American Standard UV05 User Manual

Operation Maintenance Manual OM 751-1

MicroTech II® Unit Ventilator Controls

for AAF®-HermanNelson® Classroom Unit Ventilators

Group: Applied Systems

Part Number: OM 751

Date: November 2006

DX Cooling Only-

Software Model UV05

Used with AAF-HermanNelson Classroom Unit Ventilator

Model AVV - Floor Mounted

Model AHV - Ceiling Mounted

Model AZV, AZU - Floor Mounted Self Contained Air Conditioner

IMPORTANT

Before unit commissioning, please read this publication in its entirety.

Develop a thorough understanding before starting the commissioning procedure.

This manual is to be used by the commissioner as a guide. Each installation is unique, only general topics are covered.

The order in which topics are covered may not be those required for the actual commissioning.

© 2006 McQuay International

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

Acronyms/Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Getting Started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Using the Keypad/Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Display Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Keypad Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Using the Keypad/Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Menu Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Description of Operation . . . . . . . . . . . . . . . . . . . . 12

State Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

UVC Unit Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

OFF Mode (State 9) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

Night Purge Mode (State 8) . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Fan Only Mode (State A) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Emergency Heat Mode (Super State) . . . . . . . . . . . . . . . . . . . 16

Auto Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Cool Mode (Super State) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Special Purpose Unit Modes. . . . . . . . . . . . . . . . . . . . . . . . . . 21

Unit Mode Priority . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Occupancy Modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Occupied Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Unoccupied Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

Standby Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Bypass Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Additional Occupancy Features . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Networked Occupancy Sensor Capability. . . . . . . . . . . . . . . . 25

Unit-Mounted Time-Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Unit-Mounted Tenant Override Switch . . . . . . . . . . . . . . . . . . 25

Remote Wall-Mounted Sensor Tenant Override Switch . . . . . 25

Remote Wall-Mounted Sensor Status LED. . . . . . . . . . . . . . . 25

Space Temperature Set Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Networked Set Point Capability. . . . . . . . . . . . . . . . . . . . . . . . 26

Networked Set Point Offset Capability . . . . . . . . . . . . . . . . . . 26

Networked Set Point Shift Capability . . . . . . . . . . . . . . . . . . . 26

Networked Space Temperature Sensor Capability . . . . . . . . . 26

Remote Wall-Mounted Sensor with +/–3°F

Adjustment (optional) . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Remote Wall-Mounted Sensor with 55°F to 85°F

Adjustment (optional) . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Effective Set Point Calculations . . . . . . . . . . . . . . . . . . . . . . .27

Proportional Integral (PI) Control Loops . . . . . . . . . . . . . . . . . . . . . 29

Discharge Air Temperature Control . . . . . . . . . . . . . . . . . . . . 29

PI Control Parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Proportional Band . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Integral Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

Indoor Air Fan Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Auto Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Occupied, Standby, and Bypass Operation . . . . . . . . . . . . . .31

Unoccupied Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Cycle Fan. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Off Delay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Outdoor Air Damper Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Minimum Position . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Economizer Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Networked Space Humidity Sensor Capability . . . . . . . . . . . 34

Networked Outdoor Humidity Sensor Capability . . . . . . . . . . 34

Demand Controlled Ventilation (optional) . . . . . . . . . . . 34

CO

2

Networked Space CO

ASHRAE Cycle II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Compressor Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Compressor Envelope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Compressor Cooling Lockout . . . . . . . . . . . . . . . . . . . . . . . . 35

Compressor Minimum On and Off Timers . . . . . . . . . . . . . . . 36

Compressor Start Delay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Outdoor Air Fan Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Floating-Point Actuator Auto-Zero, Overdrive and Sync . . . . . . . . 36

External Binary Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

External Binary Input 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

External Binary Input 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

External Binary Input 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

External Binary Outputs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

External Binary Output 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

External Binary Output 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

External Binary Output 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Sensor Capability . . . . . . . . . . . . . . . 34

2

UVC Input and Output Table . . . . . . . . . . . . . . . . . 40

Diagnostics and Service. . . . . . . . . . . . . . . . . . . . . 41

Alarm and Fault Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Space Temp Sensor Failure (F0). . . . . . . . . . . . . . . . . . . . . . 42

DX Pressure Fault (F1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Compressor Envelope Fault (F2) . . . . . . . . . . . . . . . . . . . . . . 42

Discharge Air DX Cooling Low Limit Indication (F3) . . . . . . . 42

Condensate Overflow Indication (optional) (F4). . . . . . . . . . . 43

Space Coil DX Temp Sensor Failure (F5) . . . . . . . . . . . . . . . 43

Outdoor Temp Sensor Failure (F6) . . . . . . . . . . . . . . . . . . . . 43

Discharge Air Temp Sensor Failure (F7) . . . . . . . . . . . . . . . . 43

Outdoor Coil DX Temp Sensor Failure (F8). . . . . . . . . . . . . . 43

Space Humidity Sensor Failure (optional) (FA) . . . . . . . . . . . 44

Outdoor Humidity Sensor Failure (optional) (Fb) . . . . . . . . . . 44

Space CO2 Sensor Failure (optional) (FC). . . . . . . . . . . . . . . 44

Change Filter Indication (FF) . . . . . . . . . . . . . . . . . . . . . . . . . 44

EPROM Memory Indicator (EE) . . . . . . . . . . . . . . . . . . . . . . . 44

Configuration Display (--) . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Troubleshooting Temperature Sensors . . . . . . . . . . . . . . . . . . . . . 44

Troubleshooting Humidity Sensors . . . . . . . . . . . . . . . . . . . . . . . . 45

Troubleshooting Carbon Dioxide (CO

) Sensors. . . . . . . . . . . . . . 46

2

UVC Configuration Parameters . . . . . . . . . . . . . . . 47

Introduction

Introduction

This manual provides information on the MicroTech II® control system used in the AAF®-

®

HermanNelson

Unit Ventilator product line. It describes the MicroTech II components, input/

output configurations, field wiring options and requirements, and service procedures.

For installation and general information on the MicroTech II Unit Ventilator Controller, refer
to IM 747, MicroTech II Unit Ventilator Controller.

For installation, commissioning instructions, and general information on a particular unit
ventilator model, refer to the appropriate manual (Table 1), as well as accompanying software
operating instruction manual (Table 4), and possible accessory manuals that may pertain to the
unit (Table 3).

For installation and maintenance instructions on a plug-in communications card, refer to the
appropriate protocol-specific installation and maintenance manual (Table 2). For a description
of supported network variables for each protocol, refer to Protocol Data Packet bulletin ED

15065.

Table 1: Model-specific unit ventilator installation literature

Description Manual #

Air Source Heat Pump IM 502 X
DDC Control Components AED-Q-MTII-811 X
Self-Contained IM 503 X X X X X X
Self-Contained DDC
Control Components
Vertical Split-system IM 817-1 X X X X
Horizontal Split-system IM 830 X X X X X X X X
Ceiling Vent AH IM 830 X X X X

AZS Q V U R MII
810

AEQ

AER

AHF

AHB

AHR

AVF

AVB

AHV

AVS

AVH

AVV

AVR

AZS

AZB

AZR

AZU

XXXXX

AZV

AZQ

ARQ

ERQ

Table 2: Protocol-specific communication card installation literature and protocol data

Description Manual #

Unit Ventilator Unit Controller LonWorks®
Communications Module

Unit Ventilator Unit Controller JCI N2 Open®
Communications Module

Unit Ventilator Unit Controller BACnet®
Communications Module

Protocol Data Packet ED-15065

IM 729

IM 730

IM 731

Table 3: Accessory-specific installation literature

Description Manual #

MTII Unit Ventilator Controls Installation IM 747
Room Temperature Sensors Installation IM 629-1
ATS Service Cable Installation for Unit Ventilators IM 762-0

McQuay OM 751 3

Introduction

Table 4: Software program literature

Description Manual #

Air Source Heat Pump with Electric Heat (Software Model 00) OM 748
Water Source Heat Pump with Electric Heat (Software Model 02)
Water Source Heat Pump without Electric Heat (Software Model 03)
DX Cooling with Electric Heat (Software Model 04) OM 750
DX Cooling Only (Software Model 05) OM 751
Electric Heat Only (Software Model 06) OM 752
DX Cooling with Hydronic Heat - Valve Control (Software Model 07)
DX Cooling with Hydronic Heat - F&BP Damper Control (Software Model 08)
2-Pipe Hydronic Heat Only - Valve Control (Software Model 09)
2-Pipe Hydronic Heat Only - F&BP Damper Control (Software Model 10)
2-Pipe Chilled Water Cooling and Hot Water Heat - Valve Control (Software Model 11)
2-Pipe Chilled Water Cooling and Hot Water Heat - F&BP Damper Control (Software
Model 12)
4-Pipe Chilled Water Cooling and Hydronic Heat - Valve Control (Software Model 13)
4-Pipe Chilled Water Cooling and Hydronic Heat - F&BP Damper Control (Software

Model 14)
2-Pipe Chilled Water Cooling Only - Valve Control (Software Model 15)

2-Pipe Chilled Water Cooling Only - F&BP Damper Control (Software Model 16)
2-Pipe Chilled Water Cooling with Electric Heat - Valve Control (Software Model 17)

2-Pipe Chilled Water Cooling with Electric Heat - F&BP Damper Control (Software
Model 18)

OM 749

OM 753

OM 754

OM 755

OM 756

OM 757

OM 758

NOTICE

This equipment generates, uses, and can radiate radio frequency energy and, if not installed
and used in accordance with this instruction manual, may cause interference to radio
communications. It has been tested and found to comply with the limits for a Class A digital
device, pursuant to part 15 of the FCC rules. These limits are designed to provide
reasonable protection against detrimental interference when the equipment is operated in a
commercial environment. Operation of this equipment in a residential area is likely to cause
detrimental interference in which case users are required to correct the interference at their
own expense. McQuay International disclaims any liability resulting from any

interference or for the correction thereof.

WARNING

Electric shock hazard. Can cause personal injury or equipment damage.

This equipment must be properly grounded. Connections and service to the MicroTech II
control panel must be performed only by personnel that are knowledgeable in the operation
of the equipment being controlled.

CAUTION

Extreme temperature can damage system components.

The MicroTech II controller is designed to operate in ambient temperatures from -20°F to
125°F. It can be stored in ambient temperatures from -40°F to 140°F. It is designed to be
stored and operated in relative humidity up to 95% (non-condensing).

CAUTION

Static sensitive components. A static discharge while handling electronic circuit
boards can damage components.

Discharge any static electrical charge by touching the bare metal inside the main control
panel before performing any service work. Never unplug any cables, circuit board terminal
blocks, relay modules, or power plugs while power is applied to the panel.

4 McQuay OM 751

Introduction

Acronyms/Abbreviations

The following table list acronyms and abbreviations that may or may not be used within this
manual. Other abbreviations for keypad displays and parameters can be found in Table 8 on
page 14 and Table 26 on page 47.

Table 5: Acronyms and abbreviations

Description

Air Fan AF
Auxiliary Heat End Differential AHED
Auxiliary Heat Start Differential AHSD
American Standard Code for Information Interchange ASCII
American Society of Heating, Refrigerating, and Air
Conditioning Engineers, Inc
Compressorized Cooling Lockout CCLO
Spac e C O
Chilled Water CW
Chilled Water Valve Position CWVP
Discharge Air DA
Discharge Air High Limit DAHL
Discharge Air Temperature DAT
Discharge Air Temperature Setpoint DATS
Demand Controlled Ventilation
DX Cooling Discharge Air Low Limit DXLL
Economizer Compare Differential ECD
Economizer IA/OA Enthalpy Differential EED
Economizer OA Enthalpy Setpoint EES
Emergency Heat Setpoint EHS
Exhaust Interlock OAD Min Position Setpoint EOAD
Outdoor Air Temperature Setpoint EOAT
End-of-Cycle EOC
EOC OAT Low Setpoint EOCS
Outdoor Air Humidity Output EORH
Space Humidity Setpoint ERH
Economizer IA/OA Temp Differential ETD
Economizer OA Temp Setpoint ETS
Source (water in) Temperature EWIT
Face and Bypass Damper Position FBDP
Federal Communications Commission FCC
Face and Bypass F & BP
Heating, Ventilating, Air Conditioning Refrigeration HVACR
Heating EOC Valve Setpoint HEOC
Hot Water HW
Indoor Air IA
Indoor Air Fan IAF
Indoor Air Temperature IAT
Light Emitting Diode LED
Local User Interface LUI
Mixed Air Low Limit MALL
Mechanical Cooling Low Limit Setpoint MCLL
National Electric Code NEC
Outside Air OA
Outside Air Dampers OAD
Energize Exhaust Fan OAD Setpoint OADE
OAD Min Position High-Speed Setpoint OADH
OAD Min Position Low-Speed Setpoint OADL
OAD Min Position Med-Speed Setpoint OADM
Outdoor Air Damper Position OADP
OAD Lockout Setpoint OALS
OAD Max Position Setpoint OAMX
Outside Air Temperature OAT

Setpoint CO2S

2

Acronym/

ASHRAE

DCV

Abr.

