How Wire a Thermostat
Thermostat Wiring Connection Tables
Hook-up Procedures for Heating, Heat Pump, or Air Conditioning Thermostats

THERMOSTAT WIRE CONNECTIONS - CONTENTS
Guide to Thermostats for Heating and Air Conditioning Systems
SHORTING THERMOSTAT WIRES to ID R W B - separate article
THERMOSTAT INSTALLATION STEPS - separate article
THERMOSTAT WIRE FUNCTIONS - separate article
THERMOSTAT WIRING DIAGRAMS - separate article
THERMOSTAT WIRING TIPS & COLOR CODES - separate article
Questions & Answers about heating, air conditioning, and heat pump thermostat installation and wiring
References

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Room thermostat installation & wiring guide: this article explains the basics of wiring connections at the thermostat for heating, heat pump, or air conditioning systems. We provide Honeywell, White Rodgers & other thermostat wiring diagrams and explanation showing how to wire a room thermostat, including just what connections to make and how wires and connectors are color coded to make things easy. 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. Other thermostat wiring schematics are provided below.

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. At THERMOSTAT INSTALLATION STEPS we provide a step by step photo guide to installing a room thermostat. We also provide THERMOSTAT WIRING DIAGRAMS and a separate explanation of THERMOSTAT WIRE FUNCTIONS.

Guide to Room Thermostat Installation, Location, & Wiring

Where to Locate & Mount a Room Thermostat & what spots to avoid

Where NOT to locate the room thermostat (C) Carson Dunlop Associates

Locate the room thermostat at about chest height on an interior wall, in a location where the thermostat won't be affected by drafts or other unusual temperature conditions.

Good thermostat locations are

in a living room or dining room,
about five feet from the floor on an interior wall and
in a position where the thermostat will be in natural air circulation (not dead air space)
but where the thermostat will not be exposed to strong drafts from windows, doorways, or from a heating or cooling air supply register.

As Carson Dunlop Associates' sketch (left) explains, there are a number of places where you should not locate the room thermostat.

Bad Room Thermostat Locations

Don't locate the room thermostat in these locations:

on an exterior building wall (exposed to outdoor temperature effects)
where drafts from an exterior door will affect its reading
above or in the line of airflow from a heating or cooling air supply register
in direct sunlight
on a wall shared with a hot space such as a kitchen or boiler room
in a kitchen, bath, or entry hallway
in an alcove, behind an open door, behind furniture
next to concealed pipes or air ducts
Do not place heat-emitting devices such as lamps or small appliances close to the thermostat. Their heat may affect its operation.

Room Installation Thermostat Installation Tips

Use new thermostat wires to avoid the risk of insulation nicks, cuts, and shorts in old wiring
Seal the hole in the building wall through which the thermostat wires pass out to the thermostat mount. Drafts through wall cavities can blow out of this hole and affect proper thermostat operation.
Do not use the thermostat power transformer to operate any other devices such as doorbells

Does the Room Thermostat Need to be Level on the Wall?

Yes for Older Mercury Bulb Switches

It's important to mount mercury-bulb thermostats as level as possible since otherwise you're putting the thermostat out of accurate temperature calibration.

That's because the coiled bimetallic spring has to move that mercury bulb to a tipped position to turn the heating or air conditioning system on or off in response to room temperature.

When we found a thermostat that did not heat a room accurately to the called-for temperature, we'd take a look to see if it was installed out of level before looking further.

Because the "set" range on these thermostats may have had a lower-end of 55 deg .F., when we wanted the thermostat to maintain a building at a temperature lower than the minimum that the thermostat dial provided, we just tilted the whole thermostat backing plate on the wall in the proper direction to shift the operating range of the switch.

No for Newer Solid State, or Digital Room Thermostats

Newer thermostats that rely on other sensor and switch designs do not have this sensitivity to being out of level and some (such as the 3M-22 thermostat) note in their installation instructions that the thermostat does not have to be level.

Our photo (above left) illustrates the red (R) and white (W) wire connections in a simple two wire heating control thermostat hookup using the Honeywell RTH2300/RTH221 series programmable wall thermostat.

Because some controls are used in common on hot water heat, hot air heat, and steam boilers, readers should see these other articles: see BOILER CONTROLS & SWITCHES, and also see BOILER COMPONENTS & PARTS for a detailed list of heating boiler controls, other heating system components, parts such as circulator pumps & draft regulators. If your building uses warm air heat, see FURNACE CONTROLS & SWITCHES. If your building uses steam heat see STEAM HEATING SYSTEMS. Also see Heat Won't Turn Off - Stop Unwanted Heat.

This article is part of THERMOSTATS our article series Guide to Finding, Using, and Adjusting Thermostats for Heating & Air Conditioning Furnaces & Boilers, Heat Pumps or Electric Furnaces or Boilers. This website answers most questions about central heating system troubleshooting, inspection, diagnosis, and repairs. We describe how to inspect, troubleshoot and repair heating and air conditioning systems to inform home owners, buyers, and home inspectors of common heating system defects.

Hooking up a 2-Wire Thermostat: How Do I Install & Wire Up a Room Thermostat like the Honeywell Round Wall T87F Series Thermostat?

Honeywell thermostat backing plate showing wiring connections

Basic 2-wire Room Thermostat Wiring Instructions

Wiring connections for a room thermostat such as the Honeywell 24-volt T87F, the Honeywell series 10 (out of production), or Penn "Rimset" low-voltage wall thermostat models are pretty simple as are the wiring instructions for White Rogers, Mercoid, General Controls, and similar thermostats.

Two wire thermostat wiring instructions: In a two-wire installation, the thermostat backing plate is mounted level on an interior wall in the room which we want to be the master temperature control for the area served by the heating or cooling system.

The red wire from the heater or air conditioner control is mounted to the "R" terminal on the backing plate. Typically the red wire is originating at the heating or air conditioning low voltage transformer and brings power to the thermostat. (See LOW VOLTAGE TRANSFORMER TEST)

The white wire from the heater or air conditioner control is mounted to the "W" terminal on the thermostat mounting plate. Typically the white wire is taking power from the thermostat to the operating control circuit board in the heater or air conditioner.

Our photo (above left) shows the backing plate that is mounted first when installing a round Honeywell Series 20 type room thermostat. Notice that the plate shows a "level" line.

