McQuay MPS040A Installation Manual
Installation and Maintenance Manual IM 842-1
Maverick II™
Commercial Packaged Rooftop Systems
Heating & Cooling
Models MPS030A – 050A
30 to 50 Tons
R–410A Refrigerant
Group: Applied Systems
Part Number: IM 842-1
Date: January 2008
© 2008 McQuay International
Contents
Introduction .............................................................. 3
General Information................................................ 3
Unit Nameplate ................................................... 3
Hazard Identification Information ........................ 3
Mechanical Installation ............................................ 4
Installer Responsibilities ......................................... 4
Receiving Inspection........................................... 4
Service Clearance .............................................. 4
Ventilation Clearance.......................................... 5
Overhead Clearance........................................... 5
Roof Curb Assembly and Installation.................. 5
Rigging and Handling ......................................... 9
Unit Piping for Condensate Drain Connection.. 10
Damper Assemblies.......................................... 10
Cabinet Weather Protection.............................. 10
Installing Ductwork............................................ 11
Installing Duct Static Pressure Sensor Taps .... 11
Installing Building Static Pressure Sensor Taps 12
Electrical Installation ............................................. 13
Field Power Wiring............................................ 13
Field Control Wiring .......................................... 14
Preparing Unit for Operation ................................. 15
Spring Isolated Fans......................................... 15
Optional Gas Heat .................................................. 16
Gas Furnace Design............................................. 16
Gas Heating Capacity Data .............................. 16
Installation ........................................................ 18
Gas Piping Routing Into Unit ............................ 20
Sequence of Operation..................................... 21
Start-Up Procedures ......................................... 21
Operating Procedures....................................... 22
Service.............................................................. 22
Maintenance ..................................................... 22
Ignition Control Module Information.................. 23
Optional Electric Heat ............................................ 24
Electric Heater Design.......................................... 24
Electric Heating Capacity Data ......................... 25
Electric Heater Data.......................................... 25
Wiring Diagrams ..................................................... 26
Unit Options ............................................................ 42
Economizer Enthalpy Control ........................... 42
External Time Clock.......................................... 42
Duct High Pressure Limit .................................. 42
Convenience Receptacle/Section Lights.......... 42
Exhaust Fan Option ......................................... 42
Sequence of Operation.......................................... 43
Operating States .................................................. 43
Start Up ............................................................ 43
Recirculation .................................................... 43
Fan Only........................................................... 43
Heating............................................................. 43
Minimum DAT .................................................. 43
Mechanical Cooling.......................................... 44
Economizer ...................................................... 44
Check, Test, and Start Procedures ...................... 45
Pre-Start of Unit ................................................... 45
Servicing Control Panel Components .............. 45
Before Start-Up ................................................ 45
Power-Up ......................................................... 45
Fan Start-Up..................................................... 45
Economizer Start-Up........................................ 45
Compressor Start-Up ....................................... 46
Sheave Alignment ............................................ 47
Drive Belt Tension Adjustment......................... 47
Air Balancing .................................................... 47
Final Control Settings............................................ 48
Controller Settings for Normal Operation ............. 48
Maintenance ........................................................... 49
Performing Service Maintenance ......................... 49
Servicing Control Panel Components .............. 49
Planned Maintenance ...................................... 49
All-Aluminum Condenser Coils ........................ 49
Unit Storage ..................................................... 50
Bearing Lubrication .......................................... 51
Setscrews......................................................... 52
Supply Fan Wheel-to-Funnel Alignment .......... 52
Refrigerant Charge........................................... 52
Servicing Refrigerant Sensors or Switches...... 52
Servicing Optional Electric Heater ................... 52
Service and Warranty Procedure ......................... 53
Replacement Parts........................................... 53
Scroll Compressor............................................ 53
All Compressors............................................... 53
In-Warranty Return Material Procedure ........... 53
Commercial Rooftop Equipment Warranty
Registration Form............................................. 54
Introduction
General Information
Introduction
This manual provides general information about the “A”
vintage McQuay Commercial Packaged Rooftop Unit model
MPS. 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.
