McQuay LIA266 User manual

Auto-changeover Electronic Thermostat
2 Heat/2 Cool, Auto or Manual Changeover, Hardwired
Part No. 668375401
For replacement parts call 1-800-377-2787
©2008 McQuay International • www.mcquay.com • 800-432-1342
● Congurable
● TwoStageHeat/2StageCoolSystems
● BacklitDisplay
● FieldTemperatureCalibration
● StatusIndicatorLight
● RelayOutputs(minimumvoltagedropinthermostat)
● NightSet-BackOverride
● Reset
Installation & Operation Manual LIA266
Group: WSHP
Supercedes: LIA204-4
Date: May 2007

Table of Contents
Parts Diagram .............................................................................................................................1
Specifications .............................................................................................................................. 2
Important Safety Information .....................................................................................................2
Package Contents/Tools Required...............................................................................................2
To Remove Existing Thermostat ................................................................................................3
To Install Thermostat ..................................................................................................................3
Remote Sensor Installation (Optional) ........................................................................................5
Terminal Designator Descriptions................................................................................................6
Wiring Diagrams..........................................................................................................................6
Configuration Mode.....................................................................................................................8
Testing the Thermostat ............................................................................................................11
Mode of Operation ....................................................................................................................12
Operating Modes ......................................................................................................................13
Troubleshooting ........................................................................................................................14
Factory Default Settings...........................................................................................................15

1
Parts Diagram
R12
W1 Y1 W2 O
S1
S2
668375401
Y2

2
Specications
Important Safety Information
WARNING! : Always turn off power at the main power supply before installing, cleaning, or removing
thermostat.
• This thermostat is for 24 VAC/VDC applications only; do not use on voltages over 30 VAC/VDC
• Do not short across terminals of system control to test operation; this will damage your thermostat and
void your warranty
• All wiring must conform to local and national electrical and building codes
• Use this thermostat only as described in this manual
Electrical rating: • 24 VAC/VDC (18-30 VAC/VDC) • 4 amp maximum total load
• 1 amp maximum per terminal
Temperature control range: 45°F to 90°F (7°C to 32°C) Accuracy: ± 1°F (± 0.5°C)
System configurations: 2-stage heat, 2-stage cool
Timing: Backlight Operation: 13 seconds after mode change or button press
Terminations: -C, +R, W1, Y1, W2, Y2, G, O, S1, S2
Package Contents/Tools Required
Package includes: Thermostat on base, thermostat cover, wiring labels, screws and wall anchors,
Installation, Operation and Application Guide
Tools required for installation: Drill with 3/16” bit, hammer, screwdriver

3
To Remove Existing Thermostat
ELECTRICAL SHOCK HAZARD – Turn off power at the main service panel by removing the fuse
or switching the appropriate circuit breaker to the OFF position before removing the existing
thermostat.
1. Turn off power to the heating and cooling system by removing the fuse or switching the appropriate
circuit breaker off.
2. Remove cover of old thermostat. This should expose the wires.
3. Label the existing wires with the enclosed wire labels before removing wires.
4. After labeling wires, remove wires from wire terminals.
5. Remove existing thermostat base from wall.
6. Refer to the following section for instructions on how to install this thermostat.
To Install Thermostat
ELECTRICAL SHOCK HAZARD – Turn off power at the main service panel by removing the fuse
or switching the appropriate circuit breaker to the OFF position before removing the existing
thermostat.
IMPORTANT: Thermostat installation must conform to local and national building and electrical
codes and ordinances.
Note: Mount the thermostat about five feet above the floor. Do not mount the thermostat on an
outside wall, in direct sunlight, behind a door, or in an area affected by a vent or duct.
1. Turn off power to the heating and cooling system by removing the fuse or switching the appropriate
circuit breaker off.

