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Thermostat wiring reference chart - simplest case two-wire thermostat (C) Daniel Friedman Wiring a Honeywell Room Thermostat

Honeywell or Resideo Thermostat Wiring Connection Tables & Hook-up Procedures

Thermostat wiring details & connections for nearly all types of Honeywell room thermostats used to control residential heating or air conditioning systems.

This article gives a table showing the proper wire connections for Honeywell brand wall or room thermostats 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.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?

Honeywell Thermostat Wiring Guide

Honeywell room thermostat

Honeywell thermostats, wiring connections, instructions, diagrams

Honeywell T87 Type & Other Thermostat Installation & Operation Manuals

Older Honeywell Thermostat Wiring Diagrams

Honeywell Thermostat Installation & Wiring Manuals

Honeywell TH611 Thermostrat wiring connections cited & discussed at Inspecdtapedia.comIllustration: wiring terminals for the Honeywell TH611 Thermostat -

More Honeywell Thermostat Types, Instructions, Manuals

Two wire (red & white) Honeywell T87 Thermostat Wiring Diagram - heat only (C) InspectApedia.com adapted from Honeywell documents cited in this article

Above & Below: Honeywell T87F Thermostats in three versions:

Heating Only (above)

Heating & Cooling (below)

Honeywell T87F Thermostat Tradeline(R) wiring for heating & cooling control adapted by InspectApedia.com from Honeywell cited in this article (C) InspectApedia.com

& below, Cooling Only

Honeywell T87 Thermostat Wiring - Cooling Only - adapted from Honeywell cited in detail in this article (C) InspectApedia.com

How to Wire the Three-Wire Honeywell Wall Series 20 Thermostat, CT-87, & T8775X

Honeywell Wall Series 20 Thermostat, CT-87, & T8775X Wire Connections

(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: [2]

Notes to the table above

1. Also see HONEYWELL THERMOSTAT WIRING DIAGRAMS - Honeywell Wall T87-F type Thermostats

2 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.

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

Honeywell the 5-2 Day Programmable Thermostat - RTH2300B1012 alternative wiring Connections
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 to the table above

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.

Wiring Instructions for Honeywell T87-F Thermostats & their Replacements

Honeywell traditional T87 Round wall thermostat, analog (C) Daniel Friedman at InspectApedia.com

Shown above is the company's original traditional T87 round thermostat

Honeywell traditional T87 Round wall thermostat, analog (C) Daniel Friedman at InspectApedia.com

non-programmable thermostat and its contemporary, digital replacement that will be wired identically: Honeywell's T8775C1005.

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

Thermostat Wiring Connections for typical Two-Wire Honeywell T87-F type Wall Thermostats 
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 to the table above

(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.

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 these other HONEYWELL T87 WALL 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 t

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

Three-Wire Honeywell Wall T87-F type Thermostat Connections

(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.

Notes to the table above

Also see these other HONEYWELLT87 WALL THERMOSTAT WIRING DIAGRAMS - Honeywell Wall T87-F type Thermostats for sketches and drawings of Honeywell thermostat wiring hookups.

 

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 - or 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:

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

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:

Honeywell 5-2 Day Thermostat Wiring Table: If the wire labels from your old thermostat hookup don't match the above, Honeywell offers additional advice that we adapt in table form provided in detail

at HONEYWELL 5-2 DAY PROGRAMMABLE THERMOSTAT - RTH2300B1012 WIRING.

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 Connections
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 to the table above

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.

Here is a copy of the HONEYWELL RTH2300/RTH221 SERIES PROGRAMMABLE THERMOSTAT OWNERS MANUAL [PDF]

Other methods for identifying thermostat wires are at THERMOSTAT WIRING COLOR CODES and at THERMOSTAT WIRE TERMINAL ID CODES / FUNCTIONS.

Honeywell RTH3100C Thermostat Installation & Wiring

Below Honeywell shows the typical wiring connections or the RTH3100C thermostat.

Be sure that you label the wires before disconnecting them from the old thermostat, or if you are installing new equipment, identify the incoming wires from the equipment terminals and its manual.

Honeywell RTH3100C Thermostat wiring summary - SEE the INSTALLATION MANUAL for details or call Honeywell - at InspectApedia.com

Below are alternative wiring connections for the Honeywell RTH3100C thermostat along with an explanation.

Honeywell RTH3100C Thermostat wiring summary - SEE the INSTALLATION MANUAL for details or call Honeywell - at InspectApedia.com

Below is the complete Honeywell RTH3100C thermostat installation manual in PDF format.

Honeywell RTH6350/ RTH6450 & RET93E / RET95E Thermostat Installation & Wiring Guide

The Honeywell RTH6350 uses the following wire connections:

Basic RTH6350 / 6450 Wire Connections

Alternate RTH6350 / RTH6450 RET93E / RET95E Wire Connections

Watch out: if your wires do not match the above see several alternative wiring installation hookups on both of the thermostat wiring manuals given just below.