The MicroTech II
®
rooftop unit controller is available on “A”
vintage rooftop units. For a detailed description of the
MicroTech II components, input/output configurations, field
wiring options and requirements, and service procedures, see
OM 843. 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 OM 844 - MD2
MPS Unit Controller
Discharge Air Control (VAV or CAV)
Space Comfort Control (SCC)
Operation manual bulletin
number
OM895 - MD3
OM847 - MD6
OM 843
.
Unit Nameplate
The unit nameplate is located on the outside of the main
control box door. It includes the unit model number, serial
number, electrical characteristics, and refrigerant charge.
Hazard Identification Information
DANGER
Dangers indicate a hazardous situation which will result in
death or serious injury if not avoided.
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
McQuay Packaged System
(030, 035, 040, 050 tons)
Nominal capacity
M P S – 030 – A G
Heat medium
Y = None (cooling only)
G = Natural gas
E = Electric
Design vintage
McQuay IM 842-1 3
Mechanical Installation
Mechanical Installation
Installer Responsibilities
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 2: Service Clearances
All units should be carefully inspected for damage when
received. Report all shipping damage to the carrier and file a
claim. In most cases, equipment is shipped 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.
Service Clearance
Allow service clearances as approximately indicated in
Figure 2. Also, McQuay recommends providing a roof
walkway to the rooftop unit as well as along each side of the
unit that provides access to most controls and serviceable
components.
4 McQuay IM 842-1
Mechanical Installation
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 may
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 2 on page 4.
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).
Do not locate outside air intakes near 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 2). This is particularly
important to maintain adequate head pressure control when
mechanical cooling is required at low outdoor air
temperatures.
Note: Low head pressure may lead to poor and erratic
refrigerant feed control at the thermostatic expansion
valve. The unit has automatic control of the condenser
fans which should provide adequate head pressure
control down to 20°F provided the unit is not exposed to
windy conditions. The system designer is responsible
for assuring the condensing section is not exposed to
excessive wind or air recirculation.
Overhead Clearance
1 Unit(s) surrounded by screens or solid walls must have no
overhead obstructions over any part of the unit.
2 The area above the condenser must be unobstructed in all
installations to allow vertical air discharge.
3 The following restrictions must be observed for overhead
obstructions above the air handler section:
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.
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.
The gasketed top surface of the curb seals against the unit
when it is set on the curb. These flanges must not support the
total weight of the duct work. See “Installing Ductwork” on
page 11 for details on duct connections. It is critical that the
condensate drain side of the unit be no higher than the opposite
side.
Assembly Instructions
Assembly of a typical roof curb is shown in Figure 3.
1 Set curbing parts A thru G per dimensions shown over roof
opening or on a level surface. Note location of supply air
opening. Check alignment of all mating screw holes.
2 Screw curbing parts together using fasteners provided.
Leave all screws loose until curb is checked to be square.
3 Square entire curbing assembly and securely tighten all
screws.
4 Position curb assembly over roof openings. Curb must be
level within .25 inches from side to side and 1.50 inches
over its length. Check that top surface of curb is flat with
no bowing or sagging.
5 Weld curb assembly in place. Caulk all seams watertight.
Remove backing from .25 x 1.50 wide gasket and apply to
surfaces shown by crosshatching.
