Table of Contents
Thermostat Wiring Colors Code Page Navigation
- Essential Thermostat Wiring Color Guide Including Manufacturers Instructions
- Thermostat Terminal Designations Quick Guide - Detail Wiring Color Guide Below
- Red-Wire - connects to the R terminal with the red wire
- RC-Wire - connects to the RC terminal RC red
- RH-Wire - connects to RH terminal RH heat
- Y-Wire - connects to the Y terminal and is for cooling stage 1 with the yellow wire
- Y2-Wire - connects to Y2 terminal and is for cooling stage 2
- W-Wire - connects to W terminal and for heat stage 1 with the white wire
- W2-Wire - connects to W2 terminal and for heat stage 2
- G-Wire - connects to G terminal and for fan operation with the green wire
- C-Wire - connects to C terminal (common 24v power) with the C wire
- O or B-Wire - connects to O or B terminal and is for reversing valve operation
- E-Wire - connects to E terminal and is for Emergency heat
- X or Aux-Wire - connects to X terminal and is for auxiliary
- S1 and S2 Wires - connects to S1/S2 terminals and is for outdoor temperature sensor
- Thermostat Wire Color Code Chart
- Tracing the Wire to the Source
- Additional Resources
What you will learn in the Thermostat Wiring Colors Code article:- First, what thermostat wire colors is likely to go to which terminal on the thermostat in your heating and cooling system
- Secondly, the function of each wire terminal on the average thermostat highlighting some of the differences in those HVAC system functions from manufacturer to manufacturer as recommended for thermostat wire color
Sometimes, the thermostat is not the problem. Please check this article for a checklist of things to check before calling a heating and cooling repair service.
Thermostat Wiring Colors Code | HVAC Control
Always follow the thermostat manufacturer’s instructions whenever changing the thermostat. Always turn the power off at the air handler and the condenser and make sure there is no voltage at the transformer before proceeding.
For instructions on how to wire a thermostat, please see how to wire a thermostat page. Refer back to this page for thermostat wire colors.
Thermostat Wiring Colors Code - High Performance HVAC Thermostat Terminal Designations
Before proceeding, we highly advise that you turn the power off at the circuit breaker. Furthermore, the power for both the condenser and the air handler/furnace. You may cause a dead short in the control circuit. Additionally, that could potentially cost you a service call for troubleshooting and repair.
Thermostat Wire Colors Code | HVAC Control
Thermostat Wiring and Wire Color Chart – Thermostat Wiring Colors Code | |
|---|---|
| Tstat Terminal Designation | Color of Wire and Termination |
| R – The R terminal is the power. It is a red wire and comes from the transformer usually located in the air handler for split systems, but you may find the transformer in the condensing unit. For this reason, kill the power at the condenser and the air handler before changing or working on the wiring at the t-stat. Lastly, if you have a package unit, then the transformer is in the package unit. | Red Wire for the R terminal - *You should be aware that this may have changed, especially if the person who wired the thermostat didn’t use conventional color coding. |
| RC – The RC terminal is designated for the power for cooling. Some HVAC systems use two transformers. A transformer for cooling and a transformer for heating. In this case, the power from the transformer in the air conditioning system would go to the thermostat terminal. Furthermore, it should be noted that a jumper can be installed between RC and RH for a heating and cooling system equipped with a single transformer. | Red Wire for RC terminal. *Although be aware that this may have changed, especially if the person who wired the thermostat didn’t use conventional color coding. |
| RH – The RH terminal is designated for the power for heating. See RC above for an explanation. It should be noted that a jumper can be installed between RC and RH. Finally, this is only for heating and cooling systems equipped with a single transformer. | Red Wire for RH terminal. *Although be aware that this may have changed, especially if the person who wired the thermostat didn’t use conventional color coding. |
| Y – This is the terminal for cooling or air conditioning and goes to the compressor relay. Typically a thermostat wire pull is made to the air handler on split systems. This wire is then spliced for the separate wire pull which is made to the condenser. Furthermore, some manufacturers put a terminal board strip near the control board in the air handler. Therefore, a splice is not needed. | Yellow Wire for Y Terminal. *Although be aware that this may have changed, especially if the person who wired the thermostat didn’t use conventional color coding. |
| Y2 – This is the terminal for cooling second stage if your system is so equipped. Finally, many systems only have a single compressor but if you have two compressors (or a two stage compressor) which should only operate off of one thermostat then you need the Y2 thermostat terminal for second stage cooling. | *The most common color I’ve seen used for this terminal and wire designation is light blue, but this varies and is entirely up to the installer what color to use. Furthermore, for the thermostat, wiring colors code for this terminal (if equipped) consult with the installer. Finally, if that is not possible, then trace the wire out to the source. |