HONEYWELL RTH6350 / RTH6450 THERMOSTAT INSTALLATION GUIDE [PDF] retrieved 2017/12/26, original source: https://customer.honeywell.com/resources/techlit/TechLitDocuments/69-0000s/69-2416ES.pdf

HONEYWELL RTH6350 / RTH 6450 and RET93E / RET95E Series Thermostats INSTALLATION & OWNERS MANUAL [PDF] retrieved 2017/12/26, original source: https://customer.honeywell.com/resources/techlit/TechLitDocuments/33-00000s/33-00116ES.pdf

HONEYWELL RTH6350 / RTH6450 Series THERMOSTAT OPERATING MANUAL [PDF] does not include wiring instructions, retrieved 2017/12/26, original source: http://pdf.lowes.com/useandcareguides/085267573672_use.pdf

Reader comment: wiring the Honeywell RTH6350 to replace a 3-wire White Rogers thermostat

(Oct 4, 2017) Ryan said:

Hi, I have a setup that I think is probably common, at least in the northeast, but that I found very difficult to get straight.

I have a boiler with a hydronic zone valve that controls two zones. The thermostat I was replacing was an old White-Rogers mercury switch. It's a 3-wire configuration. The new t-stat is Honeywell RTH6350.

Both thermostats are wired into the hydronic valve. The valve connectors are labeled with numbers 1-6.

The wires going to the T-stat I replaced were configured like so:

My final, working configuration for the Honeywell RTH6350 thermostat is:

I had some trouble getting through to Honeywell support, but I finally succeeded in communicating with someone via the live chat they offer at the bottom of their help and support page.

That worked well. One tip before using that service: start the chat on a laptop or mobile device; I was on a desktop and had to run up and down the stairs checking on wiring.

I never would have arrived at that on my own given the information in the t-stat manual and what I've found on the internet, so bravo Honeywell support person.

This comment was posted originally

at THERMOSTAT WIRE CONNECTIONS

Reply:

Thanks Ryan, that will help other readers. I'll keep your comment in our Honeywell Thermostat Wiring Instructions.

Honeywell TH9320WF5003U Thermostat Installation & Wiring

Question: using the blue wire for 24V power?

2017/09/18, Marc said:

I previously had a Source1 tstat. Battery powered. No issues. I decided to upgrade to a programmable tstat. I went with the honewell TH9320. The wiring was the same W to white, Y-yellow, and G- green. I hooked up the Red to R (previously it was hooked to the RC-RH loop).

There was an additional blue wire that was not used, but i needed now for the 24volt power. I hooked it up on the control board. Now, as soon as i connect the tstat, the blower kicks on. I have it set to auto. Even if i turn it off, it still runs. Only way to turn off the blower is to disconnect the tstat or unplug the blower

. I turned the temp up to 80 in my house. the tstat read 73, and stayed running. (this is the AC). Do these units take time to sync, or anything? Should i let it run longer? Or is my tstat defective? I hooked my old source1 back up and it is fine. turns on and off when temp is reached.

This question was posted originally

at THERMOSTAT CALIBRATION

Reply: the blue wire is typically used for a heat pump reversing or "changeover" valve, not as a standard power source

Marc,

First, did you confirm what the blue wire is doing in your wiring harness?

In the Honeywell TH9320 installation manual, as I read the wiring instructions they expect the blue wire to be operating a reversing valve - for heat pumps.

And in setup you are to "In Setup, set changeover valve to O or B."

Usually the R (red) wire or Rc wire is the power source to the thermostat and carries 24VAC.

In the thermostat Custom Setup did you make sure that your thermostat is set for the proper type of heating system:

Your system type Select Forced Air (default), Heat Pump, or Hot Water or Steam. Each option offers different choices on the following screens.

Your forced air heating system type Select how your forced air system is powered: Gas/Oil (default) or Electric.

Efficiency of your heating system - Select Standard Efficiency Forced Air (default) or High Efficiency Forced Air.

Your heating system type - If you selected Hot Water or Steam on “Your system type,” select the specific heating system here. Note: Touch the orange Help button on any screen for more information.

Number of cooling stages Select 1 Stage (default) or 2 Stages. If you are unsure, note which wires are connected: ‘Y’ wire only (1 stage) or ‘Y’ and ‘Y2.’

Number of heating stages Select 1 Stage (default) or 2 Stages. If you are unsure, note which wires are connected: W’ wire only (1 stage) or ‘W’ and W2.’

Your fan control Select whether your thermostat (default) or heating system controls the fan.

Type of changeover valve - If you selected Heat Pump on “Your system type,“ select whether it uses a cooling changeover valve (default) or heating changeover valve. If you are
unsure, note which wires you have connected.

Number of heat pump compressor stages

Select 1 Stage (default) or 2 Stages. If you are unsure, note which wires are connected: ‘Y’ wire only (1 stage) or ‘Y’ and ‘Y2.’