6 Check that electrical connections are coordinated.
McQuay IM 842-1 5
Mechanical Installation
Figure 3: Roof Curb Assembly—MPS 030A – 035A
6 McQuay IM 842-1
Figure 4: Roof Curb Layout—MPS 030A – 035A
2.00
[51 mm]
2.00
[51 mm]
23.50
[597 mm]
Mechanical Installation
21.25
[540 mm]
87.25
[2216 mm]
(INSIDE CURB)
2.00
[51 mm]
1.25
[32 mm] TYP
63.69
[1610 mm]
71.38
[1813 mm]
15.87
[403 mm]
1.63
[41 mm]
93.70
[2380 mm]
171.18 (INSIDE CURB)
[4348 mm]
PLAN VIEW
2.00
[51 mm]
1.00
[26 mm]
1.00
[26 mm]
2.00
[51 mm]
23.86
[606 mm]
3.75
[95 mm]
2.38
[58 mm]
F
KNOCKOUT DETAIL
CURB CROSS SECTION
McQuay IM 842-1 7
Mechanical Installation
Figure 5: Roof Curb Layout—MPS 040A – 050A
2.00
[51 mm]
2.00
[51 mm]
87.25
[2216 mm]
(INSIDE CURB)
2.00
[51 mm]
30.63
[778 mm]
1.25 TYP
[32 mm]
69.39
[1763 mm]
1.63
[41 mm]
105.45
[2678 mm]
28.25
[718 mm]
71.38
[1813 mm]
15.87
[403 mm]
208.57 (INSIDE CURB)
[5298 mm]
1.00
[25 mm]
2.00
[51 mm]
2.00
[51 mm]
28.92
[735 mm]
3.75
[95 mm]
PLAN VIEW
2.28
[58 mm]
F
CURB CROSS SECTION
8 McQuay IM 842-1
Mechanical Installation
Rigging and Handling
WARNING
Only trained and qualified personnel should be allowed to
rig loads or operate load rated cranes and/or hoist
assemblies. Do not use a forklift to lift or maneuver the
unit. Failure to use a load rated crane or hoist assembly to
lift or maneuver the unit can cause severe personal injury
and property damage.
WARNING
Use all lifting points. Improper lifting can cause property
damage, severe personal injury, or death.
CAUTION
Lifting points may not be symmetrical to the center of
gravity of the unit. Ballast or unequal cable lengths may be
required.
Rigging holes for shackles are integral on the unit base. All six
lifting points must be used for rigging the equipment. Use
four independent lines, securing one end of a line to a unit
base lifting point and the other end of the line to an
associated spreader bar lifting point (see Figure 7). Figure 6
is an example of an instruction label shipped with each unit.
Figure 6: Rigging Label
LIFT UNIT ONLY AS SHOWN
Table 2 lists the weight distribution at each of the six lifting
points on the unit (also refer to Figure 7). Table 3 details lifting
point locations (also refer to Figure 7).
Table 4 lists the
weights of accompanying curbs.
Table 2: Percentage of Load and Weight Points
Tot al
Unit (Tons)
030A Cooling 3525 388 388 705 846 564 635
030A Heating 3625 399 399 725 870 580 653
035A Cooling 3680 405 405 736 883 589 662
035A Heating 3780 416 416 756 907 605 680
040A Cooling 4160 458 458 832 998 666 749
040A Heating 4410 485 485 882 1058 706 794
050A Cooling 4560 502 502 912 1094 730 821
050A Heating 4870 536 536 974 1169 779 877
Weight
(lbs)
A
11%B11%C20%D24%E16%F18%
Table 3: Location of Lifting Points
Unit (tons)
030A – 035A 35.5 62.0 52.0
–
050A 40.0 69.0 89.0
040A
L1 L2 L3
Table 4: Curb Weights
Unit (Tons) / Curb Height Weight (lbs)
030A – 035A / 14" Curb 341
030A
–
035A / 24" Curb 501
–
050A / 14" Curb 481
040A
040A
–
050A / 24" Curb 708
Point
% of Total Load
Distance (inches)
SPREADER BARS REQUIRED
MUST USE ALL OF THESE
LIFTING LUGS FOR LIFTING 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, take these additional precautions:
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 Cover the supply and return air openings.
Figure 7: Rigging the Unit (MPS 030A – 035A Example)
McQuay IM 842-1 9
Mechanical Installation
Unit Piping for Condensate Drain Connection
The unit is provided with a 1" female NPT condensate drain
connection. For proper drainage, level the unit and drain pan
side to side and install a P-trap.