We left off the actual wires so that you could see the "R" and "W" by the two screw terminals at the lower left 7 and 8 o'clock positions on the thermostat backing plate.

Note: The thermostat in this HVAC/R set-up is simply acting as an "on-off" switch to turn the heater or air conditioner on or off in response to room temperature. The electrician may have run a multi-wire set of low voltage wires through the walls of the building between the low voltage transformer and the thermostat (etc), but in this simple installation the other wires at the thermostat are not being used. At the low voltage transformer you will see two wires labeled "C" for common and "R" for red. We discuss wiring the low voltage transformer itself at LOW VOLTAGE TRANSFORMER TEST.

Watch out: do not short any wires together. Turn off power & confirm it is off. Don't forget to turn off all electrical power involved with your heating system before working on thermostat wiring, and confirm that power is off where you are working by using an appropriate test instrument such as a VOM. Failure to respect this advice risks equipment damage, and in some cases electrical shock or even a building fire.

Where do the Thermostat Wires Start and Where do they End-Up?

As we explain in more detail at THERMOSTAT WIRING DIAGRAMS,

Honeywell T87F Thermostat wiring diagram for 2-wire, spst control of heating only in a typical gas fired heating system - details from Honeywell Controls

At left the thermostat wiring diagram illustrates use of a Honeywell T87F thermostat in a 2-wire application controlling a gas fired heating appliance.

In the Honeywell T87F thermostat series the single pole double throw switch makes (closes) one set of contacts when the temperature falls - to turn on the heating appliance.

In thermostats that also control a cooling system, a second set of contacts will make or close on temperature rise. This second set of contacts may also be used to operate other controls or valves in some heating systems.

[Click any image or thermostat wiring schematic to see an enlarged, detailed version]

For completeness in understanding where the red and white thermostat wires originate and end up, at below left we illustrate the red and white thermostat wires originating at the low voltage transformer, and at below right we illustrate a typical thermostat wiring connection in an R8182 Aquastat primary controller of a heating boiler, using the T and T terminals.

Low voltage transformer wires (C) Daniel Friedman

3-Wire Thermostats: Where Do We Connect the Red, White, & Blue (if present) Wires to a Typical Three-Wire Wall Thermostat?

Three-wire thermostat wiring instructions, also called "series 20 installations" we have three wires rather than two to connect.

The Red wire coming to the thermostat from the heater or air conditioner is connected to "R".

The white wire is connected to the "Y" terminal, and

The blue wire is connected to the "W" terminal on the backing plate.

Then the thermostat body is screwed in place. The screws that secure a round Honeywell traditional wall thermostat to its backing plate will also connect it properly to the wiring.

A plug connector may be used:

On other, in fact most contemporary room or wall thermostats it may be necessary to plug in a connector between the thermostat and its mounting plate.

6-Wire Thermostats: Where Do We Connect the Red, White, & Blue, Yellow, Green, Orange Wires in a Typical Six-Wire Wall Thermostat?

Color Codes and Hookups for Thermostat Wires, typical for heat pump installations and thermostats

At left you can see the 11 possible thermostat wire connectors on the 3M-22 FIltrete thermostat. In this installation only two wires, R and W, have been connected.

Typical Thermostat Wire Connections for Heat Pumps

Typical connections when wiring a heat pump are as follows:

the red is power,
the yellow is for cooling,
the white is for heat,
the green is for the fan,
the orange is for the reversing valve, and
the blue is usually always common.

Again, you will have to check to see how the installer has ran the wires from the thermostat. Also see Table of Common Heating and Cooling Thermostat Wiring Connections for added details.

Typical thermostat connections when wiring a thermostat to control only a heating system or only an air conditioning system

If your thermostat is controlling only a heating system or only an air conditioning system, you will only have a red wire, and a white wire coming form the inside unit, to the outside unit.

On an air conditioner these two wires will go on the contactor to send 24 volts to the coil to pull the contactor in to start the air conditioner.

On a heating system these two wires will go to two thermostat connections on the primary controller such as an aquastat or air handler control that turns on the heating unit. Depending on the type of heating system, the thermostat, acting simply as an "on-off" switch will

- Hot water heat In the U.S. the TT wires will turn on a hot water circulator (or open a zone valve) on a hydronic or hot water heating system; falling boiler temperature will cause the aquastat to turn on the oil or gas burner (this is the U.S. typical installation).

- Hot water heat In Canada the TT wires will activate an aquastat control that will turn on and off the boiler based on its temperature; circulators are already running.

- Hot air heat: the TT wires will turn on the furnace heating equipment (oil or gas or electric, say); when the air temperature in the furnace heating plenum is hot enough the fan limit switch will turn on the blower fan.

These are the traditional wiring schematics, again, check the thermostat to see if this is the case with yours.

Instructions for Wiring of Line Voltage 120V Wall Thermostats

We moved this topic to LINE VOLTAGE 120V Wall Thermostat Wiring - separate article in order to keep our text on line voltage thermostats together.

Tables of Common Heating and Cooling Thermostat Wiring Connections for Major HVAC & Thermostat Brands

The following thermostat wiring suggestions were derived from a thermostat wiring connection code list provided courtesy of J. Scott Meenan.

Watch out: do not short any wires together. Turn off power & confirm it is off. As we have warned before, don't forget to turn off all electrical power involved with your heating system before working on thermostat wiring, and confirm that power is off where you are working by using an appropriate test instrument such as a VOM. Failure to respect this advice risks equipment damage, and in some cases electrical shock or even a building fire.

