2
b. Disconnect wires from existing thermostat. Do not
allow wires to fall back into the wall. As each wire
is disconnected, record wire color and terminal
connection.
c. Discard or recycle old thermostat.
NOTE: Mercury is a hazardous waste and must be
disposed of properly.
3. Thermostat can be mounted directly to the wall or onto
the unit when required. See Fig. 1. An accessory wall
mounting plate is available when an existing hole in the
wall is too large for the thermostat or when mounting to a
junction box in the wall (the thermostat will not com-
pletely cover a 2 x 4-in. junction box).
4. If mounting plate is being used, install mounting plate on
wall or junction box. Mounting plate consists of two piec-
es: the metal mounting plate (see Fig. 2A) and the plastic
mounting plate (see Fig. 2B). The standard mounting
plate will cover a 2 x 4-in. or 4 x 4-in. junction box.
Accessory mounting plates of different sizes are also
available. Accessory mounting plate part numbers are
P474-0421 (7 x 4
1
/
4
-in.) or P474-0421L (5
1
/
2
x6
1
/
4
-in.).
a. Install the metal mounting plate to wall or junction
box with 2 screws provided. Use the outermost
screw holes.
b. Place plastic mounting plate over the metal mount-
ing plate. Be sure wiring exits through holes in
both mounting plates. Plastic mounting plate is
secured to metal mounting plate when the thermo-
stat mounting base is installed (Step 7).
5. Remove the thermostat cover from back plate to expose
mounting holes and wiring connections. See Fig. 1.
6. Route thermostat wires through large hole in thermostat
mounting base. Remove outer sheath from wires for add-
ed flexibility. Standard solid or multi-conductor thermo-
stat wire should be used from the thermostat to the unit.
Size and length considerations are as follows: for a
maximum distance from unit of 36 ft, use 22 AWG
(American Wire Gage) wire; for a maximum distance
from unit of 100 ft, use 18 AWG wire.
7. If accessory mounting plate is not used:
Level back plate against wall and mark wall through the
2 mounting holes in base. Drill two
3
/
16
-in. mounting
holes in wall where marked. Mounting holes are provided
if installing on unit.
Secure back plate to wall or unit with 2 screws and
anchors provided. Ensure all wires exit through hole in
back plate.
If accessory mounting plate is used:
Secure the metal mounting plate to the wall with two
screws provided. Use the outermost screw holes. Place
the thermostat back plate securely in the indentation
provided in the plastic mounting plate. Place plastic
mounting plate and thermostat back plate over metal
mounting plate. Secure mounting plates and thermostat
back plate to the wall with 2 screws provided. Ensure all
wires exit through hole in mounting base.
8. Adjust wire length and routing to allow proper closure of
the thermostat. Strip each wire at the end no more than
1
/
4
-in. to prevent adjacent wires from shorting together.
Match and connect wires to terminals on the thermostat.
See Fig. 3-7 and Tables 1 and 2.
9. Push excess wiring into wall. Seal hole in wall to prevent
drafts.
10. Re-attach thermostat cover to back plate.
11. Turn on power to unit. The thermostat will receive power
from the fan coil unit.
NOTE: The thermostat is strictly a low-voltage control.
One or two 33ZCRLYBRD relay boards must be in-
stalled to isolate any line voltage, fans, or water valves
from the fan coil.
Be careful not to drill into wiring in wall. Electrical shock
could result.
Improper wiring or installation may cause damage to the
thermostat. Check to ensure wiring is correct before pro-
ceeding with installation of unit. Do not run thermostat
wiring in same conduit as high-voltage power, or HVAC
wiring. Interference from other wiring may cause incorrect
readings or commands from thermostat.
WIRING
TERMINAL
BLOCK
HOLE FOR
WIRING
MOUNTING
HOLE
MOUNTING
HOLE
C
Y1
G3
GR
W1
G2
3 1/8"
3 1/8"
1"
CK1
H2O
RS+5
RS
Fig. 1 — Thermostat Back Plate Mounting
and Wiring
LEVEL
LEVEL
3 9/16"
3 3/4"
Fig. 2A — Metal Mounting Plate Dimensions
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