| W – This is the terminal for heating. This wire should go directly to the heating source whether it be a gas or oil furnace, electric furnace, or boiler or auxiliary heating for a heat pump. | White Wire for W Terminal. *You should be aware that this may have changed, especially if the person who wired the thermostat didn’t use conventional color coding. |
| W2 – This is the terminal used for second stage heat. There are gas furnaces with low fire and high fire and some depend on control from a two-stage heating thermostat with a W2 terminal. Heat Pumps use staging for auxiliary heat and need a W2 terminal. | *The most common color I’ve seen used for this terminal and wire designation is a brown wire, but this varies and is entirely up to the installer what color to use. Furthermore, for the thermostat, wiring colors code for this terminal (if equipped) consult with the installer or trace the wire out to the source. |
| G – This is the terminal used for the fan relay to energize the indoor blower fan. Furthermore, on a split system the blower fan is in the air handler. A package unit the blower fan is in the outdoor package unit. | Green Wire for G Terminal. The fan wire. Furthermore, *be aware that this may have changed, especially if the person who wired the thermostat didn’t use conventional color coding. |
| C – This is the terminal which originates from the transformer and is necessary to complete the 24 volts power circuit in the thermostat but only if the thermostat consumes electricity for power. Finally, many digital thermostats require 24 volts for power, so the common wire is necessary. | C stands for common, and there is no universal color used for this terminal, although black is the most common color I’ve seen. For the thermostat, wiring colors code for this terminal (if equipped) consult with the installer. Finally, if that is not possible, then trace the wire out to the source. |
| O or B – These terminals are for heat pumps and the B t-stat terminal is used on for Rheem or Ruud and any manufacturer that energizes the reversing valve in heating mode for the heat pump. Furthermore, other manufacturers of heat pumps utilize the reversing valve for cooling. The O thermostat terminal is for this purpose. This wire goes to the outside heat pump condenser, for reversing valve control. Finally, this is for heat pump thermostats. | Orange Wire for O and Dark Blue Wire for B, depending on the installer of the heat pump and the manufacturer. If you have a Trane, Carrier, Goodman, Lennox, Ducane, Heil, Fedders, Amana, Janitrol, or any other manufacturer other than Rheem or Ruud, you will be utilizing the orange wire for reversing valve. Lastly, Rheem and Ruud will usually use the blue wire for the reversing valve. |
| E – This terminal is for heat pumps and stands for Emergency Heating. Furthermore, if for whatever reason the heat pump condenser fails and it is necessary to run the heat there is an option on heat pump thermostats for emergency heating. The E terminal activates the back-up heat source. | E – There is no universal color used for this terminal designation, but this should be wired directly to the heating relay or the E terminal on a terminal stripboard in the air handler or package unit if you have a heat pump package unit. |
| X or Aux – This terminal is for back-up on a heat pump and allows for auxiliary heating from the back-up heat source usually located in the air handler. | X or Aux – There is no universal color used for this terminal designation. However, this should be wired directly to the heating relay or the Aux terminal on a terminal stripboard. It is terminated in the air handler or package unit if you have a heat pump package unit. |
| S1 & S2 or (Outdoor 1 and Outdoor 2) – Some tstats have this terminal. Furthermore, these are for an outdoor temperature sensor. Special shielded wire is used for this run and completely separate from the other thermostat wires. Finally, some manufacturers will show this the T terminals on their thermostat. | Using shielded wire prevents electromagnetic forces generated from other wires from interfering with the signal inside the shielded wire. A remote temperature sensor is a solid-state device. Furthermore, the signal needed to get an accurate temperature is sensitive to electromagnetic forces from another wire inside the structure. Finally, this type of wire is different from the typical thermostat wire and a separate wire altogether. |
Wiring Color Chart for Air Conditioners and Heat Pumps
Tracing a Wire to the Source
If you find the colors are not matching to the convention described here, you can always trace to the source. Furthermore, only if you are confident in your skills. Replacing an old thermostat with a new thermostat can be daunting so make sure to follow all thermostat wiring instructions. Lastly, follow the instructions on our How To Wire a Thermostat page for many great tips such as: Take a picture of the old thermostat wiring before you unwire it.