McQuay OM 751 5

Introduction

Description

Occupied Cooling Setpoint OCS
Occupied Heating Setpoint OHS
Occupancy Override Input OOI
Occupancy Sensor Input OSI
Proportional Integral PI
Parts Per Million PPM
Positive Temperature Coefficient PTC
Relative Humidity RH
Space Humidity Setpoint
Read Only RO
Read Write RW
Standby Cooling Setpoint SCS
Standby Heating Setpoint SHS
Thermal Expansion Valve TXV
Unoccupied Cooling Setpoint UCS
Unoccupied Heating Setpoint UHS
Unit Ventilator UV
Unit Ventilator Controller UVC
UVC (Heat/Cool) Mode Output UVCM
UVC State Output UVCS
Wet Heat Valve Position VALP
Ventilation Cooling Low Limit Setpoint VCLL
Ventilation Cooling Lockout VCLO
Ventilation Cooling Setpoint VCS
Wet Heat WH
Source (water in) Temperature Differential WITD

Acronym/

RHS

Abr.

6 McQuay OM 751

Getting Started

Getting Started

The MicroTech II Unit Vent Controller (UVC) is a self-contained device that is capable of
complete, stand-alone operation. Information in the controller can be displayed and modified
by using the keypad/display (local user interface). The following sections describe how to use
the keypad/display.

Note – Many UVC parameters are accessible both through the keypad/display and the network

interface. The shared keypad/display and the network interface variables have a “last­change-wins” relationship.

Using the Keypad/Display

The keypad/display shown in Figure 1 is provided with all MicroTech II Applied Unit
Ventilator unit controllers. With the keypad/display, operating conditions, system alarms, and
control parameters can be monitored. Set points and other parameters also can be modified.

Figure 1: Keypad/display

MicroTechTMII

FAN ONLY

COOL

HEAT

AUTO

MODE FAN

HIGH

MED

LOW

AUTO

FUNC

ON /

STOP

Display Format

The keypad/display’s 2-digit, 7-segment display normally shows the effective heating or
cooling temperature set point (Effective Set Point Output). The display also is used to view
and modify UVC parameters as explained in the following sections.

Note – When the UVC is in the OFF mode, the effective heating set point appears in the display.

All other LEDs are switched off.

Keypad Functions

Security Levels

The keypad/display provides a 4-level password security feature that can be used to restrict
access. The available security levels are shown in Table 6.

Note – All unit ventilator controllers ship with the lowest security (level 0) enabled. To change

security levels, see Figure 2. Once a security level is changed, the keypad/display
remains at that security level until the next time it is changed.

Why can’t I use the MODE or FAN key or adjust Set Point Offset?

Most likely this is due to the security feature being used. If the security feature is set higher
than level 0, then some keypad/display functionality is locked out. To ensure this is not the
problem, enter the level 0 password then try to use the keypad/display again.

McQuay OM 751 7

Getting Started

Table 6: Keypad/display security levels

Level Display What is restricted? Password

0

1

2

3

U0

Default level (access all) 10
Does not allow set point offset changes;

U1

also locks out keypad/display menu
access.

Does not allow set point offset changes
nor MODE key changes; also locks out

U2

keypad/display menu access.
Does not allow set point offset changes

U3

nor MODE and FAN key changes; also
locks out keypad/display menu access.

21

32

43

Figure 2: Changing keypad/display security levels

ON/STOP Key and LED

Use the ON/STOP key to toggle the UVC between OFF mode and running (Application Mode
Input). The ON/STOP LED is off when the UVC is in the OFF mode.

Note – When the UVC is in the OFF mode, the effective heating set point appears in the display.

All other LEDs are switched off.

– The UVC archives each change to the keypad/display FAN and MODE keys. When the

ON/STOP key is used to bring the unit out of OFF mode, the UVC implements the last
active fan and unit modes.

– Each time the UVC power cycles, the UVC is in the auto fan and auto unit modes when

power is returned.

WARNING

Off mode is a “stop” state for the unit ventilator. It is not a “power
off” state. Power may still be provided to the unit.

FAN Key

Use the FAN key to toggle through each of the fan speeds (Fan Speed Command Input): Auto,
Low, Medium, and High.

MODE Key

Use the MODE key to toggle through the keypad/display accessible unit modes (Heat/Cool
Mode Input): Auto, Heat, Cool, and Fan Only.

Arrow Keys

Use the arrow keys to scroll between parameters and to adjust parameters.

FUNC Key

Use the Func key to view the actual space temperature or to confirm selection and changes to
user-adjustable parameters.

8 McQuay OM 751

Getting Started

Using the Keypad/Display

Viewing Actual Indoor Air Temperature (IAT)

Normally, the effective set point temperature appears on the keypad/display. You also can use
the keypad/display to view the indoor air temperature (IAT). See Figure 3.

Note – When the actual indoor air temperature (Effective Space Temp Output) equals the

effective set point temperature (Effective Set Point Output), you there is no change to the
keypad/display when you view space temperature.

Figure 3: Viewing indoor air temperature

70 71 70

Effective
set point

Changing Set Points

The keypad/display can be used to make a +/–5°F (+/–3°C) offset adjustment to the effective
temperature set point. See Figure 4. Also see “Space Temperature Set Points” on page 26 to
learn more about temperature set points.

Figure 4: Adjusting the set point offset

FUNC

Enter

(5-sec)

Actual space
temperature

Effective
set point

-1

Flash
value

FUNC

Enter

0

0

Current

offset

So 69

Effective
set point

70

Effective
set point

-1

Adjusted

offset

FUNC

Save

change

So

Set point

offset

Note – The set point offset clears whenever UVC power is cycled. When you change the set point

offset after a power cycle, or for the very first time, this cleared value shows as the highest
allowed value (5°F/3°C) but is not an actual offset value.

– When using the +/–3°F (+/–1.7°C) remote wall sensor, any set point offset adjustment

made at the keypad/display causes the UVC to override and ignore the remote wall
sensor set point adjustment knob. To use the remote wall sensor set point adjustment
knob after you changed the set point offset on the keypad/display, clear the keypad/
display set point offset by cycling UVC power.

– When using the 55°F to 85°F remote wall sensor, the UVC ignores any LUI set point offset

adjustments.

Menu Reference

The keypad/display menu eases troubleshooting and simplifies UVC configuration. The user
can access the most common parameters and system status values without a PC or network
interface.

The keypad/display menu is accessed via an unmarked, hidden key. This hidden key is located
approximately behind the letter “h” in the MicroTech II logo on the keypad/display face.

The keypad/display menu consists of two levels. The first level is the keypad/display Menu
Item List containing alphanumeric characters representing each parameter. The second level is
where the parameter’s value is viewed and adjusted if the parameter is adjustable. After 15­seconds, an inactivity timer automatically causes the display to back out of the menu levels,
returning to the effective set point display.

McQuay OM 751 9

Getting Started

Figure 5: Changing a keypad/display menu item

Table 7: Keypad/display menu item list

Display Keypad menu item list Abr. Description

Reset Alarm Input Enter 1 to clear alarms (clears all inactive alarms, except filter alarm). To enable

rA

UVC (Heat/Cool) Mode

HC

Output
UVC State Output

St

Discharge Air Temp Set

d0

point Output
Discharge Air Temp

d1

Output
Ventilation Cooling Low

d2

Limit set point
Mechanical Cooling Low

d3

Limit set point
Slave Type Configuration Set slave type: 0 = Independent (slave uses own sensors), 1 = Dependent (slave

SL

Effective Occupancy

Eo

Output
Occupancy Override
Input

o(

Occupied Cooling set

(o

point
Standby Cooling Set

(S

point
Unoccupied Cooling Set

(U

point
Occupied Heating Set

ko

point
Standby Heating Set

kS

point
Unoccupied Heating Set

kU

point
Wall Sensor Type

rS

Outside Air Damper

o1

Position Output
OAD Min Position High-

o2

Speed Set point
OAD Min Position Med­Speed Set point OADM

o3

OAD Min Position Low­Speed Set point OADL

o4

the alarm again, enter 0.
Display current UVC mode. 1 = Heat, 3 = Cool, 4 = Night Purge, 6 = Off, 8 = Emerg.

UVCM

Heat, 9 = Fan Only
Display current UVC state. 1 = EconMech, 2 = Mech, 3 = Econ, 4 = DA Heat, 5 =
Heat, 6 = ActiveDehum, 7 = Full Heat, 8 = Night Purge, 9 = Off, 10 = Fan Only, 11

UVCS

= Heat Mode Cant Heat, 12 = CantCool, 13 = Emerg Heat Mode Cant Heat, 14 =
Heat Mode Low Limit, 15 = Cool Mode Low Limit

DATS Display current DA temperature set point. RO x

DAT Display current DA temperature. RO x

VCLL Adjust economizer cooling DA temperature low limit. RW x

MCLL Adjust mechanical cooling DA temperature low limit. RW x

follows master). This feature requires a network over which the master and slave
UVCs can communicate.

Display current occupancy. RO x

Set occupancy: 0 = occupied, 1 = unoccupied, 2 = bypass, 3 = standby. Adjusting
this variable is intended only for troubleshooting. Once you are done, cycle unit
power to clear this variable and return the UVC to normal operation.

OCS Adjust occupied cooling set point. RW x

SCS Adjust standby cooling set point. RW x

UCS Adjust unoccupied cooling set point. RW x

OHS Adjust occupied heating set point. RW x

SHS Adjust standby heating set point. RW x

UHS Adjust unoccupied heating set point. RW x

Set wall sensor type: 0 = +/–3F, 1 = 55°F to 85°F. RW x 0

OADP Display OA damper position. RO x

Adjust OA damper minimum position with IAF at high speed. (This variable is

OADH

factory set to 5% open when the unit is ordered with optional
Adjust OA damper minimum position with IAF at medium speed. (This variable is
not used when the optional
damper minimum regardless of fan speed.)
Adjust OA damper minimum position with IAF at low speed. (This variable is not
used when the optional
damper minimum regardless of fan speed.)

CO2 DCV is enabled. Only OADH is active as the OA

CO2 DCV is enabled. Only OADH is active as the OA

CO2 DCV.)

RO

05

1

RW

RW x

RO x

RO x

RW x 0

RW x

RW x 20%

RW x 25%

RW x 30%

Default

//

54°F

(12°C)

45°F

(7°C)

//

73.4°F
(23°C)

77°F

(25°C)

82.4°F
(28°C)

69.8°F
(21°C)

66.2°F
(19°C)

60.8°F
(16°C)

2

2

10 McQuay OM 751

Display Keypad menu item list Abr. Description

Exhaust Interlock OAD

o5

Min Position set point
Energize Exhaust Fan

o6

OAD Set point
OAD Max Position Set

o7

point

OAD Lockout Enable

o8

OAD Lockout Set point OALS

o9

Economizer Enable Set economizer status: 0 = disable, 1 = enable. RW x 1

E1

Economizer OA Temp

E2

Set point
Economizer IA/OA Temp

E3

Differential
Economizer OA Enthalpy

E5

Set point
Economizer IA/OA

E6

Enthalpy Differential

Space Humidity Output ERH Display room humidity (optional). 00 = No sensor connected. RO x

r1

Outdoor Air Humidity

r3

Output

Outdoor Air Temp Output EOAT Display OA temperature. RO x

ot

Emergency Heat Enable Set emergency heat status: 0 = disable, 1 = enable. RW x 1

k1

Emergency Heat Set

k2

point
Emergency Heat

k3

Shutdown Configuration
Auxiliary Heat Start

A1

Differential
Auxiliary Heat End

A2

Differential
Auxiliary Heat

A3

Configuration
External BI-3

b3

Configuration
External BO-3

b6

Configuration
Fan Cycling

(F

Configuration

Filter Alarm Enable Set filter alarm status: 0 = disable, 1 = enable. RW x 0

(E

Reset Filter Alarm Input Enter 1 to clear filter alarm. RW x

(r

Compressor Enable Set compressor status: 0 = disable, 1 = enable. RW x 1

(1

Compressor Cooling

(2

Lockout Set point

Compressor Heating

(3

Lockout Set point

Compressor Start Delay

(6

Space Temp Sensor

SP

Offset

Keypad/display

Un

Temperature Units

1. RW = read and write capable, RO = read only.

2. If a menu value is greater than 2-digits (higher than 99), then

Adjust OA damper position above which the exhaust fan output will be energized.

EOAD

There is a fixed –5% differential associated with this set point.
Adjust OA damper minimum position when the exhaust interlock input is

OADE

energized.

OAMX Adjust OA damper maximum position. RW x 99%

Set OA damper lockout feature status: 0 = disable, 1 = enable. (This variable is
factory set to 1 when the unit is ordered as a recirc unit with no OAD.)
Adjust OA temperature below which the OA damper closes if the OA damper
lockout is enabled. (This variable is factory set to –99°C when the unit is ordered
as a recirc unit with no OAD.)

Adjust economizer OA temperature set point. DO NOT lower this set point below

ETS

CCLO or you risk creating a deadband where no cooling occurs.

ETD Adjust economizer IA/OA temperature differential. RW x 1.8°F (1°C)

EES Adjust economizer OA enthalpy set point. RW x

EED Adjust economizer IA/OA enthalpy differential. RW x

EORH Display OA humidity (optional). 00 = No sensor connected. RO x

EHS Adjust emergency heat set point. RW x

Set emergency heat operation during shutdown, 0 = no emergency heat during
shutdown: 1 = allow emergency heat during shutdown.

AHSD Adjust auxiliary heat start differential. RW x 1.8°F (1°C)

AHED Adjust auxiliary heat stop differential. RW x 1.8°F (1°C)

Set auxiliary heat type: 0 = N.O. device, 1 = N.C. device. RW x 0

Set the function external binary Input 3: 0 = ventilation lockout, 1 = exhaust
interlock.

Set the function of external binary output 3: 0 = exhaust fan on/off signal, 1 =
auxiliary heat.

Set space fan cycles (switches off) during occupied, bypass, and standby mode: 2
= continuous, 3 = cycling.