4
To Install Thermostat (continued)
2. To remove cover, insert and twist a coin or screwdriver in the slots on the sides of the thermostat.
3. Put thermostat base against the wall where you plan to mount it (Be sure wires will feed through the
wire opening in the base of the thermostat).
4. Mark the placement of the mounting holes.
5. Set thermostat base and cover away from working area.
6. Using a 3/16” drill bit, drill holes in the places you have marked for mounting.
7. Use a hammer to tap supplied anchors in mounting holes.
8. Align thermostat base with mounting holes and feed the control wires through wire opening.
9. Use supplied screws to mount thermostat base to wall.
10. Insert stripped, labeled wires in matching wire terminals. See “Wiring Diagrams” section of this
manual (Pages 6-7).
CAUTION! : Be sure exposed portion of wires does not touch other wires.
11. Tighten screws on terminal block. Gently tug wire to be sure of proper connection. Double check that
each wire is connected to the proper terminal.
12. Seal hole for wires behind thermostat with non-flammable insulation or putty.
13. Replace cover on thermostat by snapping it in place.
14. Turn on power to the system at the main service panel.
15. Test thermostat operation as described in “Testing the Thermostat” (Page 11).

5
1. Remove cover from remote sensor housing.
2. Select an appropriate location for mounting the remote sensor.
3. Mount remote sensor unit using hardware provided.
4. Install two strand shielded wire between remote sensor and thermostat. Shielded wire must be used.
Do not run remote sensor wire in conduit with other wires.
• Wire 1 should run between the S1 terminal on the thermostat and the S1 terminal on the
remote sensor
• Wire 2 should run between the S2 terminal on the thermostat and the S2 terminal on the
remote sensor
• Connect the shielding of the wire to the S2 terminal on the thermostat
5. Disable the main sensor (R12) on the thermostat by cutting it from the circuit board.
Remote Sensor Installation (Optional)
Requires McQuay Remote Sensor Part Number 667720401

6
-C – 24 VAC/VDC common
+R – 24 VAC/VDC hot
W1 – 1st stage heat
Y1 – 1st stage cool
W2 – 2nd stage heat
Y2 – 2nd stage cooling
G – Fan
O – Override
-C OGY2W2Y1W1+R
ELECTRONIC THERMOSTAT
W
2
G W
1
Y
1
F E L U A P V +
R
-
C
O
McQUAY SINGLE CIRCUIT
Mark IV Board
Low Voltage Terminal Board
Terminal Designator Descriptions
Wiring Diagrams
Override (Optional)

7
-C GY2W2Y1W1+R
McQUAY DUAL CIRCUIT
Mark IV Board Circuit 1
Low Voltage Terminal Board
Mark IV Board Circuit 2
Low Voltage Terminal Board
ELECTRONIC THERMOSTAT
O
Override (Optional)
W
2
G W
1
Y
1
F E L U A P V +
R
-
C
O
W
2
G W
1
Y
1
F E L U A P V +
R
-
C
O

8
FILTER
DIFF
ROOM
SET
REMOTE
3. Temperature Scale (F or C) – Choose Fahrenheit or Celsius.
Press the or button to select.
Press the SW6 button to advance to the next screen.
The configuration mode is used to set the McQuay Auto-changeover Electronic Thermostat to match your heating/cooling
system. To configure the McQuay Auto-changeover Electronic Thermostat , perform the following steps:
1. Remove the cover of the thermostat by gently pulling on one of the corners.
2. S imultaneously hold the SW5 and SW6 buttons in for 5 seconds while the McQuay Auto-changeover Electronic Thermostat
is in OFF mode.
3. Press the or button to change settings within each screen.
4. Press the SW6 button to advance to the next screen.
Note: The SW5 button will return you to the previous screen.
5. To exit configuration mode, slide the Mode switch to Heat or Cool.
2. Heat Source – Set to “g”.
Press the or button to set to “g”.
Press the SW6 button to advance to the next screen.
FILTER
DIFF
ROOM
SET
REMOTE
FILTER
DIFF
ROOM
SET
REMOTE
Conguration Mode
Configuration Mode Settings
The setup screens for Configuration Mode are as follows:
1. Heat Pump and Non Heat Pump – Press the or button to
configure as heat pump, or non-heat pump system. Set to “O” for
all McQuay WSHP, PTAC, PTHP and UV units.
Press the SW6 button to advance to the next screen.