- First, as mentioned, there is high voltage in the equipment and can be hazardous to your health.
- Lastly, if you wire it wrong or accidentally touch the wrong wires together, you can blow the transformer.
Furthermore, either reason can be harmful.
Additional Resources
Also, check our thermostat category for other detailed articles on thermostats. Additionally, it includes other detailed pages about the thermostat wiring color code.
Thermostat Wiring Colors Code
We have a Rheem R96V two-stage ECM motor furnace. We want to install an Ecobee thermostat. We don’t have a C wire so I know we need to install the PEK that comes with it, at the furnace. I noticed that the Green G wire at the furnace is actually connected to the Y2 terminal in the current thermostat (G location is empty at thermostat). I believe it was done this way so that the AC will always run in the second stage…but I could be completely wrong. If we install the Ecobee the same exact way (just with the PEK added at the furnace) will it work? Please help! I can’t get a straight answer. Right now the system works great…some people are telling me that there’s no way the system could work with the way it’s wired.
Sorry for the late reply. I just notice this. Usually, I get an email with new comments but for some reason, I didn’t get any notification for this one.
I have an Ecobee thermostat at my cabin that the whole family uses for get-aways. I know people who have used the PEK but I personally do not prefer it. I would pull new wire for the thermostat and the equipment and follow the color code noted above. I know this can be a big project for most people but it is the best way to do it.
And when you purchase new thermostat wire make sure you get 18-8 meaning it is 18 gauge wire in a bundle of 8 wires. This should give you enough wires to handle everything.
Not a late reply at all! Super quick actually! Ok I’ve thought about pulling new wire. But I’m still confused as to why the Green wire is currently at Y2 and not G at the thermostat. Also if I run new wires would I need to change any dip switches at the furnace, as I’m told, right now it’s wired for single stage furnace when in fact it is a two stage.
I do not know what type of system you have but likely yes for a two-stage operation to get the blower to operate as it is supposed to operate in conjunction with the staging. If it has two-stage cooling you want to make sure the condenser is wired for that also for control.
Here is the wiring diagram for a Carrier Two-Stage Heat Pump
As you can see it can require up to 12 wires from the thermostat to the air handler depending on additional features like a humidifier or other devices requiring control.
From start to finish I would go over the entire system including wiring to any dip switch settings to make sure everything is set up properly. That would include using the traditional color code noted in the article above. Good luck.
First off, thanks for helping everyone out. Second, I had a Trane system installed last year with with a 4 zone Honeywell Controller. Unfortunately, the company that installed it went out of business and never finished. I had someone come out and finish but the system still does not have seem to operate correctly. The system is a 5 ton heat pump with a 2 speed compressor and with a 2 speed gas system with a variable blower. I can go into more specifics if needed. I believe it is wired incorrectly. The blower motor does not seem to ramp down as I think it would with only one zone calling. Also, the compressor does not seem to go into the two speeds as I think it should. The system is controlled by the Honeywell HZ432 TrueZone. Is there somewhere or can you tell me what each component wire should be hooked to? Basically, I am looking for a good/detailed wiring diagram that shows all of the wire connects from the outside unit to the inside unit and the control panel with required jumpers. I add write up how each is connected if that helps. Let me know if you can help out. Thanks. Mike
I would love to help you right now, however, I am extremely busy. In the near future, I will devote an entire article to this system (Honeywell TrueZone) and its operation. This is a layered control system where Honeywell controls some things while Trane controls other things. There are also several different settings, usually done by dip switches that will control various things including ramping the blower. And variable speed blowers can be tricky because they are so quiet. I cannot make a promise as to when but I will get to it soon. In the meantime, I would recommend you call an authorized Trane dealer, ask them if they have technicians who are familiar with your type of system. If so, then have them come out and give the system a once over check. Personally, if it was my house, I would go with several smaller systems over one big zoned system. Residential zoning, at least these types of systems, have not been perfected enough as compared to commercial systems. I’m talking about precision control for temperature and airflow. Sorry, I can’t help you at this time but firstly, as stated, I am extremely busy right now and secondly, this is a complex system that requires time to devote to details.
