commissioning procedures, sequence of operation information,
and maintenance instructions. For further information on the
optional forced draft gas-fired furnace, refer to Bulletin No.
IM 684 or IM 685.

The MicroTech II applied rooftop unit controller is available
on “C” vintage applied rooftop units. For a detailed description
of the MicroTech II components, input/output configurations,
field wiring options, requirements, and service procedures, see
IM 696-3. For operation and information on using and
programming the MicroTech II unit controller, refer to the
appropriate operation manual (see Table 1).

For a description of operation and information on using the
keypad to view data and set parameters, refer to the
appropriate program-specific operation manual (see Table 1).

Table 1: Program specific rooftop unit operation literature

Rooftop unit control configuration

VFDs Vendor IM manuals

Discharge Air Control (VAV or CAV) OM 137-2

Space Comfort Control

(CAV-Zone temperature control)

Operation manual bulletin

number

OM 138-2

Gas Burner Nameplate

On units that include gas heat, the nameplate is located on the
lower right corner of the main control box door. It includes the
burner model number, minimum/maximum input, maximum
temperature rise, and minimum cfm.

Hazard Identification Information

WARNING

Warnings indicate potentially hazardous situations, which can
result in property damage, severe personal injury, or death if
not avoided.

CAUTION

Cautions indicate potentially hazardous situations, which can
result in personal injury or equipment damage if not avoided.

Figure 1: Nomenclature

RoofPak

Unit Size
RDS 800 = 4000 – 16000 CFM
RDS 802 = 8000 – 20000 CFM
RAH 47 = 12000 – 30000 CFM
RAH 77 = 23000 – 50000 CFM

R AH — 047 C S E

Heat medium
A = Natural gas
E = Electric
F = Fuel oil
S = Steam
W = Hot water
Y = None

Cooling coil size
S = Standard (low airflow)
L = Large (high airflow)
Y = None or contractor coil

Design vintage

McQuay IM 487-5 3

Introduction

Typical Component Locations

Figure 2 shows a typical blow-through unit with the locations
of the major components. Figure 2 shows a typical
draw-through unit with the locations of the major components.

These figures are for general information only. See the
project’s certified submittals for actual specific dimensions
and locations.

Figure 2: Control locations

Supply fan

discharge

plenum

section

C9

Economizer

return air

Heat

section

DX

section

Filter

section

Control Locations

All controls are optional. If controls are ordered, Figure 2
shows the locations of the various control components
mounted throughout the units. See “Control Panel” on page 5
for the locations of control components mounted in control
panels. Additional information is included in Table 2 on
page 12 and the wiring diagram legend, which is included in
“Wiring Diagrams” on page 58. Figure 2 shows the
blow-through heat and the blow-through coil sections.

C19, 20

(optional)

RAT

LT11 (optional)

S11, REC11

SD2

(optional)

(optional)

RAE

(optional)

ACT3

ACT6

PC5

OAE

OAT

VM1

(optional)

FS1

(optional)

DAT

LT10 (optional)

S10, REC10 (optional)

SD1 (optional)

SV1, 2

SV5, 6 (optional)

4 McQuay IM 487-5

Control Panel

Introduction

The unit control panels and their locations are shown in the
following figures. These figures show a typical unit

Figure 3: Control panel locations

configuration. Specific unit configurations may differ slightly
from these figures depending on the particular unit options.

McQuay IM 487-5 5

Introduction

Figure 4: Typical main control panel, 800C to 802C, 460 volt

Keypad display

Remote

keypad

HS1 S1

Serial conn

See separate

detail, page 14.

GCB1

ERB1

S7S4

Resistor

R58

R20 R26 R27 R28

R48

R46

MMP60 MMP10 MMP20

M60

R30

M10

R24 R25 R28

R60

R45

R69

M20

F3

F1A

F1B

MCB

F1C

TB1

Power
supply

T1

DHL

SPS2

EHB1

SPS1

VFD remote

display

DS1

REC1

TB3,

first seven

blocks

TB2,

remaining

blocks

TB7

GND LUG DS1

SPS1,2 fittings

for static

pressure tubing

6 McQuay IM 487-5

Figure 5: Typical main control panel, 047C, 460 volt

Introduction

VFD remote

display

TB2

F1A

F1B

F1C

14.

GFR1

TB7

SPS1,2

fittings for

static pressure

tubing

McQuay IM 487-5 7

Introduction

Figure 6: Typical main control panel, 077C, 460 volt

14.

8 McQuay IM 487-5

Introduction

e

A

Figure 7: Typical gas heat panel, 1000 MBH

IT

R22

TD10

R20

S

R23 R21

LS2

Figure 9: VFD bypass panel, 40 HP, 460 volt)

LS1

S3

Figure 10: Electric heat panel, sizes 800, 802C

FSG

FSG Tim

FB33 FB32 FB31

Figure 8: Typical propeller exhaust panel, 3 fans, 460 volt

M33 M32 M31

FB43 FB42 FB41

M41 M42 M41

SR2

SR3

SR1

TB11

PB3

McQuay IM 487-5 9

Introduction

Figure 11: Electric heat panel, size 047C Figure 12: Electric heat panel, size 077C

FB31FB32FB33

DS3

M42

GLG3

FB31FB32FB33
M31M32M33

FB41FB42FB43

M41M43

H53

TB11

M31M32M33

FB34FB44

M34M44

FB41FB42FB43

M41M42M43

GLG3

H53

TB11

DS3

10 McQuay IM 487-5

Figure 13: Harness plug connector detail

RATS OATSDATS

FP1 OPEN1EPTS

AFD10 AFD20

SV12 SV56

ACT3 OPEN2

OAE PC7PC5

Introduction

HL22 OPEN3

GSHT1 GSHT2

SD1 SD2

DFRH DFLH OPEN4

LT11LT1 0

LT OP1 LT OP2

McQuay IM 487-5 11

Introduction

Controls, Settings, and Functions

Table 2 below lists all of the unit control devices and
associated information.

Table 2: Controls, settings, and functions

Symb

ol

DAT

DHL

EFT

FP1, 2

FS1

MCB

OAE

OAT

PC5

PC6

PC7

RAE

RAT

SD1

SD2

SPS1

Description Function

Discharge air
temperature
sensor

Duct high limit
switch

Entering fan air
temperature
sensor

Evaporator frost
protection

Freezestat

Main control board Processes input information

Enthalpy control
(electro­mechanical)

Enthalpy control
(electronic)

Outside air
temperature
sensor

Dirty filter switch Senses filter pressure drop

Dirty filter switch Senses filter pressure drop

Airflow proving
switch

Return air enthalpy
sensor

Return air
temperature
sensor

Smoke detector,
supply air

Smoke detector,
return air

Static pressure
sensor duct #1

Senses discharge air
temperature

Prevents excessive VAV duct
pressures; shuts off fan

Senses entering fan air
temperature

Senses low refrigerant
temperature

Shuts off fans, opens heating
valve, and closes outdoor
damper if low air temperature
at coil is detected

Returns outside air dampers
to minimum position when
enthalpy is too high

Returns outside air dampers
to minimum position when
outside air enthalpy is higher
than return air empalthy (use
RAE)

Senses outside air
temperature

Senses supply fan pressure
to prove airflow

Used to compare return air
enthalpy to outside air
enthalpy (used with OAE)

Senses return air temperature

Initiates unit shutdown if
smoke is detected

Initiates unit shutdown if
smoke is detected

Converts static pressure
signals to voltage signals

Rese

N/A

Auto

N/A

N/A

Auto

N/A

Auto

Auto

N/A N/A N/A

Auto

Auto

Auto

N/A

N/A

ManualDischarge air

ManualReturn air

N/A

Location Setting Range Differential Part no.

t

Discharge air

section

Main control

panel

Inlet of supply

fan

Return bends
of evaporative

coil

Heating
section

Main control

box

Economizer

section

Economizer

section

First filter

section

Final filter

section

Supply fan

section

Economizer

section

Return air

section

section

section

Main control

box

N/A N/A

3.5" w.c

(871.8 Pa)

N/A N/A

Opens at

30°F

Closes at

45°F

38°F (3°C)

or as

required

N/A N/A N/A

“B” or as
required

Fully CW

past “D”

(when used

with RAE)

As required

As required

.10" wc (25

Pa)

N/A N/A N/A

N/A N/A

N/A N/A N/A 04925001

N/A N/A N/A 04925001

N/A

0.05–5.0" wc
(12.5–1245.4

Pa)

N/A N/A

35°F–45°F

(2°C–7°C)

A–D

A–D N/A

.05-5" wc

(12.5–1245.4

Pa)

.05-5" wc

(12.5–1245.4

Pa)

.03-1.40" wc

(7.5–348 Pa)

0–5" wc
(0–1245.4 Pa)
1–6 V (dc) out

.05" wc

(12.5 Pa),

fixed

12°F (7°C),

fixed

Temperature:

3.5°F (2°C)
Humidity:

5% fixed

.05" wc

(12.5 Pa)

.05" wc

(12.5 Pa)

.03" wc

(7.5 Pa),

fixed

N/A

06000470

5

06549380

1

06000470

5

07250190

1

06583000

1

06000610

1

03070670

2

04926220

1

06000470

5

06549380

1

06549380

1

06001580

1

04926220

2

06000470

5

04954500

7

12 McQuay IM 487-5

Table 2: Controls, settings, and functions (continued)

Symb

ol

SPS2

S1

S7

Description Function

Converts static pressure
Static pressure
sensor duct #2

Static pressure
sensor: building
(space) pressure

System switch

ON-OFF-AUTO
switch

signals to voltage signals and

sends them to MicroTech II

controller

Converts static pressure

signals to voltage signals.

Shuts off entire control circuit

(except crankcase heaters)

Used to manually switch unit

Rese

t

N/A

N/A

N/A

N/A

Introduction

Location Setting Range Differential Part no.

Main control

box

Main control

box

Main control

box

Main control

box

N/A

N/A

N/A N/A N/A

N/A N/A N/A

0–5" wc
(0–1245.4 Pa)
1–6 V (dc) out

-025–0.25" wc

(-62.3–62.3 Pa)

1–5 V (dc) out

N/A

N/A

04954500

04954500

00135500

7

6

0

McQuay IM 487-5 13

Mechanical Installation

Mechanical Installation

Note – The installation of this equipment shall be in accordance

with the regulations of authorities having jurisdiction and
all applicable codes. It is the responsibility of the installer
to determine and follow the applicable codes.

CAUTION

Sharp edges on sheet metal and fasteners can cause personal
injury.
This equipment must be installed, operated, and serviced only
by an experienced installation company and fully trained
personnel.

Receiving Inspection

When the equipment is received, all items should be carefully
checked against the bill of lading to be sure all crates and
cartons have been received. If the unit has become dirty

during shipment (winter road chemicals are of particular
concern), clean it when received.

Figure 14: Service clearances, unit with housed DWDI supply fan

72"

(1829 mm)

All units should be inspected carefully for damage when
received. Report all shipping damage to the carrier and file a
claim. In most cases, equipment ships F.O.B. factory and
claims for freight damage should be filed by the consignee.

Before unloading the unit, check the unit nameplate to make
sure the voltage complies with the power supply available.

Unit Clearances

Service Clearance

Allow an approximate service clearance as indicated in
Figure 14. Also, McQuay recommends providing a roof
walkway to the rooftop unit as well as along two sides of the
unit that provide access to most controls and serviceable
components.

72"

(1829 mm)

Roof

Walkway

Note:
Sections with heating and/or cooling coils or DWDI
supply fan must have noted service clearance on the
control box side.

To Roof

Access

Location

A

(1524 mm)

B C

60"

D

Varies With Unit Arrangement

Refer to Certified Drawing & Note

E

X

Dimension "X"
RDS 800-802 = 90" (2286mm)
RAH 47-77 = 96" (2438mm)

D

C

F

24"

(635 mm)

Legend:
A = Return Air Section
B = Filter Section
C = Cooling Section
D = Cooling/Supply Fan Section
E = Heat Section
F = Discharge Plenum Section

14 McQuay IM 487-5

Figure 15: Service clearances, unit with SWSI plenum supply fan

72"

(1829 mm)

Mechanical Installation

72"

(1829 mm)

Roof

walkway

Note:
Sections with heating and/or cooling coils or DWDI
supply fan must have noted service clearance on the
control box side.

To roof

access

location

A

(1524 mm)

B C

60"

Varies with unit arrangement.
Refer to Certified Drawing and
note below.

D

96"

(2438 mm)

Ventilation Clearance

Below are minimum ventilation clearance recommendations.
The system designer must consider each application and
provide adequate ventilation. If this is not done, the unit will
not perform properly.

Unit(s) surrounded by a screen or a fence:

1 The bottom of the screen or fence should be at least 1 ft.

(305 mm) above the roof surface.

2 The distance between the unit and a screen or fence should

be as described in Figure 15.

3 The distance between any two units within a screen or

fence should be at least 120" (3048 mm).

Unit(s) surrounded by solid walls:

1 If there are walls on one or two adjacent sides of the unit,

the walls may be any height. If there are walls on more than
two adjacent sides of the unit, the walls should not be
higher than the unit.

2 The distance between the unit and the wall should be at

least 96" (2438 mm) on all sides of the unit.

3 The distance between any two units within the walls should

be at least 120" (3048 mm).

E F

X

Legend:
A = Return air section
B = Filter section
C = Cooling section
D = Cooling/supply fan section
E = Heat section
F = Discharge plenum section

Dimension "X"
RDS 800–802 = 90" (2286mm)
RAH 47–77 = 96" (2438mm)

Do not locate outside air intakes near exhaust vents or other
sources of contaminated air.

If the unit is installed where windy conditions are common,
install wind screens around the unit, maintaining the
clearances specified (see Figure 16). This is particularly
important to prevent blowing snow from entering the outside
air intake and to maintain adequate head pressure control when
mechanical cooling is required at low outdoor air
temperatures.

Overhead Clearance

1 Unit(s) surrounded by screens or solid walls must have no

overhead obstructions over any part of the unit.

2 The following restrictions must be observed for overhead

obstructions above the air handler section (see Figure 16):

a There must be no overhead obstructions above the

furnace flue, or within 9" (229 mm) of the flue box.

b Overhead obstructions must be no less than 96"

(2438 mm) above the top of the unit.

c There must be no overhead obstructions in the areas

above the outside air and exhaust dampers that are
farther than 24" (610 mm) from the side of the unit.

McQuay IM 487-5 15

Mechanical Installation

Figure 16: Overhead clearance

24" (610 mm)
Maximum

Overhead
Canopy

9" (229 mm)
Minumum to Flue Box
Typical All Sides

2" (51 mm)

Minumum

Top of Unit

to Overhead

Obstruction

Figure 17: Side discharge

Flue Box

24" (610 mm)
Maximum

Notice

On units with side discharge, access to plenum-mounted
components becomes difficult once ductwork is installed.
Installer must provide access in the ductwork for plenum
mounted controls

Side Discharge Opening
(Access in Ductwork
Must be Removed)

16 McQuay IM 487-5

Mechanical Installation

Roof Curb Assembly and Installation

Locate the roof curb and unit on a portion of the roof that can
support the weight of the unit. The unit must be supported to
prevent bending or twisting of the machine.

If building construction allows sound and vibration into the
occupied space, locate the unit over a non-critical area. It is

the responsibility of the system designer to make adequate
provisions for noise and vibration in the occupied space.

WARNING

Mold can cause personal injury. Some materials such as
gypsum wall board can promote mold growth when damp.
Such materials must be protected from moisture that can enter
units during maintenance or normal operation.

Install the curb and unit level to allow the condensate drain to
flow properly and allow service access doors to open and close
without binding.

Integral supply and return air duct flanges are provided with
the RAH roof curb, allowing connection of duct work to the
curb before the unit is set. The gasketed top surface of the duct
flanges seals against the unit when it is set on the curb. These
flanges must not support the total weight of the duct work.
Assembly of a typical RAH roof curb is shown in Figure 18 on
page 18. Parts A through H are common to all units having
bottom return openings. Depending on the unit length, Parts L
and M may be included with the roof curb kit to create the
correct overall curb length.

Assembly instructions

1 Set curbing parts A through H per dimensions shown over

roof opening or on a level surface (see Figure 18 on
page 18). Note location of return and supply air openings.

2 If applicable, set other curbing parts (D, L, M, etc.) in place

making sure that the orientation complies with the
assembly instructions (see Detail A). Check alignment of
all mating bolt holes.

3 Bolt curbing parts together using fasteners provided.

Tighten all bolts finger tight.

4 Square entire curbing assembly and securely tighten all

bolts.

5 Position curb assembly over roof openings. Curb must be

level from side to side and over its length. Check that top
surface of the curb is flat with no bowing or sagging.

6 Weld curbing in place. Caulk all seams watertight. Remove

backing from 0.25" (6 mm) thick × 1.50" (38 mm) wide
gasketing and apply to surfaces shown by cross-hatching.

7 Flash curbing into roof as shown in Detail B.

8 Parts E and F are not required on units with no return shaft

within the curb perimeter.

9 Parts G and H are not required on units with no supply shaft

within the curb perimeter.

10 Be sure that electrical connections are coordinated (see

Figure 26).

McQuay IM 487-5 17

Mechanical Installation

Figure 18: RAH roof curb assembly instructions

Detail A

Equal Length
Side Supports

M

L

D

Using remaining side supports
in this area, align lengths on
opposite sides of assembly
and install a cross support
"D" at each side.

M

L

3.50"

(90 mm)

8.75"

(222 mm)

H

81.00"

(2057 mm)

Inside

A

G

7.50"

(191 mm)

2.00"

(51 mm)

"Y"

Inside

C

G

Supply

H

Air

D

"X"

Inside

E

A

(222mm)

3.50"

(90mm)

8.75"

87.00"

(2210 mm)

Inside

90.00"

(2286 mm)

Figure 19: Roofing detail “B”

Curb gasketing

B

F

Return

Unit base

2 × 4 nailer strip

C

70.75"

D

F

Air

E

B

See Detail "A"

(1797 mm)

Dimensions

94.75"

(2407 mm)

RAH unit

047C
077C with flat cooling coil and /or 44"
SWSI plenum supply fan
077C with staggered or no cooling coil,
and/or 49" SWSI plenum supply fan

X Y

in mm in mm

38 965 28 711

157

5

157

5

38 965

46 1168

62

62

(not furnished)Counterflashing

Flashing (not furnished)

Rigid insulation

(not furnished)

Cant strip
(not furnished)

Roffing material

(not furnished)

Galvanized

curb

Main unit

curb

18 McQuay IM 487-5

Figure 20: RDS roof curb assembly instructions

C

20.00"

(508 mm)

Inside

G

D

6.80"

(173 mm)

H

H

Supply

Air

Mechanical Installation

1.50"

(38 mm)

76.00" (1930 mm)
Inside

A

G

7.50"

(191 mm)

2.00"

(5.1 mm)

B

"X"

Inside

"YY"

"XX"

E

F

A

"Y"

Inside

85.00"

(2159 mm)

F

Return

Air

Table 3: RDS roof curb assembly instructions

Unit size Fan

None 24.0 610 82.0 2083 6.8 173 1.5 38

800–802C

(2) 15” FC 24.0 610 82.0 2083 6.8 173 1.5 38 (2) 15" FC 24.0 610 82.0 2083 6.8 173 1.5 38

30" AF 30.0 762 76.0 1930 6.8 173 4.5 114 30" AF 30.0 762 76.0 1930 6.8 173 4.5 114
40" AF 36.0 914 78.0 1981 14.8 376 3.5 89 40" AF 36.0 914 78.0 1981 14.8 376 3.5 89

X Y XX YY

in mm in mm in mm in mm in mm in mm in mm in mm

C

38.80"

D

See Detail "A"

E

B

62.80"

(1594 mm)

Unit size

Return

fan

X Y XX YY

(984 mm)

None 24.0 610 82.0 2083 6.8 173 1.5 38

800–802C

McQuay IM 487-5 19

Mechanical Installation

IBC Seismic Compliant Units

It is important to follow these installation instructions for all
IBC Seismic compliant McQuay Rooftop units.

IBC Seismic compliant McQuay Rooftop units can be
mounted to either a roof curb or a post and rail setup. If using a
roof curb, it must be specifically designed for seismic restraint
and be IBC seismic compliant (spring isolated or non-isolated
type seismic roof curbs are available). Typical construction of
a seismic rated roof curb is from structural steel framing and
contains seismic hold down brackets for attachment of the
rooftop unit (see Figure 21). Post and rail arrangements rated
for seismic applications are also available (spring isolated or
non-isolated).

IMPORTANT: An acceptable IBC seismic installation
provides a direct positive attachment to both the building
structure and the roof mounted equipment.

Refer to the roof curb manufacturer’s submittal drawings for
actual roof curb assembly, attachment details and rigging
instructions for both roof curb and post and rail arrangements.

Figure 21: Typical seismic roof curb (spring isolated)

Roof Curb Arrangement

1 Set the rooftop unit on the roof curb (McQuay Rooftop

units are designed to overhang from the roof curb).

2 Adjust the seismic hold down brackets so they come into

contact with the unit base per Figures 22 and 23 on page

21.

a The seismic hold down brackets should be adjustable

and accommodate the overhang of the rooftop unit.

b If the hold down bracket cannot reach the unit base, use

a shim spacer. See Figure 23 on page 21.

3 Weld each seismic hold down bracket (and shim spacer, if

required) to the unit base as shown in the acceptable weld
zone detail in Figure 22 on page 21.

CAUTION

When welding unit to the curb, do not damage wiring (control
panel side). Weld ONLY in the specified zone in the acceptable
weld zone (see Figure 22 on page 21). Welding must comply
with weld fillet size, etc. as indicated in Figure 22 on page 21.

Note – High temperature insulation is installed at the factory to

allow for field welding along the lower front edge region of
the unit base.

Duct opening

Seismic hold down brackets

Structural steel frame

Seismic hold down brackets

Spring
isolator

20 McQuay IM 487-5

Figure 22: Welding of hold down brackets—unit base, cross-sectional view

Unit power wiring
(by factory)

Unit base

.25

Field attachment

Mechanical Installation

Unit control wiring
(by factory)

weld

Weld
zone

.50"

Acceptable weld zone

Figure 23: Shim spacers on hold down brackets

Shim

spacer

It may be necessary for
the contractor to field
fabricate spacers or new
seismic hold-downs for
rooftop units having larger
overhang dimensions.

Unit power wiring

(by factory)

Unit base

High temp
Insulation

Seismic hold down bracket

Unit control wiring
(by factory)

Roof curb

Seismic hold
down bracket

Roof curb

McQuay IM 487-5 21

Mechanical Installation

Post and Rail Arrangement

1 Set the rooftop unit on the rails. The rails should run

lengthwise and support the entire unit base.

2 Weld both sides of the unit directly to each rail as shown in

Figures 24 and 25 on page 22.
required is dependent on the length of the unit.

a Make the fillet welds 2 inches long, spaced 48 inches

apart on centers.

b Place the end welds 6 to 12 inches from the unit edge.

Figure 24: Welding of unit to rail—unit base, cross-sectional view

The total number of welds

Note – High temperature insulation is installed at the factory to

CAUTION

When welding unit to the curb, do not damage wiring (control
panel side). Weld ONLY in the specified zone in the acceptable
weld zone (see Figure 24 on page 22). Welding must comply
with weld fillet size, etc. as indicated in Figure 24 on page 22.

allow for field welding along the lower front edge region of
the unit base.

Unit base

.25

Weld
zone

2–48

.50"

Acceptable weld zone

Figure 25: Weld locations for rail arrangement

6–12"

Unit power wiring

(by factory)

Unit base

Rail

Field attachment

weld

High temp
insulation

Unit control wiring

(by factory)

Rail

Rooftop unit

.25

2–48

Weld every 48"

Rails

6–12"

22 McQuay IM 487-5

Mechanical Installation

Figure 26: Typical power wire entrance, curb view (RDS 800–802 shown; for exact values, refer to submittal)

D

B

D

Detail A

20.0

SA

OPNG

6.0

6.8

1.5

76.0

B

7.5

6.0

E

3.0 Dia.
K.O.

RPS only

97.0

B

8.0

2Typ
4Typ

K.O.

A

RA

OPNG

A

A

See Detail A

Unit length minus 6.4

12.1

5.1

3.4

C

0.9 Dia.

2.0

4.6

4.8

9.7

2.1

3.1

4.3

McQuay IM 487-5 23

Mechanical Installation

Post and Rail Mounting

When mounting by post and rail, run the structural support the
full length of the unit. Locate the structural member at the base
of the unit as shown in Figure 27, assuring the I-beam is well

supported by the structural member.

CAUTION

The unit must be level side to side and over the entire length.
Equipment damage can result if the unit is not level.

If resilient material is placed between the unit and the rail,
insert a heavy steel plate between the unit and the resilient
material to distribute the load. Seal cabinet penetrations
(electrical, piping, etc.) properly to protect against moisture
and weather.

Figure 27: Post and rail mounting

99" RAH

(2515 mm)

94" RDS

5" *

(127mm)

(2388 mm)

1 Support the unit well along the length of the base rail.

2 Level the unit (no twists or uneven ground surface).

3 Provide proper drainage around the unit to prevent flooding

of the equipment.

4 Provide adequate protection from vandalism, mechanical

contact, etc.

5 Securely close the doors.

6 If there are isolation dampers, make sure they are properly

installed and fully closed to prevent the entry of animals
and debris through the supply and return air openings.

7 Cover the supply and return air openings on units without

isolation dampers.

Figure 28 shows an example of the rigging instruction label
shipped with each unit.

WARNING

Use all lifting points. Improper lifting can cause severe personal
injury and property damage.

Figure 28: Rigging and handling instruction label

Rigging and Handling

Lifting brackets with 2" (51 mm) diameter holes are provided
on the sides of the unit.

Use spreader bars, 96" to 100" (2438 to 2540 mm) wide, to
prevent damage to the unit cabinet. Avoid twisting or uneven
lifting of the unit. The cable length from the bracket to the
hook should always be longer than the distance between the
outer lifting points.

If the unit is stored at the construction site for an intermediate
period, follow these additional precautions:

Unit has either four or six lifting points (four-point shown below).

Rigging cables must be at least as long as distance “A.”

Spreader bars

required

A

Caution: Lifting points may not
be symmetrical to center of
gravity of unit. Balast or unequal

Lift only as indicated

cable lengths may be required.