Table of Common HVAC Thermostat Wiring Connections - Generic HVAC Thermostat Control Wiring Points

Table of Standard or Most-Common Thermostat Wire Colors Matched to Thermostat Terminal Names [see other thermostat brand specific wiring notes below]
Thermostat Terminal Name	Nominal Wire "Color"¹	Function
(B)	Blue, Orange	Energize to heat. Used on some systems including Rheem/Ruud HVAC systems. See (O) below.
(B)	Blue, brown , or black	Blue, brown , or black wire, common side of the transformer. Needed on some electronic thermostats or if the system uses indicator lamps. Watch out: do not confuse this terminal with the (B) discussed above. Check you brand, model, and installation manual/wiring diagram. (Also see (X) below)
(C)		Common side of the transformer (see "B")
(E)	Blue, Pink, Gray, or Tan	Blue, pink, gray, or tan wire, emergency heat relay on a heat pump. [Active all the time when selected, usually not used -??]
(G)	Green	Furnace blower fan (used in air conditioners, heat pumps, some electric furnaces.) On most thermostats the (G) and (Y) terminals are connected together at all times when the fan switch is in the "Auto" mode.
(O)	Orange	Energize to cool, used for reversing valve on heat pump systems.
(R)	Red	Electrically live side ("hot" side) of the transformer wiring. Note 1.
(T)	Tan, Gray	Outdoor heat anticipator reset
(W) (W1) (W2)	White	"Heat", such as for a gas burner, oil burner, electric heat, or auxiliary heat on a heat pump, including the defrost output from an outdoor (condenser) that is used to activate electric heat at the compressor and to turn on the AUX heat lamp indicating that backup electric heat is in use or required. Some heat pumps require a jumper from (W) to (Y) to operate the heat pump.;
(X)		Also see (B) above.
(Y)	Yellow	Compressor activity: cooling, or cooling and heating if on a heat pump
Notes: 1. The [Honeywell 5-2 Day Programmable Thermostat - RTH2300B1012] thermostat cannot be used if your old thermostat had and used any two of the following wires: R, RC, RH, 4 and V.[5]

3M-22 Filtrete™ Room Thermostat Wiring Guide

Complete tables for Thermostat Wiring Terminal Notes for the 3M-22 Filtrete Room Thermostat. 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.

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:

American Standard, GE & Trane Thermostat Wiring Guide

How to Wire a General Electric (GE), Trane, American Standard HVAC Thermostat
Numbers		Refer to the equipment wiring diagram (usually glued inside the equipment access covers and in the the installation/service manual). May be stages of electric heat, especially on Air-Pro, Borg Warner, Coleman-Evcon, Frasier Johnson
(L)	Blue, Brown, Tan, or Gray	Service indicator lamp
(W2)	Pink or other color	Second stage of heat (may be same as (W) on heat pump or oil/gas systems.
(X2)		Second stage of electric heat on GE/Trane/American Standard systems. Also used as indicator lamp or misc. contact on other systems.
(Y2)	Blue, Pink	Compressor second stage

Flair Thermostat Wiring Guide

How to Wire a typical Flair 3-wire type Wall Thermostat (3 wires found in use at the wall thermostat) Flair model ANOVO Thermostat fed from a Flair zone valve
(4)	As wire colors may vary, note the wire colors	Wire coming from Flair zone valve terminal (4) "Open" . Note 1.
(5)	At the Flair zone valve and	Wire coming from Flair zone valve terminal (5) "Common"
(6)	Match those colors to terminals at the thermostat as shown here	Wire coming from Flair zone valve terminal (6) "Closed"
Notes: 1. The [Honeywell 5-2 Day Programmable Thermostat - RTH2300B1012] thermostat cannot be used if your old thermostat had and used any two of the following wires: R, RC, RH, 4 and V.[5]

Honeywell Thermostat Wiring Guide

How to Wire the Three-Wire Honeywell Wall Series 20 Thermostat

(3 wires found in-use at the wall thermostat)
Thermostat Terminal ID	Wire Color	Three-Wire Heat Thermostat Hookup Comments
(R)	Red	Red wire coming to the thermostat from the heater. See Note 1 in the table above.
(W)	Blue wire	For Honeywell Wall T87-F type Thermostats Connect the blue wire coming to the thermostat from the heater or air conditioner
(Y)	White wire	Watch out: For Honeywell Wall Series 20 type Thermostats connect the white wire coming to the thermostat from the heater or air conditioner to the (Y) terminal, not the (W) terminal.
1. Also see Honeywell Thermostat Wiring Diagrams - Honeywell Wall T87-F type Thermostats

How to Wire the Honeywell the 5-2 Day Programmable Thermostat - RTH2300B1012

Honeywell the 5-2 Day Programmable Thermostat - RTH2300B1012 alternative wiring tips
Old thermostat wire label	Connects to RTH2300B Terminal	Comments
C, C1, X, B	nothing - not used	Note 1
O, B, H	O/B
Y, Y1, M	Y	Note 3
R, RC, RH, 4, V	R	Note 2
G, F, L	G
W, W1, W2, H	W	Note 3

Notes: 1. Do not use C, C1 or X wire. Do not use B wire if you already have O wire. Wrap bare end of wire with electrical tape. 2. This thermostat cannot be used if your old thermostat had [and used] any two of the following wires: R, RC, RH, 4 and V. 3. Place a jumper (piece of wire) between Y and W if you have a heat pump without auxiliary/back-up heat.

How to Wire a typical Two-Wire Honeywell T87-F type Wall Thermostat

Thermostat Wiring Terminal Notes for typical Two-Wire Honeywell T87-F type Wall Thermostats (only 2 wires found in-use at the wall thermostat) Honeywell thermostat T87F type models include the Super Tradeline T87F1959 (replaces the T26A1433 and T87C1252), T87F1867, T87F2816, T87F2824, T87F2873. These thermostat T87F models vary by the operating temperature range they support and a few other simple features such as the presence or absence of a thermometer. Functionally and for wiring they are similar.
Thermostat Terminal ID	Wire Color	Two-Wire Heat Thermostat Hookup Comments
(R)	Red	Red wire coming to the thermostat from the heater. Connected to the R terminal in the room thermostat. See Note 1 in the table above.
(W)	White	White wire coming to the thermostat from the heater, connect to the W terminal in the thermostat.
Notes: 1. The [Honeywell 5-2 Day Programmable Thermostat - RTH2300B1012] thermostat cannot be used if your old thermostat had [and used] any two of the following wires: R, RC, RH, 4 and V.[5] 2. Also see Honeywell Thermostat Wiring Diagrams 3. Some thermostats will be supplied with a jumper wire or clip between the thermostat RH and RC terminal and will not provide a simple R terminal (such as the 3M-22 Filtrete). Connect the red wire to RH and leave the jumper in place.