I have an old American Standard thermostat I have purchased a new Honeywell RTH6360. From what I have read in the Honeywell installation guide. This is how they should be connected. First is the American Standard Wiring. Second would be the wiring to the new Honeywell. I have an extra wire on my American Standard T that I do not know where it should be connected
R – R
O – O/B
G – G
Y – Y
X2 – E
B – C
W – W
It is common for installers to run extra wiring in the bundle. You need 7 wires (from your description) but the bundle has 8 wires. It is simply a spare wire in the bundle. Wrap it around the bundle and wire as instructed. If in the future you have issues you will have an extra wire. Hopefully, you will not need 2 extra wires if a problem were to occur.
So I changed my old Honeywell thermostat to a digital one a few months ago which works fine. I’m wanting to change to a smart thermostat, but when I went to look at the HVAC unit since I need the Ecobee PEK adapter the wiring confused me. From when I originally took out the old thermostat, it had Y,W,G,R wires. When I went down to the HVAC unit just now to make sure everything lined up it didn’t have the Y wire going to the Y receptacle, but instead it was connected to the C receptacle and nothing connected to the Y? Any idea why or what this means?
The Y wire is running out to the condenser for the compressor contactor. Its normal for it to be that way.
Thank you for the reply! So am I able to to use the smart thermostat with the PEK adapter, or since the C receptacle is already taken will it not work?
No, the C terminal can be used for the thermostat as well as the condenser (shared common). Simply add a wire under the C terminal in the air handler. C is the opposite side of R coming from the transformer and is needed for a complete circuit. The C side of the transformer is attached to every single load on the control side of your HVAC system so having more than one wire on the C terminal makes no difference. The only difference it would make is if you exceeded the VA rating of the transformer and in this case, that is very unlikely.
Hopefully, you have an extra wire running to the thermostat as you will need five wires to make the Ecobee work. I have an Ecobee4 and it works great. When I installed it replaced an old mechanical type of thermostat that needed only 4 wires. When I took the old thermostat off the wall I pulled all the wires out and discovered there was an unused wire in the bundle. At the air handler, I attached that wire to common (the same going to the condenser) and at the other end, I attached it to the C terminal in the Ecobee4 subbase.
I could have used the PEK adapter but I would rather have the common wire attached and the system working with that. I travel a lot and can turn things on and off from afar. It’s fantastic to have remote control and monitoring. It also saves money because I do not have to run the HVAC system except when the temperatures are extreme. They also have a proximity feature that works off the app on my phone. When I am within a certain distance from the house it turns it off automatically when I travel outside of that radius and turns everything back on when travel inside of that radius.
Hello, I figured I would try here to see if I can find a solution. My brain is going to explode. I have been doing endless research, but nothing!
I just bought this home 4 months ago when the snow was still on the ground. Before buying, the home was inspected, everything. The inspector recommended having the furnace cleaned since he noticed a few things. Long story short, they replace the furnace. Now that its finally getting hot, I turn the air on and nothing worked. I assumed the contactor was bad and replace it myself. If I now hold contactor in, it powers on. But nothing from T-Stat. I took a look at the furnace and at the board, the guy never installed the two wires coming from the Contactor (low Volt Side). If I add them to R and Y, nothing happens. R to C on Board kicks on great. Problem is it wont shut off at the T-Stat just keeps going. (forgive me for my terminology, from reading through the comments I am assuming T-Stat is short for thermostat. If not, that is what I am referring to.