CAUTION

Lifting points may not be symmetrical to the center of gravity of
the unit. Ballast or unequal cable lengths may be required.

24 McQuay IM 487-5

Mechanical Installation

Lifting Points

To determine the required lifting cable lengths and whether
four-point or six-point lifting is required, use Tables 4 and 5
and Figure 29.

Referring to Figure 29, note that dimension A is the distance
between the outer lifting points. The four outer rigging cables
must be equal to or longer than dimension A. Dimension B
shows the minimum distance between the outer and the inner
lifting points for six-point lifting. Use this to roughly
determine the required length of the middle cables for six­point lifting. Determine dimension A by subtracting
dimensions X and Y from dimension Z (e.g., A = Z – X – Y).

• Where:

• Z = Total unit length in inches

(refer to certified drawings for this dimension).

• X = Outdoor/return air section length (refer to Figure 29 and
Table 5 for this dimension).

• If A ≤ 288" (7315 mm), 4-point lifting is sufficient.

• If A > 288" (7315 mm), 6-point lifting is required.

Table 4: RAH X dimension (see Figure 29) Economizer
section

Type of economizer

section

100% OA 0 0

Plenum 48” (1219 mm) 72” (1829 mm)

0–30% OA 48” (1219 mm) 72” (1829 mm)

0–100% economizer 72” (1829 mm) 96” (2438 mm)

0–100% economizer with return fan 72” (1829 mm) 96” (2438 mm)

047C 077C

Figure 29: Unit type RAH lifting points

4 Lifting Points

A

Z

X

6 Lifting Points

B

Z

A

Table 5: RDS X dimension (see Figure 29) Outdoor/return
air section

Outdoor/return air section 800C 802C

100% OA 0 0

Plenum 40” (1016 mm) 52" (1321 mm)

0–30% OA 40” (1016 mm) 52" (1321 mm)

0–100% economizer 40” (1016 mm) 52" (1321 mm)
0–100% economizer with 15" return fan 62" (1575 mm) —
0–100% economizer with 30" return fan 52" (1321 mm) 52" (1321 mm)
0–100% economizer with 40" return fan — 80" (2032 mm)

X

RDS 800: B Min. = 62" (1515 mm)
RDS 802: B Min. = 84" (2134 mm)
RAH 47: B Min. = 96" (2438 mm)
RAH 77: B Min. = 120" (3048 mm)

McQuay IM 487-5 25

Mechanical Installation

Split Units

Although units typically ship from the factory as complete
units, they can be factory split at the supply fan bulkhead and
connected later on the roof. This configuration is ordered if the
shipping length or a weight limitation prevents ordering a
packaged unit.

A single nameplate is attached to the air handler section and
power is supplied to both sections through the optional main
control box as in a packaged unit.

RAH Factory Split at Fan

Field reassembly of an RAH unit that shipped split at the fan
takes place in three phases: (1) setting the sections,

Figure 30: Set sections

Remove plywood and retaining

Remove top cap and
save for reassembly.

angles from unit and discard.

Discharge end of unit

(2) mechanically recoupling the cabinet, and (3) reconnecting
power and control wiring.

Phase I. Set sections

Remove top cap and save for Phase II, Step 1.

1

2 Remove screws on fan panel, leaving retainer clips in place

to secure bulkhead. Save screws for Phase II, Step 5.

3 Remove plywood and retaining angles from unit and

discard.

4 Carefully lower both sections of unit (fan end and

discharge end) into place, making sure the roof curb
engages the recesses in the unit base.

Fan end of unit

26 McQuay IM 487-5

Remove screws on fan panel,
leaving retainer clips in place.
Save screws for reassembly.

Phase II. Reassemble cabinet (Figure 31)

1 Reinstall top cap removed in Phase I, Step 1.

2 Caulk (watertight) ends of splice cap.

3 Caulk (watertight) vertical seam.

4 Install #10 screws (provided).

5 Install screws (.25–20 ×.75) removed in Phase I, Step 2.

6 Install splice cover (provided).

Figure 31: Reassemble cabinet

Mechanical Installation

Reinstall top cap
saved in step 1

Caulk ends
of splice cap

Splice cover,
provided

See detail

Caulk
vertical
seam

Install screws
(.25 to 20 × .75)
saved from step 1

#10 screws,
provided

Nut clip-on,
provided

McQuay IM 487-5 27

Mechanical Installation

Phase III. Reconnect power and control wiring

Once the sections are physically reconnected, the ends of the
power harness are fed back through the unit base into the
junction box, per the unit’s electrical schematics.

CAUTION

Connect the power block correctly and maintain proper
phasing. Improper installation can cause severe equipment
damage.

1 Make electrical connections and reinstall inner raceway

cover as shown in Figure 32.

Figure 32: Electrical connections and raceway cover
installation

If applicable, install as shown
with provided fasteners.

After routing wires,
install inner raceway
cover (see step 6).

3.72 ref.
(94 mm)

Field Refrigerant Piping and Charging of DX Coils

Units that ship from the factory with DX coils installed do not
include refrigerant piping or refrigerant controls. The coil
assembly is ready for field connections at the distributors and
at the suction headers. Piping kits that provide the necessary
liquid and hot gas piping and control components are available
for field installation. Field-installed refrigerant piping may exit
the unit cabinet at one of the following locations:

• Through the floor of the unit.

• Through the discharge and bulkhead of the unit.

• Through a cabinet door near the DX coil that is not required

for service areas.

CAUTION

For any of the above cabinet penetrations, tightly seal the hole
to prevent water or air leakage.

In preparing for field piping, remove the plastic plugs on the
distributors and unsweat the copper caps at the suction header
connections.

Follow piping design, sizing, and installation information
presented in ASHRAE handbooks in the design and
installation of interconnecting piping. The DX coil and
condensing unit are intended to be set at the same elevation, as
close as possible to each other to minimize refrigerant pressure
drop. Design piping to prevent liquid refrigerant carryover to
the compressor and to provide a continuous return of

compressor oil from the system.

2 When power wire reconnection is complete, reinstall the

inner raceway cover in the blank or heat section. Figure 32
shows a typical installation of the raceway cover.

3 Run the control harnesses by removing the external

raceway covers on either side of the unit split.

4 Remove the excess harness length from the external

raceway on the downstream side of the split; then route
along the raceway, through the bushed hole in the fan
section and into the junction box where control wiring
terminal blocks are provided for reconnection.

5 Make all electrical connections per the unit’s electrical

schematics.

6 Reinstall the external raceway covers after routing of the

control wires is complete.

CAUTION

The pounds of refrigerant in the system may exceed the
capacity of the condenser, depending on the amount of
refrigerant in the liquid lines between the DX coil and the
condensing unit.
Refer to condenser manufacturer for information about
refrigerant capacity. Suitable means of containing the
refrigerant is required.

CAUTION

To prevent liquid return and damage to the compressor on
systems with optional hot gas bypass, it is important to locate
the bypass solenoid valve at the condensing unit and not at the
DX coil.

28 McQuay IM 487-5

Mechanical Installation

Piping Recommendations

7 Use type K or L clean copper tubing. Thoroughly clean or

braze all joints with high temperature solder.Base piping
sizes on temperature/pressure limitations as recommended
in the following paragraphs. Under no circumstances
should pipe size be based strictly upon coil or condensing
unit piping connection size.

8 Do not exceed suction line piping pressure drop equivalent

to 2°F (1°C), 3 psi (20.7 kPa) per 100 feet (30.5 m) of
equivalent pipe length. After the suction line size is
determined, check the vertical suction risers to verify that
oil will be carried up the riser and back to the compressor.
Pitch the suction line(s) in the direction of refrigerant flow
and make sure they are adequately supported. Lines should
be free draining and fully insulated between the evaporator
and the compressor. Install a trap on the vertical riser to the
compressor.

9 To determine the minimum tonnage required to carry oil up

suction risers of various sizes, check the vertical suction
risers using Table 6. Insulate suction lines inside the unit

cabinet to prevent condensation.

Table 6: Minimum tonnage (R-22) to carry oil up suction
riser at 40°F saturated suction

Line size O.D. Minimum tonnage

1 1/8" 1.5
1 3/8" 2.5
1 5/8" 3.8
2 1/8" 7.6
2 5/8" 13.10
3 1/8" 20.4
3 5/8" 29.7
4 1/8" 41.3

10 Size the liquid line for a pressure drop not to exceed the

pressure equivalent of 2°F (1°C), 6 psi (41.4 kPa)
saturated temperature.

Leak Testing

bring the pressure to a maximum of 125 psig. The unit should
then be leak tested with halide or electronic leak detector.
After making any necessary repair, the system should be

evacuated as described in the following paragraphs.

WARNING

Do not use oxygen or air to build up pressure. Explosion hazard
can cause severe personal injury or death.

Evacuation

After determining the unit is tight and there are no refrigerant
leaks, evacuate the system. Use a vacuum pump with a
pumping capacity of approximately 3 cu.ft./min. and the
ability to reduce the vacuum in the unit to at least 1 mm (1000
microns).

1 Connect a mercury manometer or an electronic or other

type of micron gauge to the unit at a point remote from the
vacuum pump. For readings below 1 millimeter, use an
electronic or other micron gauge.

2 Use the triple evacuation method, which is particularly

helpful if the vacuum pump is unable to obtain the desired
1 mm of vacuum. The system is first evacuated to
approximately 29" (740 mm) of mercury. Then add enough
refrigerant vapor to the system to bring the pressure up to 0
pounds (0 microns).

3 Evacuate the system again to 29" (740 mm) of vacuum.

Repeat his procedure three times. This method is most
effective by holding system pressure at 0 pounds
(0 microns) for a minimum of 1 hour between evacuations.
The first pulldown removes about 90% of the
noncondensables; the second removes about 90% of that
remaining from the first pulldown. After the third
pulldown, only 1/10 of 1% of noncondensables remains.

Table 7 on page 30 shows the relationship between pressure,
microns, atmospheres, and the boiling point of water.

In the case of loss of the nitrogen holding charge, the unit
should be checked for leaks prior to charging the complete
system. If the full charge was lost, leak testing can be done by
charging the refrigerant into the unit to build the pressure to
approximately 10 psig and adding sufficient dry nitrogen to

McQuay IM 487-5 29

Before replacing refrigerant sensors or protective devices, see
“Refrigerant Charge” on page 31 for an important warning to
prevent an abrupt loss of the entire charge.

CAUTION

Mechanical Installation

Table 7: Pressure-vacuum equivalents

Absolute pressure above zero Vacuum below 1 atmosphere

Microns PSIA Mercury (mm) Mercury (in)

0 0 760.00 29.921 — —

50 0.001 759.95 29,920 1/15,200 –50

100 0.002 759.90 29.920 1/7,600 –40

150 0.003 759.85 29.920 1/5,100 –33

200 0.004 759.80 29.910 1/3,800 –28

300 0.006 759.70 29.910 1/2,500 –21

500 0.009 759.50 29.900 1/1,520 –12

1,000 0.019 759.00 29.880 1/760 1

2000 0.039 758.00 29.840 1/380 15

4,000 0.078 756.00 29.760 1/189 29

6000 0.117 754.00 29.690 1/127 39

8,000 0.156 752.00 29.600 1/95 46

10,000 0.193 750.00 29.530 1/76 52

15,000 0.290 745.00 29.330 1/50 63

20,000 0.387 740.00 29.130 1/38 72

30,000 0.580 730.00 28.740 1/25 84

50,000 0.967 710.00 27.950 1/15 101

100,000 1.930 660.00 25.980 2/15 125

200,000 3.870 560.00 22.050 1/4 152

500,000 9.670 260.00 10.240 2/3 192

760,000 14.697 0 0 1 atmosphere 212

Approximate fraction

of 1 atmosphere

H2O boiling point at each

pressure (

o

F)

Charging the System

Units are leak tested at the factory and shipped with a nitrogen
holding charge. If the holding charge has been lost due to
shipping damage, charge the system with enough refrigerant to
raise the unit pressure to 30 psig after first repairing the leaks
and evacuating the system.

1 After all refrigerant piping is complete and the system is

evacuated, it can be charged as described in the paragraphs
following. Connect the refrigerant drum to the gauge port
on the liquid shutoff valve and purge the charging line
between the refrigerant cylinder and the valve. Then open
the valve to the mid position.

2 If the system is under a vacuum, stand the refrigerant drum

with the connection up, open the drum, and break the
vacuum with refrigerant gas.

3 With a system gas pressure higher than the equivalent of a

freezing temperature, invert the charging cylinder and
elevate the drum above the condenser. With the drum in

this position and the valves open, liquid refrigerant flows
into the condenser. Approximately 75% of the total
requirement estimated for the unit can be charged in this
manner.

4 After 75% of the required charge enters the condenser,

reconnect the refrigerant drum and charging line to the
suction side of the system. Again, purge the connecting
line, stand the drum with the connection side up, and place
the service valve in the open position.

Important: At this point, interrupt the charging procedure and
do prestart checks before attempting to complete the
refrigerant charge.

Note – Stamp the total operating charge per circuit on the unit

nameplate for future reference.

CAUTION

Adding refrigerant to the suction always risks liquid-related
damage to the compressor.

30 McQuay IM 487-5

Mechanical Installation

Take special care to add refrigerant slowly enough to the
suction to prevent damage. Adjust the charging tank hand
valve so liquid leaves the tank but vapor enters the compressor.

Refrigerant Charge

Factory-installed DX coils are designed to use R-22. The total
charge per circuit is the sum of the following three values:

• Condenser section charge. Refer to manufacturer’s data.

• Evaporator coil charge.

• Charge for length of interconnecting piping, installed by

field.

Note – Factory-installed DX coils are intended for one refrigerant

Note – The total operating charge per circuit should not exceed

Table 8: Approximate DX coil refrigerant charge per circuit

Table 9: Approximate refrigerant charge per circuit

* The RDS 802C unit has two refrigerant circuits.

circuit on unit size 800 and two refrigerant circuits
containing identical weights of refrigerant on all other
sizes. The values shown in Table 8 and Table 9 are for
each circuit.

the pumpdown capacity per circuit.

Unit size

047C 3 x no. of DX rows 3.5 x no. of DX rows
077C 5 x no. of DX rows 6.5 x no. of DX rows

Unit size Evaporator coil (lbs/ckt/coil row)

802 3.30

802C* 2.45

DX Coil R-22 charge (lbs./circuit)

Flat coil Staggered coil

• Where the cooling coils have intermediate condensate pans
on the face of the evaporator coil, copper tubes near both
ends of the coil provide drainage to the main drain pan.
Check that the copper tubes are in place and open before the
unit is put into operation.

• On units with staggered cooling coils, the upper drain pan
drains into the lower coil drain pan through a copper tube
near the center of the drain pan. Check that this tube is open
before putting the unit into operation and as a part of routine
maintenance.

• Because drain pans in any air conditioning unit have some
moisture in them, algae, etc. will grow. Periodically clean to
prevent this buildup from plugging the drain and causing the
drain pan to overflow. Clean drain pans to prevent the spread
of disease. Cleaning should be performed by qualified

personnel

.

WARNING

Drain pans must be cleaned periodically.

Material in uncleaned drain pans can cause disease.

Cleaning should be performed by qualified personnel.

Figure 33: Condensate drain connection

Unit Piping

Condensate Drain Connection

• The unit is provided with a 1.5" male NPT condensate drain
connection. Refer to certified drawings for the exact
location. For proper drainage, level the unit and drain pan
side to side and install a P-trap

• Units may have positive or negative pressure sections. Use
traps in both cases with extra care given to negative pressure
sections. In Figure 33, dimension “A” should be a minimum
of 8" (203 mm). As a conservative measure to prevent the
cabinet static pressure from blowing or drawing the water
out of the trap and causing air leakage, dimension A should
be two times the maximum static pressure encountered in
the coil section in inches wc.

• Draining condensate directly onto the roof may be
acceptable; refer to local codes. Provide a small drip pad of
stone, mortar, wood, or metal to protect the roof against
possible damage.

• If condensate is piped into the building drainage system,
pitch the drain line away from the unit a minimum of 1/8"
per foot. The drain line must penetrate the roof external to
the unit. Refer to local codes for additional requirements.
Sealed drain lines require venting to provide proper
condensate flow.

S e e V i e w " A "

C o p p e r T u b e

( o n e e a c h e n d o f c o i l )

S t a t i c P r e s s u r e " P "

4 " ( 1 0 2 m m )

M i n i m u m

" A "

8 " ( 2 0 3 m m )

M i n . o r 2 x " P "

( i n . w . o . )

D r a i n P a n

V i e w A

N o t e : D r a i n l i n e m u s t

n o t b e r u n h i g h e r

t h a n t h i s l e v e l

M i n i m i z e T h i s

e n s i o n

D i m

Gas Piping

See the “Installation” section of the gas-fired furnace
installation manual, Bulletin No. IM 684 or 685.

McQuay IM 487-5 31

Mechanical Installation

s

Piping for Steam, Hot Water/ChIlled Water Coils

Factory-installed chilled water coils are installed in a coil
section that can be designed to accept a factory-installed
heating coil immediately upstream. The coil section can be
ordered in either the draw-through or blow-through position.
All chilled water piping can be done internal to the unit
without requiring a piping vestibule (except on sizes 800–802
when heating coils are included in the cooling coil section).

Steam and hot water coils can be factory installed in either a
heat section, or in the combination coil section. These sections
can be located either in the draw-through or blow-through
position. When a steam or hot water coil is installed in the heat
section, all piping can be done internal to the unit without
requiring a piping vestibule. Refer to Figure 35 and Figure 37
on page 34.

When a steam or hot water coil is installed in the combination
coil section, the coil connections project to the inside surface
of the door panel. Holes can be cut in the door panels to
connect the piping to the coils, or an accessory piping
vestibule can be added to the unit to provide piping space.
Refer to the section on vestibule assembly instructions. The
piping can then be routed back within the unit as shown in
Figure 35 on page 33.

To avoid piping penetrations through the roof external to the
curb, holes can be cut through the floor of the unit at the

locations specified on the certified drawings.

With the factory piping and valve package, the two coils are
piped in parallel and controlled through a single three-way
valve. Field piping connections are of the same NPT size as the
valve-male threads at the supply connection, female threads at
the return connection.

Figure 34: Hot water heat section (shown with factory
valve and piping)

2.12 " ODM
Copper Coil
Connection

Lower
Coil

Bypass

Air Flow

Upper
Coil

Supply

CAUTION

Seal all holes in the unit floor to prevent water leakage into the
building.

Hot Water Piping

Hot water coils are provided without valves for field piping or
piped with three-way valves and actuator motors.With the
factory piping and valve package, the two coils are piped in
parallel and controlled through a single three-way valve. Field
piping connections are of the same NPT size as the valve-male
threads at the supply connection, female threads at the return
connection.

Hot water coils are not normally recommended for use with
entering air temperatures below 40°F (4°C). No control system
can guarantee a 100% safeguard against coil freeze-up. Glycol
solutions or brines are the only freeze-safe media for operation
of water coils at low entering air temperature conditions. Refer
to the “Maintenance” section of this manual for more on
winterizing coils. The hot water section consists of two
stacked soils, as shown in Figure 34.

When no factory piping or valve is included, the coil
connections are 1.625” ODM copper on 800 and 802C, and

2.125" ODM copper on 047 and 077C.

The valve actuator spring returns to a stem up position upon
power failure. This allows full flow through the coil.

Refer to the certified drawings for the recommended piping
entrance locations. Seal all piping penetrations to prevent air
and water leakage.

Note – Factory-installed water valves and piping are bronze,

brass, and copper. Dissimilar metals within the plumbing
system can cause galvanic corrosion. To avoid corrosion,
provide proper di-electric fittings as well as appropriate
water treatment.

CAUTION

Coil freeze possible. Can damage equipment.
Follow instructions for mixing antifreeze solution used. Some
products have higher freezing points in their natural state than
when mixed with water. The freezing of coils is not the
responsibility of McQuay International. Refer to “Experience in
the field has shown that R-407C systems can be “topped off”
after a leak has been repaired and operate normally. There is
no need, except in the case of a critically charged systems, to
replace the entire charge after a leak has been repaired.” on
page 113.

32 McQuay IM 487-5

Mechanical Installation

Steam Coil Piping (All Units)

The steam heat section consists of two stacked coils pitched at
1/8" (3 mm) per foot (305 mm) as shown in Figure 35 to
provide positive condensate removal. When no factory piping
or valve is included, the coil connections are 2.5" male NPT
iron pipe.

Note – The valve actuator spring returns to a stem up position

Figure 35: Steam heat section (shown with factory valve
and piping)

With the factory piping and valve package, the two coil
supplies are piped in parallel and controlled through a single
two-way valve. The field supply connection is of the same
female NPT size as the valve. Field return connections are
made at the 2.50" male NPT fittings on each of the two stacked
coils.

Note – Refer to the sections on steam coil piping and trap

upon power failure. This allows full flow through the coil.

Upper
Coil

Lower
Coil

Supply

recommendations for additional information.The valve
actuator spring returns to a stem up position upon power
failure. This allows full flow through the coil.

2.12 " ODM
Copper Coil
Connections

Return

Return

Figure 36: Two-way valve package

Steam Piping Recommendations

1 Be certain that adequate piping flexibility is provided.

Stresses resulting from expansion of closely coupled piping
and coil arrangement can cause serious damage.

2 Do not reduce pipe size at the coil return connection. Carry

return connection size through the dirt pocket, making the
reduction at the branch leading to the trap.

3 Install vacuum breakers on all applications to prevent

retaining condensate in the coil. Generally, the vacuum
breaker is to be connected between the coil inlet and the
return main. However, if the system has a flooded return
main, the vacuum breaker to the atmosphere; the trap
design should allow venting of the large quantities of air.

4 Do not drain steam mains or takeoffs through coils. Drain

mains ahead of coils through a steam trap to the return line.

5 Do not attempt to lift condensate when using modulating or

on-off control.

6 Pitch all supply and return steam piping down a minimum

of 1" (25 mm) per 10 feet (3 m) of direction of flow.

McQuay IM 487-5 33

Mechanical Installation

Steam Trap Recommendations

1 Size traps in accordance with manufacturers’

recommendations. Be certain that the required pressure
differential will always be available. Do not undersize.

2 Float and thermostatic or bucket traps are recommended for

low pressure steam. Use bucket traps on systems with on­off control only.

3 Locate traps at least 12" (305 mm) below the coil return

connection.

4 Always install strainers as close as possible to the inlet side

of the trap.

5 A single tap may generally be used for coils piped in

parallel, but an individual trap for each coil is preferred.

Figure 37: Heating coil piping with vestibule

Steam Coil Freeze Conditions

If the air entering the steam coil is below 35°F (2°C), note the
following recommendations:

1 Supply 5 psi (34.5 kPa) steam to coils at all times.

2 Modulating valves are not recommended. Control should

be by means of face and bypass dampers.

3 As additional protection against freeze-up, install the tap

sufficiently far below the coil to provide an adequate
hydrostatic head to ensure removal of condensate during an
interruption on the steam pressure. Estimate 3 ft. (914 mm)
for each 1 psi (7 kPa) of trap differential required.

4 If the unit is to be operated in environments with possible

freezing temperatures, an optional freezestat is
recommended. See “Freeze Protection” on page 86 for
additional information.

Figure 38: Valve assembly

S t e m C l i p

S t e m

Figure 39: Steam valve package

S e t s c r e w s

34 McQuay IM 487-5

Mechanical Installation

Chilled Water Piping

Chilled water coils are provided without valves for field
piping, or piped with three-way valves with motor actuators.
Table 10 provides information on units with factory installed
piping and valve packages. The table also provides field sweat
connection information for units not furnished with factory
installed piping and valve packages.

With the factory piping and valve package, the coil assembly is
controlled through a single three-way valve. When two coils
are included in the assembly, they are piped in parallel. Field
connections are male NPT, sized as shown in Table 10. Refer
to Figure 40 for a typical cooling coil with factory valve and
piping.

Figure 40: Chilled water coil (with factory valve and piping)

Air Flow

Return

Bypass

Supply

McQuay IM 487-5 35

Mechanical Installation

Table 10: Piping connection sizes/valve size options for chilled water piping

Cabinet

size

047C

077C

Application

code

Blow-thru or

draw-thru small

coil section

Blow-thru or

draw-thru large

coil section

Face and bypass

section with

small coil

Face and bypass
section with large

coil

Blow-thru or

draw-thru small

coil section

Blow-thru or

draw-thru large

coil section

Face and bypass

section with

small coil

Face and bypass
section with large

coil

Coil size

Hx 83"

(2108 mm)

long

33 + 33

(2 coils) (838

+

838 mm)

39 + 39

(2 coils) (991

+

991 mm)

48

(1219 mm)

39 + 39

(2 coils) (991

+

991 mm)

45 + 45

(2 coils)

(1143 +

1143 mm)

63 + 63

(2 coils)

(1600 +

1600 mm)

63

(1600 mm)

54 + 54

(2 coils)

(1372 +

1372 mm)

Face area sq.

ft. (sq. m)

38.0

(3.53 m²)

45.0

(4.18 m²)

27.7

(2.57 m²)

45.0

(4.18 m²)

51.9

(4.82 m²)

72.6

(6.74 m²)

36.3

(3.37 m²)

62.3

(5.74 m²)

Available rows

(available with 8,

10, 12 fins/in)

3DRDQ——AQAP
4 DRDQBQBQBP
5DRDQ——BQAP
6 DRDQBQBQAP
8 DRDQBQBQBP
3DRCQ——AQAP
4DRCQCQCQBP
5DRCQ——CQAP
6DRCQCQCQAP
8DRCQCQCQBP
3 FUET——ASAS
4 FUETCSCSCS
5FUET——CSAS
6FUETCSCSAS
8 FUETCSCSCS
3DRCQ——AQAP
4DRCQCQCQBP
5DRCQ——CQAP
6DRCQCQCQAP
8DRCQCQCQBP
3 CRCQ——APAP
4 CRCQCPBPBP
5 CRCQ——BPAP
6 CRCQCPBPAP
8 CRCQCPBPBP
3 BQBP——APAP
4 BQBPBPBPBP
5 BQBP——BPAP
6 BQBPBPBPAP
8 BQBPBPBPBP
3 ETCS——ASAS
4 ETCSCSCSCS
5ETCS——CSAS
6 ETCSCSCSAS
8 ETCSCSCSCS
3 CRCQ——APAP
4 CRCQBPBPBP
5 CRCQ——BPAP
6 CRCQBPBPAP
8 CRCQBPBPBP

5WH 5WL 5WS 5WM 5WD

1 2 1 2 1 2 1 2 1 2

Available circuiting

Columns (see next page for explanation)

36 McQuay IM 487-5

Mechanical Installation

Table 10: Piping connection sizes/valve size options for chilled water piping

3 G T G T ——————
4 GTGTGT————
5 G T G T ——————
6 GTGTGT————
3 G T G T ——————
4 GTGTGT————
5 G T G T ——————
6 GTGTGT————
3 — L —M——— N — N
4 — L —M—M—N— N
5 — L —M——— N — N
6 — L —M—M—N— N
8 — L —M—M—N— N

10 — L —M——— N — N

3—L—M—K—N—N
4 — L —M——— N — N
5—L—M—K—N—N
6—L—M—K—N—N
8—L—M—K—N—N

10 — L — M — K — N — N

draw-thru cooling

800

or

Face and bypass

802

Blow-thru or

only coil section

Blow-thru or

draw-thru unit

coil section

section with

small coil

Blow-thru or

draw-thru

contractor coil

section

48 + 78
(1220 +

1981 mm)

48 + 78
(1220 +

1981 mm)

30 + 79

(763 +

2006 mm)

36 + 79

(915 +

2006 mm)

26.0

(2.42 m²)

26.0

(2.42 m²)

16.5

(2.57 m²)

19.8

(4.18 m²)

Table Available Circuiting Legend

Column 1:

These units are available with a factory installed package consisting of a three-way water valve and connecting piping.