Figure 8 shows the layout of the condensate drain connection.
The distance from the drain pan outlet to the horizontal run of
the P-trap should be a distance of twice the static pressure in
the drain pan.
Example: If the static pressure as measured in the drain pan is
1.5", then the distance between the drain outlet and the
horizontal run should be 3".
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.
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. Verify that the
copper tubes are in place and open before the unit is put into
operation.
Periodically clean to prevent microbial growth/algae 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 9: Damper Assembly
Economizer Dampers
As the single actuator modulates, the outside air dampers open,
the return air dampers close, and the exhaust air exits the unit
through the gravity relief dampers.
The economizer comes with manually adjustable linkage
(Figure 9). 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. 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.
Outdoor Air Dampers (0% to 30%)
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.
The damper position may be set at the unit controller keypad
(refer to OM 843 for further detail). During unit operation, the
damper is driven to the position set at the unit controller.
During the off cycle, the damper is automatically closed.
Figure 8: Condensate Drain Connection
Static Pressure (P)
at the Drain Pan
Damper Assemblies
The optional damper assemblies described in this section are
ordered with factory-installed actuators and linkages. The
following sections describe the operation and linkage
adjustment of the factory option.
10 McQuay IM 842-1
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.
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.
Mechanical Installation
Installing Ductwork
On vertical-supply/vertical-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 the unit’s duct opening. Do not support the
total weight of the duct work from the unit. See Figure 4 on
page 7 or Figure 5 on page 8.
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
.
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 11).
7 Locate the reference pressure (LO) tap near the duct
pressure tap within the building. If the tap is not connected
to the sensor, unsatisfactory operation will result.
8 Route the tubes through the curb and feed them into the
unit through the knockout in the bottom of the control panel
(see Figure 10). Connect the tubes to appropriate barbed
fittings (on SPS1) in the control panel. (Fittings are sized to
accept 1/8" ID tubing.)
Figure 10: Static Pressure Tubing Knockout Location
Installing Duct Static Pressure Sensor Taps
For all VAV units, duct static pressure taps must be field
installed and connected to the static pressure sensor 1 (SPS1)
in the unit. Sensor SPS1 is standard on VAV units and is
located in the main control panel.
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 1/8" ID 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.)
Figure 11: Duct Static Pressure Sensing Tubing Installation
Condenser Section
Roof
Ductwork
(Remote Location)
Tubing Extends
Through Approx. 1/8”
HI Line
LO Line
Remote Sense Point
To Sensor
LO Input
Main Control Panel
SPS1
To Sensor
HI Input
Rubber
Grommet
Pressure Sensing
Tubing
McQuay IM 842-1 11
Mechanical Installation
Installing Building Static Pressure Sensor Taps
If a unit has building static pressure control capability, you
must field install and connect static pressure taps to the static
pressure sensor SPS2 in the unit. This sensor is located at the
bottom of the main control panel next to SPS1.
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 or 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 through the curb and feed it into
the unit through the knockout in the bottom of the control
panel (refer to Figure 10). Connect the 1/8" ID tube to the
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 upright. Seal the
penetration to prevent water from entering. Connect the
1/8" ID tube to the LO fitting for sensor SPS2.
Figure 12: Outdoor Static Pressure Tubing Installation
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.
7 Connect the tube to the HI fitting for sensor SPS2.
12 McQuay IM 842-1
Electrical Installation
Electrical Installation
Field Power Wiring
Wiring must comply with all applicable codes and ordinances.
The warranty is voided if wiring is not in accordance with
these specifications.
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 rated
overcurrent protection device (MROPD) value appears on the
unit nameplate.
All Units
All units are provided with internal power wiring for single
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 knockouts
in the bottom of the main control panel (see Figure 13 and also
Table 5). Refer to the unit nameplate to determine the number
of power connections.