At my T-Stat the wires are G, Y, W, RH, RC They have a jumper wire from RH to RC
Also has the Letters B and O. but nothing plugged into these. Just those 4 wires and that jumper wire.
The Board at the furnace is a YORK 879598. This board as I said above does have a common (which if I plug wires from contactor into R and C, it works) But I cant get it to communicate with the T-Stat correctly I am assuming since this has no C at all? The T-Stat is a LUX TX9000LC
Is there a work around, or simple solution I’m missing here?
Thank you so much and look forward to hearing back!
Spencer
At the furnace, the wires coming from the condenser, install one on the common or “C” and connect the other one to “Y” where the Yellow wire (coming from the t-stat) should be. Problem solved so no heads explode today. Make sure to be patient and wait for the time delay (<5 mins.)
OUTSTANDING!!!!!! Thank you so much for your speedy response!! I have AC Now my friend!
Spencer!
If I may… let me share with you what an extremely experienced tech taught me several decades ago… This “Should make it easy for most”…
Ok… Take mental notes…
Green… fan like a SPRING BREEZE… this is the FAN/Blower wire.
White… When HEATed… things get WHITE HOT… heating.
Yellow… watch out where the huskies go and don’t you eat that YELLOW Snow.. Snow is cold.. Cooling.
Red… just like a car or any DC circuit EVEN THOUGH IS IS 24 VOLTS… Supply side of the 24 VAC transformer.
Black or possibly Blue… the Common or return side of the 24 VAC Transformer that runs the LOW voltage side of units.
Orange… normally the Reversing Valve wire on Heat Pumps.
Hope this helps.
So the white wire is for one heat strip, and the black wire is for the other heat strip? Is one of the white wire and black wire for Aux, whereas the other is for emergency? It seems like the white
I’m trying to determine if I’m compatible with Nest E, which does not have W-2, and does not have Aux, and only has W-1. Seems like the answer is no.
Assuming the black and white wires are properly traced, is it likely the white wire goes to W for heating, and the black wire goes to Aux or W-2?
didn’t finish my sentence above. I meant it seems like white is for heating, whereas black is for Aux.
The only real way to determine where the black goes is to trace it out. Can’t say too much about the NEST so you will have to refer to them for more details. I think their intentions are great but have read and heard a lot of negative things about NEST and their sub-bases in the HVAC community.
Hi, I currently have a Honeywell RTH2410 thermostat, and I can’t figure out a particular wire. I have a heatpump with heat strips for 2nd stage heating.
Right now, my thermostat has an orange wire in O, a green wire in G, a yellow wire in Y, a red wire in R, a blue wire taped off, and BOTH a black and white wire in W/Aux. B and RC have no wires. I cannot figure out this black wire. I think maybe it is being used as the common wire, as there is no C terminal on this thermostat. Any ideas?
https://imgur.com/a/Cyv7sNb
It looks like the white and the black wire are your electric heat strips and are terminated in the same place. It is not uncommon for it to be wired this way but unless the air handler uses a sequencer or control board to stage the electric heat then the electric heat is energized all at one time. I sure there are sequencers to control the staging though. To make this work through a thermostat you need a thermostat that has a W-2 termination. Your thermostat does not have that terminal. And to really find out the mysterious black wire you have to trace it to the air handler but be very careful because it contains high voltage and really should only be looked at by someone who has training and knows what they are looking at. And by the way, if it was a common wire it would blow a fuse or transformer when the W terminal energized. The thermostat is battery powered rather than powered from the control transformer. There is no C because of that.
Hi, our condo is heated and cooled by electric heat pump…no gas. I would like to replace the old Carrier thermostat with a WIFI smart Honeywell..model 9580. So far the wire configuration is as follows:
C ( common) to C
R to R
G to G
O/W2 to W2/AUX
Y/Y2 to Y2
W/W1 to W-O/B
This leaves 3 connections from the Carrier that I can’t place on the new Honeywell…S1, S2 and HUM. Any suggestions? The available slots on the Honeywell are K, Rc, Y and L. Are the above configurations correct?