A = This combination is not available with a factory-installed piping and valve package.
B = 300, 2.50, or 200 inch three-way valves can be specified
C = 300, 2.50, 2.00, or 150 inch three-way valves can be specified
D = 250, 200, or 150 inch three-way valves can be specified
E = 250, 200, 150, or 1.25 inch three-way valves can be specified
F = 200, 1.50, or 125 inch three-way vales can be specified
G = 1.25, 1.50, 2.00 or 2.50 inch three-way valves can be specified
Field supply and return female NPT connection sizes are the same as the valve size.

Column 2:

The following letters designate units that are not furnished with the factory installed piping/valve package. Required are field sweat
connections, at one or two coils, to male copper tubing for the supply and return water piping.

K = A single 2.00 inch NPT supply and return if fin height is 21–30 inches and 2.50 inches of fin height is 30–36 inches.
L = A single 1.50 inch NPT supply and return
M = A single 2.00 inch NPT supply and return if fin height is 21–30 inches
N = A single 2.50 inch NPT supply and return
P = Two 3.12 inch O.D. supply and two 3.12 O.D. return connections
Q = Two 2.62 inch O.D supply and two 2.62 O.D. return connections
R = Two 2.12 inch O.D. supply and two 2.12 O.D. return connections
S = One 3.12 inch O.D supply and one 3.12 O.D. return connections
T = One 2.62 inch O.D supply and one 2.62 O.D. return connections
U = One 2.12 inch O.D supply and one 2.12 O.D. return connections

McQuay IM 487-5 37

Mechanical Installation

Vestibule Assembly Instructions

An accessory vestibule is available to provide additional
piping space for coils installed in a four-foot section. A
vestibule is required to maintain door access on a combination
heating and cooling section. Assemble the vestibule to the unit
part by part as shown in Figure 41.

Note – The door, hinge, and latch assemblies from the unit are

used on the vestibule.

Step 1

Remove door from section where vestibule is to be located by
removing screws holding hinges to upright support (leave
hinges on door). Set door aside and save for Step 4.

• Remove door latch assembly from other side upright
support. Use offset Phillips screwdriver or a wrench to
remove screws holding latch assembly in place. Save door
latch assembly, screws and bushings for Step 4.

Figure 41: Step 1 illustration

Door

Door Latch Assembly

Step 2

Remove gasketing around door flange and save for use on
vestibule. See Step 4. Remove door and save for Step 4.

Figure 42: Step 2 illustration

Gasketing

Door Prop

38 McQuay IM 487-5

Mechanical Installation

Step 3

1 Assemble side panels A and B to uprights using #10 drill

screws supplied. Make certain side panels are flush against
uprights before securing into place.

2 Fasten bottom panel D to base channel using #10 drill

screws and to side panels A and B using #10 screws
supplied.

3 Set top panel C in place and fasten to side panels A and B

using #10 screws and to top panel using #10 screws
supplied.

Figure 43: Step 3 illustration

#10 Screw

#10 Drill
Screw

Step 4

Reassemble access door to vestibule by screwing hinges

1

into side panel using screws saved from Step 1. (Access
door must be attached to the vestibule in the same opening
direction as it was on the unit.)

2 Remove and discard latch handle locking screws and

retaining washer. Fasten door latch assembly to side panel
using screws and bushings saved from Step 1. (Latch must
be fastened on the same side as when located on the unit.)

3 Fasten upright angles to vestibule using #10 screws

supplied.

4 Seal between unit and vestibule with silicone sealant along

top and sides as shown.

Note – Any holes cut in the floor of the unit must be sealed to

Figure 44: Step 4 illustration

prevent water leakage.

Gasketing

Upright Angle

#10 Screw

Silicone
Sealant

Silicone
Sealant

#10 Screw

Door

Gasketing

Door
Prop

Upright
Angle

Door Latch Assembly
(See Note)

McQuay IM 487-5 39

Mechanical Installation

Damper Assemblies

The optional damper assemblies described in this section
normally are ordered with factory-installed actuators and
linkages. The following sections describe operation and
linkage adjustment of the factory option.

Economizer Dampers

Outside air intake is provided on both sides of the unit, and the
return air path is at the center of the damper set. As the single
actuator modulates the outside air dampers open, the return air
dampers close. Exhaust air exits the unit through the gravity
relief dampers provided at the end of the economizer section.

The outside air return air damper assembly (economizer)
comes with manually adjustable linkage. This adjustable

Figure 45: Economizer dampers

Outside

Air

Optional Return Air Fan

Economizer

linkage also can be used for connecting a damper operator. The
damper is set so that the crankarm moves through a 90-degree
angle to bring the economizer dampers from full open to full
close (see Figure 45). Access to the actuator and linkage is
from the filler section. Mechanical stops are placed in the
crankarm mounting bracket. Do not remove stops. Driving the
crankarm past the stops results in damage to the linkage or
damper. The unit ships with a shipping bolt securing the
linkage crankarm. Remove shipping bolt before use.

Note – For good airflow control, adjust linkages so damper

blades do not open beyond 70 degrees. Opening a
damper blade beyond 70 degrees has little effect on its
airflow.
Do not “over close” low leak damper blades. The edge
seal should just lightly contact the adjoining blade. The
blades will lock up if they are closed so far the seal goes
over center.

Outside

Air

Shaft .500 Dia.

x 1.50 Long

OA

Open

90°

Stroke

.75

RDS 800C & 802C

.25

3.00

OA

Closed

OA

Closed

.500 (13mm) Dia. Shaft

x 1.30" (33mm) Long

RAH 047C - 077C

90°

Stroke

OA

Open

.25" (6mm)

40 McQuay IM 487-5

Mechanical Installation

Intake Hood Damper (0% to 100% outside air, RAH
47–77 only)

Units requiring 100% outside air are provided with a rain hood
and dampers that can be controlled by a single actuator. The
actuator provides two-position control for opening the
dampers fully during unit operation and closing the dampers
during the off cycle. No unit mounted exhaust dampers are
provided.

Intake Hood Damper (0% to 30% outside air)

These dampers are intended to remain at a fixed position
during unit operation, providing fresh air quantities from 0 to
30% of the total system airflow, depending on the damper
setting. This setting is made at the linkage rod on units with
manually adjustable linkages.

On units provided with MicroTech II controls, the damper
position may be set at the controller keypad. During unit
operation, the two-position actuator drives the damper to the
position set on the keypad. During the off cycle, the damper is
automatically closed.

No unit-mounted exhaust dampers are provided with this
option.

Figure 47: Intake hood damper adj., 0% to 100% outside air

Airflow

Figure 46: Intake hood damper, 0% to 30% outside air

A i r f l o w

3 . 1 5 " ( 8 0 m m )
M a x . S t r o k e o f
D a m p e r L i n k a g e B a r

OA

closed

Note – Figure 46 shows the RAH 47–77 (The linkage is on the

RH side). The RDS 800–802 are the same except the
linkage is on the LH side.

90

stroke

OA

open

.25" (6mm)

McQuay IM 487-5 41

Mechanical Installation

)

Mixing Box (RAH 47–77 only)

This section uses an outside air damper and a return air
damper. Using these dampers allows outside air to blend with
return air. Synchronized operation of the dampers is
accomplished by interconnecting rods. As one damper section
opens, the other section is closed. A total of 100% cfm is
always drawn from this section. Damper positioning can be
manually or automatically adjusted. With a field-installed
controller, automatic operation can be obtained.

Figure 48: Mixing box

OA

CLOSED

These dampers provide a similar function to economizer
dampers. This option differs from an economizer in that no
unit mounted exhaust dampers are provided.

Note – For good airflow control, adjust linkages so damper

blades do not open beyond 70 degrees. Opening a
damper blade beyond 70 degrees has little effect on its
airflow. Do not “over close” low leak damper blades. The
edge seal should just lightly contact the adjoining blade.
The blades lock up if they are closed so far that the seal
goes over center.

90°

STROKE

OA

OA

CLOSED

OPEN

.25" (6 mm

OA

OPEN

.75"

(19 mm)

3.00"

(76 mm)

42 McQuay IM 487-5

Face and Bypass Dampers

Face and bypass dampers are available in a flat arrangement
for use with heating coils and standard face area cooling coils,
as well as a staggered arrangement for large face area cooling
coils. The damper sets are linked through a jack shaft for
connection to a single actuator (factory or field installed).

Figure 49: Face and bypass dampers, RDS 800–802 only

Mechanical Installation

Airflow

Face Dampers
Open

Face and
Bypass
Damper

.75"

(19mm)

90°

Stroke

3.00"

(76mm)

Face Dampers
Closed

McQuay IM 487-5 43

Mechanical Installation

Figure 50: Face and bypass dampers, staggered arrangement–RAH 47–77 only

Face Damper

Open

(19mm)

.75"

90°

Stroke

.25"

(6mm)

3.00"

(76mm)

Closed

Airflow

Figure 51: Face and bypass dampers, flat arrangement—RAH 47–77 only

Optional

Contractor

Coil

Bypass Damper

Face and Bypass
Damper

Extended
Shaft

Face and Bypass
Dampers

44 McQuay IM 487-5

Mechanical Installation

Cabinet Weather Protection

This unit ships from the factory with fully gasketed access
doors and cabinet caulking to provide weather resistant
operation. After the unit is set in place, inspect all door gaskets
for shipping damage and replace if necessary.

Protect the unit from overhead runoff from overhangs or other
such structures.

Recaulk field-assembled options such as external piping or
vestibules per the installation instructions provided with the
option.

CAUTION

Transportation, rigging, or maintenance can damage the unit’s
weather seal. Periodically inspect the unit for leakage. Standing
moisture can promote microbial growth, disease, or damage to
the equipment and building.

Installing Ductwork

On bottom-supply/bottom-return units, if a McQuay roof curb
is not used, the installing contractor should make an airtight
connection by attaching field-fabricated duct collars to the
bottom surface of either the roof curb’s duct flange or the
unit’s duct opening. Do not support the total weight of the duct
work from the unit or these duct flanges. See Figure 52.

discharge duct collars on a side discharge unit, remove the
plenum section access door and the door gasketing.

Use flexible connections between the unit and ductwork to
avoid transmission of vibration from the unit to the structure.

To minimize losses and sound transmission, design duct work
per ASHRAE and SMACNA recommendations.

Where return air ducts are not required, connect a
sound-absorbing T or L section to the unit return to reduce
noise transmission to the occupied space.

WARNING

Mold can cause personal injury. Materials such as gypsum wall
board can promote mold growth when damp. Such materials
must be protected from moisture that can enter units during
maintenance or normal operation.

Ductwork exposed to outdoor conditions must be built in
accordance with ASHRAE and SMACNA recommendations

and local building codes

.

NOTICE

Installer must provide access in the ductwork for
plenum-mounted controls.
Once duct work is installed in units with side discharge, access
to plenum-mounted components is difficult.

Units with optional back return, side discharge, or end
discharge all have duct collars provided. To expose the

Figure 52: Installing duct work

U n i t D u c t O p e n i n g

9 . 7 6 "

F l e x i b l e

C o n n e c t o r

D u c t w o r k

D u c t F l a n g e r
i n R o o f C u r b

U n i t B a s e

4 . 5 8 "

R o o f C u r b

McQuay IM 487-5 45

Mechanical Installation

Installing Duct Static Pressure Sensor Taps

For all VAV units, field install and connect duct static pressure
taps to the pressure sensors in the unit. Sensor SPS1 is
standard; additional sensor SPS2 is optional. These sensors are
located in the main control panel (see “Control Panel” on page

5).

Carefully locate and install the duct static pressure sensing tap.
Improperly locating or installing the sensing tap causes
unsatisfactory operation of the entire variable air volume
system. Below are pressure tap location and installation
recommendations. The installation must comply with local
code requirements

1 Install a tee fitting with a leak-tight removable cap in each

tube near the sensor fitting. This facilitates connecting a
manometer or pressure gauge if testing is required.

2 Use different colored tubing for the duct pressure (HI) and

reference pressure (LO) taps, or tag the tubes. McQuay
recommends 1/4" plastic tubing.

3 Locate the duct pressure (HI) tap near the end of a long

duct to ensure that all terminal box take-offs along the run
have adequate static pressure.

4 Locate the duct tap in a nonturbulent flow area of the duct.

Keep it several duct diameters away from take-off points,
bends, neckdowns, attenuators, vanes, or other
irregularities.

5 Use a static pressure tip (Dwyer A302 or equivalent) or the

bare end of the plastic tubing for the duct tap. (If the duct is
lined inside, use a static pressure tip device.)

6 Install the duct tap so that it senses only static pressure (not

velocity pressure). If a bare tube end is used, it must be
smooth, square (not cut at an angle) and perpendicular to
the airstream (see Figure 54).

7 Locate the reference pressure (LO) tap somewhere near the

duct pressure tap within the building (see Figure 53). If the
reference tap is not connected to the sensor, unsatisfactory
operation will result.

8 Route the tubes between the curb and the supply duct, and

feed them into the unit through the knockout in the bottom
of the control panel (see Figure 53). Connect the tubes to
appropriate barbed fittings in the control panel. (Fittings are
sized to accept 1/4" plastic tubing.)

Figure 53: Static pressure tubing entrance location

St atic pressure

tubing

Figure 54: Pressure sensing tubing installation

Main Contr ol Panel

"HI line"

"LO" line

To Sensor
"HI" input

Remote Sense Point

Ductwork

(Remote Location)

SPS1

Rubber
Grommet

Tubing Extends
thru Approx. 1/8"

Roof

To Sensor
"LO" Input

Pressure Sensing
Tubing

46 McQuay IM 487-5

Mechanical Installation

Installing Building Static Pressure Sensor Taps

If a unit has direct building static pressure control capability,
you must field install and connect static pressure taps to
pressure sensor SPS2 in the unit. This sensor is located at the
bottom of the main control panel next to terminal block TB2.

Carefully locate and install the two static pressure sensing
taps. Improper location or installation of the sensor taps causes
unsatisfactory operation. Below are pressure tap location and
installation recommendations for both building envelope and
lab, or “space within a space” pressure control applications.

The installation must comply with local code requirements.

CAUTION

Fragile sensor fittings.
If you must remove tubing from a pressure sensor fitting, use
care. Do not use excessive force or wrench the tubing back and
forth to remove; the fitting can break off and damage sensor.

Building Pressurization Applications

1 Install a tee fitting with a leak-tight removable cap in each

tube near the sensor fitting. This facilitates connecting a
manometer or pressure gauge if testing is required.

2 Locate the building pressure (HI) tap in the area that

requires the closest control. Typically, this is a ground level
floor that has doors to the outside.

3 Locate the building tap so it is not influenced by any source

of moving air (velocity pressure). These sources may
include air diffusers or outside doors.

4 Route the building tap tube between the curb and the

supply duct and feed it into the unit through the knockout in
the bottom of the control panel (see Figure 53). Connect the
tube to the 1/4-inch HI fitting for sensor SPS2.

5 Locate the reference pressure (LO) tap on the roof. Keep it

away from the condenser fans, walls, or anything else that
may cause air turbulence. Mount it high enough above the
roof so it is not affected by snow. Not connecting the
reference tap to the sensor results in unsatisfactory
operation.

6 Use an outdoor static pressure tip (Dwyer A306 or

equivalent) to minimize the adverse effects of wind. Place
some type of screen over the sensor to keep out insects.
Loosely packed cotton works well.

7 Route the outdoor tap tube out of the main control panel

through a small field-cut opening in the edge of the control
wiring raceway cover (see Figure 53 on page 46). Cut this
“mouse hole” in the vertical portion of the edge. Seal the
penetration to prevent water from entering. Connect tube to
the 1/4-inch LO fitting for sensor SPS2.

Lab Pressurization Applications

1 Install a “T” fitting with a leak-tight removable cap in each

tube near the sensor fitting. This facilitates connecting a
manometer or pressure gauge if testing is required.

2 Use different colored tubing for the controlled space

pressure (HI) and reference pressure (LO) taps, or tag the
tubes.

3 Regardless whether the controlled space is positive or

negative with respect to its reference, locate the HI pressure
tap in the controlled space (the setpoint can be set between
–0.2 and 0.2" wc).

4 Locate the reference pressure (LO) tap in the area

surrounding the controlled space. Not locating the
reference tap to the sensor results in unsatisfactory
operation.

5 Locate both taps so they are not influenced by any source

of moving air (velocity pressure). These sources may
include air diffusers or doors between the high and low
pressure areas.

6 Route the building tap tube between the curb and the

supply duct and feed it into the unit through the knockout in
the bottom of the control panel (see Figure 53).

7 Connect the tube to the 1/4-inch HI fitting for sensor SPS2.

McQuay IM 487-5 47

Electrical Installation

Electrical Installation

Field Power Wiring

All of the unit side panels are hinged. Do not mount disconnect
switches and/or motor starters on panels that provide access to
internal components. Wiring conduits can penetrate the cabinet
bottom, base frame, or through the hinge and latch cap without
interfering with the access panels.

Note – Seal all holes cut into the unit to prevent water leakage.

Seal conduits connecting the unit to external panels, which
will be exposed to relative humidity and air pressure
differentials. Ground the motor using copper or other corrosion
resistant conductor.

Figure 55: Field power wiring

Access
Panels

Hinge and
Latch Cap

To p

overload. Before replacing a fuse, circuit breaker, MMP, or
restarting a fan motor, identify the trouble and correct.

According to the National Electrical Code, a disconnecting
means shall be located within sight of and readily accessible
from the air conditioning equipment. The unit can be ordered
with an optional factory mounted disconnect switch. This
switch is not fused. Power leads must be over-current
protected at the point of distribution. The maximum allowable
overcurrent protection (MROPD) appears on the unit
nameplate.

All RDS and RAH Units

All units are provided with internal power wiring for single or
dual point power connection. The power block or an optional
disconnect switch is located within the main control panel.
Field power leads are brought into the unit through 3"
knockouts in the bottom of the main control panel. Refer to the
unit nameplate to determine the number of power connections.
See Figure 56 and Table 12 on page 50.

WARNING

Hazardous voltage. Can cause severe injury or death.
Disconnect electric power before servicing equipment. More
than one disconnect may be required to de-energize the unit.

Bottom

Must Seal

Access
Panel

Base
Frame

Bottom

Wiring must comply with all applicable codes and ordinances.
The warranty is voided if wiring is not in accordance with
these specifications. An open fuse, tripped circuit breaker, or
Manual Motor Protector (MMP) indicates a short, ground, or

If the unit has a factory mounted disconnect switch, generally
the switch must be turned off to open the main control panel
door. However, the door can be opened without disconnecting
power by following the procedure covered on page 114. If this
is done, use caution since power is not removed from the unit
or the controller.

Note – To wire entry points, refer to certified drawings for

dimensions.

Figure 56: RDS and RAH power wiring connections

Electric heat
control panel

Optional

disconnect

(DS3)

3" power

knockouts

Optional

disconnect (DS2)

Main disconnect (DS1)

or power block (PB1)

3" power

knockouts

48 McQuay IM 487-5

Electrical Installation

g

Figure 57: Optional side power wiring entrance

• The preferred entrance for power cables is through the
bottom knockouts provided on the unit. If side entrance is

M a i n
C o n t r o l
P a n e l

2 . 7 5 "
( 7 0 m m )

3 " ( 7 6 m m )

M a x D i a .

the only option, a drilling location is provided.

CAUTION

Wires are located in base rail. Move wires before drilling hole
through base rail.

Follow the drilling dimensions exactly to prevent damage to
the control panel. The dimensions provided are the only
possible point of side entrance for the power cables.

1 6 "

10.0

C

B

( 4 0 6 m m )

Supply air opening

A

1.50 MPT drain

20.0

10.0

6.0

76.0

3.8

86.5

R e m o v e L i f t i n g B r a c k e t
( I f L o c a t e d H e r e )
B e f o r e D r i l l i n

H o l e

Figure 58: Typical power wire entrance, unit view—RDS 800C shown (actual opening shown on submittal documents)

3.8

94.0

E

Detail B

C

3.8

0.9 Dia. K.O.
(Qty 4)

Bottom ret urn
opening

24.3

Va r ie s

based on

options

17.7

22.3

12.9

15.3

3.0 Dia. K.O.
(Qty 3)

6.8

11. 9

12.0

Reference from leaving
air end of section

8.8

7.6

6.6

3.8

McQuay IM 487-5 49

Electrical Installation

All Units

The minimum circuit ampacity (wire sizing amps) is shown on
the unit nameplate. Refer to Table 12 on page 50 for the
recommended number of power wires.

Copper wire is required for all conductors. Size wires in
accordance with the ampacity tables in Article 310 of the
National Electrical Code. If long wires are required, it may be
necessary to increase the wire size to prevent excessive voltage
drop. Size wires for a maximum of 3% voltage drop. Supply
voltage must not vary by more than 10% of nameplate. Phase
voltage imbalance must not exceed 2%. (Calculate the average
voltage of the three legs. The leg with voltage deviating the
farthest from the average value must not be more than 2%
away.) Contact the local power company for correction of
improper voltage or phase imbalance.

CAUTION

Provide proper line voltage and phase balance.
Improper line voltage or excessive phase imbalance constitutes
product abuse. It can cause severe damage to the unit's
electrical components.

A ground lug is provided in the control panel for each
disconnect or power block. Size grounding conductor in
accordance with Table 250-95 of the National Electrical Code.

In compliance with the National Electrical Code, an
electrically isolated 115V circuit is provided in the unit to
supply the factory mounted service receptacle outlet and
optional unit lights. This circuit is powered by a field
connected 15A, 115V power supply. Leads are brought in
through a 7/8" knockout in the bottom of the main control
panel, near the power wire entry point.

Table 11: Multiple point power connection options

Number of

electrical

circuits

2

2

Disconnect

designation

DS2

DS1 Balance of unit Main control panel

DS3 Electric heat

DS1 Balance of unit Main control panel

Load

Supply and return fan

motors plus controls

Location

(see Figure 2 on

page 4)

Main control panel

Electric heat

control panel

Table 12: Recommended 3-phase power wiring to ensure
disconnects and power blocks mate with power wiring

Wire

gauge

10 1 75 1 1/2 35

8 1 75 1 3/4 50
6 1 75 1 1 65
41 75 1 1 1/4 85
3 1 75 1 1 1/4 100
2 1 75 1 1 1/4 115

1 1 75 1 1 1/4 130
1/0 1 75 1 1 1/2 150
2/0 1 75 1 2 175
3/0 1 75 1 2 200
4/0 1 75 1 2 230

250 1 75 1 2 1/2 255
300 1 75 1 2 1/2 285
350 1 75 1 3 310
400 1 75 1 3 335
500 1 75 1 3 380

3/0 2 75 2 2 400
4/0 2 75 2 2 460

250 2 75 2 2 1/2 510
300 2 75 2 2 1/2 570
350 2 75 2 3 620
400 2 75 2 3 670
500 2 75 2 3 760
250 3 75 3 2 1/2 765
300 3 75 3 2 1/2 855
350 3 75 3 3 930

1.All wire sizes assume separate conduit for each set of parallel conductors.

2.All wire sizes based on NEC Table 310-16 for 75°C THW wire (copper).
Canadian electrical code wire ampacities may vary.

3.All wire sizes assume no voltage drop for short power leads.

Qty./

pole

Insulation

rating

(°C)

No. of

conduits

Conduit

(trade size, in.)

For MCA

up to

(amps)

50 McQuay IM 487-5

Field Control Wiring

2

ol

c

ng

Electrical Installation

Units are available with several control arrangements which
may require low voltage field wiring. Detailed descriptions of
various field control wiring options and requirements are
included in the “Field Wiring” section of Bulletin No. IM 696,
“MicroTech II Applied Rooftop Unit Controller.” Refer to the
unit wiring diagrams for additional installation information.

Wiring must comply with applicable codes and ordinances.
The warranty is voided if wiring is not in accordance with
these specifications.

All field control wiring connections are made at the class II
terminal block TB2, which is located in the main control panel.
Field wiring connections to the 115-volt receptacle and lights
are made at terminal block TB7, which is also located in the
main control panel. Refer to Figure 59 and “Control Panel” on
page 5. Two 7/8" knockouts are provided for wire entry.

Figure 59: Field control wiring connections

Main control panel

4V field terminal

block (TB2)

Interconnecting wiring enters the air handler unit through 7/8"
knockouts in the bottom of the main control panel. The
interconnecting wiring is connected to TB4 in the air handler
unit. Refer to Figure 60. A 7/8" knockout is also available in
the end of the unit base as shown in Figure 59.

Note – If a single conduit containing 24V and 115V wiring is run

Figure 60: Interconnecting control wiring

above the roof line between the air handler and
condensing units, install the 24V wiring as a NEC Class I
wiring system.

Main
ontrol

panel

TB4

DS2

PB1/DS1

To
condensi
unit

WARNING

Electrical shock hazard. Can cause severe injury or death.