Adjust compressor cooling lockout set point. When the OA temperature falls below
this set point, compressor cooling is not allowed. DO NOT make this setting lower

CCLO

than the factory default. There is a fixed +3.6°F (2°C) differential associated with
this set point.

Adjust compressor heating lockout set point. When the OA temperature falls below

CHLO

this set point, compressor heating is not allowed and only electric heat will be used.
Adjust compressor start delay. Where several units (inductive loads) are

connected to the same electrical supply, make this set point unique for every UVC
to prevent multiple compressors from energizing at the same time after a power
failure or occupancy change.

Adjust this setting to bias the UVC measured space temperature. RW x 0

Set keypad/display temperature units in English or SI. This set point also effects
which unit types displayed over Metasys N2 and BACnet MS/TP networks using
the appropriate optional communications modules.

// will be displayed on the keypad/display.

Getting Started

RO

05

1

RW

RW x 99%

RW x 12%

RW x 0

RW x

RW x

RW x 0

RW x 0

RW x 0

RW x 2

Default

35.6°F
(2°C)

68°F

(20°C)

25 Btu/lb

(58 kJ/kg)

1.3 Btu/lb
(3 kJ/kg)

53.6°F
(12°C)

//

RW x

RW x

RW x 0 sec

RW x F

63.5°F

(17.5°C)

25°F

(-4°C)

2

McQuay OM 751 11

Description of Operation

Description of Operation

State Programming

The MicroTech II UVC takes advantage of “state” machine programming to define and
control unit ventilator operation. “State” defines specific states or modes of operation for each
process within the unit ventilator (e.g., heating, cooling, etc.) and contain the specific logic for
each state. This eliminates some of the most common problems associated with control
sequences such as the possibility of simultaneous heating and cooling, rapid cycling, etc.

State machine programming, and the unique nature of state diagrams, can be easily used to
describe operation. It can simplify sequence verification during unit commissioning, as well as
simplify troubleshooting. With the unique combination of state machine programming and the
keypad/display’s ability to allow a technician to easily determine the active UVC state,
troubleshooting the UVC can be very simple.

The state diagrams presented in the following sections consist of several “elements” including
super states, states, conditional jumps (also called transitions) and transition points. Super
states are used as a means to group two or more related states into a single control function
such as cooling, or heating, etc. States are where all the actual work takes place, within each
state the UVC enables PI-loops and other logic sequences required to control unit ventilator
operation within that particular state, while other functions and PI-loops not needed during
that state may be disabled. Conditional jumps, or transitions, are the logic paths used by the
UVC to determine which state should be made active, these are the “questions” the UVC
continually considers. The transition point is simply a point through which a number of
conditional jumps meet. Think of it as a point where a number of questions must be
considered from which the UVC then determines which path is followed and which state is
then made active.

The UVC states and super states are used to define the “normal” unit modes, such as Off,
Night Purge, Fan Only, Emergency Heat, Auto, Cool, and Heat. The UVC also supports
several “special purpose” unit modes such as Purge, Pressurize, De-pressurize, and Shutdown,
which can be forced via a network connection and override typical UVC operation.

Note – Not all states or modes are available for all UV configurations, and some states (such as

Active Dehum) are optional.

– In the state descriptions below the terms, saturated high and saturated low, indicate that

the heating or cooling function being described has reached 100% or 0%, respectively.

12 McQuay OM 751

Figure 6: Complete UVC—state diagram

Description of Operation

CantHeat

B

EmergencyHeat

ModeSuperState

FullHeat

7

CantHeat

D

HeatMode

SuperState

Off

Heat

5

LowLimit

E

NightPurge

Econ

Mech

8

FanOnly

A

AutoMode

3

1

2

DAHeat

4

LowLimit

F

9

CoolMode

SuperState

CantCool

C

EconMech

UVC Unit Modes

The UVC provides several “normal” modes of unit operation. These include: Off, Night
Purge, Fan Only, Cool, Emergency Heat, Auto, Heat, and Cool.

Normal UVC modes can contain a single state or several states depending upon the
functionality required for each particular mode. Each UVC state is assigned a number, which
can be very helpful when trying to understand which state is currently active within the UVC.
To view the current UVC state number, use the keypad/display.

McQuay OM 751 13

Description of Operation

F

Table 8: UVC state names and numbers

Normal UVC modes State names

OFF OFF 9 9 57

Night purge Night Purge 8 8 56

Fan only Fan Only 10 A 65

Emergency heat

Heat

Auto

Cool

Full Heat 7 7 55

Cant Heat 13 D 68

Heat 5 5 53
Cant Heat 11 B 66
Low Limit 14 E 69

EconMech 1 1 49

Mech 2 2 50

Econ 3 3 51

DA Heat 4 4 52
Cant Cool 12 C 67
Low Limit 15 F 70

Decimal ASCII Hex

State numbers

WARNING

Off mode is a “stop” state for the unit ventilator. It is not a “power
off” state. Power may still be provided to the unit.

OFF Mode (State 9)

Off mode is provided so that the UVC can be forced into a powered OFF condition. OFF mode
is a “stop” state for the unit ventilator; it is not a power off state. OFF mode consists of a
single UVC state: OFF [9].

When OFF mode becomes active, the UVC stops all normal heating, cooling, and ventilation
(OA damper is closed), and fan operation ends. The UVC continues to monitor space
conditions, indicate faults, and provide network communications (if connected to a network)
in the OFF mode while power is maintained to the unit.

While in OFF mode, the UVC does not maintain DA temperatures. If the space temperature
drops below EHS while in the OFF mode, the UVC is forced into the Emergency Heat mode
(see “Emergency Heat Mode (Super State)” on page 16).

The space lighting output continues to operate based upon the current occupancy mode.

Note – Special purpose unit modes such as Purge, Pressurize, and De-pressurize can force the

UVC to perform “special” functions during which the display appears to be in the OFF
mode.

Figure 7: Off state diagram

OFF

9

UVC Mode

UVC Mode ≠ OFF

=

OF

Transition

point

14 McQuay OM 751

Description of Operation

Night Purge Mode (State 8)

Night Purge mode is provided as a means to more easily and quickly ventilate a space. Night
purge can be useful in helping to remove odor build up at the end of each day, or after
cleaning, painting, or other odor generating operations occur within the space. Night Purge
mode consists of a single UVC state: Night Purge [8].

Night Purge is a full ventilation with exhaust mode, during which room comfort is likely to be
compromised. Therefore, McQuay strongly recommends using Night Purge only when the
space is unoccupied.

When Night Purge mode becomes active, the UVC stops all normal heating and cooling. Since
any new energy used to treat the incoming air would be wasted in the purge process. In the
Night Purge mode, the space fan is set to high speed, the OA damper is set to 100% open, and
the Exhaust Fan binary output (see “External Binary Outputs” on page 38) is set to ON. If the
UVC is not set to another mode within 1 hour (fixed), the UVC automatically switches to the
Fan Only mode (see “Fan Only Mode (State A)” on page 15).

While in Purge mode, the UVC does not maintain DA temperatures. If the space temperature
drops below the EHS, the UVC is forced into the Emergency Heat mode (see “Emergency
Heat Mode (Super State)” on page 16).

Figure 8: Night purge state diagram

Night Purge

8

UVC Mode ≠

Night purge

=

Transition

point

UVC Mode

Night purge

Fan Only Mode (State A)

The Fan Only mode is provided so that the UVC can be forced into a Fan Only operation via a
keypad/display or a network connection. Fan Only mode consists of a single UVC state: Fan
Only [A].

When Fan Only mode becomes active, the UVC stops all normal heating and cooling.

While in Fan Only mode, the UVC does not maintain DA temperatures. If the space
temperature drops below the EHS, the UVC is forced into the Emergency Heat mode (see
“Emergency Heat Mode (Super State)”).

Figure 9: Fan only state diagram

UVC Mode ≠

Fan Only

Fan Only

A

Transition

point

UVC Mode

Fan Only

=

McQuay OM 751 15

Description of Operation

Emergency Heat Mode (Super State)

The Emergency Heat mode is provided for situations where the UVC is in a mode that does
not normally allow heating, such as OFF, Cool, Night Purge, or Fan Only. If Emergency Heat
mode is enabled, the UVC can automatically force itself into the Emergency Heat mode from
OFF, Cool, Night Purge, Fan Only, Purge, Pressurize, De-pressurize, and Shutdown.
Emergency Heat mode consists of UVC states: Full Heat [7] and Cant Heat [D].

Software model 05 does not have the primary or secondary heating devices. The UVC uses
auxiliary heat (if field provided and field connected) when emergency heat is required.

When the Emergency Heat mode becomes active, the UVC automatically determines which
state to make active, Full Heat [7], or Cant Heat [D], based on the transitions for each of those
states.

Figure 10: Emergency heat state diagram

Emergency Heat Mode

Super State

Full Heat

≠

Heat

Available

7

Heat

Available

UVC Mode

Emergency Heat

=

UVC Mode ≠

Emergency Heat

=

Transition

point

Cant Heat

D

Full Heat State (State 7)

The Full Heat [7] state is the “normal” state that the UVC goes into when Emergency Heat
mode is active. It is activated when the space temperature is lower than the EHS.

When Emergency Heat mode becomes active, the UVC goes into 100% heating until the space
temperature raises to the EHS plus a fixed differential (5.4°F/3°C). In the Emergency Heat
mode, the space fan is set to high speed, and the OA damper operates normally.

If the UVC automatically forces itself into the Emergency Heat mode from another mode
(e.g., Cool, Fan Only, etc.), then the UVC returns to the appropriate unit mode once the space
temperature rises to the EHS plus a fixed differential (5.4°F/3°C).

The UVC monitors the DAT to ensure it does not exceed DAHL. If the DAT does exceed
DAHL, then heating is set to 0% for a minimum of 2-minutes (fixed) and until the DAT drops
36°F (20°C) fixed differential below DAHL.

Cant Heat State (State D)

The Cant Heat [D] state is a “non-normal” state that the UVC can go into when Emergency
Heat mode is active. An IAT or DAT sensor fault during Emergency Heat mode causes the
UVC to make this state active.

When the Cant Heat state becomes active, the space fan remains at high speed as set during
the Full Heat state.

The UVC will remain in the Cant Heat state until heat becomes available.

16 McQuay OM 751

Description of Operation

Auto Mode

Auto mode is provided so that the UVC can be set to automatically determine if heating or
cooling is required. Auto mode is the default power-up UVC mode. Auto mode is made up of
the Heat and Cool modes. When the UVC is set to auto mode, the UVC automatically
determines which mode (Heat or Cool) to use.

Heat Mode (Super State)

When in Heat mode, the UVC will use auxiliary heat (if field provided and field connected to
the unit) as needed to maintain the effective heating setpoint (see “Space Temperature Set
Points” on page 26). The keypad/display or a network connection can be used to force the unit
into the Heat mode. Additionally, the UVC when set to Auto mode can automatically force the
unit into the Heat mode as needed. When the UVC is in Auto mode, it is “normal” for the
UVC to “idle” in Heat mode when there is no need to switch to another mode.

The Heat mode super state consists of UVC states: Heat [5], Low Limit [E], and Cant Heat
[B].

When the Heat mode super state becomes active, the UVC automatically determines which of
the Heat Mode states to make active based upon the transitions for each state.

Figure 11: Heat mode super state diagram

Transition

point

UVC Mode = Heat

OR

=

Space

Auto AND

≠

Warm

UVC Mode ≠ Heat AND

UVC Mode

UVC Mode

Warm AND Heat Pl = Sat Low

≠

Auto

OR

=

Auto AND Space =

Heat Mode

Super State

UVC Mode

Heat

≠

Cant Heat

B

Heat

Available

Heat = Available

AND

Low Limit = Inactive

Heat = Available

AND

Low Limit = Inactive

≠

Available

Heat Pl = Sat Hi

(2 minutes)

DAT<VCLL

AND

DAT<(VCLL + 1.8F)

Low Limit

Heat

5

LLPl = Sat Lo

(2 minutes)

AND

E

Heat State (State 5)

The Heat state is the “normal” state during Heat mode. When the Heat state becomes active,
the UVC will (within State) continually calculate the DATS (“Discharge Air Temperature
Control” on page 29) required to maintain the effective heat setpoint (see “Space Temperature
Set Points” on page 26). The calculated DATS will not be allowed to go above DAHL. The
UVC will use auxiliary heat (if field provided and field connected to the unit) as needed to
maintain the current DATS.The auxiliary heat binary output will be used as needed. The Heat
Timer (3-minutes fixed) will begin counting. The CO
will be active, if the unit is equipped for CO

control (see “CO2 Demand Controlled

2

demand controlled ventilation function

2

Ventilation (optional)” on page 34), and the OA damper will be adjusted as needed to maintain
the CO

setpoint. The UVC will remain in this state until one of the transition out conditions

2

become true, or until one of the super state transition out conditions becomes true.

McQuay OM 751 17

Description of Operation

Note – The OAD is considered to be in “alarm” when the OAD is forced below the active minimum

position in the Low Limit state. This is not an actual unit “alarm” or “fault” condition, but
only a condition used for the purpose of transition arguments.

Low Limit State (State E)

The Low Limit state is a “non-normal” state the UVC can go into while Heat mode is active
when the unit reaches 100% heating and still cannot meet the current DATS (see “Discharge
Air Temperature Control” on page 29) required to maintain the effective heating set point (see
“Space Temperature Set Points” on page 26). This is likely to occur only if the OA
temperature is very cold, the OA damper minimum position is set too high, the unit ventilator
is oversized for the application, or if the electric heating has failed, or is set incorrectly.