How to Wire the Three-Wire Honeywell Wall T87-F type Thermostat

(3 wires found in-use at the wall thermostat)
Thermostat Terminal ID	Wire Color	Three-Wire Heat Thermostat Hookup Comments
(R) (RH)	Red	Red wire coming to the thermostat from the heater. See Note 1 in the table above.
(W)	Blue wire	For Honeywell Wall T87-F type Thermostats Connect the blue wire coming to the thermostat from the heater or air conditioner
(Y)	White wire	Watch out: For Honeywell Wall T87-F type Thermostats connect the white wire coming to the thermostat from the heater or air conditioner to the (Y) terminal, not the (W) terminal.
1. Also see Honeywell Thermostat Wiring Diagrams - Honeywell Wall T87-F type Thermostats

White Rodgers Thermostat Wiring Guide

Thermostat Wiring Terminal Notes for White Rodgers 1F90 Low Voltage Programmable Digital Comfort-Set
White Rodgers 1F90 Used For 2-wire Heating Only Systems
(W)	White	White wire coming to the thermostat from the heater or from the secondary (C) terminal on the transformer, routed through a White Rodgers isolation relay.
(RH)	Red	Red wire coming to the thermostat from transformer secondary (R) terminal. The same transformer (R) terminal typically also feeds a gas valve or vent damper, but not through the thermostat. See Note 1 in the table above.

White Rodgers 1F90 Used For 3-Wire Series 10 Heating Systems
(W)	White	White wire coming to the thermostat from the heater
(RH)	Red	Red wire coming to the thermostat from the heater. From transformer secondary (R) terminal. Note 1
(B)	jumper wire	Add a jumper between (R) and (B) on the primary control
(R)	jumper wire	Add a jumper between (R) and (B) on the primary control. Note 1.
Notes: 1. The [Honeywell 5-2 Day Programmable Thermostat - RTH2300B1012] thermostat cannot be used if your old thermostat had and used any two of the following wires: R, RC, RH, 4 and V.[5] 2. Color: markings in the thermostat wall plate or in some models at other terminals on the thermostat body itself may indicate conventional wire colors that connect to this terminal, or the terminal ID with a letter such as "R" = red, as we illustrate above. Watch out: the colors of the wires that you connect to these terminals do not necessarily match the nominal "terminal ID", as we illustrated above at "How Do I Install & Wire Up a Room Thermostat ". To allow for someone not following thermostat wire color conventions, when replacing an existing wall thermostat we identify and label the wires according to the letters marked on the terminal block to which the wires were actually connected. 3. Also see White Rodgers Thermostat Wiring Diagrams for more illustrations

Lennox thermostat and equipment wiring color codes may vary significantly from common usage. Be sure to consult with Lennox and obtain the proper installation manual for your equipment.

These White Rodgers Tables Map Old Thermostat Wires to New (White Rodgers) Thermostat Terminals & Help Identify Old Thermostat Types

Old Thermostat Terminal Marking or ID					Old Thermostat Type
White Rodgers Thermostat Terminal Identification Table
4	W	RC	Y	G	1
RH	W	RC	Y	G	2
M	H	V	C	F	3
RS	4		Y6	G	4
R	W		Y	G	5
Notes: 1. Source: White Rodgers 1F90 Low Voltage Digital Comfort Set Thermostat Installation Instructions [7]

Map of Old White Rodgers Thermostat Terminals (4 M R R5 RH H W) to New White Rodgers Thermostat Terminals
Old Thermostat Type	New	Old	New	Old	New	Old	New	Old	New	Old
1	RH	4	W	W	RC	RC	Y	Y	G	G
2	RH	RH	W	W	RC	RC	Y	Y	G	G
3	RH	M	W	H	RC	V	Y	C	G	F
4	RH	R5	W	4			Y	Y6	G	G
5	RH	R	W	W			Y	Y	G	G
Notes: 1. Source: White Rodgers 1F90 Low Voltage Digital Comfort Set Thermostat Installation Instructions [7]

...

Frequently Asked Questions (FAQs) about how to wire all types of room thermostats for controlling heating or cooling systems

Question: possible shorted thermostat wires

Our furnace thermostat failed after an adjacent water heater installation. I noticed that wires were pinched between the water heater and the gas pipe. After I loosened the safety straps and freed the wire, the thermostat works. (I reset the furnace). Were squished wires the cause of a temporary short and will the wires keep working if they are undisturbed? - Larry 8/2/11

Reply: check for shorted wires and for thermostat transformer damage as well as for blown fuse

Yes it's surely possible that your thermostat wires were shorted. Now a short in those wires sometimes lets you off the hook with no trouble, since the wires and thermostat are basically an "on-off" switch that calls for heat (or no heat).

But a thermostat wire short at the transformer could burn out the low voltage transformer that powers the thermostat and heating controls or maybe even damage the thermostat itself.

Find and check the low voltage transformer (often it's mounted near your furnace, on an electrical junction box, or it may be integral in your heater control unit). See How to Troubleshoot Low Voltage Transformers for Heating & Air Conditioning Thermostats

Question: 3-zone radiant heat: Honeywell RHT2300B thermostat can't talk to Azel i-Link SP83 zone controller

I am installing a 3 zone in-floor radiant system in my home. Every thing is going well so far, except I am running into an issue where Honeywell (my T-Stat manufacture) is telling me my RHT2300B t-stat cannot be used with my in-floor zone controller (Azel i-Link sp-83) when I call their tech support hotline.

They cannot tell me why or what their letter designations mean.

I am an industrial controls electrician of 23 years, who I must confess, does not have much experience with HVAC.

All I need is a simple t-stat that sends voltage (24vac) when heat is called for to my controller and opens back up (back to zero volts) when the set-point is achieved. I am having a hard time believing that this t-stat is not capable of doing that. Can any one help?
Eric - Eric 9/9/11

Reply: get the thermostat and controller product numbers correct and it's easy to find wiring instructions

Eric,

I found two important details in researching your question:

1. you gave me an in-valid Honeywell thermostat number, but I was able to guess at the correct one and easily obtain wiring instructions from Honeywell. Correctly your thermostat is the Honeywell 5-2 Day Programmable Thermostat - RTH2300B1012

2. For the Honeywell thermostat model that you mention, correctly named, Honeywell's instructions point out that

The [Honeywell 5-2 Day Programmable Thermostat - RTH2300B1012] thermostat cannot be used if your old thermostat had [and used] any two of the following wires: R, RC, RH, 4 and V.[5]

Call back and ask for senior service tech or service manager. So if, when you spoke with the Honeywell service technician, and if your old thermostat included and used any two of the wire labels I quote above, then indeed, even if s/he couldn't explain why, indeed you cannot use this thermostat model for your application.

