Robertshaw 9420 - Manual (Page 2)

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 New Label Description
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
NOTE: THIS THERMOSTAT REQUIRES A 24V COMMON WIRE FOR PROPER OPERATION.
Table 1
2
Figure 1
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