Step 1: Replacing Existing Thermostat - Robertshaw 9420 User Manual

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IMPORTANT SAFETY INFORMATION WARNING:
• Always turn off power at main fuse or circuit breaker panel before
installing, removing, cleaning, or servicing thermostat.
• Read all the information in this manual before installing this
thermostat.
• This is a 24 VAC low-voltage thermostat. Do not install on voltages
higher than 30 VAC.
• All wiring must conform to local and national building and electrical
codes and ordinances.
• Do not short (jumper) across terminals on the gas valve or at the
system control to test installation. This will damage the thermostat
and void the warranty.
• Do not connect ground to any terminal in this unit.

Step 1: Replacing Existing Thermostat

1. Turn off power to heating and cooling system.
2. Remove cover from old thermostat to expose wires (Figure 1).
3. Disconnect wires one at a time from existing terminals. Use enclosed labels
to mark existing wires. Refer to cross references in Table 1 if existing wiring
does not directly match the labels.
4. Remove existing thermostat base from wall.
Old Terminal
R, V-VR or VR-R
Y, Y1 or M
O or R
B
F or G
Y2
W2 or W-U
C, X or B
L or X
E
NOTE: THIS THERMOSTAT REQUIRES A 24V COMMON WIRE FOR PROPER OPERATION.
Figure 1
New Label
R
Y1
O
B
G
Y2
W2
C
L
E
Table 1
Description
24 VAC, Return
Compressor Relay (Stage 1)
Reversing Valve (Cool Active)
Reversing Valve (Heat Active)
Fan Control Relay
2nd Stage Cooling Circuit
2nd Stage Heating Control
24 VAC, Transformer Common Side
System Monitor
Emergency Heating Circuit
2