Wiring Details & Troubleshooting for the Honeywell 5-2 Day Programmable Thermostat - RTH2300B1012

Remember that ultimately a thermostat is simply an on-off switch, or provides several on-off functions. But with multiple zone heat, you should expect to provide a thermostat for each individual zone - else they're not heating zones at all. In a traditional hot water heating system that does not use the Azel i-Link controller the first thermostat is wired directly to an aquastat that controls the first zone; the second two thermostats are wired to individual circulator relays (if individual circulator pumps are used) or to individual zone valves (if a single circulator runs the whole system).

Where zone valves are used, an end switch closes to turn on the circulator (a logical inclusive OR function with the other zone valves) when the zone valve opens to allow hot water to flow. That same principle is used when wiring the Azel i-Link Zone Switching Relay. And the company makes clear that their controller is compatible with standard thermostats:

ALL - controls are compatible with 2, 3 or 4 wire type thermostats. 24VAC output can be used to supply power to the thermostat. For thermostats requiring the 24VAC Common, simply connect C terminal from the thermostat to COM terminal on the 24VACoutput.[4]

First let's make sure you've identified your Honeywell thermostat model correctly.

Your [Honeywell thermostat] model number will begin with the letters, T, TH, RTH, C, or CT and is on the back of the thermostat.[5]

Honeywell RHT2300B - the number you gave, doesn't look right, but you probably meant RTH-2300-B. Calling Honeywell with the right product number (Tel: 800-468-1502) might produce better results. Honeywell has done a great job making installation and operations manuals available for their equipment, but you've got to search with the right product number.

Searching the Honeywell site for the corrected thermostat number delivers a single product that's probably yours, the 5-2 Day Programmable Thermostat - RTH2300B1012. In fact this thermostat is widely sold including at Home Depot stores, and I've installed and used this very model myself to control an add-on hot water heating zone and Taco circulator in an older home. According to Honeywell, this thermostat is compatible with:

Gas, oil or electric furnace
Central air conditioner
Millivolt system
Central heating and cooling system
Heat pump without auxiliary/backup heat. (This thermostat cannot be used on heat pumps with auxiliary heating or on multistage systems.)

For your model you want Honeywell document 69-2326ES - found at http://customer.honeywell.com/Honeywell/getliterature.axd?LiteratureID=69-2326ES.pdf - owners operation manual or

document 69-2327ES - for installation materials - found at
http://customer.honeywell.com/Honeywell/getliterature.axd?LiteratureID=69-2327ES.pdf

Here are details from that manual's instructions for wiring the Honeywell RTH-2300-B 5-2 Day Programmable Thermostat beginning with the inspection of the existing wires:

How to Correctly Identify the existing thermostat wires

3. Identify and label each of the existing thermostat wires by using not the wire colors (someone could have made a wire color error and violated convention) but rather, identify each existing thermostat wire by noting the letter next to the old thermostat wiring block terminals where each wire was connected to a screw. Identify and label the wires that are connected as

R (convention would be red wire)
W (convention would be white wire)
Y (convention would be yellow wire)
G (convention would be green wire)
C (convention would be "common" wire)

If any wires are not attached to your old thermostat or are attached to a terminal marked C or C1, they will not be connected to your new thermostat. Wrap the bare metal end of each of these wires with electrical tape, so it cannot touch and short other wires.

Watch out: since here we are focusing on connections, I am leaving out some important procedure and safety details like removing and taping each wire end to avoid shorting, etc. so be sure to consult the installation manual in detail.

On your new thermostat, the Honeywell the 5-2 Day Programmable Thermostat - RTH2300B1012, connect the wires you labeled as follows:

Wire labeled R (convention would be red wire) is connected to the "R" terminal on the thermostat
Wire labeled W (convention would be white wire) is connected to the "W" terminal on the thermostat
Wire labeled Y (convention would be yellow wire) is connected to the "Y" terminal on the thermostat
Wire labeled G (convention would be green wire) is connected to the "G" terminal on the thermostat
C (convention would be "common" wire) - you won't use this on the new thermostat

If the wire labels from your old thermostat hookup don't match the above, Honeywell offers additional advice that we adapt in table form:

Honeywell the 5-2 Day Programmable Thermostat - RTH2300B1012 alternative wiring tips
Old thermostat wire label	Connects to RTH2300B Terminal	Comments
C, C1, X, B	nothing - not used	Note 1
O, B, H	O/B
Y, Y1, M	Y	Note 3
R, RC, RH, 4, V	R	Note 2
G, F, L	G
W, W1, W2, H	W	Note 3

Notes: 1. Do not use C, C1 or X wire. Do not use B wire if you already have O wire. Wrap bare end of wire with electrical tape. 2. This thermostat cannot be used if your old thermostat had [and used] any two of the following wires: R, RC, RH, 4 and V. 3. Place a jumper (piece of wire) between Y and W if you have a heat pump without auxiliary/back-up heat. Other methods for identifying thermostat wires are at THERMOSTAT WIRING TIPS & COLOR CODES and at THERMOSTAT WIRE FUNCTIONS.

Azel i-Link Multi-Zone Switching Relay Wiring Details

In a radiant floor heating system that uses a controller, the additional thermostats must be wired to instruct that controller to send heat to their zones. Azel Technologies, a Canadian heating controller manufacturer, provides installation instructions and wiring diagrams for their controllers, including the Azel i-Link SP83-here is a copy.

Or contact Azel Technologies Inc., P.O. Box 53138 10 Royal Orchard Blvd. Thornhill, Ontario, Canada L3T 7R9 Ph: 905-223-5567 Fax: 905-223-3778 Email: info@azeltec.com, Website: www.azeltec.com.