When the Low Limit state becomes active, the Low Limit PI-loop can override the OA
damper position (see “Outdoor Air Damper Operation” on page 32) and adjust the OA damper
toward closed as necessary to maintain the current DATS (see “Discharge Air Temperature
Control” on page 29).

Cant Heat State (State B)

The Cant Heat state is a “non-normal” state the UVC can go to when Heat mode is active. An
IAT or DAT sensor fault during the Heat mode causes the UVC to make this state active.

When the Cant Heat state becomes active, no heating or ventilation takes place. The OA
damper goes to the minimum position unless it is forced closed by other functions such as
freezestat (T6) or morning warm-up.

Cool Mode (Super State)

When in Cool mode the UVC uses primary cooling (economizer) and secondary cooling
(mechanical, DX) as needed to maintain the effective cooling set point (see “Space
Temperature Set Points” on page 26). The keypad/display or network connection can be used
to force the unit into the Cool mode. When the UVC is in Auto mode, it is “normal” for the
UVC to “idle” in Cool mode when there is no need to switch to another mode. The Cool mode
super state consists of the following UVC states: Econ Mech [1], Mech [2], Econ [3], DA Heat
[4], Low Limit [F], and Cant Cool [C].

When the Cool mode super state becomes active, the UVC will automatically determine which
UVC state to make active based upon the transitions for each state.

If the space temperature drops below EHS, and the Emergency Heat function is enabled, the
UVC will be forced into the Emergency Heat mode (see “Emergency Heat Mode (Super
State)” on page 16).

18 McQuay OM 751

Figure 12: Cool mode super state diagram

Econ

EconMech

Mech

3

1

2

CantCool

C

CoolMode

SuperState

DAHeat

LowLimit

4

F

LLPI=SatLow (2min)

AND

DAT>(VCLL+1.8F)

HeatPI=SatHi(2min)

AND DAT<VCLL

Space≠HighCO2

AND

HeatPI=SatLow

AND

DAT>VCLL

Space=HighCO2

OR

DAT<VCLL

UVCMode≠Cool AND UVCMode≠Auto

OR

UVCMode=Auto AND Space=Cold AND

MechPI=SatLow(3min) AND

EconPI=SatLow

UVCMode=Cool

OR

UVCMode=Auto AND Space=Warm

Econ≠Available

AND

MechCool

≠

Available

Econ = Available

AND

MechCool

≠

Available

Econ≠Available

AND

MechCool=Available

MechPI=SatLow (3min) AND

EconMechTimer=Expired

(3 minutes) OR

MechCool

≠

Available

Econ≠Available

Econ=Available

MechCool≠Available

Econ≠Available

AND

MechCool=Available

Transition

Point

EconTimer=Expired

(3 minutes) AND

EconPI=SatHi AND

MechCool=Available

Description of Operation

Econ State (State 3)

The Econ state is a “normal” state during Cool mode. The Econ state typically is active in the
Cool mode when primary cooling (economizer) is available and adequate to meet the cooling
requirements.

When the Econ state becomes active, the UVC uses economizer cooling (see “Economizer
Operation” on page 32) as needed to maintain the effective cooling set point (see “Space
Temperature Set Points” on page 26). If cooling is not required while in the Econ state, the
UVC can “idle” in the Econ state until cooling is required or until there is a call to switch to
another mode or state.

The UVC monitors the DAT to ensure it does not fall below VCLL.

The CO
Controlled Ventilation (optional)” on page 34) and the OA damper is adjusted as needed to
maintain the CO

demand controlled ventilation function (optional) will be active (see “CO2 Demand

2

set point.

2

McQuay OM 751 19

Description of Operation

Figure 13: Econ state operation (occupied mode and auto fan)

Econ Mech State (State 1)

The Econ Mech state is a “normal” state during Cool mode. The Econ Mech state typically is
active in the Cool mode when primary cooling (economizer) alone is not adequate to meet the
cooling requirements and both primary cooling and secondary cooling (compressor) are
available.

When the Econ Mech state becomes active, the OA damper is set to 100% open, and the UVC
uses the units mechanical cooling capabilities as needed to maintain the effective cooling set
point (see “Space Temperature Set Points” on page 26).

The UVC monitors the DAT to ensure it does not fall below MCLL.

Figure 14: Econ mech state operation (occupied mode and auto fan)

Mech State (State 2)

The Mech state is a “normal” state during Cool mode. The Mech state typically is active in the
Cool mode when primary cooling (economizer) is not available and secondary cooling
(compressor) is available.

When the Mech state becomes active, the UVC uses the unit’s mechanical cooling capabilities
as needed to maintain the effective cooling set point (see “Space Temperature Set Points” on
page 26). If cooling is not required while in the Mech state, the UVC can “idle” in the Mech
state until cooling is required or until there is a call to switch to another mode or state.The
UVC monitors the DAT to ensure it does not fall below MCLL.

20 McQuay OM 751

Description of Operation

The CO2 demand controlled ventilation function (optional) is active (see “CO2 Demand
Controlled Ventilation (optional)” on page 34), and the OA damper is adjusted as needed to
maintain the CO

Figure 15: Mech state operation (occupied mode and auto fan)

set point.

2

Discharge Air (DA) Heat State (State 4)

The DA Heat state is a “normal” state during Cool mode. The DA Heat state typically is active
when reheat is required to maintain DATS while maintaining the required OA damper
position. The DA Heat state can also be made active if the optional CO
provided and CO

levels are high, requiring the OA damper to open beyond what is required

2

DCV feature is

2

for economizer cooling.

When DA Heat state is active, the UVC uses the units heating capability as needed to maintain
VCLL. The CO
Demand Controlled Ventilation (optional)” on page 34), and the OA damper is adjusted as
needed to maintain the CO

demand controlled ventilation function (optional) is active (see “CO2

2

set point.

2

Low Limit State (State F)

The Low Limit state is a “non-normal” state during Cool mode. The Low Limit state typically
follows the DA Heat state when the UVC reaches 100% heat and still cannot maintain VCLL.

When the Low Limit state becomes active, the Low Limit PI-loop overrides the OAD
minimum position (see “Outdoor Air Damper Operation” on page 32) and adjusts the OAD
toward closed as necessary to maintain the DAT set point (see “Discharge Air Temperature
Control” on page 29).

Cant Cool State (State C)

The Cant Cool state is a “non-normal” state during Cool mode. The Cant Cool state typically
becomes active when both primary (economizer) and secondary (compressor) cooling are not
available (or they are disabled) or when an IAT, DAT or OAT sensor failure occurs.

When the Cant Cool state becomes active, no cooling is available.

Special Purpose Unit Modes

There are some additional UVC modes that are considered special purpose unit modes. These
special purpose modes include Pressurize, Depressurize, Purge, Shutdown, and Energy Hold
Off. These modes force the UVC to perform very specific and limited functions. Use these
with caution and only for short periods as needed.

McQuay OM 751 21

Description of Operation

In each of these special purpose UVC modes, if the space temperature drops below EHS and
the Emergency Heat function is enabled, the UVC is forced into the Emergency Heat mode
(see “Emergency Heat Mode (Super State)” on page 16) and then return once the Emergency
Heat function is satisfied.

Table 9: Actions during special purpose unit modes

Action

Pressurize High 100% Open Off

Depressurize Off Closed On

Purge High 100% Open On

Shutdown Off Closed Off

Energy hold off Off Closed Off

Indoor air fan

(IAF)

Outdoor air

damper (OAD)

Exhaust fan

output

Pressurize Mode

When in Pressurize mode, the UVC uses the IAF, OAD, and exhaust output as needed to
pressurize the space. The UVC stops all normal heating and cooling but does allow emergency
heat if required. The pressurize mode can only be accessed via a network connection.

Depressurize Mode

When in Depressurize mode the UVC will use the IAF, OAD, and exhaust output as needed to
depressurize the space. The UVC stops all normal heating and cooling but does allow
emergency heat if required. The de-pressurize mode can only be accessed via a network
connection or with ServiceTools for MicroTech II Applied Terminal Unit Controllers (ATS).

Purge Mode

When in Purge mode, the UVC uses the IAF, OAD, and exhaust output as needed to purge the
space. The UVC stops all normal heating and cooling but does allow emergency heat if
required. The purge mode can only be accessed via a network connection or with ServiceTools
for MicroTech II Applied Terminal Unit Controllers (ATS).

Shutdown Mode

Shutdown mode is the equivalent of the Off mode, but is an Off mode forced by a network
connection. When in Shutdown mode, the UVC stops all normal heating, cooling, ventilation
(OA damper is closed), and fan operation. By default emergency heat is not be used during the
shutdown mode, however, the UVC can be configured (Emergency Heat Shutdown
Configuration) to allow emergency heat operation during shutdown mode. The shutdown
mode can be accessed via a network connection, a binary input to the UVC, or with
ServiceTools for MicroTech II Applied Terminal Unit Controllers (ATS).

WARNING

Shutdown mode and energy hold off mode are a “stop” state for
the unit ventilator. It is not a “power off” state.

Energy Hold Off Mode

The UVC supports an energy hold off state, which when active forces the UVC to stop all
normal heating, cooling and ventilation. Typically used by a network connection to force the
UVC to cease heating, cooling and ventilation when conditions exist where heating, cooling
and ventilation are not required or desired. Energy hold off mode is very similar to shutdown
mode except that energy hold off always allows emergency heat if required. The energy hold
off mode can only be accessed via a network connection or with ServiceTools for
MicroTech II Applied Terminal Unit Controllers (ATS).

22 McQuay OM 751

Description of Operation

Unit Mode Priority

The UVC uses the network variables and binary inputs listed in Table 10 and Table 11 to
determine the current unit mode. Special purpose UVC unit modes have higher priority than
the normal UVC unit modes as shown in the tables.

Each table lists the highest priority items on the left to the lower priority items to the right. The
right-most columns indicate unit operation as a result of the left-most columns. The term
“Don’t care” in these tables implies that another network variable or binary input to the left
has a higher priority.

Table 10: Special purpose UVC unit mode priority

Priority result

Emergency override

input

Normal

1

3

Pressurize Don’t care Don’t care Don’t care Off Pressurize

De-pressurize Don’t care Don’t care Don’t care Off De-pressurize

Purge Don’t care Don’t care Don’t care Off Purge

Shutdown Don’t care Don’t care Don’t care Off Off

1. Network input.

2. Network output.

3. Normal indicates the UVC power-up condition.

4. De-energized indicates that the contacts connected to this binary input are open.

5. Energized indicates that the contacts connected to this binary input are closed.

Remote shutdown

binary input

De-energized

Energized

4

5

Energy hold

off input

1

Normal Normal

Energy hold

off output

2

Unit mode

output

2

See the normal

UVC mode priority (Table 11)

Energy hold off Energy hold off Off Off

Don’t care Energy hold off Off Off

Actual UVC action

Table 11: Normal UVC mode priority

Priority result

Application override

input

1

Normal (Auto)

Heat Don’t care Heat
Cool Don’t care Cool

Night purge Don’t care Night purge

Off Don’t care Off

Emergency heat Don’t care Emergency heat

Fan only Don’t care Fan only

1. Network input.

2. Network output.

3. Normal (Auto) is the normal UVC power-up state.

Unit mode override

Normal (Auto)

3

Night purge Night purge

Emergency heat Emergency heat

input

1

Unit mode output

3

Heat

Cool

Emergency heat

Heat Heat

Cool Cool

Off Off

Fan only Fan only

2

McQuay OM 751 23

Description of Operation

Occupancy Modes

The UVC is provided with four occupancy modes: Occupied, Standby, Unoccupied, and
Bypass. The occupancy mode affects which heating and cooling temperature set points are
used, affects IAF operation, and affects OAD operation. The Manual Adjust Occupancy and
Networked Occupancy Sensor network variables, along with the Unoccupied and Tenant
Override binary inputs, are used to determine the Effective Occupancy. The term “Don’t care”
in Table 12 implies that another network variable or binary input to the left has a higher
priority.

Note – The Occupancy Override Input is provided as a way for a network connection to manually

force the UVC into a particular occupancy mode. The Occupancy Override Input can
override the tenant override feature. For example, if the network uses the Occupancy
Override Input to force the unit into unoccupied mode, then the tenant override switch
does not operate as expected. Therefore, McQuay strongly recommends using the
Occupancy Sensor Input to control occupancy modes over a network and only using the
Occupancy Override Input if there is reason to ensure tenant override does not occur.

Table 12: Occupancy mode priority

Priority result

Occupancy

Override input

Occupied Don’t care Don’t care Occupied

Unoccupied Don’t care Don’t care Unoccupied

Bypass

Standby Don’t care Don’t care Standby

Null (default)

1. Network input.

2. Network output.

3. Typical operation is defined in this row of the table.

4. The tenant override switch (unit or wall sensor mounted) can be used here to force the UVC
into bypass.

Occupancy

sensor input

Occupied Don’t care Occupied

Unoccupied Don’t care Bypass

Null (default)

Occupied Don’t care Occupied

Unoccupied Don’t care Unoccupied

3

Null (default)

Unoccupied binary input

1

Contacts open (Occupied) Occupied

Contacts Closed (Unoccupied) Bypass

Contacts open (Occupied) Occupied

Contacts closed (Unoccupied) Unoccupied

Effective

occupancy

output

2

4

4

Occupied Mode

The occupied mode is the normal day time mode of UVC operation. During occupied mode
the UVC uses the occupied heating and cooling set points, the OAD operates normally, and by
default the IAF remains on.