Your backup heat No or Yes (default) you can determine whether you have backup heat.

Older Honeywell Thermostat Wiring Diagrams

2-Wire Gas Heat Honeywell T87F Thermostat wiring diagram

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.

A second set of contacts will make or close on temperature rise. This second set of contacts is typically used to operate a cooling or air conditioning system but 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]
Honeywell T87F Thermostat wiring diagram for 2-wire, spst control of heating only in a typical gas fired heating system - details from Honeywell Controls

2-Wire Oil Heat Honeywell T87F Thermostat wiring diagram

Above the thermostat wiring diagram illustrates use of a Honeywell T87F thermostat in a 2-wire application controlling an oil fired heating appliance.

Two wire (red & white) Honeywell T87 Thermostat Wiring Diagram - heat only (C) InspectApedia.com adapted from Honeywell documents cited in this article

[Click to enlarge any image]

For a table of wiring connections for this thermostat also see

3-Wire High Limit Honeywell T87F Thermostat wiring diagram

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 typical 3-wire, open contact, high limit control such as on an oil fired heating boiler.

3-Wire SPDT Honeywell T87F Thermostat wiring diagram

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 3-wire application as a spdt (single pole double throw) switch such as used to control low voltage motors, electric radiator valves, zone valves.

The thermostat makes a contact on both a rise and on a fall of room temperature.


4-Wire Honeywell RTH2300 5+2 Programmable Thermostat wiring

Honeywell RTH2300 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 the typical wiring connections when installing a Honeywell RTH2300 (or similar) programmable room thermostat. Be sure to identify and label the existing thermostat wires before disconnecting them from the terminals on the old thermostat you are replacing.

Watch out: existing thermostat wires that will not be used in the new thermostat installation, such as wires attached to C or C1 terminals on the old thermostat should have their ends taped so as not to accidentally touch and short other thermostat wires or connectors.

Here is a copy of the HONEYWELL RTH2300/RTH221 SERIES PROGRAMMABLE THERMOSTAT OWNERS MANUAL [PDF]

Need More help? Call Honeywell at 1-800-468-1502 for assistance with your Honeywell thermostat.


Honeywell Series 10 Thermostats & Controls

Honeywell Series 10 control schematic

Honeywell Series 10 controllers such as the Honeywell R19A use a simple relay and built-in transformer and one or more line voltage contactors.

These are spst switch type controls (such as heat-only).

The No. 1 is a low voltage holding contact while the No. 2 is a line voltage contactor. The "coil" shown may be a magnetic coil that pulls in the armature of the No. 1 relay or it may be a relay type coil used in a gas control valve. The holding contact closes when the coil is energized.

In this sketch from a 1949 Honey Heating Control Handbook the thermostat has been satisfied (both contacts are open) and the system is not calling for heat. On a drop in temperature the flexible blade makes the white contact, and subsequently connects the stiff blade. On a rise in temperature the contacts break (or open) in the opposite order. [Line voltage circuits are not shown].

Symptoms of Broken or Shorted Thermostat Wires in a Series 10 SPST type circuit

Understanding the wiring details of series 10 controls and circuits can help us diagnose heating and cooling system operating snafus. Here are more examples from the Handbook.[12]

Symptoms of an open thermostat wiring circuit (broken wire, bad splice, loose screws)

  1. White wire broken: thermostat cannot pull in the relay and cannot hold it open - after a momentary shorting of the W-B terminals at the relay or valve
  2. Blue wire broken: thermostat cannot pull in the relay or valve, but once the relay is forced in (closed) the circuit can hold
  3. Red wire broken (or a loose heater plug screw) causes short cycling on the blue contact - single point operation

Symptoms of a short circuit in the thermostat wiring

  1. White wire shorted to the blue wire: relay or valve stays "on" unless all electrical power is shut off by the limit control switch, by disconnecting a wire at the low voltage transformer, or by turning off power to the system
  2. White wire shorted to the red wire: thermostat can start the heater's burner but can't stop it
  3. Red wire shorted to blue wire: short cycling (single pointing) on the white contacts alone

Mis-wiring of thermostat wires: wires connected to the wrong terminals

  1. White & blue wires swapped incorrectly: causes short cycling on the blue contact
  2. Blue and red wires swapped: short cycling on the white contact
  3. Red and white wires swapped: normal operation except that the heater is effective too quickly - resulting in short on-cycles and inefficient operation

 

More Honeywell Thermostat References & Guides

 

Thank you to our readers for their generous comments

I almost cried after reading your article. Thanks so much man. It worked!

inspectapedia.com.moderator, Tried for hours looking up diagrams, from old units to new thermostats.

I almost cried after reading your article. R is for red and also Rc but they seem to be bridged now. Y is for yellow, w is for white, don't bothered with common. Thanks so much man. It worked! Ill give a tramp $20 on your behalf tonight. On 2021-03-17 by Mark

by danjoefriedman (mod)

@Mark, really glad this worked for you

...


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