3-1
Existing Wired Thermostat Removal
Use the following procedure to review and record the wiring configuration
before disconnecting an existing wired thermostat .
Before beginning the installation procedure, turn
off power to the fan coil system .
Section 3
SC102ZB/ST103ZB Installation and Operation Manual
SC102ZB Fan Coil Controller Installation
If replacing an existing wired thermostat,
review and record the wiring configuration of the existing
thermostat:
• Remove existing thermostat from the wall to expose the wiring terminals
• Take a photograph or note the wire colors and connections (see Table 3 .1 below)
• Attach wire labels to each of the wires
Table 3.1: Wire Designation Record
Terminal
Wire Color
Function
4 Pipe System
2 Pipe System
R
24 VAC Input
24 VAC Input
C
24 VAC Common
24 VAC Common
Gl
Fan – Low Speed
Fan – Low Speed
Gm
Fan – Medium Speed
Fan – Medium Speed
Gh
Fan – High Speed
Fan – High Speed
WY
Heat Supply Valve Actuator
Heat/Cool Supply Valve Actuator
YA
Cooling Supply Valve Actuator
Auxiliary Heat
Ac
Accessory Contact
Accessory Contact
Ac
Accessory Contact
Accessory Contact
Tp
Supply Pipe Temp . Sensor
Supply Pipe Temp . Sensor
Tx
External Temp Sensor (wired)
External Temp Sensor (wired)
Ts
Temperature Setback
Temperature Setback
Tc
Tx/Tp/Ts Common
Tx/Tp/Ts Common
After labeling the wires, disconnect them from the thermostat terminals and remove the
thermostat mounting plate (if necessary).
Paint the mounting surface, if desired, before mounting the new thermostat back plate to ensure
complete wall coverage .