Unoccupied Mode

The unoccupied occupancy mode is the normal night time mode of UVC operation. During
unoccupied mode the UVC uses the unoccupied heating and cooling set points, the OAD
remains closed, and the IAF cycles as needed for heating or cooling. The IAF remains off
when there is no need for heating or cooling.

Standby Mode

The standby mode is a special purpose daytime mode of UVC operation. During standby,
mode the UVC uses the standby heating and cooling set points, the OAD remains closed, and
by default the IAF remains on.

24 McQuay OM 751

Description of Operation

Bypass Mode

The bypass mode (also called Tenant Override) is the equivalent of a temporary occupied
mode. Once the bypass mode is initiated, it remains in effect for a set period of time (120
minutes, default). During the bypass mode, the UVC uses the occupied heating and cooling set
points, the OAD operates normally, and by default the IAF remains on.

Additional Occupancy Features

Networked Occupancy Sensor Capability

A networked occupancy sensor can be interfaced with the Occupancy Sensor Input variable to
select occupancy modes. When the Occupancy Sensor Input variable is used, it automatically
overrides any hard-wired unoccupied binary input signal.

Unit-Mounted Time-Clock

An optional unit-mounted factory-installed electronic 24-hour/7-day time clock can be
provided on stand-alone unit ventilator configurations. It is factory wired to the UVC
unoccupied binary input and can be set to automatically place the unit into occupied and
unoccupied modes based upon its user configured schedule.

Unit-Mounted Tenant Override Switch

A tenant override switch is factory installed in all floor mounted units and is located near the
LUI on the unit. This switch provides a momentary contact closure that can be used by room
occupants to temporarily force the UVC into the bypass occupancy mode from unoccupied
mode.

Note – The Occupancy Override Input can override the tenant override feature. For example, if

the network uses the Occupancy Override Input to force the unit into unoccupied mode,
then the unit-mounted tenant override switch does not operate as expected. Therefore,
McQuay strongly recommends using the Occupancy Sensor Input to control occupancy
modes over a network and only using the Occupancy Override Input if there is reason to
ensure tenant override does not occur.

Remote Wall-Mounted Sensor Tenant Override Switch

The optional remote wall-mounted sensors include a tenant override switch. This switch
provides a momentary contact closure that can be used by room occupants to temporarily force
the UVC into the bypass occupancy mode from unoccupied mode.

Note – The Occupancy Override Input can override the tenant override feature. For example, if

the network uses the Occupancy Override Input to force the unit into unoccupied mode,
then the wall sensor tenant override switch does not operate as expected. Therefore,
McQuay strongly recommends using the Occupancy Sensor Input to control occupancy
modes over a network and only using the Occupancy Override Input if there is reason to
ensure tenant override does not occur.

Remote Wall-Mounted Sensor Status LED

The optional remote wall-mounted sensors each include a UVC status LED. This status LED
aids diagnostics by indicating the UVC occupancy mode and fault condition.

Table 13: Remote wall-mounted sensor status LED

Indication LED operation

Occupied On continually

Unoccupied On 1 second/off 9 seconds

Bypass On continually

Standby On 9 seconds/off 1 second

Fault On 5 seconds/off 5 seconds

McQuay OM 751 25

Description of Operation

Space Temperature Set Points

The UVC uses the six occupancy-based temperature set points as the basis to determine the
Effective Set point Output. The effective set point is calculated based on the unit mode, the
occupancy mode, and the values of several network variables. The effective set point then is
used as the temperature set point that the UVC maintains.

Table 14: Default occupancy-based temperature set points

Temperature set point Abbreviation Defaults

Unoccupied cool UCS 82.4°F (28.0°C)

Standby cool SCS 77.0°F (25.0°C)

Occupied cool OCS 73.4°F (23.0°C)

Occupied heat OHS 69.8°F (21.0°C)

Standby heat SHS 66.2°F (19.0°C)

Unoccupied heat UHS 60.8°F (16.0°C)

Networked Set Point Capability

The Space Temp Setpoint Input variable is used to allow the temperature set points for the
occupied and standby modes to be changed via the network; the unoccupied set points are not
affected by this variable.

Networked Set Point Offset Capability

The Networked Set Point Offset Input variable is used to shift the effective occupied and
standby temperature set points by adding the value of the Setpoint Offset Input variable to the
current set points; the unoccupied points are not affected by this variable. This variable is
typically set bound to a supervisory network controller or to a networked wall module having
a relative set point knob.

Use the keypad/display to make adjustments to the value of the Setpoint Offset Input variable.
See “Changing Set Points” on page 9.

Note – The keypad/display and the network both affect the Set Point Offset Input variable. Keep

in mind that changes to this variable are last-one-wins.

Networked Set Point Shift Capability

The Set Point Shift Input variable is used to shift the effective heat/cool set points. It typically
is bound to a networked supervisory controller or system that provides functions such as
outdoor air temperature compensation. All occupied, standby, and unoccupied set points are
shifted upward (+) or downward (

–) by the corresponding value of the Set Point Shift Input

variable.

Note – The Set Point Shift Input capability is not available through the BACnet® interface.

Networked Space Temperature Sensor Capability

A networked space temperature sensor can be interfaced with the Space Temp Input variable.
When the Space Temp Input variable is used (valid value), it automatically overrides the hard­wired space temperature sensor.

26 McQuay OM 751

Description of Operation

Remote Wall-Mounted Sensor with +/–3°F
Adjustment (optional)

When the optional remote wall-mounted sensor with +/–3°F adjustment dial is used, the UVC
effectively writes the value of the set point adjustment dial to the Set Point Offset Input
variable.

Note – If a network connection is used to adjust the Set Point Offset Input variable, you must not

use the optional remote wall-mounted sensor with +/–3°F adjustment.

– If the keypad/display is used by room occupants to adjust the Set Point Offset, do not use

the optional remote wall-mounted sensor with +/–3°F adjustment.
If you have the optional remote wall-mounted sensor with +/–3°F adjustment and an
occupant uses the keypad to make Set Point Offset adjustments, this overrides any
+/–3°F adjustment on the optional remote wall-mounted sensor since the keypad/display
has higher priority. If you find that changes to the +/–3°F adjustment on the remote wall­mounted sensor have no effect, it is likely that an occupant used the keypad/display to
make a Set Point Offset change. Cycle unit power to clear this situation and restore the
ability to change the Set Point Offset from the +/–3°F adjustment on the remote
wall-mounted sensor.

Remote Wall-Mounted Sensor with 55°F to 85°F
Adjustment (optional)

When the optional remote wall-mounted sensor with 55°F to 85°F adjustment dial is used, the
UVC will effectively write the value of the set point dial to the Space Temp Set Point Input
variable.

Note – If a network connection is using the Space Temp Set Point Input variable, do not use the

optional remote wall-mounted sensor with 55°F to 85°F adjustment.

– If it is intended that the LUI will be used by room occupants to adjust the Setpoint Offset,

then you must not use the optional remote wall-mounted sensor with 55
adjustment. When using the optional remote wall-mounted sensor with 55
adjustment, the UVC will ignore any Setpoint Offset changes made at the LUI.

°F to 85°F

°F to 85°F

Effective Set Point Calculations

The UVC calculates the effective set point (Effective Set Point Output) based on several
factors. These factors include the six occupancy set points for heating and cooling (Occupancy
Temperature Set Point), occupancy mode, the value of the network variables Space Temp Set
Point Input, Set Point Offset Input, and the Set Point Shift Input as well as the optional wall­mounted sensor’s set point adjustment knob. As always, network inputs have priority over
hardwired connections.

The UVC determines if heating or cooling is required based on the current unit mode (Heat/
Cool Mode Output) and then calculates the required set point for heating or cooling. After
calculating, the Effective Set Point Output network variable is set equal to the calculated set
point. The Effective Set Point Output is the temperature set point that the UVC maintains,
which normally appears on the keypad/display.

McQuay OM 751 27

Description of Operation

Figure 16: Effective set point calculations

Occupancy Temperature Setpoints
(network configuration variables)

Occupied Cooling Set Point (OCS)

Standby Cooling Set Point (SCS)

Unoccupied Cooling Set Point (UCS)

Occupied Heating Set Point (OHS)

Standby Heating Set Point (SHS)

Unoccupied Heating Set Point (UHS)

Space Temp
Set Point Input
(network input)

WallSensorType

Config. Value

Set Point

Offset Input

(network input)

SetptShift (network inputs)

Occupied Cooling Set Point Shift (OCSS)

Standby Cooling Set Point Shift (SCSS)

Unoccupied Cooling Set Point Shift (UCSS)

Occupied Heating Set Point Shift (OCSS)

Standby Heating Set Point Shift (SHSS)

Unoccupied Heating Set Point Shift (UHSS)

Network Value

55°F/85°F

Wall Sensor

1

0

+3°F/–3°F

Wall Sensor

Local User

Interface

+5°F/–5°F

Network Value

Set Point

SetptOffset

Effective Set Point Calculations for each Occupancy Mode

AbsOffsetOccupied = Setpoint - (OCS + OHS)/2
AbsOffsetStandby = Setpoint - (SCS + SHS)/2

Occupied and Bypass Modes
EffectiveCoolSetpoint = OCS + AbsOffsetOccupied + SetptOffset + OCSS
EffectiveHeatSetpoint = OHS + AbsOffsetOccupied + SetptOffset + OHSS

Standby Mode
EffectiveCoolSetpoint = SCS + AbsOffsetStandby + SetptOffset + SCSS
EffectiveHeatSetpoint = SHS + AbsOffsetStandby + SetptOffset + SHSS

Unoccupied Mode
EffectiveCoolSetpoint = UCS + UCSS
EffectiveHeatSetpoint = UHS + UHSS

If both entering paths have
valid values, then the network
value has priority.

If both entering paths have
valid values, then the keypad/display value
has priority.

Table 15: Set point calculation examples

Given

OccupancyMode = Occupied or BypassHeat/CoolMode = Heat

SpaceTempSetpoint = (not used)

SetpointOffset = (not used) = 0.0°F

SetpointShift = (not used) = 0.0°F

OHS = 69.8°F

Example A

Effective set point calculations

EffectiveSetpoint = OHS + SetpointOffset + SetpointShift = 69.8 + 0.0 + 0.0 = 69.8°F

Given

OccupancyMode = Occupied or BypassHeat/CoolMode = Heat

SpaceTempSetpoint = 71.0°F

SetpointOffset = -1.0°F (occupant adjustment on remote wall sensor, or LUI)

SetpointShift = (not used) = 0.0°F

OCS = 73.4°F, OHS = 69.8F

Effective set point calculations

Example B

AbsoluteOffset = (OCS – OHS) / 2 =(73.4°F – 69.8°F) / 2 = 1.8°F

EffectiveSetpoint = SpaceTempSetpoint – AbsoluteOffset + SetpointOffset + SetpointShift = 71.0 -

1.0 - 1.0 + 0.0 = 68.2°F

28 McQuay OM 751

Proportional Integral (PI) Control Loops

The MicroTech II UVC uses PI-loop control for heating, cooling and ventilation processes

within the unit ventilator. Numerous PI algorithms can be used depending upon the unit

ventilator configuration. The UVC uses “single” and “cascading” PI loops where needed.

Table 16: PI loop list

PI loops PI loop type Set point

PI-1 Space Temperature

PI-2 Primary Cooling (Economizer)

PI-3 Secondary Cooling

PI-4 Primary Heating

PI-5

PI-6 Low Limit Single

CO2 (optional) Single Effective CO2 Setpoint Space CO

Cascading

Effective Heating or Cooling

Temperature Setpoint

Calculated Discharge Air Temperature

Setpoint Output

Calculated Discharge Air Temperature

Setpoint Output

Calculated Discharge Air Temperature

Setpoint Output

Calculated Discharge Air Temperature

Setpoint

Feedback

(controlled

variable)

Space Temperature

Discharge Air

Temperature

Discharge Air

Temperature

Discharge Air

Temperature

2

Discharge Air

Temperature

Description of Operation

Output

Calculated Discharge Air

Temperature Setpoint Output

Position the OA Damper

Operate the Compressor

Position the Wet Heat Valve or

F&BP Damper

Position the OA Damper

Position the OA Damper

Figure 17: PI loop graphic for CO

CO

Effective

2

set point

+

-

Space CO

sensor

PI - 5

2

2

Position the
OA damper

Discharge Air Temperature Control

The UVC uses two “cascading” PI loops to aid in providing very stable space temperature

control. The Space Temperature PI-loop is used to calculate the Discharge Air Temperature

Setpoint Output required to meet the Effective Temperature Setpoint Output. A second PI-loop

(Primary Cooling, Secondary Cooling, or Primary Heating) is then activated to control the

heating or cooling device required to achieve the calculated Discharge Air Temperature

Setpoint Output.

Figure 18: Cascading PI loop graphic 1 (primary heat)

Figure 19: Cascading PI loop graphic 2 (primary cool—economizer)

McQuay OM 751 29

Description of Operation

PI Control Parameters

Associated with each PI loop is a set of two adjustable parameters: Proportional Band and
Integral Time. When the unit ventilator is properly sized for the space, the factory settings for
these parameters provides the best and most robust control action (see Figure 20).

If field problems arise, first ensure these parameters are set back to the factory default settings.
If adjustment is required, only make small adjustments to one parameter at a time. After each
adjustment, allow enough time for the system to stabilize before making further adjustments.
If you do not have the means to graph the space performance, record the actual measured
value and set point for several minutes and then plot the results using a spreadsheet to
determine the correct action to change the PI parameter.

CAUTION

Adjusting PI parameters can cause erratic unit operation,
and potentially damage the equipment.