Question: Adding a third heating zone with its one zone valve

I am adding a third zone (basement) to my oil fired hot water baseboard heating and have it all planned as far as the plumbing is concerned. The zone will have it's own 24V zone valve so will require a wall mounted thermostat. I'm only looking for heat so I believe a 2 wire thermostat is sufficient. My other two zones have their own valves and thermostats and the wiring at the valves is all connected with wire nuts and doesn't make any sense to me.
I guess my question is, can I just connect my new valve and thermostat directly to the aquastat terminals that "appear" to power the other valves and thermostats ?

If so, is there anything I need to be aware of, like possibly wiring it backwards and frying something ?
If I can just add the new "loop" directly to the aquastat, in what order are the connections made ? Example, aquastat to one connection at valve, 2nd connection at valve to one connection at thermostat, other connection at thermostat back to aquastat ?

If you need me to provide more detail on the types of thermostat, aquastat and zone valve I am using I can. My zone valve has two red wires and two yellow wires. The instructions seem to indicate that I only use the yellow wires and the red wires were for auxiliary, whatever that is.
Would much appreciate your input. Thanks. - Will 11/10/11

Reply:

Will I think this will help clear things up a little for wiring a 3rd heating zone using a zone valve approach:

When the TT calls for heat (yes 2 wire is fine) it tells the zone valve for its zone to OPEN. When the zone valve is fully open it in turn tells the circulator pump to start pumping. (There is an "end switch" in the zone valve that performs this second function).

So you'll find a pair of wires from TT to the zone valve and a pair of wires from the zone valve to the circulator relay.

Watch out though: the wiring connections can vary a bit among zone valve brands - if all of yours are the same brand you can look at the existing valve, follow the wires, and you'll see how the zone valve is hooked up. If there are different brands you'll need to ask for a clue from your HVAC supplier or the manufacturer.

Reader follow-up:

Dan, thanks for the information. So I effectively have two circuits to connect. One 24v circuit runs in series as follows - transformer, zone valve, thermostat, transformer. Please can you confirm this.
The other circuit is simply connecting the other two wires on the zone valve to the connections on the circulator relay.
For the first circuit, do you know where my transformer is likely to be located ? I have the box on the front of my furnace which contains controls for how hot the water gets and when it needs to be heated. Would it be in there ?
For the second circuit to the relay, I'm assuming the relay is attached to the circulator pump itself.

Question: Replacing a round Honeywell T87 with a Digital Honeywell Thermostat

Hello - I am replacing a round Honeywell thermostat with a non-programmable digital Honeywell unit. I have a hot water system with multiple zones and with no air conditioning. There are three wires at the thermostat. On the old round unit the red wire went to the R terminal, the white wire went to the w terminal and a green wire went to B terminal. I hooked up the new stat the same way but it would not work. If I selected "fan on" instead of "fan auto" the zone would heat up but would not shut off (hot water kept flowing even if I selected a temp below room temp). Appreciate your help. - Patrick - 1/20/12

Reply:

Patrick, typically the three wire thermostat hookups would be exactly the same for the old and new thermostats.

For details of wiring a typical and simple digital Honeywell thermostat, see Honeywell 5-2 Day Programmable Thermostat - RTH2300B1012.

For help in understanding the wiring of your old thermostat, see Three-Wire Honeywell Wall T87-F type Thermostat wiring and also see Generic HVAC Thermostat Control Wiring Points

Question: reader comments on shorting out thermostat wires & fusing requirements

Greetings, not sure if anyone saw this or not, but whoever S.R. is above in the description about shorting out wires seems to maybe have missed the fact that the "E" they refer to is actually a "3" amp fuse and not a 4 amp fuse. My HVAC installer of 30 years who recently installed 2 furnaces for us and is installing my heat pump agrees that it is a 3 amp fuse. We purchased an extra one just in case. Putting a 4 amp in there may not be good for the board as it may allow too much current for a relay or something and you may fry a piece on the board which is most likely not cheap. I hope this helps - D.M. - 3/12/12

Reply:

Thanks D.M., We posted your important fuse size comment right in the article at Shorting Out Thermostat Wires - Leads to Loss of Heat.

Question: Wiring a non-programmable White Rodgers Thermostat

I have a 1f86 Non programmable White Rogers i matched up the R to Red W to White and O/B to Black But I Get nothing and unfortunately I stay in a condo with base floor panels so i cant really hear if the heat comes on or not. How do i wire this thermostat correctly - Anon 4/24/12

Reply:

Anon, see These White Rodgers Tables Map Old Thermostat Wires to New (White Rodgers) Thermostat Terminals & Help Identify Old Thermostat Types

Question: Replacing a mercury thermostat with a digital unit

I am replacing an old mercury thermostat with a digital. my system is a heat pump. my neighbor gave me the digital, no instructions, no box. i'm trying to decide if this is even a heat pump compatible thermostat. on the therm it has c, g, rc, rh (which are linked by a black wire.) w, y, b, and o. coming out of my wall is, white connected on old therm w2, yellow connected to y, green conn g, black conn e, red to r, blue to b and bro to x. any help would be great. - Kurt 6/4/12

Reply:

Kurt, as you see in the examples at For help in understanding the wiring of your old thermostat, see Three-Wire Honeywell Wall T87-F type Thermostat wiring and also see Generic HVAC Thermostat Control Wiring Points. Many thermostat wiring setups are straightforward or "cookbook" but why not find the brand name on your thermostat and then you can obtain the installation instructions right from the manufacturer?

Also, Honeywell's thermostat replacement advice (and most likely that of all thermostat manufacturers) warns:

Watch out: MERCURY NOTICE: Do not put your old thermostat in the trash if it contains mercury in a sealed tube. Contact your local waste management authority for instructions regarding recycling and proper disposal.[5]

Question/Comment: Helpful Pointers Regarding 24V Thermostat Wiring & Heat-Anticipators

- Helpful Pointers Regarding 24V T, 10/7/2012

Reply:

Helpful, thanks so much for the detailed tips on wiring 24-volt room thermostats. I've inserted your remarks into the main article body above, beginning at 9 Thermostat Wiring Tips for 24V Thermostats. You are welcome to email me with contact information if you want to be identified or receive reader referrals. Also, sorry that the comment form software chopped off the end of your text point 9 -thanks for filling it in. We are dedicated to making our information as accurate, complete, useful, and unbiased as possible: we very much welcome critique, questions, or content suggestions for our web articles. Working together and exchanging information makes us better informed than any individual can be working alone. - Ed.