Thanks
Can’t really say the connections are absolutely correct without looking at the system and verifying the terminations at the air handler. The S1 and S2 are attached to an outdoor air temperature sensor. The HUM is for a humidifier as the current thermostat is also a thermidistat or a humidistat/thermostat combined. You have a few options if you really want to do this but I don’t recommend it. You can buy a humidistat and mount it somewhere near the thermostat. A humidifier helps in the winter and can save you money so I don’t recommend abandoning it but that is an option. The outside air temperature can be done by the new Honeywell over WiFi pulling the local temperature and using that for display and sometimes control depending on the type of system you have.
Honestly, I recommend that you call a professional to do this properly mainly for the humidifier problem. With the new WiFi thermostat, the S1 and S2 wires can be abandoned. I would not cut them off completely but rather tape them to the thermostat wire in case you want to switch back in the future. If you do switch back and the outdoor air temperature sensor is more than ten years old I would test it for calibration to make sure it is accurate. It seems like you have staging there which can be a lot more efficient with control algorithms in the thermostat that are dependent on an outside air temperature reference. This can get complex (especially when the word algorithm is used) but the control is much more precise when it is done properly and in the long run that will save you money.
If you want to dive deeper into this subject and see how I answered this question for someone else who had a similar issue you can see this article for a reference: Honeywell Heat Pump Thermostat Troubleshooting with a Carrier System
Good Luck!!
It took over ten web searches to finally land on your AWESOME webpage! Since I didn’t have such great information yesterday, I proceeded to install a new Emerson Series 80 programmable thermostat on our Goodman heat pump system. The Goodman is three years old and was installed with a Braeburn standard thermostat. The Braeburn had a separate slot for O (orange) and B (blue). The new Emerson has O/B on one slot. In my haste I put both the blue wire and the orange wire into this slot. Ran a test, nothing worked. Then put the blue wire into the C slot but still nothing is running. Could putting both orange and blue together blow something out? Breaker was off until the test phase. I’m about to reinstall the old unit just to make sure it still works. Thank you very much for your response.
The answer to your question is yes. Putting them together could have blown a fuse or even the transformer if it didn’t have fuse protection. If you have a fuse on the system it is either near the transformer or a low voltage/amp fuse on the circuit board. Some circuit boards don’t have fuses. The solution to your problem is to trace all the wires out to make sure they are terminated properly at the thermostat. You have to go to the air handler, kill the power, open the panel, and find out which wires go where. You are likely okay with the standard colors like Yellow, Red, Green, and White. It is the blue and the orange wire you need to figure out. I am guessing with a Goodman, the blue wire will be common and the orange wire will be the reversing valve if you have a heat pump. Some people think they have one type of system but they really have another. Not saying you don’t know just saying from my experience. I get calls from people telling me their furnace is broken and when I get there they have a boiler. Anyhow, hope you figure it out.
I have a thirty yr. old intertherm thermostat I would like to change to a honeywell programable TH 4210d1005. the intertherm has more wires and different lettering then the Honeywell I have a 2heat 1 cool system/w heat pump. the wiring in the intertherm is:W2 brown,X pink,Z orange, T black, W1 white, Y yellow,K blue, R red, G green Can you tell me how to wire the honeywell with this info. this is in a manufactured home. the model no. for the furnace is MSH-o65-AA-o3 and model no. for the heat pump is PCSB -030K(911262). This an oil furnace. The Honeywell does have em heat setting.
Call a professional.
I have a comfortnet 2 stage cooling (not sure about heat) system. My current thermostat only has 4 wires (power, common, 1, and 2 with 1 being cool or heat and 2 being the other I think). There is no fan wire. If I install a smart thermostat (with no fan wire), would the fan be controlled by the air handler? Or is there a special communication going on that the comfortnet thermostat interprets and controls the fan? Any idea of the functionality I might lose by doing this?