PI control parameters should only be adjusted by trained
personnel having a complete understanding of how these
parameters affect system operation. Generally these parameters
do not need to be adjusted from the factory default settings.

Figure 20: Optimized PI loop control

Proportional Band

The proportional band, or proportional action, causes the controlled output to changes in
proportion to the magnitude of the difference between the sensor value and set point.

A proportional band setting that is too small (see Figure 21) causes control oscillations that go
fully above and below the set point.

Figure 21: Proportional bands

A proportional band setting that is too large (see Figure 21) causes an offset between the actual
measured oscillation center and the set point. A small offset is not necessarily a problem since
most systems have a small “natural” offset and the integral function automatically works to
eliminate or reduce this effect.

30 McQuay OM 751

Description of Operation

In general, it is best to start with a relatively large proportional band setting (the factory

default setting is best) and adjust to smaller values.

If you want the system to respond strongly to small changes in the space, adjust the

proportional band to a higher setting.

If you want the system to react weakly to small changes in the space, adjust the proportional

band to a higher setting.

Integral Time

The integral time, or integral action, causes the controlled output to change in proportion to

time difference between the sensor value and set point. The difference over time between the

actual value and set point forms an “area under the curve” (see Figure 22). The integral action

works to reduce this “area under the curve” and to eliminate any natural system offset.

Figure 22: Integral time

Area Under The Curve

Too Small

The smaller the integral time, the faster the output ramps up or down with small changes in the

space. The smaller the integral time, the quicker the system reacts to small changes in the

space. If the Integral Time is set too small, long oscillations occur (see Figure 22).

In general, it is best to start with a relatively large integral time setting (the factory default

setting is best) and adjust to smaller values. If you want the system respond strongly to small

changes in the space, lower the integral time. If you want the system to react weakly to small

changes in the space, adjust the integral time to a higher setting.

Indoor Air Fan Operation

The UVC supports a three-speed indoor air (IA) fan; low, medium, and high. The UVC

calculates the effective fan speed and operation based on the unit mode, the occupancy mode,

and the values of several network variables.

Auto Mode

The UVC is provided with a user selectable auto fan mode feature. When in auto fan mode,

the UVC uses the space temperature PI loop to automatically adjust the fan speed as needed to

maintain space temperature. This ensures that the UVC maintains the lowest and quietest fan

speeds whenever possible. When in auto fan mode, a maximum of six fan speed changes per

hour is allowed (by default). This prevents frequent automatic fan speed changes from

disturbing room occupants.

Occupied, Standby, and Bypass Operation

During occupied standby and bypass modes, the IA fan, by default, remains On.

McQuay OM 751 31

Description of Operation

Unoccupied Operation

During unoccupied mode, the IA fan typically remains off and cycles with calls for heating
and cooling.

Cycle Fan

The UVC is provided with a Fan Cycling Configuration variable that can be used to force the
IA fan to cycle with calls for heating and cooling during the occupied, standby, and bypass
occupancy modes. When the fan is off, the OA damper is closed. McQuay recommends using
this feature only when it is acceptable that normal ventilation is not required.

When the IA fan is set to cycle, the UVC is configured to continue fan operation for a time
period after heating or cooling is complete.

Off Delay

When the UVC is placed into off mode or shutdown mode, the UVC is configured to continue
fan operation for a short time period and then shutdown.

Outdoor Air Damper Operation

The UVC is configured for an OA damper operated by a floating-point actuator. The OA
damper actuator contains a spring that ensures the OA damper is closed upon loss of power.
The floating-point actuator is driven by the UVC using two binary (Triac) outputs. The OA
damper typically is open to the current minimum position during the occupied and bypass
occupancy modes and closed during the unoccupied and standby occupancy modes.

A Triac output is best tested under load using a 24 V relay for verification. To verify:

1 Put a relay across the Triac outputs.

2 Cycle the power.

3 Verify the relay’s closed contacts during calibration.

Minimum Position

The UVC is configured to maintain three OA damper minimum positions based on the
operation of the IAF fan. This allows each unit to be field configured to provide the amount of
fresh air required to the space at each of the three IA fan speeds.

Table 17: Default OA damper minimum positions

IAF speed Without CO

High 20% 5%

Medium 25% 5%

Low 30% 5%

Note – If the CO2 Demand Controlled Ventilation (DCV) option is used, the UVC only uses the IA

fan high speed OA damper minimum position regardless of fan speed. The DCV function
adjusts the OA damper above this minimum as needed to maintain CO

2

With CO

2

set point.

2

Economizer Operation

The economizer function is used by the UVC to determine if the OA is adequate for
economizer (primary) cooling. When both the economizer and mechanical cooling are
available, the economizer is used as primary cooling and the UVC adds mechanical cooling
only if the economizer is not adequate to meet the current cooling load (e.g., the OA damper
reaches 100% and cooling is still required).

The UVC supports three economizer functions:

• Basic (default)—Temperature Comparison Economizer

32 McQuay OM 751

Description of Operation

• Expanded (optional)—Temperature Comparison with OA Enthalpy Setpoint Economizer
(Strategy 1)

• Leading Edge (optional)—Temperature Comparison with Enthalpy Comparison Economizer
(Strategy 2)

Temperature Comparison Economizer (default)

If the default Basic economizer function is selected, the unit ventilator is provided from the
factory without the optional IA and OA humidity sensors. In this case, the UVC is factory set
for Economizer Strategy 1—the UVC automatically detects that no OA humidity sensor is
present and adjusts to use the Temperature Comparison Economizer function.

Temperature Comparison with OA Enthalpy Setpoint Economizer (optional)

If the optional Expanded economizer function is selected, the unit ventilator is provided from
the factory with the optional OA humidity sensor, which is used along with the OA
temperature sensor to calculate OA enthalpy. In this case, the UVC is factory set for
Economizer Strategy 1 and uses the Temperature Comparison with OA Enthalpy Setpoint
Economizer function.

Note – Temperature Comparison with OA Enthalpy Setpoint Economizer requires an optional OA

humidity sensor.

Temperature Comparison with Enthalpy Comparison Economizer (optional)

If the optional Leading Edge economizer function is selected, the unit ventilator is provided
from the factory with both the IA humidity and OA humidity sensors, which are used along
with the IA temperature and OA temperature sensors to calculate IA enthalpy and OA
enthalpy. In this case, the UVC is factory set for Economizer Strategy 2 and uses the
Temperature Comparison with Enthalpy Comparison Economizer function.

Note – Temperature Comparison with Enthalpy Comparison requires both an optional OA

humidity sensor and an optional IA humidity sensor.

Table 18: Economizer enable/disable tests defined

Economizer

Tests

enable/disable tests

A OA temp set point EffectiveOATemp < (EconOATempSetpt – EconTempDiff) EffectiveOATemp >= EconOATempSetpt
B IA/OA differential temp EffectiveOATemp < (EffectiveSpaceTemp – 3.6°F – EconTempDiff) EffectiveOATemp >= (EffectiveSpaceTemp – 3.6°F)

C OA enthalpy set point

IA/OA differential

D

enthalpy

EffectiveOAEnthalpy < (EconOAEnthalpySetpt –

EffectiveOAEnthalpy < (EffectiveSpaceEnthalpy –

Table 19: How economizer enable/disable tests are selected

Economizer

strategy

All

Basic

Expanded Reliable Reliable Don’t care Reliable

Leading Edge

Space temp sensor OA temp sensor

Unreliable Don’t care Don’t care Don’t care OA damper closed

Don’t care Unreliable Don’t care Don’t care OA damper closed

Reliable Reliable Don’t care Unreliable Test B
Reliable Reliable Don’t care Reliable Test C

Reliable Reliable Reliable Reliable Test D and Test B
Reliable Reliable Unreliable Reliable Test B
Reliable Reliable Reliable Unreliable Test B
Reliable Reliable Unreliable Unreliable Test B

Note: The hard-wired sensor and the equivalent input must both be unreliable for the value to be considered

unreliable.

Enable test Disable test

EconEnthalpyDiff)

EconEnthalpyDiff)

Space humidity

sensor

EffectiveOAEnthalpy >= EconOAEnthalpySetpt

EffectiveOAEnthalpy >= EffectiveSpaceEnthalpy

OA humidity sensor

Economizer enable/

disable tests

Test C and Either

Tes t B or Te s t A

McQuay OM 751 33

Description of Operation

Networked Space Humidity Sensor Capability

A networked space humidity sensor can be network interfaced with the Space Humidity Input
variable. When the Space Humidity Input variable is used (valid value), it automatically
overrides the hard-wired space humidity sensor (if present).

Networked Outdoor Humidity Sensor Capability

A networked outdoor humidity sensor can be network interfaced with the Outdoor Humidity
Input variable. When the Outdoor Humidity Input variable is used (valid value), it
automatically overrides the hard-wired outdoor humidity sensor (if present).

CO2 Demand Controlled Ventilation (optional)

Ventilation equipment typically uses fixed damper positions to determine the amount of OA
for proper ventilation within the space. Most commonly, the fixed position of the OA damper
is based on the maximum number of occupants the space is designed to accommodate.
However, this fixed OA damper operation ignores the fact that most spaces during the day
have varying occupancy levels and may only rarely reach maximum design occupancy levels.
This type of fixed damper control for ventilation is energy wasteful since you are treating OA
not actually needed for ventilation during low occupancy levels.

People produce CO

when they breath; the CO2 level within the space has a direct relationship

2

with the number of people within that space.

The UVC can optionally be factory configured to provide CO
Ventilation (DCV). The CO

DCV function is useful in saving the energy typically wasted in

2

-based Demand Controlled

2

treating OA not actually needed for ventilation within a space during occupancy levels below
maximum design. The CO
above the minimum position as needed to maintain the Space CO

DCV function uses a PI-loop control to adjust the OA damper

2

Setpoint (1200 PPM

2

default).

The minimum damper position used with CO
minimum position that would be used without CO
damper position typically is 20% then when using CO

DCV typically can be set at ~20% of the

2

DCV. For example, if the minimum OA

2

DCV, you could set the new minimum

2

OA damper position as low as 4% (e.g., 20% × 0.20 = 4%). This new, smaller minimum OA
damper position then should provide enough ventilation to keep odors in check within the
space for most applications.

Note – The CO2 DCV function can increase the OA damper position past that required by the

economizer and vice versa.

– If odors within the space become a problem, increase the OA damper minimum position

as needed to eliminate these odors. It may be necessary with new construction or after
renovation to raise the minimum position for some time period to help reduce odor build­up due to the out-gassing of new construction material and then return the minimum OA
damper position at a later date.

– If the CO

fan high speed OA damper minimum position regardless of fan speed. The DCV function
adjusts the OA damper above this minimum as needed. In this case, the IA fan high speed
OA damper minimum position is factory set at 5%.

Demand Controlled Ventilation (DCV) option is used, the UVC only uses the IA

2

Networked Space CO2 Sensor Capability

A networked space CO2 sensor can be network interfaced with the Space CO2 Input variable.
When the Space CO
wired space CO

34 McQuay OM 751

Input variable is used (valid value), it automatically overrides the hard-

2

sensor (if present).

2

Description of Operation

)

ASHRAE Cycle II

The UVC supports ASHRAE Cycle II operation. The basis of ASHRAE Cycle II is to
maintain the required minimum amount of ventilation whenever possible, which can be
increased during normal operation for economizer cooling or CO

DCV control or reduced to

2

prevent excessively cold discharge air temperatures.

A discharge air temperature sensor is installed in all unit ventilators. If necessary, the
ASHRAE II control algorithm overrides room control and modifies the heating, ventilating,
and cooling functions (as available) to prevent the discharge air temperature from falling
below the VCLL set point.

Compressor Operation

The UVC is configured to operate the compressor as secondary (mechanical) cooling when the
economizer is available. When the economizer is not available and the compressor is
available, the UVC uses the compressor when cooling is required.

Compressor Envelope

The compressor envelope protects the compressor from adverse operating conditions that can
cause damage and or shortened compressor life by ending compressor operation if coil
temperatures exceed the defined operating envelope.

For self-contained units, the UVC is configured to monitor both the inside air/refrigerant and
outside air/refrigerant coil temperatures to prevent compressor operation under adverse
conditions.

For split-system units, the UVC is configured at the factory to only monitor the inside air/
refrigerant coil as part of the compressor envelope function.

Figure 23: Compressor envelope in self-contained units

DX cooling

160˚F (71.1˚C)

2

40˚F (4.4˚C)

(indoor air coil)

Evaporator temperature

Condenser temperature

Area for compressor operation envelope.

1 Area where liquid slugging could occur.

2

Area where starving could occur.

1

28˚F (-2.2˚C) 120˚F (48.9˚C

(outdoor air coil)

Compressor Cooling Lockout

The UVC is configured to lockout compressor cooling when the OA temperature falls below
the Compressor Cooling Lockout set point (63.5°F/17.5°C). Below this point, only
economizer cooling is available.

McQuay OM 751 35

Description of Operation

Compressor Minimum On and Off Timers

The UVC is provided with minimum On (3-minute default) and minimum Off (5-minute
default) timers to prevent adverse compressor cycling.

Compressor Start Delay

The UVC is provided with a Compressor Start Delay configuration variable, which is intended
to be adjusted as part of the start-up procedure for each unit. This variable is used to delay
compressor operation each time the compressor is required.

Note – To prevent strain on a building’s electrical supply system from multiple unit compressors

all starting at the same time after a power failure or after an unoccupied-to-occupied
changeover, McQuay strongly recommends configuring each unit or groups of units at
start-up with different start delays.