Control wiring raceway
cover (remove for access
to harness from main contr
box to unit-mounted
control devices)

Connect only low voltage NEC Class II circuits to terminal block
TB2.
Reinstall and secure all protective deadfront panels when the
wiring installation is complete.

McQuay IM 487-5 51

Preparing Unit for Operation

This bracket is added,

ns

a

Preparing Unit for Operation

WARNING

Moving machinery hazard. Can cause severe injury or death.
Before servicing equipment, disconnect power and lock off.
More than one disconnect may be required to de-energize unit.

Figure 61: RAH spring mount hold down fasteners

Hold-down
fasteners

Hold-down
fasteners

Spring Isolated Fans

Releasing Spring Mounts

The optional spring-mounted supply and return fans are locked
down for shipment. Hold-down fasteners are located at each
spring mount. Remove these fasteners before operating the
fans. Figure 64 shows a typical spring mount. Note that the
3/8" hold-down bolt securing the fan base to the unit cross
channel must be removed.

After removing the hold-down fasteners, rock the fan assembly
by hand to check for freedom of movement.

Figure 62: Spring mounted hold-down fasteners, all units

Figure 63: Fan spring mount adjustment

Leveling
screw

Spring
mount

assembly

Cross

channel

* Grossly out-of-adjustment thrust restraints can affect this

dimension. Recheck after thrust restraints are adjusted.

Jam nut

Fan base

3/8" ± 1 /4"
with fan running

Adjusting Spring Mounts

To change spring compression:

Loosen the .625-18 UNF hex nut.

Place some additional weight on the fan sled frame (use a lever
to slightly compress the spring/or raise the sled) to allow the
bolt to turn freely.

Place one or two drops of oil on the threads if needed. Use a
wide, flat, blade socket drive bit with a recommended 1/2”
drive handle. Ensure that as the slotted bolt is turned, the
upper-rebound plate also turns. This action allows the bolt to
compress/decompress the compression plate, while having the
same affect on the spring. If the spring is compressed too
much, lift the sled before turning. If the spring is not
compressed enough, place weight on the sled corner to force it
down before turning.

Re-adjust the position of the lower-rebound plate so that the
sled has at lest 3/4” travel and no more than 1.25” travel.

Figure 64: Spring mount

and these 3/8" tie dow

are used for RDS 800C.

This bracket is added,

and these 3/8" tie downs

re used for RDS 800C.

52 McQuay IM 487-5

WARNING

Moving machinery hazard. Can cause severe injury or death.
Start the fans for the first time according to the “Check, Test,
and Start Procedures” on page 97. If this is not done, equipment
damage, severe personal injury, or death can occur.

Relief Damper Tie-Down

Preparing Unit for Operation

Figure 66: Thrust restraint adjustment

Jam nut A

Nut B

Spring clip

Washer

Nut C

Fan bulkhead

Economizer sections with a 30" or 40" return fan have a relief
damper that is tied down for shipping. Remove the two
brackets and two screws before operation to allow free
movement of dampers. Access is from inside the economizer
section.

Adjusting Scroll Dampers

Two sets of scroll dampers are provided in the housing of the
twin 15" x 6" supply fan to allow control of air volume to each
fan wheel. At the factory, these dampers are fully closed,
unrestricting airflow. If fan paralleling occurs, correct it by
loosening the adjustment screw on top of the fan housing (see
Figure 65) and slightly lowering the rod until air distribution
between the fans is even.

Figure 65: Scroll damper adjustment

Adjustment assembly

Scroll damper

Jam nut A

Thrust restraint angle

Fan housing frame

Detail A

See Detail A

Thrust restraint adjustment (with fan off)

1. Loosen jam nuts A.

2. Turn nut C until spring cup and washer contact thrust restraint angle.

3. Turn nut B until spring is compressed by two turns of nut B.

Adjusting Supply Fan Thrust Restraints

4. Tighten jam nuts A.

Thrust restraints are provided when housed double-width fans
are mounted on springs. After the spring mounts are adjusted
for level operation when the fan is running, check the thrust
restraints. With the fan off, set the adjustment nuts so the
spring is slightly compressed against the angle bolted to the
fan housing frame. Refer to Figure 66. When the fan is turned
on, the fan moves back to a level position and the thrust
restraint spring compresses.

McQuay IM 487-5 53

Preparing Unit for Operation

Adjusting Seismic Restraints

Spring-mounted supply air and return air fans can be ordered
with factory-installed seismic restraints. The system consists
of four snubbers, one located next to each spring isolator.
These snubbers allow free movement of the fan assemblies
during normal operation because normal operation does not
cause fan movements that exceed .25" (6 mm). However, if an
abnormal condition occurs, they restrain the fan assembly and
limit movement to .25" (6 mm) in any direction.

The position the fan assumes during normal operation is
determined by actual job site airflow and static pressure.
Therefore, for proper operation, field adjust the seismic
restraints as part of the normal “Check, Test and Start”
procedure. When the fan is operating in a normal manner,
there should be no contact between the snubber restrainer
angle and the snubber neoprene bumper. However, in a
“seismic event,” the snubber limits movement of the spring
mounted fan assembly to .25" (6 mm) in any direction, thereby
helping to prevent the fan from being tossed about and
damaged, or causing damage.

When a seismic restraint is properly adjusted and the fan is
operating normally, the neoprene center bumper is centered
within the 2" (51 mm) diameter hole in the restrainer angle,
and the restrainer angle is centered vertically between the
flanges of the neoprene center bumper. This results in .25"
(6 mm) clearance in all directions. When the fan is turned off,
the restrainer angle may come to rest on the neoprene center
bumper.

Figure 67: Cross section of seismic restraint

Fan base channel

Snubber restrainer angle

Adjust up or down
or back and forth

Snubber neoprene

bumper

.25 (6 mm) gap

(fan running)

Snubber neoprene

bumper

Adjust in and out

The seismic restraint is adjustable in all directions. Vertical
slots in the restrainer angle and horizontal slots in the blower
base allow the restrainer angle to be adjusted up and down and
back and forth. The neoprene center bumper is mounted on a
slotted hole allowing in and out adjustment.

Removing the neoprene center bumper bolt allows removal,
disassembly, and replacement of the neoprene components.

54 McQuay IM 487-5

Sequences of Operation

Sequences of Operation

The following sequences of operation are for a typical “C”
vintage applied rooftop unit equipped with MicroTech II, an
economizer, 3 to 1 turn down burner, variable frequency drives
(VFD), a return air fan and an external time clock. These
sequences describe the ladder wiring diagram logic in detail;
refer to “Wiring Diagrams” on page 58 as you read them. Note
that your unit’s sequences of operation may vary from those
described here. Refer to the wiring diagrams supplied with the
unit for exact information.

For detailed description of operation information relating to
the MicroTech II controller's software, refer to the appropriate
operation manual (see Table 1 on page 3). These manuals
describe the various setpoints, parameters, operating states,
and control algorithms that affect rooftop unit operation.

Power-up

When primary power is connected to the unit, 115VAC power
is fed through control circuit transformer T1 and control circuit
fuse F1C (line 168) to compressor crankcase heaters HTR-1,
HTR-2, HTR-3 and HTR-4 (lines 815, 848, 820, and 853).

When system switch S1 (line 203) is closed, low voltage
transformers T2 (line 203), T3 (line 301)and T9 (line 802)
energize, and 115VAC power is supplied to the following:

• Smoke detectors (lines 265 and 267)

• Economizer actuator ACT3 (line 313)

• M30A to energize the supply fan VFD (line 426)

• M40A to energize the return fan VFD (line 430)

• Heating control panel (line 603)

• Compressor circuit switches CS1 and CS2 (lines 805 and

838)

Transformer T2 supplies 24VAC power to terminals 24V and
COM on the main control board MCB (lines 207 and 208).
Transformer T2 supplies 24VAC power to the following:

• Switch S7 On-Auto-Off (line 217)

• Enthalpy sensor OAE (line 250)

• External time clock contacts (line 215)

• External exhaust fan status contacts (line 257, VAV only)

• Airflow interlock switch PC7 (line 228)

• Dirty filter switches PC5 and PC6 (lines 242 and 247)

• Duct high limit switch DHL (line 260, VAV only)

• Gas furnace alarm relay R24 (line 225)

• Freezestat switch FS1 (line 231, hot water or steam heat

only)

• Smoke detectors SD1 and SD2 (line 237)

When the field supplied Cool Enable switch is in the OFF
position, field wiring terminal TB2 105 de-energizes (line

220). Binary input MCB-BI3 de-energizes and the cooling is
disabled. When the field supplied Heat Enable switch is in the
OFF position, field wiring terminal TB2 106 de-energizes (line

223). Binary input MCB-BI4 de-energizes and the heating is
disabled.

Note – Unit ships with factory installed jumpers between TB2 101

and 105 and between 101 and 106.

Fan Operation

When the main control board (MCB) commands the supply
and return fans to start, the unit enters the Startup operating
state. As a result, a 3-minute timer is set, output MCB-BO3
(line 307) energizes, and relay R26 energizes (line 306).

After the 3-minute timer expires, the unit enters the Recirc
operating state. As a result, output MCB-BO1 energizes relay
R67 (line 401). This gives a start signal to supply fan drive
AFD10 (line 445). Four seconds after MCB-BO1 is energized,
output MCB-BO2 energizes relay R68 (line 404). This gives a
start signal to return fan drive AFD20 (line 445).

Within 120 seconds after the fans start, the controller expects
airflow switch PC7 (line 228) to close and thus energize binary
input MCB-BI6. (If MCB-BI6 does not energize, the controller
assumes the fans did not start. It then shuts down the unit and
generates an alarm.)

During the Recirc operating state, the outside air damper is
held closed. The controller does this by energizing output
MCB-BO5 (line 318). On VAV units, output MCB-BO12, the
VAV box output, is also de-energized (line 309) during the
Recirc state.

McQuay IM 487-5 55

Sequences of Operation

The supply fan adjustable frequency drive (AFD10) is
modulated to maintain the duct static pressure setpoint. When
energized, output MCB-BO14 (line 407) drives AFD10 toward
increased capacity; MCB-BO13 (line 405) drives it toward
decreased capacity. On VAV units or CAV units equipped with
return fan capacity control, the adjustable frequency drive
(AFD20) is modulated to maintain an acceptable building
static pressure (using either VaneTrol logic or direct
measurement of building pressure; see the appropriate OM for
more information). When energized, output MCB-BO16 (line

409) drives AFD20 toward increased capacity; MCB-BO15
(line 411) drives them toward decreased capacity.

Note – If the inverter bypass switch S4 (lines426 and 430) is in

the bypass position, MMP30 and MMP40 (line 132 and

144) protect the fans from excessive current draw. If
either the supply or return fan is drawing excessive
current, one of the MMPs triggers an auxiliary contacts
(line 426) and open the circuit, causing both fans to stop.

Economizer Operation

When the outdoor air is suitable for free cooling, the switch in
enthalpy sensor OAE is in position “3” (line 252) energizing
binary input MCB-BI11. When MCB-BI11 energizes, the
economizer is enabled. (Note: If selected from the keypad, the
enthalpy decision can be made based on outdoor temperature.
In that condition, if the outdoor air temperature is less than or
equal to the changeover set point, the economizer is enabled.)
If cooling is required, the economizer dampers (ACT3) are
modulated to maintain the discharge air temperature setpoint.
When energized, output MCB-BO6 drives the outdoor air
dampers toward the open position; MCB-BO5 drives them
toward the closed (line 318). If the outdoor air dampers are
wide open and more cooling is required, the dampers hold
their positions and mechanical cooling is activated (see
below).

When the outdoor air is not suitable for free cooling, the
switch in enthalpy sensor OAE is in position “1,”
de-energizing binary input MCB-BI11. (Alternatively, the
outdoor air temperature is above the changeover setpoint plus
the economizer changeover differential). When the economizer
is disabled, the dampers are held at their minimum position.

56 McQuay IM 487-5

Heating

Sequences of Operation

Gas Furnace, Modulating Burner (3 to 1 turn down)

Refer to “Standard Mod, furnace control (1000 MBh)” on page
79 as you read this sequence of operation. Note that the gas
furnace wiring diagrams supplied with the units include a
detailed sequence of operation. Refer to the wiring diagram
supplied with the unit for exact wiring and sequence of
operation information.

When system switch S1 is closed, 115 V (ac) power is supplied
to the furnace control circuit. If burner switch S3 and safeties
HL22, HL23 are closed (line 603), terminal 5 (line 609) on the
flame safeguard control (FSG) energizes as does the
modulating gas valve VM1. If heating is enabled (MCB-BI4 is
energized—line 223) and heating is required, the MCB-BO11
energizes relay R20 (line 413). The normally open R20
contacts (line 603) close, and if manual burner switch S3 and
safeties HL22, HL23, FLC (high limit switch) (line 603), LP5,
and HP5 are closed (optional, not shown on page 79), terminal
6 (line 618) on the flame safeguard control (FSG) energizes.
FSG energizes terminal 4 to start the blower motor (BM) (line

609) through contactor M29 on large burners. If the blower is
operational, air switch AS (line 621) closes and makes
electrical continuity from FSG terminal 6 to 7. After a 90­second prepurge period, FSG terminals 8 (line 613) and 10
(line 621) energize. As a result, ignition transformer IT and
pilot gas valve GV1 energize. The pilot flame ignites and is
detected by FSG through flame rod FD (line 612). Upon
detection of pilot flame after the 10-second trial for ignition
period, the FSG de-energizes terminal 10 and energizes
terminal 9 to energize main gas valves GV2 and GV3 (lines
617, 619) and low fire start relay R23 (line 624). The R23
contacts (lines 632 and 633) allow the MCB to modulate gas
valve actuator VM1 as required to satisfy the heating demand.

Whenever the burner is operating, its firing rate is determined
by the position of gas valve actuator VM1. This actuator
modulates the butterfly gas valve and combustion air damper,

thus varying the furnace firing rate between 33% and 100% of
full capacity. When the MCB-BO10 energizes (line 634), VM1
modulates toward open and the firing rate increases. When
MCB-BO9 energizes (line 633), VM1 modulates toward
closed and the firing rate decreases. When both MCB-BO10
and MCB-BO9 are open, VM1 holds its position and the firing
rate remains constant.

When heating is no longer necessary, MCB-BO11 opens,
de-energizing relay R20 and opening its contacts (line 603). As
a result, the flame safeguard control de-energizes, all gas
valves close, the combustion air blower motor stops, and gas
valve actuator VM1 closes. If the furnace is warm enough to
close it, the FLC fan controls switch (line 602) overrides
supply fan start/stop output MCB-BO1 through R25 (line 402)
and keeps the supply fan running until the furnace cools down
(this might happen during night setback operation).

If the furnace overheats, the FLC high limit control (line 603)
cycles the burner, preventing the furnace temperature from
exceeding the limit control’s setpoint. When the furnace cycles
off, low fire start relay R23 de-energizes. The normally closed
R23 contacts (line 633) cause VM1 to drive to its minimum
position, overriding MicroTech II control of VM1 via
MCB-BO10 and MCB-BO9. Because relay R23 de-energizes
whenever GV2 de-energizes, the burner always starts at low
fire.

Safety Lockout

If the pilot flame does not ignite or the flame safeguard fails to
detect its flame within 10 seconds, the flame safeguard control
enters the “safety lockout” state. FSG terminals 4, 8, 9, and 10
de-energize and the burner shuts down. FSG terminal 3
energizes relay R24 (line 610). The R24 contacts (line 225)
signal the controller that the problem exists by energizing the
input to MCB-BI5. If a safety lockout occurs, manually reset
the flame safeguard control.

McQuay IM 487-5 57

Wiring Diagrams

Wiring Diagrams

Legend

General Notes

1. Field wiring

2. Factory wiring

3. Shielded wire/cable

4. Main control box
terminals

5. Auxilliary box

6. Field terminals

7. Plug connector

8. Wire/harness number

200/ H200

terminals

ID Description Standard location

CB11 Circuit breaker, evaporative

condenser fan(s)

CB20 Circuit breaker, return/

exhaust fan

CB60 Circuit breaker, energy

recovery wheel

CCB1, 2 Compressor control boards,

refrig. circuits

CPC Circuit board, main, micro

controller

CPR Circuit board, expansion,

micro controller

DAT Discharge air temperature

sensor
DFLH Design flow lefthand sensor Return section
DFRH Design flow righthand sensor Return section
DHL Duct hi-limit Main control box
DS1 Disconnect, total unit or cond/

heat
DS2 Disconnect, SAF/RAF/

controls
DS3 Disconnect, electric heat Electric heat box
EAT Exhaust air temperature

sensor
EFT Entering fan air temperature

sensor
EHB1 Staged electric heat board Main control box
ERB1 Energy recovery board Main control box
ERM1 Energy recovery wheel motor #1Energy recovery section

ERM2 Energy recovery wheel motor #2Energy recovery section

Main/cond. control box

Main control box

Main control box

Main control box

Main control box

Main control box

Discharge section

Main control box

Main control box

Energy recovery section

Supply fan section

WN7

9. Wire nut/ID

ID Description Standard location

ACT3, 4 Actuator motor, economizer Economizer section
ACT5 Actuator motor, discharge

isolation damper

ACT6 Actuator motor, return air

isolation damper

ACT7 Actuator motor, heat face/

bypass

ACT8 Actuator motor, cool face/

Bypass

ACT10, 11Actuator motor, exhaust

dampers

ACT12 Actuator motor, enthalpy

wheel bypass damper

AFD10 Adjustable frequency drive,

supply fan

AFD11 Adjustable frequency drive,

evap cond. fans

AFD20 Adjustable frequency drive,

return/exhaust fan

AFD60 Adjust. freq. drive, energy

recovery wheel(s)
AS Airflow switch, burner blower Gas heat box
BM Burner blower motor Heat section, gas
C10 Power factor capacitors,

supply fan
C20 Power factor capacitors,

return fan
CB10 Circuit breaker, supply fan Main control box

Discharge section

Return section

Coil section, heat

Coil section, cool

Return section

Energy recovery section

AFD/supply fan section

Main/RCE control box

AFD/ret. ex. fan section

Energy recovery section

Supply Fan section

Return section

F1A, B Fuse, control circuit

transformer (T1), primary

F1C Fuse, control circuit

transformer (T1), secondary

F2 Fuse, control circuit

transformer (T2), primary
F3 Fuse, burner blower motor Main control box
FB31–40 Fuseblock, electric heat (top

bank)
FB41–50 Fuseblock, electric heat (bot.

bank)
FD Flame detector Heat section, gas
FLC Fan limit control Heat section, gas
FP1, 2 Frost protection, refrig. circuits Coil section, cool
FS1, 2 Freezestat control Coil section, heat/cool
FSG Flame safeguard Gas heat box
GCB1 Generic condenser board,

refrig. circ.
GFR1, 2 Ground fault relay Main control box
GFS1, 2 Ground fault sensor Main control box
GRD Ground All control boxes
GV1 Gas valve, pilot Heat section, gas
GV2 Gas valve, main/safety Heat section, gas
GV3 Gas valve, redundant/safety Heat section, gas
GV4–8 Gas valve, main, hi turn down Heat section, gas
HL1–10 Hi-limits, pwr, elec heaters

(top bank)
HL11–20 Hi-limits, pwr, elec heaters

(bot. bank)
HL22 Hi-limits, gas heat (pre-filters) Supply fan section
HL23 Hi-limits, gas heat (final filters) Final filter section
HL31–40 Hi-limits, ctl. elec heaters (top

bank)
HL41–50 Hi-limits, ctl. elec heaters (bot.

bank)
HP5 Hi-pressure controls, gas Heat section, gas

Main control box

Main control box

Main control box

Electric heat box

Electric heat box

Main control box

Heat section, electric

Heat section, electric

Heat section, electric

Heat section, electric

58 McQuay IM 487-5

Wiring Diagrams

ID Description Standard location

HS1 Heat switch, electric heat

HS3 Heat switch, electric heat

HTR65 Heater, sump Evap. condenser section
HTR66 Heater, vestibule Evap. condenser vestibule
HUM1 Humidstat sensor Energy recovery section
IT Ignition transformer Gas heat box
LAT Leaving air temperature

LP5 Low-pressure control, gas Heat section, gas
LR10 Line Reactor, supply fan Inverter bypass box
LR20 Line reactor, return/exhaust

LS1, 2 Limit switch, low fire, high fire Gas heat box
LT10–23 Light, cabinet sections Supply fan section
M10 Contactor, supply fan Main control box
M20 Contactor, return fan Main control box
M29 Contactor, burner motor Gas heat box
M30 Contactor, reversing, invertor

M31–39 Contactor, electric heat (top

M40 Contactor, reversing, Invertor

M41–50 Contactor, electric heat (bot.

M60 Contactor, energy recovery

MCB Microprocessor circuit board Main control box
MJ Mechanical Jumper All control boxes
MMP1–8 Manual motor protector,

MMP10 Manual motor protector,

MMP11–18Manual motor protector, cond.

MMP20 Manual motor protector, return

MMP21–28Manual motor protector, cond.

MMP30 Manual motor protector, invrtr.

MMP40 Manual motor protector, invrtr.

MMP51,
52, 53

MMP60 Manual motor protector,

MP1–6 Motor protector, compr.#1-6 On compressors
OAE Outside air enthalpy sensor Economizer section
OAT Outside air temperature

PB1, 2 Power block, power

PB3 Power block, power

PB9, 10 Power block, supply fan Junction box, split unit
PB11, 12 Power block, power

PB19, 20 Power block, return/exhaust

PC5 Pressure control, clogged filter Pre filter section
PC6 Pressure control, clogged final

PC7 Pressure control, proof airflow Supply fan section
PC8 Pressure control, minimum

PM1 Phone modem Main control box
PVM1, 2 Phase voltage monitor Main control box
R20 Relay, Heat, gas/ steam/ hot

shutdown

deadfront interlock

sensor

fan

bypass, supply fan

bank)

Bypass, Return Fan

bank)

wheel

compressors

supply fan

fans, ckt#1

fan

fans, ckt#2

bypass, sup. fan

bypass, ret. fan
Manual motor protector,

exhaust fan(s)

energy recovery wheel

sensor

distribution

distribution, electric heat

distribution

fan

filter

airflow

water

Main control box

Electric heat box

Energy recovery section

Inv. bypass/main cont. box

Inverter bypass box

Electric heat box

Inverter bypass box

Electric heat box

Main control box

Main/cond. control box

Main control box

Main/cond. control box

Main control box

Main/cond. control box

Inverter bypass box

Inverter bypass box

Prop exhaust box

Main control box

Economizer section

Main control box

Electric heat box

Main control box

Junction box, split unit

Final filter section

Coil section, cool

Gas heat/main cont. box

ID Description Standard location

R21, 22 Relay, heat, gas (hi-turn

down)
R23 Relay, heat, gas & electric Gas/electric heat box
R24 Relay, heat alarm, gas Main control box
R25 Relay, heat, gas, start supply

fan inverter
R26 Relay, isol/exh. dampers,

open/close
R28 Relay, isolation damper,

safety
R29 Relay, remote fire alarm Main control box
R30 Relay, cool valve with face

bypass
R45 Relay, UV lights Main control box
R46, 47 Relay, supply fan inverter,

incr/decr
R48, 49 Relay, return fan inverter, incr/

decr
R58,59 Relay, heat wheel inverter,

incr/decr
R60 Relay, energy recovery wheel,

enable
R61 Relay, smoke detector,

discharge air
R62, 63, 65Relay, use on specials Main control box

R66 Relay, smoke detector, return

air
R67 Relay, supply fan, enable Main control box
R68 Relay, return fan, enable Main control box
R69 Relay, Inv. bypass VAV box

interlock
R70–79 Relay, use on specials Main control box
RAE Return air enthalpy sensor Return section
RAT Return air temperature sensor Return section
REC1 Receptacle, main box Main control box
REC3 Receptacle, field power, 115V Discharge bulkhead
REC10–23Receptacle, cabinet sections Cabinet sections

S1 Switch, system on/off Main control box
S3 Switch, furnace on/off Gas heat box
S4 Switch, inverter bypass, on/ off Main control box
S7 Switch, local on/auto/off to

controller
S10–23 Switches, cabinet section

lights
S40–45 Switches, door interlock, UV

lights
SD1 Smoke detector, supply Discharge section
SD2 Smoke detector, return Return section
SPS1, 2 Static pressure sensors, duct/

building
SR1-3 Sequencing relays, electric

heat
T1 Transformer, main control

(line/115 V (ac)
T2 Transformer, control input

(115/24 V (ac)
T3 Transformer, control output

(115/24 V (ac)
T4 Transformer, exh. damper

actuator (115/12 V (dc)
T5 Transformer, electric heat Electric heat box
T6 Transformer, dew point

controller (115/24 V (ac)
T9 Transformer, refrig. circuit 24V Main control box
TB1 Terminal block, internal Main control box
TB2 Terminal block, field Main control box
TB3 Terminal blocks, factory Main control box
TB4 Terminal block, RFS, field Main control box
TB7 Terminal block, 115V

convenience outlet, field

Gas heat box

Main control box

Main control box

Main control box

Main control box

Main control box

Main control box

Main control box

Main control box

Main control box

Main control box

Main control box

Main control box

Cabinet sections

Cabinet sections

Main control box

Electric heat box

Main control box

Main control box

Main control box

Main control box

Main control box

Main control box

McQuay IM 487-5 59

Wiring Diagrams

ID Description Standard location

TB11 Terminal block, heat Heat control box
TB25, 26,

27, 28
TD5–8 Time delay, part winding,

TD10 Time delay, hi turn down

TR1, 2 Transducer, pressure Main control box
UV Ultra-violet light(s) Coil/discharge section
VM1 Valve motor #1, heating Gas heat box/ heat section
VM5 Valve motor #5, cooling Coil section, cool
VV1 Vent valve, gas heat Heat Section, Gas
ZNT1 Zone temp. sensor, setback Field installed

Terminal block, split unit
junction box

compr #1 - 4

burner

Junction box, split unit

Main control box

Gas heat box

60 McQuay IM 487-5

Figure 68: Power package only, main power

Wiring Diagrams

100

101

102

103

104

ELECTRICAL

105

106

T2A

T1A

T1B

DS1

L1

SUPPLIED

CUSTOMER

CIRCUIT #1

107

108

T2B

L2

POWER

109

(Schematic continues on next page.)

