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3M-22 Thermostat wire connection terminals (C) Daniel FriedmanHow Wire a 3M Filtrete Thermostat
3M-22 Filtrete Thermostat Wiring Connection Tables

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Thermostat wiring details & connections for the 3M-22 Filtrete room thermostat. This article gives a table showing the proper wire connections for the 3M-22 Filtrete thermostat used to control heating or air conditioning equipment.

Room thermostat installation & wiring guide: this article series explains the basics of wiring connections at the thermostat for heating, heat pump, or air conditioning systems. Our page top sketch, courtesy of Honeywell Controls, illustrates the wiring diagram for a traditional Honeywell T87F thermostat used for 2-wire single pole single throw control of heating only in a typical gas-fired heating system.



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3M-22 Filtrete™ Room Thermostat Wiring Guide

Complete tables for Thermostat Wiring Terminal Notes for the 3M-22 Filtrete Room Thermostat are given here. Our photo just below shows all eleven possible thermostat control wire connection points on this device. (We don't like that sharp crimp in the red wire, nor should you.) Note the white wire connected to W and the red wire connected to RH and the jumper left in place between RH and RC. Wired as shown this thermostat works only from its own internal battery power.

3M-22 Thermostat wire connection terminals (C) Daniel Friedman

How to Wire a 3M-22 Filtrete Room Thermostat For 2-wire Heating Only Systems

Thermostat
Terminal ID
Wire Color
or ID
Two-Wire Heat Thermostat Hookup - Comments
W
White or W White wire coming to the thermostat from the heater or from the secondary (C) terminal on the transformer, this wire connects the heat.
RH
Red
or R or RH

Red wire coming to the thermostat from transformer secondary (R) terminal. This connects the heat power.

Leave in place the jumper wire between RH and RC.

C
C
if present
If a third "C" wire is present this wire is used to provide power to the 3M-22 thermostat. Otherwise this thermostat is powered only by its batteries.

Notes:

This wiring procedure works for 2-wire heat, oil or gas millivolt or 24VAC systems

On a call for heat (room temperature drops below the thermostat set point, the thermostat connects W - RH to turn on the heating system.

Watch out: this is a battery-operated thermostat. If the batteries fail the thermostat may fail to provide heating or cooling and the building may suffer accordingly.


How to Wire a 3M-22 Filtrete Room Thermostat For 3-Wire Heat Systems

Thermostat
Terminal ID
Wire Color
or ID
Comments
W
White or W W connects to heat
RH
Red
or R or RH
RH connects to heat power
G
 
Green
or G or F (fan)
This wire (if present) controls the fan in forced warm air systems, fan convector heaters, and similar systems that use a fan.
C
C - Common If a "C" wire is also present this wire is used to provide power to the 3M-22 thermostat. Otherwise this thermostat is powered only by its batteries.
Notes:

How to Wire a 3M-22 Filtrete Room Thermostat For 4-Wire Heating & Air Conditioning Systems

Thermostat
Terminal ID
Wire Color
or ID
Comments
W
White or W W connects to heat
Y 
Yellow or Y Y connects to the cooling compressor/condenser unit
RH
Red
or R or RH
RH connects to heat power
G
 
Green
or G or F (fan)
This wire (if present) controls the fan in forced warm air systems, fan convector heaters, and similar systems that use a fan.
C
C - Common If a "C" wire is also present this wire is used to provide power to the 3M-22 thermostat. Otherwise this thermostat is powered only by its batteries.
Notes:

How to Wire a 3M-22 Filtrete Room Thermostat For 4-Wire Heat Pump System

Thermostat
Terminal ID
Wire Color
or ID
Comments
B
O or B wire

Connect the O or B wire to terminal O - this operates the reversing or "change-over" valve that switches between heating & cooling mode.

If both O & B wires are present (as with Trane heat pumps), connect O wire to O terminal

For Trane heat pumps connect the B wire to the C terminal.

For other HVAC equipment, tape off the B wire.

Watch out: do not connect the B wire to the B terminal on this thermostat.

Y 
Yellow or Y Y connects to the cooling compressor/condenser unit
RH
Red
or R or RH
RH connects to heat power
G
 
Green
or G or F (fan)
This wire (if present) controls the fan in forced warm air systems, fan convector heaters, and similar systems that use a fan.
C
C - Common If a "C" wire is also present this wire is used to provide power to the 3M-22 thermostat. Otherwise this thermostat is powered only by its batteries.
Notes:

How to Wire a 3M-22 Filtrete Room Thermostat For 5-Wire Heating & Air Conditioning Systems

Thermostat
Terminal ID
Wire Color
or ID
Comments
W
White or W W connects to heat
Y 
Yellow or Y Y connects to the cooling compressor/condenser unit
RC-RH Jumper
Jumper wire between these two terminals Remove this jumper wire or clip so that RC and RH are no longer connected together
RH
Red
or R or RH
RH connects to heat power
RC
RC wire RC connects power
G
 
Green
or G or F (fan)
This wire (if present) controls the fan in forced warm air systems, fan convector heaters, and similar systems that use a fan.
C
C - Common If a "C" wire is also present this wire is used to provide power to the 3M-22 thermostat. Otherwise this thermostat is powered only by its batteries.
Notes:

How to Wire a 3M-22 Filtrete Room Thermostat For 5-Wire Heat Pump with Auxiliary or Backup Heat

Thermostat
Terminal ID
Wire Color
or ID
Comments
B
O or B wire

Connect the O or B wire to terminal O - this operates the reversing or "change-over" valve that switches between heating & cooling mode.

If both O & B wires are present (as with Trane heat pumps), connect O wire to O terminal

For Trane heat pumps connect the B wire to the C terminal.

For other HVAC equipment, tape off the B wire.

Watch out: do not connect the B wire to the B terminal on this thermostat.

W2
W2 wire

The W2 wire controls the auxiliary heat or backup heat source.

Y 
Yellow or Y Y connects to the cooling compressor/condenser unit
RH
Red
or R or RH
RH connects to heat power
G
 
Green
or G or F (fan)
This wire (if present) controls the fan in forced warm air systems, fan convector heaters, and similar systems that use a fan.
C
C - Common If a "C" wire is also present this wire is used to provide power to the 3M-22 thermostat. Otherwise this thermostat is powered only by its batteries.

Notes:

Some heat pumps with auxiliary / backup heat use staged backup heat and additional controls and wires may be required. See the next table.


How to Wire a 3M-22 Filtrete Room Thermostat For Heat Pump with Two-Stage Auxiliary or Backup Heat

Thermostat
Terminal ID
Wire Color
or ID
Comments
W
White or W W or W1 operates the auxiliary stage 1 backup heat
W2
W2 wire W2 operates the auxiliary stage 2 backup heat
Y 
Yellow or Y Y or Y1 operates the first stage cooling system
Y2
Y2 wire Y2 operates the second stage of 2-stage cooling systems
RH
Red
or R or RH
RH connects to heat power
C
C - Common If a "C" wire is also present this wire is used to provide power to the 3M-22 thermostat. Otherwise this thermostat is powered only by its batteries.
Notes:

We provide thermostat wiring connections for just about every type of residential heating or cooling room thermostat as well as a description of thermostat wiring color codes & conventions.

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