Outdoor Air Fan Operation

The UVC is configured with a fan on delay that delays OA fan operation for a time period (10
seconds, default) after the compressor starts. The OA fan stops with the compressor.

Floating-Point Actuator Auto-Zero, Overdrive and Sync

The UVC at power-up auto-zeros all floating-point actuators (OA damper) before going into
normal operation to ensure proper positioning. During auto-zero, the unit remains off. The
actuators all open approximately 30% and then are driven full closed. The overdrive feature
then is used to continue forcing the actuators closed for one full stroke period. Once the
zeroing process is complete, normal unit operation begins.

The UVC is configured such that whenever a floating-point actuator is commanded to go to
0% or 100%, the UVC overdrives the actuator one full stroke period past the 0% or 100%
position to ensure proper positioning.

Additionally, the UVC is configured to sync all floating-point actuators once every six hours
of operation. To do this, the UVC forces the actuator to the closest rail position (0% or 100%),
uses the overdrive feature, and then returns to the required position. For example, if the
actuator is at 20% when the six-hour limit is reached, the UVC then forces the actuator to 0%,
overdrive for one full stroke and then returns to the 20% position.

36 McQuay OM 751

Description of Operation

External Binary Inputs

The UVC is provided with three binary inputs that provide the functions described below.

Figure 24: Binary inputs

Binary Inputs

3 sets of dry contacts to signal UVC

Input 1: Unoccupied (default)

Input 2: Remote shutdown

Input 3: Ventilation lockout (default)

or

Exhaust interlock system

These inputs each allow a single set of dry contacts to be used as a signal to the UVC. Multiple
units can be connected to a single set of dry contacts. For wiring examples, see MicroTech II
Unit Ventilator Controller IM 747.

Note – Not all of the functions listed can be used at the same time. The UVC is provided with

configuration parameters that can be adjusted to select which function is used for these
inputs where multiple functions are indicated below.

External Binary Input 1

This input can be configured as an unoccupied (default) or dew point/humidity signal.

Unoccupied Input Signal

This input allows a single set of dry contacts to be used to signal the UVC to go into
unoccupied or occupied mode. When the contacts close, the UVC goes into unoccupied mode.
When the contacts open, the UVC goes into occupied mode. Additional variables can effect
occupancy mode and override this binary input. See “Occupancy Modes” on page 24.

External Binary Input 2

This input can only be used for remote shutdown.

Remote Shutdown Input Signal

This input allows a single set of dry contacts to be used to signal the UVC to go into shutdown
mode. When the contacts close (shutdown), the UVC goes into shutdown mode. When the
contacts open. the UVC returns to normal operation. See “Special Purpose Unit Modes” on
page 21.

External Binary Input 3

This input can be configured as a ventilation lockout (default) or exhaust interlock signal.

Ventilation Lockout Input Signal

This input allows a single set of dry contacts to be used to signal the UVC to close the OA
damper. When the contacts close (ventilation lockout signal), the UVC closes the OA damper.
When the contacts open, the UVC returns to normal OA damper operation.

McQuay OM 751 37

Description of Operation

Exhaust Interlock Input Signal

This input allows a single set of dry contacts to be used to signal the UVC that an exhaust fan
within the space is energized. The UVC repositions the OA damper to a user adjustable
minimum position (Exhaust Interlock OA Damper Min Position Setpoint). When the contacts
close (exhaust fan on signal), the UVC uses the value defined by the Exhaust Interlock OA
Damper Min Position Setpoint as the new minimum OA damper position regardless of IA fan
speed. When the contacts open, the UVC returns to normal OA damper operation.

External Binary Outputs

The UVC is provided with three binary outputs that provide the functions described below.

Figure 25: Binary outputs

Binary Outputs

3 relay type outputs w/signal voltage

Output 1: Relay output for light signal

Output 2: Fault signal

Output 3: Exhaust fan operation (default)

or

Auxiliary heat device

These outputs are relay type outputs that are intended to be used with signal level voltages (24
VAC maximum) only. For wiring examples, see MicroTech II Unit Ventilator Controller IM

747.

Note – Not all of the functions listed can be used at the same time. The UVC is provided with

configuration parameters that can be adjusted to select which function will be used for
these outputs when multiple functions are indicated below.

External Binary Output 1

This output can only be used as a signal for space lights.

Lights On/Off Signal

This relay output provides one set of Normally Open dry contacts that can be used to signal
the operation of the space lights. When the UVC is in occupied, standby, or bypass occupancy
modes, the relay output signals the lights ON (contacts closed). When the UVC is in
unoccupied occupancy mode, the relay output signals the lights OFF (contacts open).

External Binary Output 2

This output can only be used as a fault signal.

Fault Signal

This relay output provides Normally Open, Normally Closed, and Common connections that
can be used to signal a fault condition. When a fault exists, the UVC energizes this relay
output. When the fault or faults are cleared, the UVC de-energizes this relay output.

External Binary Output 3

This output can only be used to signal exhaust fan operation (default) or operate an auxiliary
heat device.

38 McQuay OM 751

Description of Operation

Exhaust Fan ON/OFF Signal

This relay output provides one set of Normally Open dry contacts that can be used to signal
the operation of an exhaust fan. When the OA damper opens more than the Energize Exhaust
Fan OA Damper set point, then the relay output signals the exhaust fan ON (contacts closed).
When the OA damper closes below this set point, the relay output signals the exhaust fan OFF
(contacts open).

Auxiliary Heat Signal

This relay output provides one set of Normally Open dry contacts that can be used to operate
an auxiliary heat device. The UVC by default is configured to operate a Normally Open
auxiliary heat device (de-energize when heat is required), such as a wet heat valve actuator
with a spring setup to open upon power failure. However, the Auxiliary Heat Configuration
variable can be used to set the UVC to use a Normally Closed auxiliary heat device (energize
when heat is required), such as electric heat.

Table 20: Auxiliary heat start/stop calculation

Start/Stop Calculation

Auxiliary heat
starts when:

Auxiliary heat
stops when:

Primary Heat PI-Loop = saturated high (100%) for
more than two minutes
AND

≤

EffectiveSpaceTemp
AuxiliaryHeatStartDifferential
EffectiveSpaceTemp ≥ (EffectiveSetpoint –
AuxiliaryHeatStartDifferential) +
AuxiliaryHeatStopDifferential

EffectiveSetpoint –

McQuay OM 751 39

UVC Input and Output Table

UVC Input and Output Table

All UVC input and output connections and their corresponding unit ventilator usage are shown
in the following table.

Table 21: Inputs and outputs, software model 05—DX cooling only

I/O Description

BO-1 Inside Fan High
BO-2 Inside Fan Medium
BO-3 Electric Heat 1
BO-4 Electric Heat 2
BO-5 Electric Heat 3
BO-6 External Output Option 2: Fault Indication
BO-7
BO-8
BO-9 Compressor

2

BI-1 Condensate Overflow
BI-2
BI-3

External Input Option 3:Ventilation Lockout (default) or Exhaust

BI-4

Interlock

3

BI-5 External Input Option 2: Remote Shutdown
BI-6 External Input Option 1: Unoccupied (default)
BI-7
BI-8

BI-9
BI-10
BI-11
BI-12 DX Press Switch (NC)

4

AI-1 IA Temp. Sensor + T.O.

AI-2 Remote Setpt. Adjust. Pot.

AI-3 OA Coil DX Temp Sensor

5

AI-4 OA Temp Sensor

AI-5 IA Coil DX Temp Sensor

AI-6 DA Temp Sensor

Expansion board

xBO-1 External Output Option 1: Lights On/Off

xBO-2

External Output Option 3: Exhaust Fan On/Off (default) or
Auxiliary Heat

1

xBO-3 OA Damper Open
xBO-4 OA Damper Close
xBO-5
xBO-6
xBO-7 Outdoor Fan
xBO-8 Inside Fan Low

xAI-1 IA Humidity Sensor
xAI-2 OA Humidity Sensor
xAI-3 Indoor CO2 Sensor

5

6

6

6

xAI-4

1. Field selectable external output options (all possible options are shown).

2. This is the condensing unit on/off signal on split-systems.

3. Field selectable external input options (all possible options are shown).

4. DX pressures switch not installed on split-systems; this input is then wired
for constant no-fault condition.

5. Not installed or wired on split-systems.

6. Optional.

1

3

1

40 McQuay OM 751

Diagnostics and Service

Diagnostics and Service

The most important aspect of troubleshooting unit ventilator controls is to isolate the source of
the problem into one of two categories:

1 The problem resides within the UVC.

2 The problem is external to the UVC. Under most circumstances the problem is external to

the UVC.

Alarm and Fault Monitoring

The UVC is programmed to monitor the unit for specific alarm conditions. If an alarm
condition exists, a fault occurs. When a fault exists, the following occurs:

• The UVC indicates the fault condition by displaying the fault code on the keypad/display.

• The remote wall-mounted sensor (optional) LED flashes a pattern indicating that a fault

condition exists.

• The fault signal binary output energizes.

• The fault performs the appropriate control actions as described for each fault.

Manual reset faults can be reset in one of three ways:

• By cycling the unit power.

• Via the keypad/display menu.

• Via the network interface.

Table 22: Alarm and fault code summary

Priority Fault description Reset

1 Space Temp Sensor Failure Auto
2 DX Pressure Fault 2-Auto in 7 days, then Manual

Compressor Envelope Fault 2-Auto in 7 days, then

3

4 Discharge Air DX Cooling Low Limit Indication Auto
5 Condensate Overflow Indication Auto
6 Space Coil DX Temp Sensor Failure Auto
7 Outdoor Temp Sensor Failure Auto
8 Discharge Air Temp Sensor Failure Auto

9 Water Coil DX Temp Sensor Failure Auto
10 Water-out Temp Sensor Failure Auto
11 Space Humidity Sensor Failure Auto
12 Outdoor Humidity Sensor Failure Auto
13 Space CO2 Sensor Failure Auto
14 Not used
15 Not used
16 Change Filter Indication Manual
17 EPROM Memory Indicator Replace conroller board
18 Configuration Display Download file

* Rev 1_27 has auto reset

Manual*

Keypad/

display fault

codes

F0
F1

F2

F3
F4
F5
F6
F7
F8
F9
FA
Fb
FC
Fd
FE
FF
EE

--

McQuay OM 751 41

Diagnostics and Service

Space Temp Sensor Failure (F0)

The Space Temp Sensor Failure fault occurs when the UVC detects open or short conditions
from the sensor.

Effect:

• Space fan de-energizes (unless in emergency heat mode).

• Compressor immediately de-energizes.

• Outdoor fan (if present) de-energizes.

• Outside air damper is forced closed.

• Electric heat stages are de-energized.

• Fault is indicated.

DX Pressure Fault (F1)

The DX Pressure Fault occurs when the UVC detects a switch open condition from the
refrigerant pressure switch.

Effect:

• Compressor immediately de-energizes.

• Outdoor fan (if present) de-energizes.

• Fault is indicated.

Compressor Envelope Fault (F2)

The UVC monitors refrigerant temperatures. The Compressor Envelope Fault occurs when the
UVC detects compressor operation that exceeded the allowed operating parameters.

Effect:

• Compressor immediately de-energizes.

• Outdoor fan (if present) de-energizes.

• Fault is indicated.

Cause:

• Poor air or water flow through the refrigerant coils. Check fans for proper rpm. Check air
filters.

• If the unit has a three-phase scroll compressor, check for proper electrical phasing.

• Refrigerant circuit component failure or improper adjustment. Check refrigerant pressures

and TXV adjustment.

• Coil sensors may have lost proper contact with the refrigerant coil. Check coil sensors.

Discharge Air DX Cooling Low Limit Indication (F3)

The Discharge Air DX Cooling Low Limit Indication fault occurs when the UVC detects a
low discharge air temperature (DAT < MCLL) during compressor cooling.

Effect:

• Compressor immediately de-energizes.

• Outdoor fan (if present) de-energizes.

• Fault is indicated (on earlier software versions).

42 McQuay OM 751

Diagnostics and Service

Condensate Overflow Indication (optional) (F4)

The Condensate Overflow Indication fault will occur when the UVC detects high condensate
levels within the units indoor coil drain pan.

Effect:

• Compressor is immediately de-energized if in cooling.

• Outdoor fan (if present) is de-energized.

• Fault is indicated.

Space Coil DX Temp Sensor Failure (F5)

The Space Coil DX Temp Sensor Failure fault occurs when the UVC detects open or short
conditions from the sensor.

Effect:

• Compressor immediately de-energizes.

• Outdoor fan (if present) de-energizes.

• Fault is indicated.

Outdoor Temp Sensor Failure (F6)

The Outdoor Temp Sensor Failure fault occurs when the UVC detects open or short conditions
from the sensor.

Effect:

• Outside air damper is forced closed.

• Compressor immediately de-energizes.

• Fault is indicated.

Discharge Air Temp Sensor Failure (F7)

The Discharge Air Temp Sensor Failure fault occurs when the UVC detects open or short
conditions from the sensor. Emergency heat mode is available during this fault condition.

Effect:

• Space fan is immediately de-energized (unless in emergency heat mode).

• Outside air damper is forced closed.

• Electric heat stages are de-energized.

• Compressor immediately de-energizes.

• Outdoor fan (if present) immediately de-energizes.

• Fault is indicated.

Outdoor Coil DX Temp Sensor Failure (F8)

The Outdoor Coil DX Temp Sensor Failure fault occurs when the UVC detects open or short
conditions from the sensor.

Effect:

• Compressor immediately de-energizes.

• Outdoor fan (if present) de-energizes.