T3A

T3B

GLG1

G

L3

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

McQuay IM 487-5 61

Wiring Diagrams

Figure 69: Power package only, main power, continued

+NB

SUPPLY-FAN

HSAF-1

T1

HSAF-2

MTR

T2

T3

HSAF-3

+NB

RETURN-FAN

T1

HRAF-1

MTR

HRAF-2

T3

T2

168C

T1_N

/4.00

/2.00/2.00

HRAF-3

567

8

GRD

T1

H4

X1X2

H3

H2

X3

T1L1

T3

M10

T2

426

L3

L2

(Schematic continues on previous page.)

M20

T1L1

T3

T2

431

L3

L2

H1

164A

162A

21

F1A

168B

21

21

F1C

F1B

T3A

T3B

T2A

T1A

T2B

T1B

L3A

L2B

L2A

139

138

T2-3

383940

426

L3B

108

T3-3

414243

44

45

MMP20

46

47

484950

MMP10

L1B

L1A

137

DS1

T1-3

35

36

37

T3A

T3B

T2A

T1A

T2B

T1B

426

162

DS1

T1-1

626364

164

T2-1

L3B

L3A

L2B

L2A

L1B

L1A

151

149

150

DS1

T1-5

108

T3-5

T2-5

51

52

53

54

55

565758

596061

123

4

TB1A TB1A

168A

666768

T1_115VAC

69

108

T3-1

65

62 McQuay IM 487-5

Figure 70: Power package only, control power

CUSTOMER SUPPLIED POWER

168C

204B

Wiring Diagrams

426221 256

114 54

TB2 TB2

227B

P20

+PP

5

2

4

115 VAC

REC1

201B 201C

TB7 TB7

102

H235-5

H237-4

H265-2

R63

17

1415GRD

16

TB1B

T2

1

4

24V

115V

CLASS 2

2

3

101112

203D

G

TB7

GND29

23

24

201D

G

N

TB1D

H

H N

13

TB1B

204A

219A

13

21

219

R63

DHL

SUPPLY AIR

SMOKE DETEKTOR

(24 VOLT SIGNAL FROM THE FIELD)

TB2

RETURN AIR

SMOKE DETEKTOR

(24 VOLT SIGNAL FROM THE FIELD)

21

S1

TB2 TB2 TB2

16

SD1

+NB

55

+PP

PL21

SD2

+NB

56 113 53

227A

H235-6

H 115

6

H265-1

H237-3

P20

1

+PP

3

228C 228D

+PP

+PP

PL11

PL11

6

5

2

H237-5

H267-2

17

16

H 115

6

H267-1

H237-3

1

+PP

PL21

3

228A 228B

+NB

ACT3

+PP

PL11

21

H313-2

WHT

(ECON/OADM)

BLK

H313-1

4/R-COM

+PP

86

H315-8

2-CW

1-CCW

H315-6

PL11

238A

+PP

H316-7

(Schematic continues on next page.)

238B

TB2

PL11

239A

7

TB2

(CLOSE) (OPEN)

(20VA PILOT DUTY MINIMUM CONTACT RATING)

67 68 69

TB2

/1.68 /1.68

168A

T1_115VAC T1_N

T2_115VAC

00010203040506070809101112131415161718192021222324252627282930313233343536373839404142

McQuay IM 487-5 63

Wiring Diagrams

Figure 71: Power package only, control power, continued

(Schematic continues on previous page.)

104108

TB2TB2

1413

426

M10

26OA 260B

(S.A. FAN AUX CONTACT)

TB2TB2

R63

76

256A 256B

105106

219

(DUCT HI-LIMIT)

NOTE: THESE CONTACT ARE FOR USE IN A 24 VOLT A.C. CLASS #2 CIRCUIT.

44454647484950515253545556575859606162636465666768

69

64 McQuay IM 487-5

Figure 72: VAV fan power (with SAF and RAF VFDs and manual bypass)

+NB

SUPPLY-FAN

HSAF-1

Wiring Diagrams

MTR

T1

T3

T2

HSAF-2

HSAF-3

PB11

109A

T1

T3

M30B

MMP30

T2

L1

L3

L2

135B

134B

133B

T3A

T3B

T2A

T1A

T2B

T1B

L3B

L3A

L2B

L2A

L1B

L1A

+BB

L3B

L3A

L2B

L2A

L1B

L1A

+BB

111A

110A

T1

T3

427

+BB

426

T2

134A 138A 138B

425

L3

L2

V2

W2

GND

V1

W1

H140

C2

B2

C1

B1

135A 139A 139B

GND10

G

M30I

L1

U2

440

+NB

AFD10

U1

A2

+BB

LR10

A1

133A 137A 137B

(Schematic continues on the next page.)

H139

H137

H138

T2

T1

T3

CB10

L3L3

L1L1

L2L2

T3A

T2A

T1A

DS2

CIRCUIT #1

ELECTRICAL

107

108

T1B

L1

SUPPLIED

CUSTOMER

109

T2B

L2

POWER

110

T3B

GLG1

G

L3

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

PB11

139

138

137

109

L3-3

L2-3

L1-3

137

138

139

140

141

142

McQuay IM 487-5 65

Wiring Diagrams

Figure 73: VAV fan power (with SAF and RAF VFDs and manual bypass), continued

+NB

MTR

RETURN-FAN

T1

T3

T2

HRAF-1

HRAF-2

HRAF-3

168C

T1_N

/2.66

/8.00

/6.00

/4.00

/3.00

/2.00

T1

T3

M40B

MMP40

T2

L1

L3

L2

T3A

T3B

T2A

T1A

T2B

T1B

L3B

L3A

L2B

L2A

L1B

L1A

+BB

+BB

(Schematic continues on the previous page.)

T1

T3

+NB

M40I

AFD20

+BB

CB20

LR20

440

145A 149A 149B

H149

T2

430

L1

L3

L2

V2

W2

U2

GND

V1

W1

U1

H152

C2

B2

A2

C1

B1

A1

147A 151A 151B

146A 150A 150B

GND20

G

F1A

H151

H150

T2

T1

T3

L3L3

L1L1

L2L2

PVM1

162

203

3

2

1

164

163

H4

H3

H2

H1

164A

162A162

21

F1B

567

8

GRD

T1

X1X2

X3

168B

21

115T1/2.00

21

F1C

123

4

TB1A TB1A

432

+BB

426

151

149

143

144

145

146

147

148

PB11

149

150

109

L3-6

L2-6

L1-6

150

151

152

153

154

155

156

157

158

159

160

161

PB11

162

164

109

L3-1

L2-1

L1-1

163

164

165

166

167

168A

T1_115VAC

168

/8.00

/2.00

169

170

66 McQuay IM 487-5

Figure 74: Constant volume fan power (SAF and RAF)

106

1071081091101111121

1331341351361371381391401

)

L3B

L3A

L2B

L2A

L1B

L1A

PB11

SUPPLY-FAN

HSAF-1

T1

MTR

HSAF-2

T2

Wiring Diagrams

T3

HSAF-3

109A

T1

DS1

L1

CIRCUIT #1

ELECTRICAL

SUPPLIED

CUSTOMER

110A

T2

L2

POWER

T3

L3

111A

T1L1

T3

T2

M10

137A

138A

T2A

T1A

T1B

GLG1

G

MMP10

PB11

L2A

L1B

L1A

137

138

L1-3

13

426

L3

L2

139A

T3A

T3B

T2B

L3B

L3A

L2B

139

109

L3-3

L2-3

(Schematic continues on next page.

426

41

McQuay IM 487-5 67

Wiring Diagrams

Figure 75: Constant volume fan power (SAF and RAF), continued

MTR

RETURN-FAN

T1

T3

T2

HRAF-1

HRAF-2

HRAF-3

168C

T1_N

/2.00

/3.00

/4.00

/8.00

567

8

GRD

T1

H4

X1X2

H3

H2

X3

T1L1

T3

T2

M20

431

L3

L2

F1A

T3A

T3B

T2A

T1A

T2B

MMP20

PB11

T1B

426

L3B

L3A

L2B

L2A

L1B

L1A

151

149

150

109

L3-6

L2-6

L1-6

PB11

(Schematic continues on the previous page.)

162A

162

H1

168B

164A

21

F1B

21

21

F1C

123

4

TB1A TB1A

164

109

L3-1

L2-1

L1-1

168A

/8.00

/2.00

T1_115VAC

144

145

146

147

148

149

150

151

152

161

162

163

164

165

166

167

168

169

170

68 McQuay IM 487-5

Wiring Diagrams

8

N

Figure 76: VAV control inputs

168C

SENSOR)

(RETURN AIR

H224-2

DRN-4

2

225C

224C

BLK

DRN

214B

SENSOR)

(OUTDOOR AIR

OAT

+NB

C

A

H227-2

H226-1

4

1

PL3

+PP

227C

226C

WHT

BLK

DRN-4

2

227D

DRN

TEMPERATURE)

(ENTERING FAN

EFT

+NB

H228-1

H229-2

4

PL5

1

+PP

229C

228C

WHT

BLK

+NB

DRN-4

2

230C

DRN

DFRH_DS

3

H230-3

4

+PP

PL22

SIDE)

(DRIVE

1

2

H232-2

DRN-4

H231-1

1

2

3

4

233C

232C

231C

RED

WHT

BLK

DRN

G

5V+

5VDC

PWR

PWR SUP

H

5V-

204B

1415GRD

1610

TB1B

T2

1

4

24V

115V

CLASS 2

2

3

111213

TB1B

23

24

DISPLAY

KEYPAD

208C

209C

WHT

N2+/8.06

210C

BLK

TO CCB1

N2-/8.06

REF/8.07

210D

DRN

214A

+NB

SPACE

ZNT1

ZONE OR

3

OVERRIDE

120

TB2

WHT

BLK

SENSOR

EXTERNAL RESET

TEMPERATURE

DISCHARGE AIR

4

REQ'D FOR NIGHT SETBACK OR SPACE RESET

121

132

GRD

133

219C

218C

217C

DRN

WHT

BLK

SENSOR)

(DISCHARGE AIR

RAT

+NB

DAT

+NB

C

A

DRN-4

H221-2

H220-1

H223-1

4

PL1

1

PL2

+PP

1

+PP

2

GRD

223C

221C

221D

220C

DRN

WHT

WHT

BLK

DRN

115T1/1.68

TB1D

24VAC

J1

COM

REF

N2-

N2+

204A

MCB

BCNT

COMM. CARD

BACNET-MSTP

REF

N2-

N2+

MICROPROCESSOR CONTROL BOARD

WHT

BLK

DRN

211A

210A

209A

168B

21

F3

43

203

S1

PVM1

S1

203A

54

156

21

200

TB2

BACnet MSTP

128

connection shown.

129

LON and BACnet IP

GRD

wiring not shown.

201A 200A

S1/6.00

INPUT

ANALOG

RS232 PORT

P1

BINARY

OR UNOCCUPIED

SHOWN IN NIGHT

A (DB9-MALE) CONNECTION

IS LOCATED ON DEADFRONT

+NB

CONN.

SERIAL

RS-232

1

AI1

NJ=VDC

3=NTC

2=MA

1=RTD

SW1

1

INPUT

BI1

215A 215C

102

TB2

3

MODE

TIME_CLOCK

NOTES TO FIELD:

1. REFER TO I.M. FOR

2

1C

3

2

1=RTD

NJ=VDC

1

v
t

#1

R

BI2

AUTO

OFF

ON

1

2

S7

MANUAL_ENABLE

MUST NOT BE

CONFIGURATION.

TERMINALS 101 & 102

MICROTECH II ALARM

INTERNAL TIME CLOCK,

2. TO ENABLE SOFTWARE

AI2

2C

2

3=NTC

2=MA

13

v
t

SW1

#2

2

217A

104

TB2

TB2

JUMPERED

ENABLE SWITCHES

INSTALLING COOL/HEAT

JUMPERS WHEN

THE FIELD TO REMOVE

3.

3

AI3

3C

3

2

NJ=VDC

3=NTC

2=MA

1=RTD

1

SW1

#3

3

BI3

220

105

TB2

COOL_ENABLE

101

v
t

R

TB2

4

AI4

3

2

NJ=VDC

3=NTC

2=MA

1=RTD

1

SW1

4

BI4

223

106

TB2

HEAT_ENABLE

101

TB_101

5

4C

NJ=VDC

3=NTC

2=MA

1=RTD

v
t

#4

5

BI5

225A

111

TB2

DURING NORMAL OPERATION

CONTACT MUST BE OPEN

35

610

R24

GAS HEAT ALARM

6

AI5

2

SW1

AI6

5C

3

1

2

NJ=VDC

3=NTC

2=MA

1=RTD

v
t

SW1

#5

6

R

BI6

228A

108

TB2

+PP

PL15

PC7

+NB

12

AIR FLOW

H228-4 H228-1

41

+PP

PL15

7

AI7

NJ=VDC

1=RTD

231A

7

2=MA

3=NTC

2

SW1

BI7

7C

13

v

t

#7

(Schematic continues on next page.)

6C

3

1

v
t

#6

112

TB2

3/Y1/R

FS1

+NB

H231-1 H231-3

101

TB_101

TB2

/1.68 /1.6

168A

T1_115VAC T1_

200

201

202

203

204

205

206

207

208

209

210

211

212

213

214

215

216

217

218

219

220

221

222

223

224

225

226

227

228

229

230

231

232

233

McQuay IM 487-5 69

Wiring Diagrams

Figure 77: VAV control inputs, continued

445

445

204B

SIG_SD/2.41

313

ACT3

+NB

+PP

PL23

DFLH_ODS

DRN-4

H234-2

4

234C

SIDE)

(OPP

DRIVE

1

3

2

H235-1

H236-3

1

2

3

214B

236C

235C

+NB

(OP)CW(CL)

CCW

7

8

4

H239-3

DRN-9

H240-4

+PP

PL11

9

3

240C

214B

238C

H243-4

H241-5

5

4

+PP

PL18

241C

214B

107

TB2

24VCOM/2.51

VM1

+NB

(OP)

CW

(CL)

CCW

T

Y

G

H244-2

H245-3

DRN-1

1

3

2

4

131

TB2

+S

PWRCOM

+NB

SHS1

SPS1

(DUCT STATIC

SPACE

SENSOR

HUMIDITY

OUT

(0-5V)

126

PRES SENSOR)

-

127

GRD

440

+NB

AFD10

7+

500HOM

H262-8

H261-10

PL7

+PP

10813

8-

DRN-13

440

+NB

AFD20

7+

8-

500HOM

DRN-3

H264-6

H265-8

PL8

+PP

683

TB2

266C

265C

264C

263C

262C

244C

245C

246C

252C

253C

254C

257C

261C

WHT

BLK

RED

WHT

BLK

DRN

RED

WHT

BLK

DRN

WHT

RED

BLK

DRN

WHT

BLK

DRN

DRN

INPUT

OPEN ANALOG

8

AI8

8C

2

3=NTC

1=RTD

NJ=VDC

2=MA

1 3

v

t

SW1

#8

R

8

BI8

113

237A

TB2

(Schematic continues on previous page.)

PL20

+PP

+PP

PL20

5

H237-4

H235-5

17

16

235A

265267

6

SD1

+NB

H237-3

+PP

PL21

6

35

+PP

PL20

H237JMP

H235-6

+PP

PL21

H237-5

17

16

6

SD2

+NB

H237-3

+PP

PL21

3 4

9

NJ=VDC

AI9

9C

2

3=NTC

1=RTD

2=MA

1 3

v

t

SW4

#9

FILTER

FOR FIELD

INDICATION

243A

10

AI10

10C

2

3=NTC

1=RTD

NJ=VDC

2=MA

1 3

v

t

SW4

#10

9

BI9

11

AI11

11C

3

2

NJ=VDC

3=NTC

2=MA

1=RTD

1

v

t

SW4

#11

10

R

BI10

NJ=VDC

12

3=NTC

1=RTD

2=MA

11

13

AI12

12C

2

1=RTD

NJ=VDC

2=MA

1 3

15V DC

v

t

SW4

#12

12

R

BI11

BI12

252A

109

SIG_SD/2.38

TB2

242A

1

3

+PP

PL14

24VCOM/2.47

204B

+PP

+PP

2

PL13

PL13

204B

H252-2

H242-3

H243-1

2

87

R61

R66

3

87

PC5

1

+NB

PRE FILTER

H242-4

+PP

4

PL14

H250-4

1

3

TR1TR

OAE

+NB

+PP

HUM

2

+

SR

JPR

H25O-+

H252-1

H25O-SR

S

+

14

PL13

RAE

+NB

OPEN ANALOG

14

AI13

13C

2

3=NTC

1=RTD

NJ=VDC

2=MA

1 3

v

t

SW4

#13

13

BI13

257A

103

TB2

EXS

+NB

EXTERNAL EXHAUST SWITCH

(SHOWN WITH FAN IN OFF POSITION)

INPUT

AI14

3=NTC

R

WHT

BLK

DRN

WHT

BLK

DRN

15

14C

2

1 3

SW4

3=NTC

1=RTD

NJ=VDC

2=MA

3=NTC

1=RTD

NJ=VDC

2=MA

v

t

#14

14

BI14

260A

31

DHL

16

AI15

2

2

1 3

1 3

SW4

SW4

AI16

15C

v

v

t

t

#15

#15

15

16C

2

2

3=NTC

1=RTD

NJ=VDC

2=MA

3=NTC

1=RTD

NJ=VDC

2=MA

1 3

1 3

v

v

t

t

SW4

SW4

#16

#16

16

R

BI15

BI16

168C

T1_N

/1.68

+PP

+PP

PL21

21

2

PL20

H265-2

H267-2

115

115

SD1

SD2

+NB

+NB

H

H

DUCT HI-LIMIT

SA SMOKE DETECTOR

RA SMOKE DETECTOR

H265-1

H267-1

1

+PP

+PP

PL21

PL20

203B

/8.01

/4.00

/3.00

T2_115VAC

233

234

235

236

237

238

239

240

241

242

243

244

245

246

247

248

249

250

251

252

253

254

255

256

257

258

259

260

261

262

263

264

265

266

267

268

269

270

70 McQuay IM 487-5

Wiring Diagrams

/1.68 /1.68

N

Figure 78: CV control inputs

168C

(RETURN AIR

RAT

H224-2

1

224C

AI4

2

3=NTC

SW1

4

223

TB_101

SENSOR)

BLK

4C

3

1

#4

106

DRN-4

2

225C

v
t

214B

SIDE)

+PP

4

DFLH_ODS

+NB

DRN-4

PL23

234C

DRN

H234-2

4

BLK

(OPP

DRIVE

1

3

2

H235-1

H236-3

1

2

3

214B

236C

235C

RED

WHT

SENSOR)

(OUTDOOR AIR

OAT

+NB

C

A

H226-2

H226-4

H225-1

4

DRN

4

PL3

1

+PP

2

226C

227D

227C

WHT

BLK

DRN

DFRH_DS

+NB

SIDE)

(DRIVE

1

2

3

H232-2

H230-3

DRN-4

H231-1

1

2

+PP

3

PL22

233C

232C

231C

RED

WHT

BLK

DRN

INPUT

OPEN ANALOG

5

NJ=VDC

1=RTD

5

BI5

6

AI5

3=NTC

2=MA

SW1

AI6

5C

3

2

NJ=VDC

3=NTC

2=MA

1=RTD

1

v
t

SW1

#5

6

R

BI6

7

AI7

NJ=VDC

7C

2

3=NTC

1=RTD

2=MA

13

v
t

SW1

#7

7

BI7

6C

3

2

1

v
t

#6

8

AI8

8C

2

3=NTC

1=RTD

NJ=VDC

2=MA

13

v
t

SW1

#8

R

8

BI8

1133113

TB2

TB2

PL21

235A

H235-6

H235-6

237A

PL20

+PP

+PP

5

H235-5

H235-5

17

265267

SD1

+NB

6

+PP

+PP

+PP

17

SD2

+NB

+PP

PL20

PL21

PL20

H237-4

H237-4

H237-3

H237-3

H237JMP

H237JMP

PL21

H237-5

H237-5

H237-3

H237-3

(Schematic continues on next page.)

16

6

35

16

6

3 4

228A

TB2

+PP

PL15

231A

108

112

TB2

+PP

3/Y1/R

TB_101

+NB

FS1

H231-1 H231-3

101

TB2

PC7

+NB

12

AIR FLOW

H228-4 H228-1

41

+PP

PL15

G

5V+

5VDC

PWR

PWR SUP

H

204B

GRD

14

15

1610

TB1B

T2

1

4

24V

115V

CLASS 2

2

3

111213

TB1B

23

24

TB1D

COM

24VAC

TO CCB1

N2+/8.06

N2-/8.06

REF/8.07

210D

210C

209C

DISPLAY

KEYPAD

WHT

BLK

DRN

208C211C

J1

REF

N2-

N2+

204A

MCB

BCNT

COMM. CARD

BACNET-MSTP

REF

N2-

N2+

MICROPROCESSOR CONTROL BOARD

WHT

BLK

DRN

128

129

GRD

TB2

54

PVM1

203A

21

S1

BACnet MSTP

connection shown.

LON and BACnet IP

wiring not shown.

5V-

A (DB9-MALE) CONNECTION

RS232 PORT

P1

IS LOCATED ON DEADFRONT

CONN.

SERIAL

RS-232

+NB

3

214A

TB2

BLK

INPUT

ANALOG

NJ=VDC

1=RTD

INPUT

BINARY

215A 215C

TB2

MODE

OR UNOCCUPIED

SHOWN IN NIGHT

+NB

TIME_CLOCK

ZNT1

1

2=MA

1

NOTES TO FIELD:

ZONE

SENSOR

OVERRIDE

120

RED

AI1

3

2

3=NTC

1

SW1

BI1

102

ON

3

MICROTECH II ALARM

1. REFER TO I.M. FOR

4

121

1C

v
t

#1

R

AUTO

S7

CONFIGURATION.

2. TO ENABLE SOFTWARE

SETPOINT

HEATING

COOLING &

6

132

217C

WHT

DRN

2

AI2

3=NTC

1=RTD

NJ=VDC

2=MA

SW1

2

BI2

217A

TB2

OFF

1

2

MANUAL_ENABLE

JUMPERED

MUST NOT BE

TERMINALS 101 & 102

INTERNAL TIME CLOCK,

THE FIELD TO REMOVE

3.

WALLSTAT

+PP

GRD

2C

2

13

v
t

#2

104

COOL_ENABLE

101

TB2

ENABLE SWITCHES

INSTALLING COOL/HEAT

JUMPERS WHEN

C

PL2

220C

NJ=VDC

220

TB2

+NB

H220-1

WHT

3

2=MA

1=RTD

3

SENSOR)

(DISCHARGE AIR

DAT

A

H221-2

1

221C

BLK

AI3

3

2

3=NTC

1

SW1

BI3

105

+NB

H223-1

DRN-4

4

PL1

+PP

2

223C

222C

DRN

WHT

4

3C

NJ=VDC

2=MA

1=RTD

v
t

#3

R

BI4

TB2

HEAT_ENABLE

101

TB2

168A

T1_115VAC T1_

000102

McQuay IM 487-5 71

03

04050607080910

11

1213141516

171819

202122

2324252627

282930

31

32

203B

3334353637

Wiring Diagrams

(Schematic

continues

on

previous

page

)

Figure 79: CV control inputs, continued

131

131

TB2

TB2

PWRCOM

PWRCOM

252

+NB

+NB

SHS1

SHS1

SPACE

SPACE

SENSOR

SENSOR

HUMIDITY

HUMIDITY

OUT

OUT

(0-5V)

(0-5V)

127

127

GRD

GRD

126

126

TB2

TB2

254C

253C

252C

WHT

BLK

DRN

WHT

BLK

DRN

DFRH_DS

+NB

+PP

3

H230-3

PL22

RED

(DRIVE

H231-1

3

231C

WHT

107

TB2

24VCOM/2.51

ACT3

+NB

DRN-9

PL11

238C

DRN

CCW

H239-3

9

214B

RED

313

(OP)CW(CL)

8

4

H240-4

3

4

240C

WHT

7

H241-5

5

241C

BLK

SIDE)

4

+NB

+PP

DFLH_ODS

DRN-4

H234-2

4

PL23

234C

DRN

BLK

(OPP

DRIVE

1

3

2

H235-1

H236-3

1

236C

RED

+PP

3

214B

2

235C

WHT

SIDE)

1

2

H232-2

DRN-4

1

2

233C

232C

BLK

DRN

343

VM1

+NB

(OP)

CW

(CL)

CCW

8

7

4

H243-4

H244-2

H245-3

DRN-1

1

3

2

4

+PP

PL18

246C

245C

244C

214B

RED

DRN

WHT

BLK

.

