Robertshaw 9420 User Manual

• 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.

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.

R, V-VR or VR-R 

R

24 VAC, Return

Y, Y1 or M

Y1

Compressor Relay (Stage 1)

O or R

O

Reversing Valve (Cool Active)

B

B

Reversing Valve (Heat Active)

F or G

G

Fan Control Relay

Y2

Y2

2nd Stage Cooling Circuit

W2 or W-U

W2

2nd Stage Heating Control

C, X or B

C

24 VAC, Transformer Common Side

L or X

L

System Monitor

E

E

Emergency Heating Circuit

2

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