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Thermostat wiring reference chart - simplest case two-wire thermostat (C) Daniel Friedman How Wire a Honeywell Room Thermostat
Honeywell Thermostat Wiring Connection Tables
Hook-up Procedures for Honeywell-Brand Heating, Heat Pump, or Air Conditioning Thermostats

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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.



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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 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 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 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 - 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 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.

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

[Click to enlarge any image]

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 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.I f 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.

...


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