INPUT

+PP

PL6

H247-4

+NB

+PP

PC6

PL6

NJ=VDC

BI10

4

2

H247-1

11

1=RTD

10

248A

H248-2

1

1

OPEN ANALOG

AI11

11C

3

2

3=NTC

2=MA

1

v

t

SW4

#11

NJ=VDC

NJ=VDC

12

AI12

2

2

3=NTC

1=RTD

2=MA

3=NTC

1=RTD

2=MA

13

13

SW4

SW4

11

BI11

252A

24VCOM/2.47

204B

+PP

+PP

2

3

+NB

FINAL FILTER

+PP

2

PL13

PL13

H252-2

H250-4

1

3

TR1TR

OAE

PL13

HUM

2

+

SR

JPR

H25O-+

H252-1

H25O-SR

S

+

14

RAE

+NB

NJ=VDC

9

AI9

9C

2

3=NTC

1=RTD

2=MA

13

v

t

SW4

#9

FILTER

FILTER

TB2

TB2

FOR FIELD

FOR FIELD

INDICATION

INDICATION

10

AI10

10C

2

3=NTC

1=RTD

NJ=VDC

2=MA

13

v

t

SW4

#10

9

R

BI9

243A

109

109

242A

1

1

3

+PP

PL14

H242-3

H242-3

H243-1

H243-1

2

3

PC5

1

+NB

PRE FILTER

H242-4

H242-4

+PP

4

PL14

7

AI7

7C

2

3=NTC

1=RTD

NJ=VDC

2=MA

231A

13

v

t

SW1

#7

7

BI7

112

TB2

3/Y1/R

FS1

+NB

H231-1 H231-3

101

204A

TB_101

TB2

8

AI8

8C

2

3=NTC

1=RTD

NJ=VDC

2=MA

13

v

t

SW1

#8

235A

H235-6

H235-6

8

BI8

113

113

237A

PL20

+PP

+PP

PL20

5

H237-4

H237-4

H235-5

H235-5

17

16

265267

6

SD1

+NB

H237-3

H237-3

6

35

3

+PP

+PP

PL20

H237JMP

H237JMP

+PP

PL21

H237-5

H237-5

17

16

6

SD2

+NB

H237-3

H237-3

+PP

PL21

3 4

R

TB2

TB2

+PP

PL21

INPUT

253 253

253 253

OPEN ANALOG

13

12C

#12

#12

AI13

2

3=NTC

1=RTD

NJ=VDC

2=MA

13

15V DC

v

v

t

t

SW4

12

R

BI12

INPUT

OPEN ANALOG

14

AI14

13C

v

t

#13

14C

2

3=NTC

1=RTD

NJ=VDC

2=MA

13

v

t

SW4

#14

R

13

BI13

INPUT

OPEN BINARY

INPUT

OPEN ANALOG

15

AI15

15C

2

3=NTC

1=RTD

NJ=VDC

2=MA

13

v

t

SW4

#15

15

14

BI14

INPUT

INPUT

OPEN ANALOG

16

AI16

16C

2

3=NTC

1=RTD

NJ=VDC

2=MA

13

v

t

SW4

#16

16

R

BI15

BI16

168C

T1_N

/1.68

OPEN BINARY

+PP

+PP

PL21

21

2

PL20

H265-2

H265-2

H267-2

H267-2

115

115

SD1

SD2

+NB

+NB

H

H

SA SMOKE DETECTOR

RA SMOKE DETECTOR

H265-1

H265-1

H267-1

H267-1

1

+PP

+PP

PL21

PL20

203B

230

231

232

233

234

235

236

237

238

239

240

241

242

243

244

245

246

247

248

249

250

251

252

253

254

255

256

257

258

259

260

261

262

263

264

265

266

/3.00

T2_115VAC

267

268

269

72 McQuay IM 487-5

/8.01

Figure 80: Control actuator outputs (CV, stream, or hot water, plus economizer)

364 362

168C

T1_NT2_115VAC

/1.68/2.68

2 COILS

EXCEED 15 VA

MUST HAVE 24VAC CLASS

MOUNTED RELAYS CAN NOT

THE TOTAL VA OF THE FIELD

NOTES TO FIELD:

1. ALL FIELD MOUNTED RELAYS

117115

TB2TB2

R26

2.

102

Wiring Diagrams

(EXT_ALARM_SIGNAL)

T3

1

4

24V

115V

CLASS 2

303A 303B

TB1C TB1C

305A

1819 20 21

jprs

24V SRC

4NO4

BO4

2

3

MCB

207

SOURCE 1-8

WIRED INTERNAL

TO MOTHERBOARD

(FAN_OPERATION)

116

TB2

307A

jprs

24V SRC

3NO3

BO3

207

207

MCB

1-8

SRC

/4.00 /4.00

T3_24V T3_COM

+NB

+PP

+PP

239

ACT3

PL11

H313-2

H313-1

PL11

+PP

PL11

86

21

6NO6

BO6

207

PL11

(OPEN)

MCB

jprs

24V SRC

318A

5NO5

BO5

207

(CLOSE)

MCB

jprs

24V SRC

(Schematic continues on next page.)

H315-8

L2

3-CCW

+PP

H316-7

7

X-COM

(ECON/ACT)

L1

2-CW

H315-6

+PP

PL11

315A 315B

203B

300

301

302

303

304

305

306

307

308

309

310

311

312

313

314

315

316

317

318

319

320

321

322

323

324

325

326

327

328

329

330

331

332

333

334

McQuay IM 487-5 73

Wiring Diagrams

Figure 81: Control actuator outputs (CV, stream, or hot water, plus economizer), continued

jprs

24V SRC

B09

(CLOSE)

+PP

PL18

H343-9

9

jprs

24V SRC

10NO10 9NO9

B10

207 207

(OPEN)

MCB M CB

339A 339C

(Schematic continues on previous page.)

+NB

243

VM1

+PP

PL18

+PP

5

87

PL18

H343-5H343-6

H344-8

L2

3-CCW2-CW

HEAT

X-COM

L1

H344-7

PL18

+PP

+PP

PL18

6

SIDE)

RELIEF

DAMPER

(OPP.DR

+NB

ACT11

BLK

WHT

H969

H968

5555555

6666666

H365-1

H366-3

3

1

+PP

PL17

363B

6

7

11

R26

9

5

R26

306

306

362A 362B

33

TB1F

8

TB1F

+NB

SIDE)

(DRIVE

RELIEF

DAMPER

ACT10

WHT

BLK

H965

H964

T4

X2

L2

12V

115V

X1

L1

368A

367A

35

34

TB1F

TB1F

AC

AC

-+
DC

RECTIFIER

RECT

36

338

339

340

341

342

343

344

345

346

347

348

349

350

351

352

353

354

355

356

357

358

359

360

361

362

363

364

365

366

367

368

369

74 McQuay IM 487-5

Figure 82: VFD control (SAF and RAF)

/1.68/2.68 /3.11 /3.11

427 445

T1_NT2_115VAC

432 445

168C

Wiring Diagrams

631603

445

137

PL7

+PP

2

309

445

133

149

145

PL8

+PP

11

303B

102

R67

102

H1C

R46_47

H1DN

447

H1UP

R68

R48_49

H1DN

H1C

447

+PP

PL18

H1UP

C3C1

R20

+GB

A2A1

+BB

+BB

M30I

M30B

I

H427-9

H425-12

PL7

+PP

PL7

+PP

12

H425-2

H429-11

A2A1

I

R69

9

A2A1

+BB

M40I

87

H429-10

PL8

+PP

A2A1

+BB

M40B

I

I

H431-7

PL8

+PP

7

10

427B

35

604

R25

409A

407A

405A

1NO1

207

SUPPLY FAN

404A

jprs

jprs

jprs

BO2

MCB

24V SRC

2NO2

207

RETURN FAN

24V SRC

BO13

MCB

24V SRC

14NO14

13NO13

BO14

207

207

SAF DECR

MCB

SAF INCR

jprs

jprs

24V SRC

15NO15

BO16

BO15

207

RAF DECR

MCB

MCB

401A

jprs

24V SRC

BO1

MCB

411A

24V SRC

H413-7 H413-6

+PP

76

PL18

413A

jprs

24V SRC

16NO16

11NO11

BO11

207

207

RAF INCR

HEAT ENABLE

MCB

425A

INVERTER

S4

1NC

AIR

SUPPLY

426B

PL8

+PP

13

401

R67

429A

427A

1NO

BYPASS

INVERTER

1C

S4

SIG_1/6.01

2NC

AIR

RETURN

13

404

R68

431A 431B

2ND

BYPASS

2C

46

(Schematic continues on next page.)

H426-4H426-6H426-3

+BB

MMP40

H426-1

PL8

1

+BB

+PP

426A

PL7

+PP

MMP30

PL7

+PP

12(32)11(31) 12(32)11(31)

3

133 145

T3_24V T3_COM

45 42

TB2 TB2

SOURCE 9-16

WIRED INTERNAL

TO MOTHERBOARD

MCB

9-16

SRC

207

303A

203B

00

01

02

03

04

05

06

07

08

09

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

McQuay IM 487-5 75

Wiring Diagrams

Figure 83: VFD control (SAF and RAF), continued

149

264

14

9

1216

RAF

+NB

AFD20

ABB401

10

8

1113

+PP
PL8

H443-2

2

+PP
PL8

H443-5

5

443H

H2DNH2VH2UP

DECRINCR

443G

409

35

R48_49

R66

76

404 241430

R68

445C 445D

PL8

+PP

15

H443C

+PP
PL8

H443-12

12

+PP
PL7

H443-1

137

261

14

9

(Schematic continues on previous page.)

1216

SAF

+NB

AFD10

ABB401

10

8

1113

1

+PP
PL7

H443-4

4

H443A

H443-15

1413

+BB

M40I

443E

443D

H2DNH2VH2UP

DECRINCR

443C

405

351413

R46_47

R61M30I

76

401 239425

R67

445A 445B

PL7

+PP

14

H443-14

+BB

+PP

H443-7

7

PL7

443A

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

76 McQuay IM 487-5

Figure 84: Super Mod gas furnace control (1000 MBh)

Wiring Diagrams

402

H604-5

NB

+PP

PL19

T1_N

/1.68

168C

+MB

R25

TB11

5

87

604B

+PP

3

PL19

H604-3

10

TB11

RED_G602-L1

604A

L2

L4

FLC

L1

L3

RED_G603-L3

42

413

RED_G602-L1

R20

5

7

1

S3

4

8

2

TB11

RED_G602-L2

10

11

607A

602A

8

9

TB11

H603-4

+PP

PL19

H602-2

603A 603B 603C

+PP

2

PL19

PL16

+PP

H603-2

426B

SIG_1/4.28

21 42

HL22

225

627

NB

TB11

31

R22

20202020202020

R24

+MB

87

WHITE

WHITE

WHTBLK

GV1A

1

+PP

PL19

BLACK

H610-1

1

BLKBLK

BM

6

19191919191919

GV1B

WHITE

WHITE

WHTBLK

WHTBLK

WHTBLK

GV4A

GV4B

BLACK

BLACK

BLACK

SEE THE PIPING SCHEMATIC BELOW

REQUIRED FOR YOUR BURNER SIZE

FOR THE NUMBER OF MAIN GAS VALVES

21212121212121

C2C1

R23

L2

L1

TB11

RED_G609-L WHT_G609-R

RED_G613-L

LS1

RED_G617-L WHT_G617-R

NOCOM

R23

5

31

625

TB11

3

BLACK BLACK

TB11

TB11

610A 610B

3

4

8

L2

613A 613B

611A

4K1

617A

9

2K2

621C

107

5K12K11K1

3K1

I

T

R

E

MICROCOMPUTER

M

FIER

FSG

AMPLI

FLAME

FSG-F

FSG-G

FD

(FLAME ROD)

(FLAME SAFEGUARD)

(PLUG-IN TYPE

CONTROLLER)

6

621B

NO

ASLS2

COM

621A

NO

COM

FSG

6K1

(L1)

5

2

TB11

632615

632628

C2C1

R21

IGNITION TRANSFORMER

X2

115V

6000V

X1

IT

4

2131

TD10

628A

42

612

R22

7

TB11

R21

10NO10

BO10

207

MCB

+MB

jprs

jprs

+MB

+PP

9

PL19

H632-9

24V SRC

24V SRC

9NO9

BO9

207

MCB

+PP

PL18

+PP

9

8

PL18

H633-9

H634-8

11

12

TB11

TB11

633A 633B

625

R23

R21

631A

5

R20

4

YEL_G632-R

VM1

VALVE

ACTUATOR

(FLOATING)

GAS & AIR

MODULATING

BLK WHT

RED_G630-B WHT_G630-W

628

634A 634B

5

4

6

628

5

46

632A 632B

413

6

YEL_G634-2

OPEN

2

CCW

G

(Schematic continues on next page.)

(CL)

YEL_G633-1

COM

CLOSE

1

R

(OP)

CW

T

Y

H603-1

1

+PP

PL16

S1/2.01

201A

600

601

602

603

604

605

606

607

608

609

610

611

612

613

614

615

616

617

618

619

620

621

622

623

624

625

626

627

628

629

(FSG) CONTROLLER.

COMBINATION VALVE WITH PRESSURE

LIGHTS ARE PART OF THE FLAMESAFEGUARD

IS THE SECOND VALVE OF A REDUNDANT

1.POWER, PILOT & MAIN VALVE INDICATION

2. GV-A IS THE FIRST VALVE AND GV-B

NOTE:

630

631

REGULATION AND MANUAL SHUTOFF

632

633

634

635

636

McQuay IM 487-5 77

Wiring Diagrams

Figure 85: Super Mod gas furnace control (1000 MBh), continued

(THRU 1/2 P.S.I.)

COCK

SHUTOFF

PIPING DIAGRAM

COCK

SHUTOFF

REG.

HIGH PRESS.

OVER 1/2 P.S.I.

WHEN 120 VOLT

(Schematic continues on previous page.)

SAFEGUARD (FSG). UPON A CALL FOR HEAT, THE CONTROL SYSTEM WILL CLOSE (BO#11) ON THE MAIN CTRL BRD (MCB), THUS ENERGIZING RELAY (R20).

WHEN THE ROOFTOP UNIT IS ENERGIZED 120 VOLT POWER IS SUPPLIED TO THE SYSTEM ON-OFF SWITCH (S1), TO BURNER ON-OFF SWITCH (S3) AND 24 VOLTS TO THE (BO#11)

POWER IS FURNISHED THROUGH THE SYSTEM ON-OFF SWITCH (S1), THROUGH THE BURNER ON-OFF SWITCH (S3), THROUGH RELAY (R20 CONTACTS, THROUGH THE HIGH LIMIT

CONTACTS ON THE MAIN CTRL BRD (MCB). BURNER ON-OFF SWITCH (S3) WILL POWER THE MODULATING GAS VALVE ACTUATOR (VM1) AND TERMINAL #5(L1) ON THE FLAME

SEQUENCE OF OPERATION

PREPURGE PERIOD WILL BEGIN.

BLOWER MOTOR (BM). WHENEVER POWER IS RESTORED TO THE FLAME SAFEGUARD, THE FLAME SAFEGUARD WILL GO THROUGH A 10 SECOND INITIATION PERIOD BEFORE THE

CONTROL (FLC) AND TERMINAL #6 ON THE FLAME SAFEQUARD (FSG) IS POWERED. THE FLAME SAFEGUARD THEN ENERGIZES ITS TERMINAL #4, WHICH POWERS THE BURNER COMBUSTION AIR

THE BURNER AIR CONTROL VALVE WILL BE AT THE MINIMUM POSITION DURING OFF CYCLES. UPON A CALL FOR HEAT OR ANY OTHER TIME THAT A PREPURGE CYCLE OCCURS

AIR SWITCH (AS). THIS INITIATES THE 60 SECOND PREPURGE CYCLE. CONCURRENTLY, (LS2) POWERS TIMER (TD10) WHICH WILL ENERGIZE RELAY (R21) AFTER 20 SECONDS.

POSITION FOR PREPURGE. WHEN THE AIR CONTROL VALVE REACHES THE FULL OPEN POSITION SWITCH (LS2) IS 'MADE', POWERING (FSG) TERMINAL #7 THROUGH THE BURNER

FOR A NEW CALL FOR HEAT, (VM1) THROUGH THE N/O CONTACTS OF (R20) AND THE N/C CONTACTS OF (R21), WILL RE-POSITION THE BURNER AIR VALVE TO ITS MAXIMUM OPEN

WHEN (R21) IS ENERGIZED (VM1) WILL START THE AIR CONTROL VALVE ON ITS WAY TOWARD THE MINIMUM AIR VALVE POSITION THROUGH THE N/O CONTACT OF (R21) AND THE

(VM1), THROUGH THE N/C CONTACTS OF (R20) AND (R23), POSITIONS THE BURNER AIR AND GAS CONTROL VALVES TO MINIMUM AFTER A RUN CYCLE. WHEN (R20) IS ENERGIZED

THE AIR CONTROL VALVE WILL BE RE-POSITIONED TO THE MAXIMUM POSITION FOR THE PREPURGE AND THEN RETURNED TO THE MINIMUM POSITION FOR LOW FIRE START.

IGNITION PERIOD TERMINAL #10 (IGNITION TRANSFORMER--IT) WILL BE DE-ENERGIZED AND TERMINAL #9 (RELAY R23 COIL AND MAIN GAS VALVES--GV4 & GV5) WILL BE ENERGIZED

AND THE CONTROL SYSTEM WILL BE ALLOWED TO CONTROL THE FIRING RATE. THE FLAME SAFEGUARD CONTAINS "LEDS"(LOWER LEFT CORNER) THAT WILL GLOW TO INDICATED OPERATION.

(LS1) WILL BE 'MADE'. IF (LS1) IS NOT 'MADE' THE COMBINATION GAS CONTROL START VALVES (GV1) WILL NOT OPEN AND THE BURNER WILL GO OUT ON SAFETY LOCKOUT.

N/C CONTACT OF (R23). AT THE COMPLETION OF THE 60 SECOND PREPURGE CYCLE THE VALVE WILL BE AT THE MINIMUM OPEN POSITION AND THE MINIMUM POSITION SWITCH

TERMINAL #10 (IGNTION TRANSFORMER--IT) WILL BE ENERGIZED. IF FLAME IS BEING DETECTED THROUGHT THE FLAME ROD (FD) AT THE COMPLETION OF THE 10 SECOND TRIAL FOR

AFTER COMPLETION OF THE 60 SECOND PREPURGE PERIOD THERE WILL BE A 10 SECOND TRIAL FOR IGINITION DURING WHICH TERMINAL #8 (COMBINATION GAS VALVE--GV1) AND

AFTER THE FLAME HAS LIT AND BEEN PROVEN, RELAY (R23) IS ENERGIZED ALLOWING (VM1), AS CONTROLLED BY (BO#9) & (BO#10) ON THE MAIN CTRL BRD (MCB), TO POSITION

AT ITS PRESENT POSITION. THE HEATING CAPACITY IS MONITORED BY THE MAIN CTRL BRD (MCB) THROUGH (AI#10) VIA A POSITION FEEDBACK POTENTIOMETER ON THE ACTUATOR.

THE ACTUATOR WILL RE-POSITION TOWARD A LOWER FIRING RATE. IF NEITHER (BO#9) OR (BO#10) ON THE MAIN CONTROL BOARD (MCB) ARE CLOSED, THE ACTUATOR WILL REMAIN

WILL RE-POSITION TOWARD A HIGHER FIRING RATE UNTIL (BO#10) OPENS OR THE ACTUATOR REACHES ITS MAXIMUM POSITION. WHEN THE MAIN CONTROL SYSTEM CLOSES (BO#9),

THE BURNER AIR AND GAS VALVES FOR THE REQUIRED FIRING RATE. WHEN THE MAIN CONTROL SYSTEM CLOSES (BO#10) ON THE MAIN CTRL BRD (MCB), THE GAS VALVE ACTUATOR

INPUT #5 ON THE MICROTECH II MAIN CONTROL BOARD (MCB).

TERMINAL #3 WILL ENERGIZE THE HEAT ALARM RELAY (R24), WHICH WOULD THEN ENERGIZE THE REMOTE 'HEAT FAIL' INDICATOR LIGHT AND SEND A FAIL SIGNAL TO BINARY

THUS DE-ENERGIZING THE BURNER AND TERMINAL #3 WILL BECOME ENERGIZED. THE FLAME SAFEGUARD WOULD THEN BE ON SAFETY LOCKOUT AND WOULD REQUIRE MANUAL RESETTING.

IN THE EVENT THE FLAME FAILS TO IGNITE OR THE FLAME SAFEGUARD FAILS TO DETECT ITS FLAME WITHIN 10 SECONDS, TERMINALS #4, 8, 9, AND 10 WILL BE DE-ENERGIZED,

--FIRST

VALVE AND

GV1A

MANUAL VALVE.

(TYPICAL)

PRESS. REG.

TEST

COCK

TEST

CONN.

V

GV4B GV4A

V

GV5B GV5A

MODULATING

ACTUATOR

AIR

BURNER

BLOWER

SWITCH

--MAIN

VALVE AND

COMBINATION GAS CONTROLS

GV1B

THE EARLIER DESCRIBED PREPURGE CYCLE WITH THE WIDE OPEN AIR VALVE WILL BE REPEATED.

IF AN ATTEMPT IS MADE TO RESTART THE BURNER BY RESETTING THE FLAME SAFEGUARD, OR IF AN AUTOMATIC RESTART IS INITIATED AFTER FLAME FAILURE,

IF THE UNIT OVERHEATS, THE HIGH LIMIT CONTROL (FLC) WILL CYCLE THE BURNER, LIMITING FURNACE TEMPERATURE TO THE LIMIT CONTROL SET POINT.

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

78 McQuay IM 487-5

Figure 86: Standard Mod, furnace control (1000 MBh)

402

H604-5

NB

TB11

+PP

5

PL19

T1_N

/1.68

168C

+MB

87
8

R25

604B

+PP

3

PL19

H604-3

10

TB11

RED_G602-L2

FLC

RED_G602-L1

L2

L1

R20

TB11

RED_G602-L1

L4

L3

RED_G603-L3

31

413

604A

225

NB

TB11

R24

+MB

87

1

+PP

PL19

BLK

H610-1

1

BLKBLK

BM

GV1

BLK

6

BLACK BLACK

TB11

RED_G609-L WHT_G609-R

WHT_G617-R

GV2

BLACK WHITE

RED_G617-L

TB11

Wiring Diagrams

632

C2C1

202020202020

20

WHT

WHT

GV3

BLK

BLK

BLACK WHITE

21212121212121

619

5

R23

624

IGNITION TRANSFORMER

L2

X2

115V

6000V

X1

L1

IT

BLACK BLACK

10NO10

BO10

207

jprs

MCB

+MB

24V SRC

jprs

9NO9

BO9

24V SRC

207

MCB

+MB

633B

634B

632B

+PP

PL19

H632-9

64

PL18

+PP

9

9

8

PL18

H633-9

H634-8

11

12

TB11

TB11

625

633C

5

+PP

R23

S1/2.01

600

S3

SIG_1/4.28

TB11

4

YEL_G634-2

OPEN

(CL)

CCW

G

(Schematic continues on next page.)

YEL_G632-R

YEL_G633-1

COM

CLOSE

1

2

R

WHTBLK

VMI

VALVE

ACTUATOR

(FLOATING)

GAS & AIR

MODULATING

(OP)

CW

T

Y

RED_G630-B WHT_G630-W

1

4

11

8

2

607A

602A

8

9

TB11

611A

610A 610B

609

3

4

L2

H603-4

+PP

PL19

H602-2

603A 603B 603C

+PP

2

PL19

+PP

PL16

H603-2

3K1

FSG

6K1

MICROCOMPUTER

(L1)

5

426B

2

21 42

TB11

3

TB11

(FLAME SAFEGUARD)

(PLUG-IN TYPE

2K2

CONTROLLER)

617A

9

621C

107

5K12K11K1

6

621B

NO

AS

COM

618

613A

8

4K1

I

T

R

E

M

FIER

FSG

AMPLI

FLAME

FSG-F

FSG-G

FD

(FLAME ROD)

10

5

7

HL22

H603-1

1

+PP

PL16

201A

601

602

603

604

605

606

607

608

609

610

611

612

613

614

615

616

617

618

619

620

621

622

623

624

625

626

627

628

629

630

(FSG) CONTROLLER.

LIGHTS ARE PART OF THE FLAMESAFEGUARD

1.POWER, PILOT & MAIN VALVE INDICATION

NOTE:

631

632

633

634

635

636

McQuay IM 487-5 79

Wiring Diagrams

Figure 87: Standard Mod, furnace control (1000 MBh), continued

(THRU 1/2 P.S.I.)

COCKCOCK

SHUTOFFSHUTOFF

(THRU 1/2 P.S.I.)

PIPING DIAGRAMPIPING DIAGRAM

COCKAIR COCK

SHUTOFFSHUTOFF

REG.REG.

HIGH PRESS.

HIGH PRESS.

OVER 1/2 P.S.I.

OVER 1/2 P.S.I.

(Schematic continues on the previous page.)

WHEN THE ROOFTOP UNIT IS ENERGIZED 120 VOLT POWER IS SUPPLIED TO THE SYSTEM ON-OFF SWITCH (S1), TO BURNER ON-OFF SWITCH (S3) AND 24 VOLTS TO THE (BO#11)

CONTACTS ON THE MAIN CTRL BRD (MCB). BURNER ON-OFF SWITCH (S3) WILL POWER THE MODULATING GAS VALVE ACTUATOR (VM1) AND TERMINAL #5(L1) ON THE FLAME

SEQUENCE OF OPERATION

WHEN 120 VOLT

THE PILOT FLAME WILL IGNITE AND BE DETECTED BY THE FLAME SAFEGUARD THROUGH

ALSO, THE FLAME SAFEGUARD CONTAINS "LED'S" (LOWER LEFT CORNER) THAT WILL GLOW TO INDICATE OPERATION.

THE RELAY DRIVES THE GAS VALVE ACTUATOR (VM1) TO THE MINIMUM FIRING RATE POSITION WHENEVER THE FLAME IS NOT

UPON DETECTION OF PILOT FLAME, TERMINAL #10 (IGNITION TRANSFORMER--IT) WILL BE DE-ENERGIZED AND TERMINAL #9 (MAIN GAS VALVES--GV2 & GV3)

THE BURNER COMBUSTION AIR BLOWER MOTOR (BM). WHENEVER POWER IS RESTORED TO THE FLAME SAFEGUARD, THE FLAME SAFEGUARD WILL GO THROUGH A 10 SECOND

CONTROL (FLC) AND TERMINAL #6 ON THE FLAME SAFEQUARD (FSG) IS POWERED. THE FLAME SAFEGUARD THEN ENERGIZES ITS TERMINAL #4, WHICH POWERS

SAFEGUARD (FSG). UPON A CALL FOR HEAT, THE CONTROL SYSTEM WILL CLOSE (BO#11) ON THE MAIN CTRL BRD (MCB), THUS ENERGIZING RELAY (R20).

POWER IS FURNISHED THROUGH THE SYSTEM ON-OFF SWITCH (S1), THROUGH THE BURNER ON-OFF SWITCH (S3), THROUGH RELAY (R20) CONTACTS, THROUGH THE HIGH LIMIT

BLOWER OPERATION IS SENSED BY THE AIR SWITCH (AS), WHICH MAKES TERMINAL #6 TO #7. AFTER A 90 SECOND PREPURGE PERIOD, TERMINAL #8 (FIRST GAS VALVE

INITIATION PERIOD BEFORE THE PREPURGE PERIOD WILL BEGIN.

THE FLAME ROD (FD).

(PILOT)--GV1) AND TERMINAL #10 (IGNITION TRANSFORMER--IT) WILL BE ENERGIZED.

GAS VALVE AND COMBUSTION AIR DAMPER AND CAN SET THE FIRING RATE BETWEEN 33% AND 100% OF NORMAL RATE. WHEN THE MAIN CONTROL SYSTEM CLOSES (BO#10) ON THE

WHENEVER THE BURNER IS IN OPERATION ITS FIRING RATE WILL BE DETERMINED BY THE "FLOATING" GAS VALVE ACTUATOR (VM1). THIS ACTUATOR POSITIONS THE BUTTERFLY

WILL BE ENERGIZED AND THE MAIN FLAME WILL COME ON.