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.
Note: To wire entry points, refer to certified drawings for
dimensions.
Figure 13: MPS Power Wiring Knockout Locations
The preferred entrance for power cables is through the bottom
knockouts provided on the unit. If a side entrance is the only
option, a hole may be drilled in the stationary upright.
The minimum circuit ampacity (MCA) is shown on the unit
nameplate. Refer to Table 5 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. Wires should be sized 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. Size the
grounding conductor in accordance with Table 250-95 of the
National Electrical Code.
In compliance with the National Electrical Code, a 115 V
factory mounted service receptacle outlet is provided. This
outlet must be powered by a field connected 15 A, 115 V
power supply. Leads are brought into the unit through a 7/8"
knockout in the bottom of the main control panel.
Table 5: Recommended Field Power Wiring
Ampacity
(MCA)
30 1 10 75
40 1 8 75
55 1 6 75
70 1 4 75
85 1 3 75
95 1 2 75
130 1 1 75
150 1 1/0 75
175 1 2/0 75
200 1 3/0 75
230 1 4/0 75
255 1 250 75
300 2 1/0 75
350 2 2/0 75
400 2 3/0 75
460 2 4/0 75
510 2 250 75
600 3 3/0 75
690 3 4/0 75
765 3 250 75
Notes:
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.
# of Power
Wires Per
Phase
Wire Gauge
Insulation
Temperature
Rating (°C)
McQuay IM 842-1 13
Electrical Installation
Field Control Wiring
The Maverick rooftop units are available with the following
field control connections:
• Space sensor.
• Space sensor with setpoint adjustment.
• Fan operation output.
• VAV box output.
• Remote alarm output.
• External discharge air temperature reset.
• Outdoor air damper minimum position adjustment.
Descriptions of these field connections are included in the
MicroTech II Unit Controls manual (OM 843).
WARNING
Electrical shock hazard. Can cause severe injury or death.
Connect only low voltage NEC Class II circuits to terminal block
TB2.
14 McQuay IM 842-1
Preparing Unit for Operation
Preparing Unit for Operation
Spring Isolated Fans
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. Prior to operating the fans for the first time, refer to “Check,
Test, and Start Procedures” on page 45.
Releasing Spring Mounts
The spring-mounted supply fan is locked down with four
shipping bolts for shipment. Remove each shipping bolt before
operating the fans. Figure 14 shows a typical spring mount
with a height adjustment nut and a shipping bolt.
After removing the shipping bolts, rock the fan assembly by
hand to check for freedom of movement.
Figure 14: Spring Mounts
Adjusting Spring Mounts
During operation all fans should ride level. Level the fan
assembly by performing the following:
1 Loosen the 3/8" cap screw (do not remove).
2 Loosen the spring cap nut.
3 Rotate the 5/8" adjustment nut counter-clockwise to raise
the fan assembly, or clockwise to lower the fan assembly.
4 Tighten the 3/8" cap screw.
5 Tighten the spring cap nut.
McQuay IM 842-1 15
Optional Gas Heat
Optional Gas Heat
Gas Furnace Design
This section of the manual covers the optional furnace
(Figure 15). If the 8th digit in the model number is a “G”, the
rooftop unit was furnished with a factory installed furnace
(Example, MPS035AG). The Maverick commercial rooftop
units are available with either the low heat input or the high
heat input furnace (see capacities in Table 6). This packaged
gas heat rooftop unit is designed for outdoor non-residential
installations only.
The gas heat furnace design consists of a tubular heat
exchanger, in-shot burner manifold with gas valve, induced
combustion blower, gas heat DDC control module and all
operational safeties. The tubular heat exchanger can come with
the standard aluminized steel construction or the optional
stainless steel construction. The safety switches include a highlimit temperature switch (Figure 15), an auxiliary high-limit
switch (Figure 15), a combustion blower proof of airflow (see
Figure 16), and the flame roll-out switch (see Figure 16).
