McQuay MT 168 0-10 VDC/4-20mA, MT 168 0-10 VDC Maintenance Manual

Installation and Maintenance Manual IM 1017

LOW VOLTAGE

CONNECTIONS

LINE V

OL

TAGE

CONNECTIONS

FAN

L2 OR NEUTRAL

OPTIONAL REMOTE PROBE

OPTIONAL PIPE SENSOR

L1 (HOT)

LO FAN

MED FAN

HIGH FAN

OR SINGLE SPEED

24 VAC 1

24 VAC 2

SETBACK

24 VAC
XFMR

MAIN 1

0-10 VDC

OUTPUT

SECONDARY

0-10 VDC

1 OUTPUT

FAN

OUTPUT

AUXILIARY

HEAT

OUTPUT

DAMPER
OUTPUT

10

11

12

13

14

15

16

17

1

2

3

4

5

6

7

MT 168 0-10 VDC/4-20mA Thermostat

Installation

DANGER

READ THESE INSTRUCTIONS CAREFULLY BEFORE
ATTEMPTING TO INSTALL, OPERATE OR SERVICE THIS
THERMOSTAT.

Failure to observe safety information and comply with
instructions could result in PERSONAL INJURY, DEATH
AND/ OR PROPERTY DAMAGE.

To avoid electrical shock or damage to equipment, disconnect
power before installing or servicing. Use only wiring with
insulation rated for full thermostat operating voltage. Use
copper wire only. Insulate or wire-nut all un-used leads. Any
wiring, including the remote probe, may carry the full operating
voltage of the thermostat.

To avoid potential fire and/ or explosion do not use in
potentially flammable or explosive atmospheres.

Retain these instructions for future reference. You must review
your application and national and local codes to ensure that
your installation will be functional and safe.

Figure 1: Mounting

Figure 2: Typical Wi ring *

Group: Applied Air Systems
Part Number: 910102992
Date: August 2009

CAUTION

Care should be used to avoid electrostatic discharge to the
microprocessor.

This unit has configuration dip switches and jumpers. You may
need to reconfigure the thermostat for your application.

1 Install the thermostat with the two furnished mounting

screws to a standard 4-1/16" x 2-1/8" square device box
with a 2" x 4" adapter ring.

2 For wall installations, mount the thermostat on an inside

wall approximately 5 feet above the floor. The location

should provide circulation at average room temperature.
Avoid direct sunlight or sources of hot or cold air in the
room or wall.

IM 1017 / Page 1 of 3 © 2009 McQuay International 800-432-1342 www.mcquay.com

Note: * Specific models may have fewer connections.

3 Remove the cover. Mount thermostat base assembly to

the outlet box using screws provided. Tighten the screws
evenly but do not overtighten. Connect wires per wiring
diagram.

4 To use a remote sensor on units with local sensing

capability, remove jumper JP-1 to disable local sensing.
Failure to remove JP-1 will cause improper operation of
thermostat.

5 Connecting a jumper between terminals 16 and 17 will

disable the secondary output and change the main output
to heat mode.

6 Connection of a 24 VAC set-back signal will force the

control into unoccupied mode (see diagram). Pressing an
arrow key or the mode buttons on the thermostat cover
will disable the setback input for one hour.

7 Remove the LCD plastic protective film to complete the

installation. Reinstall the cover assembly. Install cover
locking screw provided.

8 Checkout: After wiring and installation are complete,

energize the system and check the operation. Adjust the
thermostat as necessary to complete at least one cycle.
Be sure the thermostat and all other equipment are
functioning correctly.

Electrical Ratings

Table 1: Fan switch (terminals 1-4) line voltage connections

Voltage

Rating

24 VAC N.A. N.A. N.A. 24 VA 10 VA
120 VAC 5.8 34.8 6.0 125 VA NA
240 VAC 2.9 17.4 5.0 125 VA NA
277 VAC 2.4 14.4 4.2 125 VA NA

Inductive Resistive

FLA LRA

Amps

Pilot
Duty

Thermostatic

Switching

Application Notes

1 When no changeover pipe sensor is used, the main

output controls cooling and the secondary output
controls heating.

2 The fan output, terminal 12, is energized whenever there

is a demand for heating or cooling. This output can be
connected to a relay that can be used to provide fan
cycling to terminal 1.

3 The changeover pipe sensor should be mounted on the

main coil input for water system operation and in the
main duct system for forced air operation.

4 The set point and operating mode will be retained on a

loss of power.

5 When using either a remote probe or pipe sensor, run

wiring away from any electrical motors or power wiring.

6 The auxiliary heat output supplies a 24 VAC signal with

call for heat. This output is shipped configured for staged
heat.

7 The thermostat is shipped with all dip switches in the

"ON" (closed) position.

8 The damper output is ON when mode is AUTO, HEAT

or COOL. Damper is OFF in set back.

Thermostat Operation

These thermostats are designed to control 0-10 VDC/4-0 mA
valves. These units may include a fan switch with one or more
fan speed selections.

Mode Button Operation

OFF: All thermostat outputs are off, fan is still operational if
connected to a manual fan switch.

AUTO: The thermostat automatically selects heating or
cooling mode depending upon the relationship of the setpoint
and the room temperature. The appropriate HEAT or COOL
indicator is enabled in addition to AUTO. A 3°F dead band is
provided to prevent short cycling between heating and cooling
modes. After changeover, the control points automatically shift
so that the heating off-point equals the set point temperature or
the cooling off-point equals the set point temperature.

COOL: The thermostat operates as a cooling only thermostat.
The heating outputs are disabled.

HEAT: The thermostat operates as a heatin- only thermostat.
The cooling outputs are disabled.

Fan Speed Switch Operation

Fan speed is determined by manual selection from fan switch
OFF to HIGH, MEDIUM and/or LOW. In the OFF position,
all outputs are off and the display is blank.

Up/Down Arrow Operation

A first touch of either arrow will display the setpoint (a single
set point is employed for both heating and cooling). Continued
pressure on either arrow will scroll the setpoint to new values.
After three consecutive seconds on either arrow, the selected
setpoint becomes effective and the display of the room
temperature resumes.

Configuration

Table 2: Circuit Board Jumpe r Configuration

Jumper Closed On* Open Off

JP1 Local Sensing Remote Sensing
JP2 2 Pipe System 4 Pipe System
JP3 Factory Use Only
JP4 0-10 VOC Main Output 4-20 mA Main Output

JP5

0-10 VOC Secondary

Output

4-20 mA Secondary

Output

© 2009 McQuay International 800-432-1342 www.mcquay.com IM 1017 / Page 2 of 3