• Fault is indicated.

McQuay OM 751 43

Diagnostics and Service

Space Humidity Sensor Failure (optional) (FA)

The Space Humidity Sensor Failure fault occurs when the UVC detects open or short
conditions from the sensor.

Effect:

• IA/OA Enthalpy comparison economizer (if used) is disabled.

• Dehumidification function (optional) is disabled.

• Fault is indicated.

Outdoor Humidity Sensor Failure (optional) (Fb)

The Outdoor Humidity Sensor Failure fault occurs when the UVC detects open or short
conditions from the sensor.

Effect:

• IA/OA Enthalpy comparison or OA Enthalpy economizer (if used) is disabled.

• Fault is indicated.

Space CO2 Sensor Failure (optional) (FC)

The Space CO2 Sensor Failure fault occurs when the UVC detects open or short conditions
from the sensor.

Effect:

• CO

Demand Controlled Ventilation function is disabled.

2

• Fault is indicated.

Change Filter Indication (FF)

The Change Filter Indication fault occurs when the UVC calculates that the total fan run time
has exceeded the allowed number of hours since the last filter change.

Effect:

• Fault is indicated.

EPROM Memory Indicator (EE)

The EPROM Memory Indicator occurs when an unusual electrical event has scrambled the
EPROM memory within the controller board. In the event that this happens, the controller
board must be replaced.

Configuration Display (--)

The Configuration Display occurs when the display file “**.cfg” is incorrect or has not been
downloaded with the appropriate file from service tools.

Troubleshooting Temperature Sensors

The UVC is configured to use passive positive temperature coefficient (PTC) sensor whose
resistance increases with increasing temperature. The element has a reference resistance of
1035 ohms at 77°F (25°C). Each element is calibrated according to the tables shown.

Use the following procedure to troubleshoot a suspect sensor.

1 Disconnect both sensor leads from the UVC.

2 Using some other calibrated temperature sensing device, take a temperature reading at the

sensor location.

44 McQuay OM 751

Diagnostics and Service

3

Use the temperature reading from Step 2 to determine the expected sensor resistance from
Table 23 .

4 Using a calibrated ohmmeter, measure the actual resistance across the two sensor leads.

5 Compare the expected resistance to the actual resistance.

6 If the actual resistance value deviates substantially (more than 10%) from the expected

resistance, replace the sensor.

Table 23: Temperature versus resistance

°F (°C) Resistance in ohms °F (°C) Resistance in ohms

–40 (–40) 613 113 (45) 1195
–31 (–35) 640 122 (50) 1237
–22 (–30) 668 131 (55) 1279
–13 (–25) 697 140 (60) 1323

–4 (–20) 727 149 (65) 1368

5 (–15) 758 158 (70) 1413

14 (–10) 789 167 (75) 1459

23 (–5) 822 176 (80) 1506

32 (0) 855 185 (85) 1554

41 (5) 889 194 (90) 1602
50 (10) 924 203 (95) 1652
59 (15) 960 212 (100) 1702
68 (20) 997 221 (105) 1753
77 (25) 1035 230 (110) 1804
86 (30) 1074 239 (115) 1856
95 (35) 1113 248 (120) 1908

104 (40) 1153

Troubleshooting Humidity Sensors

The UVC is configured to use a 0–100% RH, 0–5 VDC, capacitive humidity sensor. Each
sensor is calibrated according to the table shown.

CAUTION

The humidity sensor is not protected against reversed polarity.
Check carefully when connecting the device or damage can
result.

Use the following procedure to troubleshoot a suspect sensor:

1 Disconnect the sensors output voltage lead from the UVC analog input.

2 Using some other calibrated humidity sensing device, take a humidity reading at the sensor

location.

3 Use the humidity reading from Step 2 determine the expected sensor voltage from

Table 24 .

4 Using a calibrated multi-meter, measure the actual voltage across the yellow and white

sensor leads.
Wire color definitions:

White = ground

Yellow = output VDC

Blue = supply VDC

5 Compare the expected voltage to the actual voltage.

6 If the actual voltage value deviates substantially (more than 10%) from the expected

voltage, replace the sensor.

McQuay OM 751 45

Diagnostics and Service

Table 24: Humidity versus voltage.

RH (%) VDC (mV) RH (%) VDC (mV)

10 1330 55 2480
15 1475 60 2600
20 1610 65 2730
25 1740 70 2860
30 1870 75 2980
35 1995 80 3115
40 2120 85 3250
45 2235 90 3390
50 2360 95 3530

Troubleshooting Carbon Dioxide (CO2) Sensors

The UVC is configured to use a 0–2000 PPM, 0–10 VDC, single beam absorption infrared gas
sensor. Each sensor is calibrated according to the table shown.

Use the following procedure to troubleshoot a suspect sensor.

1 Disconnect the sensors output voltage lead from the UVC analog input (xAI-3).

2 Using some other calibrated CO

3 Use the CO

reading from Step 2 to determine the expected sensor voltage from Table 25.

2

4 Using a calibrated multi-meter, measure the actual voltage across the lead removed from

xAI-3 and ground.

5 Compare the expected voltage to the actual voltage.

6 If the actual voltage value deviates substantially (more than 10%) from the expected

voltage, replace the sensor.

sensing device, take a CO2 reading at the sensor location.

2

In the unlikely event that the CO

sensor requires calibration, consult the factory for

2

information on obtaining calibration equipment and instructions.

Table 25: CO2 versus voltage table

CO2 (PPM) VDC (V) CO2 (PPM) VDC (V)

300 1.5 1200 6.0
400 2.0 1300 6.5
500 2.5 1400 7.0
600 3.0 1500 7.5
700 3.5 1600 8.0
800 4.0 1700 8.5
900 4.5 1800 9.0

1000 5.0 1900 9.5

46 McQuay OM 751

UVC Configuration Parameters

UVC Configuration Parameters

The UVC is been provided with a number of configuration variables as listed in the following
table. These configuration variables are stored in UVC non-volatile memory. For a description
of supported network variables for each protocol, refer to Protocol Data Packet bulletin ED

15065.

Table 26: UVC configuration parameters (OM 751)

Configuration Parameter Name Abr. Notes Default

Occupied Cooling Setpoint

Standby Cooling Setpoint

Unoccupied Cooling Setpoint

Occupied Heating Setpoint

Standby Heating Setpoint

Unoccupied Heating Setpoint

Local Bypass Time Tenant override

Spac e C O

Space Humidity Setpoint

Emergency Heat Enable 0 = disable, 1 = enable (uses auxiliary heat where primary heat is

Emergency Heat Setpoint

Emergency Heat Shutdown
Configuration
Wall Sensor Type

Slave Type Configuration2 0 = independent slave, 1 = dependent slave

OAD Min Position High-Speed Setpoint

OAD Min Position Med-Speed Setpoint

OAD Min Position Low-Speed Setpoint

Exhaust Interlock OAD Min Position
Setpoint

Energize Exhaust Fan OAD Setpoint

OAD Max Position Setpoint

OAD Lockout Enable 0 = disable, 1 = enable (this variable will be factory set to 1 when

OAD Lockout Setpoint

Economizer Enable 0 = disable, 1 = enable

Economizer OA Temp Setpoint

Economizer IA/OA Temp Differential

Economizer OA Enthalpy Setpoint

Economizer IA/OA Enthalpy Differential

External BI-3 Configuration 0 = Ventilation Lockout, 1 = Exhaust Interlock

External BO-3 Configuration 0 = Exhaust Fan On/Off, 1 = Auxiliary Heat

Filter Alarm Enable 0 = disable, 1 = enable

Filter Change Hours Setpoint fan run hours between filter change alarms

Setpoint

2

2

2

2

OCS 73°F (23°C)

SCS 77°F (25°C)

UCS 82°F (28°C)

OHS 70°F (21°C)

SHS 66°F (19°C)

UHS 61°F (16°C)

120 min

CO2S 1200 PPM

used with both active (reheat) and passive dehumidification

RHS

sequences

not applicable)

EHS 54°F (12°C)

0 = no emergency heat during shutdown, 1 = emergency heat
available during shutdown
0 = +/- 3°F, 1 = 55°F to 85°F

(this variable will be factory set to 5% open when the unit is ordered

OADH

with optional CO
(this variable is ignored when the unit is ordered with optional CO2

OADM

DCV)
(this variable is ignored when the unit is ordered with optional CO2

OADL

DCV)
OA damper minimum position when the exhaust interlock input is

EOAD

energized
defines position above which exhaust fan output will be energized

OADE

OAMX 99% open

the unit is ordered as a recirc unit with no OAD)
OA temperature below which the OA damper will remain closed

OALS

(this variable will be factory set to –99°C when the unit is ordered
as a recirc unit with no OAD)

ETS 68°F (20°C)

ETD 2°F (1°C)

EES 25 btu/lb (58 kJ/kg)

EED 1.3 btu/lb (3 kJ/kg)

DCV)

2

60% Rh

20% open

25% open

30% open

99% open

12% open

36°F (2°C)

700 hrs

LUI Menu

1

Item

Co
C5
CU
Ho
H5
HU

1

H1

H2

0

0

0

H3

r5
SL

o2

o3

o4

o5

o6
o7

0

o8

o9

1

E1
E2
e3
e5
e6

0

0

0

B3
B6
CE

McQuay OM 751 47

UVC Configuration Parameters

Configuration Parameter Name Abr. Notes Default

Primary Cool Proportional Band

Primary Cool Integral Time

Secondary Cool Proportional Band

Secondary Cool Integral Time

Discharge Air Temp Proportional Band

Discharge Air Temp Integral Time

CO2 Proportional Band2

CO2 Integral Time2

Ventilation Cooling Low Limit Setpoint

Mechanical Cooling Low Limit Setpoint

Discharge Air High Limit

Space Fan Off Delay

Fan Cycling Configuration space fan operation during occupied, standby and bypass

Space Fan Speed Changes Per Hour example: 6/60min = 10min (maximum of 1 fan speed change every

Space Fan Run Time Reset reset total run time: 1 = reset (you must return the variable back to

Compressor Run Time Reset reset total run time: 1 = reset (you must return the variable back to

Compressor Enable 0 = disable, 1 = enable

Compressor Minimum On Time

Compressor Minimum Off Time

Compressor Cooling Lockout Setpoint

Compressor Envelope Cool Max In

Compressor Envelope Cool Min In

Compressor Envelope Cool Max Out

Compressor Envelope Cool Min Out

Compressor Envelope Cool Max Ratio

Compressor Envelope Cool Max Offset

Compressor Envelope Cool Min Ratio

Compressor Envelope Cool Min Offset

Auxiliary Heat Start Differential

Auxiliary Heat End Differential

Auxiliary Heat Configuration 0 = normally open heat device (hot water valve, etc.),

Space Humidity Sensor Enable

Outdoor Humidity Sensor Enable

2

2

discharge air low limit during ventilation or economizer cooling

VCLL

discharge air low limit during mechanical (compressor) cooling

MCLL

DAHL 140°F (60°C)

occupancy modes: 2 = continuous, 3 = cycle

10min when fan in auto)

0 after reset)

0 after reset)

OA temperature below which compressor cooling is not allowed

CCLO

degrees above auxiliary heat start point where auxiliary heat ends

AHSD

degrees above auxiliary heat start point where auxiliary heat ends

AHED

1 = normally closed heat device (electric heat, etc.)
0 = disable, 1 = enable (this variable will be factory set to 1 when
the unit is ordered with optional humidity sensor)
0 = disable, 1 = enable (this variable will be factory set to 1 when
the unit is ordered with optional humidity sensor)

18°F (10°C)

180 sec

18°F (10°C)

600 sec

4°F (2.22°C)

300 sec

100 PPM

600 sec

54°F (12°C)

45°F (7°C)

30 sec

180 sec

300 sec

63.5°F (17.5°C)

120°F (48.89°C)

28°F (-2.22°C)

160°F (71.11°C)

40°F (4.44°C)

88°F (48.89°C)

-4°F (-2.22°C)

2°F (1°C)

2°F (1°C)

2

6

0

0

1

0.00

0.0

0

0

0

LUI Menu

1

Item

d2
d3

CF

C!

A1
A2

A3

48 McQuay OM 751

UVC Configuration Parameters

Configuration Parameter Name Abr. Notes Default

OAD Stroke Time

Split-System OA/DX Coil Temp used on split-system units only to partially disable the compressor

envelope by setting the outside DX coil temperature to a fixed valid
value, enter 122°F (50°C) on split-systems, use 327.67 for self­contained units (327.67 = invalid)

Application Name and Version Label

Compressor Start Delay adjust the compressor delay used to prevent multiple compressor

units from starting simultaneously (each unit or group of units
should have a different delay setting)

Outdoor Fan Delay

1. Indicates parameters accessible through the keypad/display.

2. Requires optional equipment.

90 sec

327.76

0 sec

10 sec

LUI Menu

1

Item

C6

McQuay OM 751 49

McQuay Training and Development

Now that you have made an investment in modern, efficient McQuay equipment, its care should be a high priority.
For training information on all McQuay HVAC products, please visit us at www.mcquay.com and click on training, or
call 540-248-9646 and ask for the Training Department.

Warranty

All McQuay equipment is sold pursuant to its standard terms and conditions of sale, including Limited Product
Warranty. Consult your local McQuay Representative for warranty details. Refer to Form 933-43285Y. To find your
local McQuay Representative, go to www.mcquay.com.

This document contains the most current product information as of this printing. For the most up-to-date product
information, please go to www.mcquay.com.

© 2006 McQuay International • www.mcquay.com • 800-432-1342