The high limit switch is an automatic reset switch and it opens
up at 160°F to shut the furnace down and closes at 130°F. The
auxiliary limit switch is a manual reset and opens up at 180°F
to shut the furnace down.
Figure 15: Gas Heat Section
Gas Heating Capacity Data
Table 6: MPS 030A – 050A Gas Heating Capacities
Unit Size
Data
Heating Input (MBh) 300 600
Heating Output (MBh)
Steady State Efficiency
Number of Stages
Minimum Airflow 3800 7400
Maximum Temperature Rise
Gas Main Pressure
Natural Gas (in. wc) 7-147-147-147-147-147-147-147-14
Liquid Propane (in. wc) 12-14 12-14 12-14 12-14 12-14 12-14 12-14 12-14
Manifold Pressure
Natural Gas (per gas valve)
Stage 1 (in. wc) 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2
Stage 2 (in. wc) 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2
Propane
Stage 1 (in. wc) 2.3 2.3 2.3 2.3 2.3 2.3 2.3 2.3
Stage 2 (in. wc) 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0
Connection Size 3/4" 3/4" 3/4" 3/4" 3/4" 3/4" 3/4" 3/4"
Quantity 12121212
030A
(Lo Heat)
240 480
80% 80% 80% 80% 80% 80% 80% 80%
24
60°F 60°F 60°F 60°F 60°F 60°F 60°F 60°F
030A
(High Heat)
035A
(Lo Heat)
300 600 400 800 400 800
240 480 320 640 320 640
242424
3800 7400 4900 9800 4900 9800
035A
(High Heat)
040A
(Lo Heat)
040A
(High Heat)
050A
(Lo Heat)
(High Heat)
050A
16 McQuay IM 842-1
Figure 16: Burner Assembly
4
5
6
7
Optional Gas Heat
1
2
3
Item # D escr ip ti on
1Furnace
2 I nduced Co mbus tion Bl ower
3 P late-Induc er Orifice
4 T rans forme r-40VA
5 S park I gnito r
12
11
10
9
8
6IgnitionControl
7 G as Val ve-2 S tage
8 M anifold A ss embly Test Port
9 B urner Ins hot
10 Fl ame R ollout Switc h
11 Fl ame S ensor
12 Pr oof of A irflow S witch
Warranty Exclusion
Warranty is void if the furnace is operated in the presence of
chlorinated vapors, if the airflow through the furnace is not in
accordance with rating plate, or if the wiring or controls have
been modified or tampered with.
WARNING
Hot surface hazard. Can cause severe equipment damage,
personal injury, or death. Allow burner assembly to cool
before servicing equipment.
WARNING
Units equipped with gas heating must not be operated in
an atmosphere contaminated with chemicals which will
corrode the unit such as halogenated hydrocarbons,
chlorine, cleaning solvents, refrigerants, swimming pool
exhaust, etc. Exposure to these compounds may cause
severe damage to the gas furnace and result in improper
or dangerous operation. Operation of the gas furnace in such
a contaminated atmosphere constitutes product abuse and will
void all warranty coverage by the manufacturer. Questions
regarding specific contaminants should be referred to your
local gas utility.
Ventilation & Flue Pipe Requirements
The McQuay rooftop unit is equipped with an outdoor air hood
to supply adequate combustion air. The unit also has a flue
outlet assembly and requires no additional chimney, flue pipe,
Breidert cap, draft inducer, etc.
Factory Checkout
This complete furnace was fired and tested at the factory. The
unit was fired through several complete sequences of start-up
through shutoff to check operation. A check was made of the
air switch, gas pressure switch, high limit operation.
This checkout normally eliminates on-the-job start-up
problems; however, the equipment is subject to variable job
conditions and shipping shocks can change adjustments, cause
damage, and loosen connections and fasteners. Therefore, it is
necessary to go through the complete start-up procedure even
though the unit may appear to be operating properly.
McQuay IM 842-1 17
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