ON, AND HOLDS IT THERE UNTIL THE FLAME HAS LIT AND BEEN PROVEN.

LOW FIRE START IS PROVIDED BY RELAY (R23).

REG.

REG.

MAIN

MAIN

PRESS.

PRESS.

COCKCOCK

PILOT

PILOT

PRESS. REG.PRESS. REG.

GV2GV2

GV3

GV3

MAIN GAS VALVES

MAIN GAS VALVES

TEST

TEST

GAS

GAS

MOD.

MOD.

TEST

TEST

(BO#9) OR (BO#10) ON THE MAIN CONTROL BOARD (MCB) ARE CLOSED THE ACTUATOR WILL REMAIN AT ITS PRESENT POSITION. THE HEATING CAPACITY IS MONITORED BY THE

POSITION. WHEN THE MAIN CONTROL SYSTEM CLOSES (BO#9) ON THE MAIN CTRL BRD.(MCB), THE ACTUATOR WILL REPOSITION TOWARD A LOWER FIRING RATE. IF NEITHER

MAIN CTRL BRD.(MCB), THE GAS VALVE ACTUATOR WILL REPOSITION TOWARD A HIGHER FIRING RATE UNTIL EITHER (BO#10) OPENS OR THE ACTUATOR REACHES ITS MAXIMUM

MAIN CONTROL BOARD (MCB) THROUGH (AI#10) VIA A POSITION FEEDBACK POTENTIOMETER ON THE ACTUATOR (VM1).

DE-ENERGIZED, THUS DE-ENERGIZING THE BURNER. THE FLAME SAFEGUARD WOULD THEN BE ON SAFETY LOCKOUT AND WOULD REQUIRE MANUAL RESETTING. THE HEAT ALARM

RELAY (R24) WOULD THEN BE ENERGIZED AND WOULD THEN ENERGIZE THE REMOTE "HEAT FAIL" INDICATOR LIGHT AND SEND A FAIL SIGNAL TO BINARY INPUT #5 ON THE

IN THE EVENT THE PILOT FAILS TO IGNITE OR THE FLAME SAFEGUARD FAILS TO DETECT ITS FLAME WITHIN 10 SECONDS, TERMINALS #4, 8, 9, AND 10 WILL BE

IF THE UNIT OVERHEATS, THE HIGH LIMIT CONTROL (FLC) WILL CYCLE THE BURNER, LIMITING FURNACE TEMPERATURE TO THE LIMIT CONTROL SET POINT.

MICROTECH II MAIN CONTROL BOARD (MCB).

COCK

COCK

VALVE

VALVE

CONN.

CONN.

GV1

GV1

PILOT VALVE

PILOT VALVE

TEST

TEST

CONN.

CONN.

AIR

AIR

BURNER

BURNER

BLOWER

BLOWER

SWITCH

SWITCH

AIR

DAMPER

DAMPER

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

80 McQuay IM 487-5

Figure 88: Electric heat control

PB3

Wiring Diagrams

L1

HL14

(MANUAL)

518G

M44

FB44

518E 518F

PB3

PB3

HTR4B

3

1

T1

L1

T1

L1

L1-8

L1-4

519E 519F

L3

L2

4

2

T3

T2

556

L3

L2

T3

T2

L2

L3

520D 520E 520F

500

L3-8

L2-8

500

L3-4

L2-4

HL12

(MANUAL)

510G

M42

FB42

510E 510F 510H

PB3

PB3

L1

HTR2B

3

1

T1

L1

T1

L1

L1-6

L1-2

511G

511E 511F 511H

L3

L3

L2

4

2

T3

T2

548

L3

L2

T3

T2

L2

L3

512D 512E 512F

500

L3-6

L2-6

500

L3-2

L2-2

L1

HL13

(MANUAL)

514G

M43

FB43

514E 514F

PB3

PB3

L2

4

3

2

1

515G

T1

T3

T2

552

L1

L3

L2

T3

T2

T1

L1

L2

L3

515E 515F

516D 516E 516F

500

L3-7

L2-7

L1-7

500

L3-3

L2-3

L1-3

HTR1B

L3

L1

L2

4

3

HL11

2

1

(MANUAL)

507G

506G

T1

T3

T2

507E 507F 507H

547

L3

L2

T3

T2

L2

L3

508D 508E 508F

500

L3-5

L2-5

500

L3-1

L2-1

M41

L1

T1

FB41

L1

506E 506F 506H

PB3

L1-5

L3B

L3A

L2B

L2A

L1B

L1A

L1-1

PB3

L3

L2

L1

FB31

T1

T3

T2

508B 508C

507C 507D

506C 506D

M31

506B

HL1

(MANUAL)

L1

T1

3

1

507B

546

L3

L2

T3

T2

4

2

FB32

510C 510D

M32

510B

HL2

(MANUAL)

508A

507A

506A

L2

L1

L3

510A

HTR1A

00

01

020304

05

06

07

080910

11

121314

L1

L1

T1

L1

T1

3

1

HTR2A

511C 511D

511B

511A

L3

L2

T3

T2

512B 512C

550

L3

L2

T3

T2

4

2

FB33

514C 514D514A

M33

514B

HL3

(MANUAL)

512A

L2

L3

15

16

17

18

19

202122

L1

L1

T1

L1

T1

3

1

HTR3A HTR3B

515C 515D

515B

515A

L3

L2

T3

T2

516B 516C

553

L3

L2

T3

T2

4

2

FB34

518C 518D518A

M34

518B

HL4

(MANUAL)

516A

L3

L2

L1

T1

T3

T2

520B 520C

519C 519D

554

L1

L3

L2

T1

T3

T2

519B 519G

4

3

2

1

520A

519A

L2

L3

L2

L1

L3

HTR4A

23

24

25

26

27

28

29

30

31

32

33

(Schematic continues on next page.)

McQuay IM 487-5 81

Wiring Diagrams

534535536537538539540541542543544545546547548549550551552553554555556557558559560561562563564565566567568569570

P

534535536537538539540541542543544545546547548549550551552553554555556557558559560561562563564565566567568569570

P

Figure 89: Electric heat control, continued

PL12+P

PL12+P

168C

2

168C

T1_N/1.68

T1_N/1.68

2

TB11

NB2

NB2

TB11

544C

506

506

514

506

506

514

544C

522

514

514

522

522

530

530

530

530

522

(Schematic continues on previous page.)

UNDER HEATER

T1_115VAC/1.68

(Schematic continues on previous page.)

HS3

DEADFRONT

536A 536B

TB11

+PP

PL12

43

HS3

DEADFRONT

43

UNDER HEATER

536A 536B

171

TB11

933

171

TB11

+PP

PL12

168A

T1_115VAC/1.68

+PP

PL12

168A

538B

ON SWITCH BRACKET

IN MAIN CONTROL PANEL

HS1

21

ON SWITCH BRACKET

538A

IN MAIN CONTROL PANEL

+PP

T3_COM/3.11T3_24V/3.11

HS1

933

TB11

N2+B/1

PL12

538B

21

538A

NC-B/1

T3_COM/3.11T3_24V/3.11

303B

303A

REFB/1

24C

24V

N2+B/1

NC-B/1

REFB/1

N2+A/1

303B

24C

24V

N2+

303A

N2-A/1

N2-

N2+A/1

N2-A/1

REFA/1

N2-

N2+

REF

J10

BO11

MCB

T3_24V/3.11

REFA/1

REF

544B

T3_24V/3.11

9-16

9-16

9-16

9-16

MCB

SRC

BI12

303A

BO11

M31

M31

A1 A2

21

(AUTO)

HL31

(AUTO)

546B 546C

94

TB11

+PP

4

+PP

PL12

546A

STAGE 1

1

BI12

J10

STAGE 1

544B

11NO11

207

MCB

3

9-16

9-16

9-16

9-16

11NO11

MCB

SRC

207

303A

M41

M42

M42

A1 A2

A1 A2

M41

A1 A2

M32

A1 A2

M43

M43

A1 A2

M32

A1 A2

A1 A2

549A

549A

21

21

HL42

(AUTO)

21

HL42

(AUTO)

21

HL41

(AUTO)

HL32

(AUTO)

548B 547A

95

TB11

95

TB11

5

+PP

PL12

5

548A

+PP

+PP

PL12

PL12

2

548A

STAGE 2

54

STAGE 3

STAGE 2

6

54

HL43

(AUTO)

21

HL43

(AUTO)

21

HL32

(AUTO)

552B 552C

550B 550C

552B 552C

550B 550C

96

TB11

TB11

96

TB11

TB11

6

+PP

+PP

PL12

PL12

6

550A

552A

+PP

PL12

550A

552A

STAGE 3

STAGE 4

6

87

STAGE 4

87

HL31

PL12

(AUTO)

546B 546C

TB11

546A

21

HL41

548B 547A

94

4

1

2

3

M34

M34

A1 A2

A1 A2

M33

A1 A2

A1 A2

M33

A1 A2

A1 A2

555A

555A

21

21

(AUTO)

(AUTO)

HL33

HL33

21

(AUTO)

21

(AUTO)

HL34

HL34

21

21

(AUTO)

(AUTO)

554B 553A

554B 553A

97

98

TB11

97

98

TB11

7

8

+PP

PL12

7

8

554A

+PP

+PP

PL12

11

554A

STAGE 5

11

910

STAGE 5

910

M44

M44

+PP

STAGE 6

STAGE 6

HL44

HL44

556B 556C

TB11

PL12

PL12

556A

556B 556C

TB11

556A

A1 A2

A1 A2

21

21

99

99

9

9

120 KW

4 B

M44

HEATER

8 B

BANK "B"

13 12

HEATER

BANK "B"

M31

13 12

HEATER

BANK "A"

HEATER

BANK "A"

1 A

5 A

M41

3 B

2 B

1 B

M43

M42

7 B

120 KW

4 B

M44

120 KW

8 B

2 A

M32

6 A

M31

1 A

5 A

M41

3 B

2 B

1 B

M43

M42

7 B

4 A

3 A

M33

M34

120 KW

2 A

3 A

4 A

M32

M33

M34

6 A

82 McQuay IM 487-5

Wiring Diagrams

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

433

Figure 90: Fan control, power package only

/1.68

00

01

02

03

04

05

06

07

08

09

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

R63

811

219

MMP20MMP10

426A 426B 426C426D

76757675

149137

TB4

207

SUPPLY FAN ON/OFF

TB4

208

M10

A1 A2

28

29

30

31

32

RETURN FAN ON/OFF

TB4

431A

209

M20

A1 A2

McQuay IM 487-5 83

T1_N115VAC_GF/1

137
260

149

Wiring Diagrams

Figure 91: CV fan control (SAF and RAF)

/3.11

115VAC_GF/1 T1_N

11(31)

T3_24V

SOURCE 9-16

MCB

WIRED INTERNAL

TO MOTHERBOARD

207

SRC 9-16

MMP10

12(32) 11(31)

jprs

MCB

TB2

45

MMP20

TB2

42

12(32)

1 1NO

207

SUPPLY FAN

MCB

2 2NO

207

RETURN FAN

BO1

24V SRC

401A

jprs

BO2

24V SRC

404A

R67

3

1

401

426C426B426A

/3.11

T3_COM

R67

10

2

R68

2

10

M10

A2A1

/1.68

R68

3

1

404

431A

M20

A2A1

Figure 92: Light and receptacle power

FIELD SUPPLIED 115V/60/1

REC1

H

TB7

CP SL

GRD

1004B

1003B1003A

TB7

1005B1005A

SLCP

PL31

PL32

H1006-1

1

1

84 McQuay IM 487-5

H775

H775

S10

H775

S11

H775

REC10

H

REC11

H

BLK WHT

N

G

BLK WHT

N

G

LT10

LT11

w

H776

G1009

w

H776

G1012

H1006-2

30

H1010-2H1010-1

31

PL31

2

PL32

2

N

G

TB7

G1004

Unit Options

Unit Options

Enthalpy Control

Outside Air Enthalpy Control (OAE)

Units with MicroTech II control and an economizer come
standard with an electromechanical enthalpy control device
(OAE) that senses both the humidity and temperature of the
outside air entering the unit. This device has an enthalpy scale
marked A through D. Table 13 shows the control points at 50%
RH for settings A through D. Figure 93 shows this scale on a
psychrometric chart. When the outside air conditions exceed
the setting of the device, the outside air dampers are positioned
to the minimum outside air intake position by the MicroTech II

controller.

Table 13: Enthalpy control settings

Control curve Control point temperature at 50% RH

A73°F (23°C)
B70°F (21°C)
C 67°F (19*C)
D63°F (17°C)

Differential Enthalpy Control (OAE/RAE)

An optional electric differential enthalpy control arrangement
(OAE/RAE) is available on units with MicroTech II control. In
this configuration a solid-state humidity and temperature
sensing device is located in both the return (RAE) and outside
intake (OAE) airstreams. This OAE device has the same A
through D scale as the device described above. However, with
the OAE/RAE arrangement the switch on, OAE must be set all
the way past the D setting. With this done, the MicroTech II
controller adjusts the return and outside air dampers to use the
airstream with the lowest enthalpy.

Ground Fault Protection

The ground fault protection is designed to protect motors from
destructive arcing ground faults. The system consists of a
ground fault relay and a ground fault current sensor. The
ground fault relay employs solid state circuits that will
instantly trip and open a set of relay contacts in the 115-volt
control circuit to shut the unit down whenever a ground fault
condition exists. The ground fault relay is self powered. The
ground fault sensor is a current transformer type of device

located on the load side of the power block through which the
power wires of all phases are run.

Figure 93: Enthalpy control settings

8 5

9 0

9 5

1 0 0

( 2 9 . 5 )

( 2 6 . 5 )

( 3 2 )

0 . 8 0

0 . 9 0

0 . 7 0

0 . 6 0

0 . 5 0

A

B

8 0

8 5

9 0

( 2 9 . 5 )

( 3 2 )

4 6

4 4

4 2

8 0

( 2 6 . 5 )

4 0

3 8

3 6

3 4

3 2

3 0

2 8

2 6

E N T H A L P Y  B T U P E R P O U N D D R Y A I R

2 4

2 2

2 0

1 8

1 6

1 4

1 2

( 1 . 5 )

4 5

( 7 )

4 0

( 4 . 5 )

3 5

3 5

4 0

4 5

( 1 . 5 )

( 4 . 5 )

( 7 )

6 0

( 1 5 . 5 )

5 5

( 1 3 )

B

5 0

C

( 1 0 )

D

5 0

5 5

6 0

( 1 0 )

( 1 3 )

( 1 5 . 5 )

A

( 1 8 . 5 )

6 5

( 1 8 . 5 )

7 5

( 2 4 )

7 0

( 2 1 )

C

D

6 5

7 0

7 5

( 2 1 )

( 2 4 )

1 0 5

( 3 5 )

( 3 8 )

( 4 0 . 5 )

R E L A T I V E

H U M I D I T Y

0 . 4 0

0 . 3 0

0 . 2 0

0 . 1 0

9 5

1 0 0

1 0 5

0 . 5 )

( 3 5 )

( 3 8 )

( 4

Phase Voltage Monitor

The phase voltage monitor (see page 116) protects against high
voltage, phase imbalance, and phase loss (single phasing)
when any one of three line voltages drops to 74% or less of
setting. This device also protects against phase reversal when
improper phase sequence is applied to equipment, and low
voltage (brownout) when all three line voltages drop to 90% or
less of setting. An indicator run light is ON when all phase
voltages are within specified limits. The phase voltage monitor
is located on the load side of the power block with a set of
contacts wired to the 115-volt control circuit to shut the unit
down whenever the phase voltages are outside the specified
limits.

McQuay IM 487-5 85

Unit Options

External Time Clock

You can use an external time clock as an alternative to (or in
addition to) the MicroTech II controller’s internal scheduling
function. The external timing mechanism is set up to open and
close the circuit between field terminals 101 and 102. When
the circuit is open, power is not supplied to binary input
MCB-BI1. This is the normal condition where the controller
follows the programmable internal schedule. When the circuit
is closed, power is fed to BI1. The MicroTech II controller
responds by placing the unit in the occupied mode, overriding
any set internal schedule.

For more information, see the “Digital Inputs” section of
Bulletin No. IM 696, “MicroTech II Applied Rooftop Unit
Controller.”

Smoke and Fire Protection

McQuay optionally offers factory installed outdoor air, return
air, and exhaust air dampers as well as smoke detectors in the
supply and return air openings, complete with wiring and
control. These components often are used in the building’s
smoke, fume, and fire protection systems. However, due to the
wide variation in building design and ambient operating
conditions into which our units are applied, we do not
represent or warrant that our products will be fit and sufficient
for smoke, fume, and fire control purposes. The owner and a
fully qualified building designer are responsible for meeting
all local and NFPA building code requirements with respect to

smoke, fume, and fire control.

be restarted until the alarm is manually cleared. Refer to the
operation manual supplied with the unit for information on
clearing alarms (OM138 or OM137).

The smoke detectors themselves must be reset manually once
they have tripped. Power must be cycled to the smoke detector
to reset.

Freeze Protection

An optional freezestat is available on units with MicroTech II
control that have hot water, chilled water, or steam heating
coils. The sensing element is located on the downstream side
of the heating coil in the heating section of the unit. If the
freezestat detects a freezing condition and closes, the
MicroTech II controller takes different actions, depending on
whether the fans are on or off. The freezestat is an auto reset
type of control; however, the controller alarm that it causes is
manually reset if the fan is on and auto reset if the fan is off.

Fan On Operation

If the freezestat detects a freezing condition while the fan is
on, the MicroTech II controller shuts down the fans, closes the
outdoor air dampers, opens the heating valve, and sets a 10­minute timer. The MicroTech II controller’s active alarm is
“Freeze Fault.”

When the 10-minute timer expires, the controller begins
checking the freezestat again. If the freezestat is open, the
heating valve closes. If the freezestat closes again, the heating
valve opens, and the 10-minute timer resets.

WARNING

Improper smoke, fire, or fume air handling can result in
severe personal injury or death.

Smoke Detectors

Optional smoke detectors can be located at the supply and
return openings. The wiring for these smoke detectors is
shown on any of the “Typical Main Control Circuit” wiring
schematics within the “Wiring Diagrams” section on pages
65–88.

The sequence of operation for these detectors is as follows:
When smoke is detected by either sensor, the normally closed
sensor contacts open. This removes power from binary input
BI8 on the Main Control Board.

The MicroTech II controller responds by shutting down the
unit. The controller is placed in the Alarm Off state and cannot

The unit remains shut down until the “Freeze Fail” alarm is
manually cleared. Refer to the operation manual supplied with
the unit for information on clearing alarms (OM138 or
OM137).

Fan Off Operation

If the freezestat detects a freezing condition while the fan is
off, the MicroTech II controller opens the heating valve and
sets a 10-minute timer. The MicroTech II controller’s active
alarm is “Freeze Problem.”

When the 10-minute timer expires, the controller begins
checking the freezestat again. If the freezestat is open, the
heating valve closes. If the freezestat closes again, the heating
valve opens, and the 10-minute timer resets.

When the freezestat opens again, the “Freeze Prob” alarm
automatically clears. This feature protects the coil and allows
the system to start normally after a cold night.

86 McQuay IM 487-5

Unit Options

Entering Fan Temperature Sensor

The entering fan temperature (EFT) sensor and an associated
“Lo Airflow Problem” alarm are provided on VAV units with
MicroTech II control and gas or electric heat. The EFT sensor
is located in the supply fan section of the unit at the supply air
funnel.

Heat is disabled whenever the airflow is detected to be too low
for safe heating operation. This condition is indicated when the
supply air temperature exceeds the mixed air temperature by
more than 60°F (16°C).

Note – This value is not always 60°F. It depends on whether the

unit is gas or electric heat and on the burner/baffling
arrangement on gas heat units.

In this case, a “Lo Airflow Problem” alarm is generated and
heat is not enabled until the alarm is manually cleared. Refer to
the operation manual supplied with the unit for information
clearing alarms (OM 138 or OM 137).

Duct High Pressure Limit

The duct high pressure limit control (DHL) is provided on all
VAV units. The DHL protects the duct work, the terminal
boxes, and the unit from over pressurization, which could be
caused by, for example, tripped fire dampers or control failure.

The DHL control is factory set to open when the discharge
plenum pressure rises to 3.5" wc (872 Pa). This setting should
be correct for most applications; however, it is adjustable.
Removing the front cover of the device reveals a scale
showing the current setting. Turning the adjustment screw
(located on the bottom of the device) adjusts the setting up or
down.

If the DHL switch opens, digital input MCB BI 14 on the Main
Control Board de-energizes. The MicroTech II controller then
shuts down the unit and enters the Off-Alarm state. The alarm
must be manually cleared before the unit can start again. Refer
to the operation manual supplied with your unit for more
information on clearing alarms (OM 138 or OM 137).

MicroTech II™ Remote User Interface (UI)

Both a unit mounted and an identical, remote mounted keypad
and display are provided with this option. A remote-mounted
user interface (UI) is available as an option with all rooftop
units. The following items are provided:

• Unit mounted UI

• Unit mounted power supply and R485 isolator for the

remote UI

• Selector switch to activate either the unit mounted UI or the
remote UI. Only one UI is active at a time.

• Wall mounted electrical box that contains the remote UI. See
Figure 94.

Cable and Wiring Recommendations

Remote wiring to connect the unit to the remote UI is not
included. See Figure 95 on page 88 for wiring information and
the following recommendations.

• No more than 1200 feet of wiring can be used to connect the
remote user interface to the unit.

• Use overall foil shield, 3 twisted pairs, 22 AWG stranded
connectors with drain wire.

• UL 910 plenum rated = Belden 6542FE-1000-877

• Non-plenum rated = Belden 5542FE-1000-8

McQuay IM 487-5 87

Unit Options

odule

Figure 94: Factory-assembled remote user interface

4.4 "

7.2 "

(4) #6-32
Hex Nuts

(4) #6 Split
Lock Washers

6.9 "

Enclosure
with Cover

Surface Mount,
Modular Jack
with 6 contacts,
Screw Terminals

Cable Assembly

Keypad/Display
M

Ground

Figure 95: Remote user interface wiring diagram

88 McQuay IM 487-5

Unit Options

Variable Frequency Drive Operation

Refer to the vendor instructions supplied with the unit.

Convenience Receptacle/Section Lights

A Ground Fault Circuit Interrupter (GFCI) convenience
receptacle is provided in the main control box on all units.

To use this receptacle, connect a separate field-supplied 115
V power wiring circuit to the 115V field terminal block
TB7, located in the main control box.

Optional lights are available for certain sections in the unit.
Each light includes a switch and convenience receptacle and is
powered by the external 115V power supply connected to
TB7.

DesignFlow™ Outdoor Air Damper Option

DesignFlow™ airflow measurement stations are located inside
the louvered outdoor air intake doors between the intake
louver and outside air dampers. Essentially, they consist of a
vane that is repositioned by airflow, the amount of rotation
indicating the amount of airflow. They are calibrated precisely
at the factory and no further calibration is required. However, a
leveling adjustment is required in the field so that the
DesignFlow unit is in the same orientation as when it was
factory calibrated. See “DesignFlow Station Startup” below.

The rotational position of the DesignFlow unit vane is
translated into CFM by the microprocessor in the MicroTech II
control system. The position of the vane is determined by two
things—the force of the airflow impacting the vane and the
gravitational effect on the vane. Gravity is the only factor at
the lower CFM end of the range. On a correctly leveled unit,
this gravitational effect will be the same as when the unit was
calibrated in the factory.

Accurately leveling a station involves applying a precise
mechanical force against the vane. This force should cause the
vane to move to a specific position if the DesignFlow unit is
correctly leveled.

DesignFlow Station Startup

• Before initial startup of the rooftop unit, carry out the
following procedure on both the right-hand (control panel
side) and left-hand (side opposite the control panel)
DesignFlow station vanes (see Figure 96).

Note – This procedure is much easier to carry out with two

people—one making the mechanical adjustments and the
other viewing and recording readings on the MicroTech II
control panel.

1 Verify that power is supplied to the unit’s MicroTech II

control system. The DesignFlow startup procedure cannot
be completed without use of the MicroTech II controls.

2 Unlock and open the louvered outdoor air intake door on

the side of the unit (see Figure 96).

3 The swinging vane on the measurement station is locked in

place for shipment. Unlock it by removing the two shipping
screws. One is located one inch from the top of the vane
and the other one inch from the bottom of the vane. Both
are about eight inches in from the outer edge of the vane.

4 Examine the station for shipping damage. Manually rotate

the vane and verify that it does not rub against anything.

Figure 96: DesignFlow station

Manually hold the vane closed against the mechanical stop

5

at the top of the assembly. Then, read the current vane
leveling position on the MicroTech II keypad/display.

Do this by viewing the LH Lvl Pos= or RH Lvl Pos=
parameter in the DesignFlow setup menu. The LH Lvl
Pos= parameter indicates the current position of the vane
for the left-hand DesignFlow station (side opposite the
control panel). The RH Lvl Pos= parameter indicates the
current position of the vane for the right-hand DesignFlow
station (control panel side).

Important: Wait several seconds until the value on the
keypad stabilizes before taking the reading.

For detailed information regarding operation and
navigation through the unit keypad, refer to Operation
manual OM 137 (discharge air control units) or OM 138
(zone control units).

6 Confirm the value of the reading. Ideally, it should read

close to 20.00 (19.50 to 20.50 is acceptable). If the reading
is out of range, loosen the screws fixing the mechanical
stop at the top of the assembly, make a small adjustment,
and recheck until the reading is in the specified range.

Note: Generally, adjustments should not be necessary.

7 Locate the leveling component kit, which is shipped with

the unit, in the unit mail control panel.

8 Duct tape the fulcrum alignment plate to the bottom corner

of the vane (see Figure 97) aligning it as follows:

a The bottom edge of its notches should be flush with the

bottom edge of the vane.

b The side of one notch should be even with the bend near

the outer edge of the vane.

McQuay IM 487-5 89

Unit Options

e

c

The plate should be flat against the outer surface of the
vane.