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[2] Thanks to reader S.R. for discussing loss of heat due to a thermostat wiring mistake, October 2010
[3] Thank to Mr. Scott Meenen, G&S Mechanical Services, for providing some common thermostat wiring codes also found at Mr. Meenen's web page http://toad.net/~jsmeenen/wiring.html . Mr. Meenan provides heating, heat pump, and air conditioning repair services in Maryland, Washington D.C., and northern Virginia. He can be contacted at 301-591-1646 or by Email to jsmeenen@toad.net - 10/2010. Quoting:
We service American Standard, Amana, Arco, Arco-Air, Bryant, Carrier, Coleman Evcon, Comfortmaker, Day/Night/Payne, Dunham-Bush, Fedders, Fredrich, Goodman, General Electric, Heil, Intertherm, ICP, Janitrol, Lennox (Armstrong, Johnson Air-Ease), Miller, Modine, Nordyne, Rheem/Ruud/Weatherking, Sears, Stewart Warner, Trane, Weather King, Williams, White-Westinghouse, Whirlpool, Weil Mclain, York, (Frasier Johnson/Borg Warner) and others.
[4] Azel Technologies Inc., P.O. Box 53138 10 Royal Orchard Blvd. Thornhill, Ontario, Canada L3T 7R9 Ph: 905-223-5567 Fax: 905-223-3778 Email: info@azeltec.com, Website: www.azeltec.com.
[5] Honeywell Controls, the company wants you to use their contact form at this web page: http://www51.honeywell.com/honeywell/contact-support/contact-us.html
Honeywell Consumer Products, 39 Old Ridgebury Road Danbury, CT 06810-5110 - (203) 830-7800
World Headquarters, Honeywell International Inc., 101 Columbia Road, Morristown, NJ 07962, Phone: (973) 455-2000, Fax: (973) 455-4807 1-800-328-5111
- Honeywell product model numbers & instruction Manuals: see http://yourhome.honeywell.com/home/Applications/FindYourModelNumber.aspx
[6] White Rodgers Thermostats and HVAC controls,
Homeowner information: http://www.emersonclimate.com/en-US/brands/white_rodgers/Pages/wr-homeowner-info.aspx
Contractor information: http://www.emersonclimate.com/en-US/brands/white_rodgers/wr_contractor_info/Pages/white-rodgers-contractor-info.aspx
White Rodgers Product Catalog (don't misspell the company's name as White Rogers Thermostats) -
http://www.emersonclimate.com/Documents/thermostats.pdf - Thermostat Catalog
[7] White Rodgers 1F90 Low Voltage Digital Comfort-Set thermostat Installation Instructions, PN 37-3654, White-Rodgers Division, Emerson Electric Co., 9797 Reavis Rd., St. Louis MO 63123
[8] "Automatic Oil Burner Controls - Thermostats", Domestic and Commercial Oil Burners, 3rd Ed., Charles H. Burkhardt, McGraw Hill, 1969 (and later editions), ASIN B0000EG4Y8
[9] Thermostat wiring color codes & conventions, Thanks to reader " Helpful Pointers" Regarding 24V T, 10/7/2012
[10] Domestic Central Heating Wiring Systems and Controls, 2d Ed., Raymond Ward, Newnes, ISBN-10: 0750664363, ISBN-13: 978-0750664363, Quoting from Amazon.com:
This unique A-Z guide to central heating wiring systems provides a comprehensive reference manual for hundreds of items of heating and control equipment, making it an indispensable handbook for electricians and installers across the country. The book provides comprehensive coverage of wiring and technical specifications, and now includes increased coverage of combination boilers, recently developed control features and SEDBUK (Seasonal Efficiency of Domestic Boilers in the UK) boilers ratings, where known.
In addition to providing concise details of nearly 500 different boilers fuelled by electric, gas, oil and solid fuel, and over 400 programmers and time switches, this invaluable resource also features numerous easy-to-understand wiring diagrams with notes on all definitive systems. Brief component descriptions are provided, along with updated contact and website details for most major manufacturers.
[11] Proliphix Corporate Headquarters, 3 LAN Drive Suite #100 Westford, MA 01886 Phone: +1.978.692.3375 Toll Free (U.S.): 866-IP-LIVING (866.475.4846) Fax: +1.978.692.3378 - Email: sales@proliphix.com or Customer support: support@proliphix.com Website: http://www.proliphix.com/ - quoting from the company's website:
All Proliphix Network Thermostats come with our free Uniphy Remote Management Service. This unique offering lets you monitor and control your HVAC systems by simply pointing your Browser to our secure Proliphix Web Site. Enjoy the convenience of programming a thermostat from any location, using a simple graphical interface. No computer equipment or software is required. And since Proliphix takes care of the network configuration for you, you’ll be up and running in no time. We’ll even proactively monitor your thermostats and send you an immediate email or SMS message when an HVAC problem is detected.
[12] "Heating Control Handbook for the Installer and Service Man,Oil Burner, Gas Burner and Stoker Controls", Honeywell Corporation, March 1949 [copy on file as HoneywellControlsHandbookSA1399-2-1949.pdf] . Some of the controls discussed in detail here include the
- Honeywell T1 and T11A = Series 10
- Honeywell T21A (T2) = Series 20
- Honeywell T847A = Series 80
- Honeywell RA117A (RA1) = Series 10
- Honeywell LA101A = Series 10,
- Honeywell LA419A (LA4) = Series 40
- V155A = Series 10, V435A = Series 40, V575A = Series 50, V835A = Series 80
[13] Trane TCONT800 Series Touch Screen Programmable Comfort Control Ownes Guide, American Standard, Inc., Troup Highway, Tyler TX 75711, January 2005, Telephone: Customer Service: 1-877-3381, website: www.trane.com
Domestic and Commercial Oil Burners, Charles H. Burkhardt, McGraw Hill Book Company, New York 3rd Ed 1969.
National Fuel Gas Code (Z223.1) $16.00 and National Fuel Gas Code Handbook (Z223.2) $47.00 American Gas Association (A.G.A.), 1515 Wilson Boulevard, Arlington, VA 22209 also available from National Fire Protection Association, Batterymarch Park, Quincy, MA 02269. Fundamentals of Gas Appliance Venting and Ventilation, 1985, American Gas Association Laboratories, Engineering Services Department. American Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209. Catalog #XHO585. Reprinted 1989.
The Steam Book, 1984, Training and Education Department, Fluid Handling Division, ITT [probably out of print, possibly available from several home inspection supply companies] Fuel Oil and Oil Heat Magazine, October 1990, offers an update,
Principles of Steam Heating, $13.25 includes postage. Fuel oil & Oil Heat Magazine, 389 Passaic Ave., Fairfield, NJ 07004.
The Lost Art of Steam Heating, Dan Holohan, 516-579-3046 FAX
Principles of Steam Heating, Dan Holohan, technical editor of Fuel Oil and Oil Heat magazine, 389 Passaic Ave., Fairfield, NJ 07004 ($12.+1.25 postage/handling).
"Residential Steam Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
"Residential Hydronic (circulating hot water) Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
"Warm Air Heating Systems". Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
Heating, Ventilating, and Air Conditioning Volume I, Heating Fundamentals,
Boilers, Boiler Conversions, James E. Brumbaugh, ISBN 0-672-23389-4 (v. 1) Volume II, Oil, Gas, and Coal Burners, Controls, Ducts, Piping, Valves, James E. Brumbaugh, ISBN 0-672-23390-7 (v. 2) Volume III, Radiant Heating, Water Heaters, Ventilation, Air Conditioning, Heat Pumps, Air Cleaners, James E. Brumbaugh, ISBN 0-672-23383-5 (v. 3) or ISBN 0-672-23380-0 (set) Special Sales Director, Macmillan Publishing Co., 866 Third Ave., New York, NY 10022. Macmillan Publishing Co., NY
Installation Guide for Residential Hydronic Heating Systems
Installation Guide #200, The Hydronics Institute, 35 Russo Place, Berkeley Heights, NJ 07922
The ABC's of Retention Head Oil Burners, National Association of Oil Heat Service Managers, TM 115, National Old Timers' Association of the Energy Industry, PO Box 168, Mineola, NY 11501. (Excellent tips on spotting problems on oil-fired heating equipment. Booklet.)
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Guide to Room Thermostat Installation, Location, & Wiring

Where to Locate & Mount a Room Thermostat & what spots to avoid

Good thermostat locations are

Bad Room Thermostat Locations

Room Installation Thermostat Installation Tips

Does the Room Thermostat Need to be Level on the Wall?

Yes for Older Mercury Bulb Switches

No for Newer Solid State, or Digital Room Thermostats

Hooking up a 2-Wire Thermostat: How Do I Install & Wire Up a Room Thermostat like the Honeywell Round Wall T87F Series Thermostat?

Basic 2-wire Room Thermostat Wiring Instructions

Where do the Thermostat Wires Start and Where do they End-Up?

3-Wire Thermostats: Where Do We Connect the Red, White, & Blue (if present) Wires to a Typical Three-Wire Wall Thermostat?

6-Wire Thermostats: Where Do We Connect the Red, White, & Blue, Yellow, Green, Orange Wires in a Typical Six-Wire Wall Thermostat?

Color Codes and Hookups for Thermostat Wires, typical for heat pump installations and thermostats

Typical Thermostat Wire Connections for Heat Pumps

Typical thermostat connections when wiring a thermostat to control only a heating system or only an air conditioning system

Instructions for Wiring of Line Voltage 120V Wall Thermostats

Tables of Common Heating and Cooling Thermostat Wiring Connections for Major HVAC & Thermostat Brands

Table of Common HVAC Thermostat Wiring Connections - Generic HVAC Thermostat Control Wiring Points

Table of Standard or Most-Common Thermostat Wire Colors Matched to Thermostat Terminal Names

3M-22 Filtrete™ Room Thermostat Wiring Guide

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

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

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

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

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

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

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

American Standard, GE & Trane Thermostat Wiring Guide

How to Wire a General Electric (GE), Trane, American Standard HVAC Thermostat

Flair Thermostat Wiring Guide

How to Wire a typical Flair 3-wire type Wall Thermostat

Flair model ANOVO Thermostat fed from a Flair zone valve

Honeywell Thermostat Wiring Guide

How to Wire the Three-Wire Honeywell Wall Series 20 Thermostat

How to Wire the Honeywell the 5-2 Day Programmable Thermostat - RTH2300B1012

How to Wire a typical Two-Wire Honeywell T87-F type Wall Thermostat

How to Wire the Three-Wire Honeywell Wall T87-F type Thermostat

White Rodgers Thermostat Wiring Guide

Thermostat Wiring Terminal Notes for White Rodgers 1F90 Low Voltage Programmable Digital Comfort-Set

White Rodgers 1F90 Used For 2-wire Heating Only Systems

White Rodgers 1F90 Used For 3-Wire Series 10 Heating Systems

These White Rodgers Tables Map Old Thermostat Wires to New (White Rodgers) Thermostat Terminals & Help Identify Old Thermostat Types

White Rodgers Thermostat Terminal Identification Table

Map of Old White Rodgers Thermostat Terminals (4 M R R5 RH H W) to New White Rodgers Thermostat Terminals

Frequently Asked Questions (FAQs) about how to wire all types of room thermostats for controlling heating or cooling systems

Question: possible shorted thermostat wires

Reply: check for shorted wires and for thermostat transformer damage as well as for blown fuse

Question: 3-zone radiant heat: Honeywell RHT2300B thermostat can't talk to Azel i-Link SP83 zone controller

Reply: get the thermostat and controller product numbers correct and it's easy to find wiring instructions

Wiring Details & Troubleshooting for the Honeywell 5-2 Day Programmable Thermostat - RTH2300B1012

How to Correctly Identify the existing thermostat wires

Azel i-Link Multi-Zone Switching Relay Wiring Details

Question: Adding a third heating zone with its one zone valve

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Question: Replacing a round Honeywell T87 with a Digital Honeywell Thermostat

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Question: reader comments on shorting out thermostat wires & fusing requirements

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Question: Wiring a non-programmable White Rodgers Thermostat

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Question: Replacing a mercury thermostat with a digital unit

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Question/Comment: Helpful Pointers Regarding 24V Thermostat Wiring & Heat-Anticipators

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