Figure 97: Tape fulcrum alignment plate to vane

Vane

Duct tape

This edge flush
with bottom of vane

These edges flush
with bottom of van

9 Locate and install the fulcrum used in the leveling

Alignment plate

Fulcrum

Duct tape

procedure as follows (see Figure 97):

a Wipe the bottom of the louver door where the fulcrum

will be located so that the duct tape will stick to it.

b Pre-apply duct tape to the top surface of the bottom

portion of the fulcrum, extending it about one inch
beyond the edges on three sides.

c With the alignment plate taped to the vane and the vane

in the zero airflow position, locate the fulcrum parallel
to and against the alignment plate.

Note – The zero airflow position is when the vane is swung away

from the back wall and gently resting against its stop.

d Once the fulcrum is in position, press the duct tape

extensions down to hold the fulcrum in place.

e Remove the alignment plate after installing the fulcrum.

10 Close and latch the louvered intake door.

11 Remove the cover from the access opening in the bottom

blade of the outdoor air intake louver (see Figure 100).

12 Verify that the unit fans are off and that the outdoor air

dampers are closed. If there is a wind, cover the outdoor air
louvers with poly film, cardboard, or other suitable material
to prevent adverse readings due to wind.

13 Rest the leveling weight assembly on the fulcrum, as shown

in Figure 98, so that:

a Its bottom two thumbscrews rest on the top edge of the

fulcrum.

b Its top thumbscrew rests against the vertical alignment

mark on the vane.

Note: The alignment mark is located 0.50 inch in from the

bend on the outer edge of the vane. It intersects with
a hole located one inch up from the bottom outer
edge of the vane.

Figure 98: Place leveling weight on fulcrum

14 Set up the leveling test as follows:

a While holding the weight so it stays on the fulcrum,

manually rotate the vane to the wide-open position,
manually return it to the zero CFM position, and gently
release the vane.

b Locate the leveling weight assembly so its contact point

is against the vertical mark on the vane.

c While the weight assembly teeters on the fulcrum,

gently rap the base frame to slightly vibrate the
assembly and encourage the vane to seek its equilibrium
point.

15 Read the current LH Lvl Pos= (or RH Lvl Pos=) parameter

in the DesignFlow Setup menu on the keypad/display.
These parameters vary from 20% to 80% depending on the
position of the DesignFlow vane

16 If the value indicated by the LH Lvl Pos= (or RH Lvl Pos=)

parameter is not within the range of 23.64% to 24.08%,
adjust the level of the DesignFlow unit using the procedure
described in “Making Level Adjustments” below.

17 When the LH Lvl Pos= (or RH Lvl Pos=) value is in range,

remove the fulcrum and leveling weight assembly and
replace the access opening cover in the louvered door.

90 McQuay IM 487-5

Unit Options

Making Level Adjustments

The DesignFlow unit is mounted so that it pivots at the top
when three lock nuts are loosened, two at the top and one at
the bottom of the assembly (see Figure 99). Leveling the unit
involves precisely pivoting the assembly with a known force
applied to the vane until the vane opens to a specific position.

If after performing Steps 13 through 15 (previous page), the
vane does not come to rest within the specified range, carry out
the following steps:

1 Unlock and open the louvered outdoor air intake door on

the side of the unit.

2 Loosen the two .25-20 NC lock nuts at the top of the

DesignFlow frame (see Figure 99).

Figure 99: DesignFlow frame

Top lock nuts

Vane

Pivot point

7 When finished making the adjustments, tighten the .25-20

NC lock nut in the slotted hole at the bottom of the
DesignFlow frame (see Figure 101).

8 Gently rap the base frame to slightly vibrate the assembly

to encourage the vane to seek its equilibrium point.

9 Recheck the vane position compared to the range specified

in Step 16 (previous page). Readjust the level as necessary.

10 When the level is correct, unlock and open the louvered

outdoor air intake door on the side of the unit and tighten
the two .25-20 NC lock nuts at the top of the DesignFlow
frame (see Figure 99).

11 Close and lock the intake door.

12 Recheck the vane position and readjust the level as

necessary.

13 When the vane position is correct, replace the access

opening cover in the louvered door.

Figure 100: Remove covers from access opening

Louvered
door

Bottom lock nut

3 Close and lock the intake door.

4 Remove the cover from the access opening in the bottom

blade of the outdoor air intake louver (see Figure 100).

5 Loosen the .25-20 NC lock nut in the slotted hole at the

bottom of the DesignFlow frame (see Figure 101).

6 If the LH Lvl Pos= (or RH Lvl Pos=) value obtained in

step 15 above is HIGHER than the specified range,
move the bottom of the DesignFlow frame closer to the
outdoor air dampers (away from the back end of the unit).
Do this by turning the long adjuster nut to increase the L
dimension in Figure 101.

If the LH Lvl Pos= (or RH Lvl Pos=) value obtained in
step 15 above is LOWER than the specified range,

move the bottom of the DesignFlow frame away from the
outdoor air dampers (toward the back end of the unit). Do
this by turning the long adjuster nut to decrease the L
dimension in Figure 101.

Note: If the necessary adjustment cannot be made using

the long adjuster nut, reposition the two .25-20 NC
jam nuts on the threaded rod to make larger
adjustments (see Figure 101).

Access opening

Cover

Figure 101: Leveling adjustment

Threaded adjuster

assembly

Long adjuster nut

Jam nuts

To INCREASE L dimensionLTo INCREASE L dimension

Right hand adjuster Left hand adjuster

Locknut

L

McQuay IM 487-5 91

Unit Options

A

Propeller Exhaust Fan Option

Economizer units may include propeller exhaust or centrifugal
return fan options. This section covers maintenance and
operating instructions for the propeller exhaust option.
Centrifugal return fan construction, maintenance and operation
is similar to that for supply fans and covered in other sections
of this manual.

Figure 102: Two fans with back return shown

Fans and motors

substantial increase in horsepower required from the motor.
Always check motor load amperage and compare to name
plate rating when changing fan speed.

Figure 103: Fan rotation

i r f l o w

R o t a t i o n

A i r f l o w

R o t a t i o n

Once the fan is put into operation, set up a periodic
maintenance program to preserve the reliability and
performance of the fan. Items to include in this program are:

• Belts

• Bearings

• Fasteners

• Setscrews

• Lubrication

• Dust/dirt removal

VFD

Starters

Prestarting Checks

Check all fasteners and set screws for tightness. This is
especially important for bearing set screws.

The propeller should rotate freely and not rub on the fan panel
venturi. Rotation direction of the propeller should be checked
by momentarily turning the unit on. Rotation should be in the
same direction as the rotation decal affixed to the unit or as
shown in Figure 103. For three-phase installations, fan rotation
can be reversed by simply interchanging any two of the three
electrical leads. For single phase installations follow the wiring
diagram located on the motor.

The adjustable motor pulley is preset at the factory for the
specified fan RPM. Fan speed can be increased by closing (or
decreased by opening) the adjustable pulley. Two or three
groove variable pitch pulleys must be adjusted an equal
number of turns open. Any increase in fan speed represents a

Belts

Premature belt failures are frequently caused by improper belt
tension (either too tight or too loose) or misaligned pulleys.
The proper tension for operating a V-belt is the lowest tension
at which the belts will not slip peak load conditions. For initial
tensioning, the proper belt deflection half way between pulley
centers is 1/64" for each inch of belt span. For example, if the
belt span is 64 inches, the belt deflection should be one inch
using moderate thumb pressure at midpoint of the drive
(see Figure 104).

Check belt tension two times during the first 24 hours of
operation and periodically thereafter. To adjust belt tension,
simply loosen four fasteners (two on each side of the motor
plate) and slide the motor plate away from the fan shaft until
proper belt tension is attained. On some fans, fasteners
attaching the motor to the motor plate must be loosened to
adjust the belt.

It is very important that the drive pulleys remain in proper
alignment after adjustments are made (see Figure 105).
Misalignment of pulleys results in premature belt wear noise,

vibration, and power loss.

WARNING

Rotating parts can cause severe personal injury or death.
Replace all belt/fan guards that are removed temporarily for
service.

92 McQuay IM 487-5

Figure 104: Belt adjustment Figure 105: Drive pulley alignment

e

e

M u s t b e
p a r a l l e l

D e f l e c t i o n =

B e l t S p a n

B e l t S p a n

6 4

Unit Options

B e a r i n g

M o t o r

M u s t b e
p a r a l l e l

Table 14: Propeller exhaust fan troubleshooting

Problem Cause Corrective Action

Reduced

Airflow

Excessive

Noise

System resistance is too
high.

Check backdraft dampers for proper operation. Remove obstructions in ductwork. Clean dirty filters.

Check for adequate supply for air exhaust fans or exhaust air for supply fans.
Unit running backwards. See “Prestarting Checks” on page 92
Fan speed too low. Increase fan speed
Excessive dirt on propeller. Clean propeller
Bearings Tighten bearing collars and setscrews. Lubricate bearings. Replace defective bearings.
V-Belt drive Tighten pulleys on motor shaft and fan shaft. Adjust belt tension. Align pulleys. Replace worn belts or pulleys.
Excessive vibration Clean dirt build-up from propeller. Check all setscrews and fasteners for tightness. Check for worn bearing.

Correct propeller imbalance. Check for loose dampers, guards or ductwork.
Defective motor Replace motor.

C e n t e r l i n e s
m u s t c o i n c i d

A d j u s t a b l e
S h e a v e

Figure 106: Propeller exhaust fan replacement parts list

1

9

11

2

8

7

1 0

4

3

6

5

1 . F a n pa n e l
2 . P r o p e l l e r
3 . D r i v e fr a m e
ch a n n e l ( 2 )
4 . M o to r pl a te
5 . M o to r
6 . M o to r pu l l e y
7 . S h a ft p u l l e y
8 . F a n sh a ft
9 . B e a r i n g s

1 0. B e l t

a r i n g pl a t

1 1. B e

McQuay IM 487-5 93

Unit Options

Bearings

Bearings are the most critical moving part of the fan and
should be inspected at periodic intervals. Locking collars and
set screws, in addition to fasteners attaching the bearings to the
bearing plate, must be checked for tightness. In a clean
environment and temperatures above 32°F/below 200°F, fan
shaft bearings with grease fittings should be lubricated
semiannually using a high quality lithium based grease. If
unusual environmental conditions exist temperatures below
32°F/above 200°F, moisture or contaminants, more frequent
lubrication is required.

With the unit running, add grease very slowly with a manual
grease gun until a slight bead of grease forms at the seal. Be
careful not to unseat the seal by over lubricating or using
excessive pressure. Bearings without grease fittings are
lubricated for life.

Fasteners and Setscrews

Any fan vibration has a tendency to loosen mechanical
fasteners. A periodic inspection should include checking all
fasteners and set screws for tightness. Particular attention
should be paid to setscrews attaching the propeller to the shaft
and the shaft to the bearings. Loose bearing set screws will
lead to premature failure of the fan shaft.

manufacturer’s instructions printed on the motor. Use a high
grade SAE 20 machine oil and use caution not to over
lubricate.

Motors supplied with grease fittings should be greased
according to directions printed on the motor.

Removal of Dust/Dirt

Thoroughly clean the exterior surface of the motor, fan panel,
and entire propeller periodically. Dirt can clog cooling
openings on motor housings, contaminate bearing lubricant,
and collect on propeller blades causing severe imbalance if left
unchecked. Use caution and do not allow water or solvents to
enter the motor or bearings. Under no circumstances should
motors or bearings be sprayed with steam or water.

Exhaust Fan On/Off Control

The exhaust fans are turned on and off based on building static
pressure, outdoor air damper position, and discharge fan
capacity. Exhaust fans do not have to always run while the
supply fan is on, as does a return fan. They are turned on and
off through output MCB-B02 on the Main Control Board. For
detailed information on Propeller Exhaust Fan Control, refer to
the operation manual supplied with the unit (OM 138 or
OM 137).

Lubrication

Refer to “Bearings” for bearing lubrication. Many fractional
horsepower motors installed on the smaller fans are lubricated
for life and require no further attention. Motors equipped with
oil holes should be oiled in accordance with the

Exhaust Fan Troubleshooting

Table 14 provides guidelines for troubleshooting problems
with the propeller exhaust fan options. A list of parts is
provided in Figure 106.

94 McQuay IM 487-5

Unit Options

Ultraviolet Lights Option

When this option is employed, ultraviolet C light bathes the
moist surfaces on the coil and drain pan, killing most micro­organisms that can grow there.

Typically, ultraviolet lights are installed on the leaving side of
the cooling coils in the unit. Each light module is mounted on a
rail and is removable for convenient bulb replacement.

UV Light Power Disconnect switches (two per door) are
factory installed on every door that allows a direct line of sight
to the UV lamps when opened. These switches are designed to
prevent UV exposure when cabinet doors are opened and must
not be disabled.

A viewing window near the UV lights allows viewing to
determine if the lights are energized. The viewing windows
use specially designed glass that blocks harmful UV light.

WARNING

UVC exposure is harmful to the skin and eyes. Looking at an
illuminated bulb can cause permanent blindness. Skin
exposure to UVC can cause cancer.
Always disconnect power to unit before servicing. Do not
operate if disconnect switch has been disabled.

Figure 107: Typical ultraviolet light installation

Cooling
Coil

View
Window

AIRFLOW

Light Power
Disconnect
Switch

Ultraviolet
Light
Units

Light Power
Disconnect
Switch

McQuay IM 487-5 95

Unit Options

Ultraviolet Light Operation

Refer to the wiring schematic below. 115VAC power for the
UV lights is provided by control circuit transformer T1. The
lights operate whenever the unit is powered, system switch S1
is closed, and all doors with door power disconnect switches
are closed. To turn the lights off, disconnect power to the entire
unit, or open system switch S1.

Figure 108: Typical ultraviolet light wiring schematic

The normally open disconnect switches are wired in series in a
circuit that supplies 24VAC to the coil of relay R45. When all
doors are closed, relay R45 is energized, and its normally open
contacts (in series with system switch S1) provide 115VAC to
the UV lights.

96 McQuay IM 487-5

Check, Test, and Start Procedures

Check, Test, and Start Procedures

All units are completely run tested at the factory to promote
proper operation in the field. Nevertheless, the following
check, test, and start procedures must be performed to properly
start the unit. To obtain full warranty coverage, complete and
sign the check, test, and start form supplied with the unit and
return it to McQuay International.

WARNING

Electric shock and moving machinery hazard. Can cause
severe equipment damage, personal injury, or death.
Disconnect and tag out all electrical power before servicing this
equipment.
All start-up and service work must be performed only by trained,
experienced technicians familiar with the hazards of working on
this type of equipment.
Read and follow this manual: “MicroTech II Applied Rooftop
Unit Controller” manual (Bulletin IM 696), and operation manual
(Bulletin OM 137 or OM 138) before operating or servicing.
Bond the equipment frame to the building electrical ground
through grounding terminal or other approved means.

A representative of the owner or the operator of the equipment
should be present during start-up to receive instructions in the
operation, care, and maintenance of the unit.

If the unit has a factory mounted disconnect switch, use the
switch’s bypass mechanism to open the main control panel
door without de-energizing the control panel (see page 114 for
instructions).

Whenever accessing the main control panel while it is still
energized, keep the inner deadfront protective panels on to
avoid exposure to high voltage power.

Servicing Control Panel Components

WARNING

Hazardous voltage. Can cause severe injury or death.
Disconnect electric power before servicing equipment. More
than one disconnect may be required to de-energize the unit.

Disconnect all electric power to the unit when servicing
control panel components located behind the protective
deadfront panels. Unless power is disconnected to the unit, the
components behind the protective deadfront panels are
energized with high voltage. Always inspect units for multiple
disconnects to ensure all power is removed from the control
panel and its components before servicing.

Before Start-up

1 Verify that the unit is completely and properly installed

with ductwork connected.

2 Verify that all construction debris is removed, and that the

filters are clean.

3 Verify that all electrical work is complete and properly

terminated.

4 Verify that all electrical connections in the unit control

panel and compressor terminal box are tight, and that the
proper voltage is connected.

5 Verify all nameplate electrical data is compatible with the

power supply.

6 Verify the phase voltage imbalance is no greater than 10%.

7 Verify that gas piping is complete and leak tight.

8 Verify that the shutoff cock is installed ahead of the

furnace, and that all air has been bled from the gas lines.

9 Manually rotate all fans and verify that they rotate freely.

10 Verify that the belts are tight and the sheaves are aligned.

11 Verify that all setscrews and fasteners on the fan assemblies

are still tight. Do this by reading and following the
instructions in “Setscrews,” which is in the “Maintenance”
section of this manual.

12 Verify that the coding coil condensate drain is trapped and

that the drain pan is level.

13 If unit is curb mounted, verify that the curb is properly

flashed to prevent water leakage.

14 Before attempting to operate the unit, review the control

layout description to become familiar with the control
locations.

15 Review the equipment and service literature, the sequences

of operation, and the wiring diagrams to become familiar
with the functions and purposes of the controls and devices.

16 Determine which optional controls are included with the

unit.

17 Before closing (connecting) the power disconnect switch,

open (disconnect) the following unit control circuit
switches:

a Main Control Panel

– Turn system switch S1 to OFF.

– Electric heat units: turn switch HS1 to OFF.

b Furnace Control Compartment

– Turn furnace switch S3 to OFF.

– Main Control Panel Switch

S7 to OFF.

McQuay IM 487-5 97

Check, Test, and Start Procedures

18

If the DAC or SCC unit does not have an optional zone
temperature sensor (ZNT1) connected to it, you may need
to change the keypad entry under Setup/Service \ Unit
Configuration \ Space Sensor= from YES to NO.

Note – If desired, you can significantly reduce all MicroTech II

internal control timers by the changing the entry under
keypad menu Setup/Service\Unit Configuration\Timer
Settings\Service= from “0 min” to “X min” where X is the
number of minutes you want the unit to operate with fast
timers.

Economizer Start-up

CAUTION

Adjust dampers properly. Improper adjustment can damage the
dampers.
When an economizer is ordered without an actuator, the
linkage requires a 3.14" linear stroke to open it fully. Do not
allow dampers to be driven beyond their normal full closed or
full open position.

Power Up

1 Close the unit disconnect switch. With the control system

switch S1 in the OFF position, power should be available
only to the control circuit transformer (TI) and the
compressor crankcase heaters.

2 Turn the Switch S1 to ON. Power should now be supplied

to the control panel and the LEDs on MCB1 should follow
the normal startup sequence (refer to the “MCB LED
Power-Up Sequence” of IM 696).

Fan Start-up

1 Verify all duct isolation dampers are open. Unit mounted

isolation dampers may be mounted in the supply or return
sections.

2 Place the unit into the “Fan Only” mode through the

keypad menu System Summary\System\Ctrl Mode= Fan
Only.

3 Turn Switch S7 to ON. The controller should enter the

“Startup Initial” operating state. If the fan does not run:

a Check fuses F1 and F3.

b Check the manual motor protectors or that the circuit

breakers have not tripped.

c Check the optional phase monitor.

4 If the fans are equipped with optional spring isolators,

check the fan spring mount adjustment. When the fans are
running they should be level. Refer to “RAH spring mount
hold down fasteners” on page 52.

5 Verify the rotation is correct.

6 Verify the DHL safety is opening at a pressure compatible

with duct working pressure limits.

Note – The supply and return fan drives usually are selected for

operation in the drive's midspeed range. The return fan
drives are usually shipped with fixed pitch sheaves that
will provide the selected fan speed; however, the supply
fan drives are usually shipped with variable pitch sheaves
that are adjusted to provide the minimum fan speed. Both
drives should be adjusted for proper airflow during air
balancing. For more information, refer to “Air Balancing”
on page 99.

1 Check whether the outdoor air is suitable for free cooling

by displaying the keypad menu Temperature\OA
Damper\OA Ambient=. “Low” indicates low outdoor air

enthalpy; “High” indicates high outdoor air enthalpy. See
“Enthalpy Control” on page 85 to verify that the enthalpy
changeover control is working properly. You may want to
take temperature and humidity measurements.

2 Verify that switches PS1 and PS2 are at OFF. This prevents

compressor operation during the procedure.

3 At the keypad, set the cooling setpoint low enough so the

controller calls for cooling. Adjust the value in
Temperature\Zone Cooling\Occ Clg Spt= below the
temperature shown in Temperature\Zone Cooling\Control

Te mp =. In addition, on DAC units, adjust the value in
Temperature\Discharge Cooling\DAT Clg Spt= below the
temperature shown in Temperature\Discharge
Cooling\Disch Air=.

4 Place the unit into cooling mode through the keypad menu

System Summary\System\Ctrl Mode= Cool Only.

5 Observe the outdoor air dampers:

a If the outdoor enthalpy is low, the control algorithm

should start to modulate the dampers open to maintain
the discharge air setpoint.

b If the outdoor enthalpy is high, the dampers should

maintain their minimum position. Look at menu
Temperature\OA Damper\MinOA Pos=. Change this
entry to another value. Verify that the dampers move to
the new minimum position setpoint.

6 If the unit is equipped with the electromechanical enthalpy

changeover control (Honeywell H205) and the outdoor air
condition is borderline, attempt to change its input to the
MicroTech II controller by turning the switch adjustment to
“A” or “D.” Check enthalpy status in keypad menu
Temperature \ OA Damper \ OA Ambient=. If this reading
is “Low,” go to step 5a. If it is “High,” go to step 5b.

Note – It may not be possible to check the economizer operation

in both low and high enthalpy states on the same day. If
this is the case, repeat this procedure on another day
when the opposite outdoor air enthalpy conditions exist.

98 McQuay IM 487-5

Check, Test, and Start Procedures

Heating System Start-up

General

1 At the keypad, set the heating setpoints high enough so that

the controller will call for heating. The value in
Temperature \ Zone Heating \ Occ Htg Spt= will need to be
adjusted above the temperature shown in Temperature \
Zone Heating \ Control Temp=. In addition, on DAC units,
the value in Temperature \ Discharge Heating \ DAT Htg
Spt= will need to be adjusted above the temperature shown
in Temperature \ Discharge Heating \ Disch Air=.

2 Place the unit into heating mode through the keypad menu

System Summary \ System \ Ctrl Mode= Heat Only.

3 Verify that the high ambient heat lockout temperature

setpoint, Temperature \ Zone Heating \ OATHtg Lock= is
set above the current outside air temperature (shown in
System Summary \ Temperatures \ OA Temp=).

Gas Furnace

Refer to the “Start-up and Operating Procedures” section of
the Forced Draft Gas Fired Furnace Installation Manual,
Bulletin No. IM 684 or 685. Perform the start-up procedures
given in it.

Electric Heat

Turn the electric heat switch HS1 to ON. The electric heaters
should energize. If the unit has multistage electric heat, the
MicroTech II Auxiliary Control board EHB1 should energize
the heaters in successive stages. The rate of staging is set in
keypad menu Setup/Service \ Heating Setup \ Stage Time=. The
default value of “5 min” can be adjusted from 2 to 60 minutes.

Steam Heat

The steam valve actuator should open the valve. The steam
valve is open when the valve stem is up. If the unit loses
power, the spring in the actuator should drive the valve wide
open. Check this by opening system switch S1.

Hot Water Heat

The hot water valve actuator should open the valve to the coil.
The three-way hot water valve is open to the coil when the
valve stem is down. If the unit loses power, the spring in the

actuator should drive the valve wide open to the coil. Check
this by opening system switch S1.

Air Balancing

Air balancing should be performed by a qualified air balancing
technician. Note that the supply fan motors are usually shipped
with variable pitch sheaves which are typically set at the low
end of the drive’s fan rpm range. See “Mounting and Adjusting
Motor Sheaves” on page 101. The return fan motors are

usually shipped with fixed pitch sheaves.

WARNING

Moving machinery hazard. Can cause severe personal injury
or death.
Do not use a mechanically driven tachometer to measure the
speed of return fans on this fan arrangement. Use a strobe
tachometer.

The following should be performed as part of the air balancing
procedure:

1 Check the operating balance with the economizer dampers

positioned for both full outdoor air and minimum outdoor
air.

2 Verify that the total airflow will never be less than that

required for operation of the electric heaters or gas furnace.

3 For VAV units that have fan tracking control, adjust the

supply/return fan balance by using the MicroTech II
controller's built-in, automatic capability. For complete
information on using this feature, see the “Return Fan
Airflow Control: Fan Tracking” section in Bulletin No.
OM 137, “MicroTech II Applied Rooftop Unit Controller.”

4 When the final drive adjustments or changes are complete,

check the current draw of the supply and return fan motors.
The amperage must not exceed the service factor stamped
on the motor nameplate.

5 Upon completion of the air balance, replace variable pitch

motor sheaves (if any) with comparably sized fixed pitch
sheaves. A fixed pitch sheave will reduce vibration and

provide longer belt and bearing life.

WARNING

Rotating parts can cause severe personal injury or death.
Replace all belt/fan guards that are temporarily removed for
service.

McQuay IM 487-5 99

Check, Test, and Start Procedures

e

Sheave Alignment

Mounting:

1 Verify both driving and driven sheaves are in alignment and

the shafts are parallel. The center line of the driving sheave
must be in line with the ce1nter line of the driven sheave.
See Figure 109.

2 Verify that all setscrews are torqued to the values shown in

Table 20 on page 111 before starting drive. Check setscrew
torque and belt tension after 24 hours of service.

Figure 109: Sheave alignment (adjustable shown)

M u s t b e
p a r a l l e l

B e a r i n g

M o t o r

C e n t e r l i n e s
m u s t c o i n c i d

Drive Belt Adjustment

General Rules of Tensioning

1 The ideal tension is the lowest tension at which the belt will

not slip under peak load conditions.

2 Check tension frequently during the first 24 - 48 hours of

operation.

3 Over tensioning shortens belt and bearing life.

4 Keep belts free from foreign material which may cause

slippage.

5 Make V-drive inspection on a periodic basis. Adjust tension

if the belt is slipping. Do not apply belt dressing. This may
damage the belt and cause early failure.

Tension Measurement Procedure

1 Measure the belt span. See Figure 110.

2 Place belt tension checker squarely on one belt at the center

of the belt span. Apply force to the checker, perpendicular
to the belt span, until the belt deflection equals belt span
distance divided by 64. Determine force applied while in
this position.

3 Compare this force to the values on the drive kit label

found on the fan housing.

M u s t b e
p a r a l l e l

A d j u s t a b l e
S h e a v e

Figure 110: Drive belt adjustment

D e f l e c t i o n =

B e l t S p a n

B e l t S p a n

6 4

100 McQuay IM 487-5