The communicating thermostat uses computer speak to communicate back and forth to the air handler and the condenser. If you are going to install a new smart thermostat you will need to run additional wires for that. To do that you need to know what you have for heating. If you have a two-stage furnace with a two stage air conditioner then you need extra wires for that (as described in the article above for staging) plus you need a common wire. So you need to either run new conventional wire (18-gauge copper solid in a multiple bundle) or keep what you have. This is why I recommend to people, when they select the communicating thermostats when they buy a new system, to make sure the contractor leaves the conventional wiring in the wall. That is in case you decide to switch to a digital thermostat the wires are available.
And the fan will not work in cooling. You need the G terminal functionality for that. In heat the fan will work as it is usually based on a timer in the control board in the furnace. (assuming you have a furnace)So recapping, you need to pull new wire to make it work. Check out our page on running new thermostat wiring for tips. You will find it on the thermostat menu or in the thermostat category.
Thanks for the quick response. Your answer is the most detailed info I’ve been able to find. It seems that comfortnet really keeps the details of their systems under lock and key. So, theoretically, the additional wires should make the unit functional, just maybe at a cost of variable fan speed control from the thermostat. Is that correct? Would any other features (like the two stage compressor) that would be negatively affected?
No, the fan speed control is typically handled by a control board in the air handler but in cooling the G circuit needs to be completed so it knows it is in the cooling mode. In heating mode, the control board typically handles the fan speed entirely without the G circuit being completed. Heating has a different control than the cooling in most systems and the reason is for humidity control. You want to dehumidify more in the summer when the humidity is higher. The less humidity in the air the cooler you will feel. Trane calls it the Comfort R and other manufacturers call it something different.
I want to install a new Honeywell Lyric T6 and need a common wire to power the unit. When I trace the thermostat wires back to my Goodman high efficiency furnace (2012) it appears that the red and green wires are connected normally, but the 2 wires from the AC compressor are attached to the white (aux) terminal in the furnace and the yellow terminal of the thermostat. The yellow terminal on the furnace circuit board is not being used. I also have a humidifier connected to the the white and common terminals. Can I switch the AC compressor from the white to the yellow terminal? Should the humidifier be attached to the green terminal? Thanks.
Sorry, I cannot advise you on this. You are descriptive but without seeing it for myself I cannot advise you. Send some detailed photos using our upload feature.
I saw the pics you sent. I’ not telling you how to wire it because honestly, if I was you, I would call a pro to do this. However, if it was me, I would take that blue wire you see that’s wrapped around the bundle in the thermostat sub-base pic, and use that wire for common. In other words, control board (air handler) that blue wire should be un-used the same as it is un-used at the sub-base. Attach that wire to the C terminal at both the new thermostat and the control board. And if the humidifier is working fine along with the condensing unit I would not touch any of the other wiring.
Thanks. That was my thought also, leave well enough alone. I connected the blue wire to common and left the others as is with the new thermostat. Since it was a mild day (68 F) I tested both heat and cool. Both worked so it should be good to go.
No problem, glad to help.
Hello,
I have a Lennox furnace with a Lennox “communicating” thermostat. Inside, the 4 connections are labelled R I+ I- C
I would like to replace it with a Honeywell WiFi system that requires “normal” wiring. Is this possible?
I looked inside the furnace and the thermostat connections are corresponding with a small section on the motherboard…however, just to the right of that, I see the “normal” wiring letters on a different section of the motherboard.
Would it make sense just to disconnect the “communicating” port and go straight to the other port on the motherboard? Or is it more complicated than that?
Thanks in advance for your input.
Yes, it is possible however I recommend you get a knowledgeable Lennox tech to do it because it may require some settings changes on the board dip switches. Additionally, the existing wire you are talking about will not work on the Honeywell thermostat. Hopefully, the conventional wiring is still there and they did not cut it out when they installed the communicating tstat wiring. I’ve seen installers remove the old wiring before or in new construction it was never installed in the first place. It is why I recommend on my reviews pages that if you select the new communicating feature (with a new HVAC system) that they leave the existing wiring in place in case you want to revert to a conventional system. It depends on what you have for an HVAC system but heat pumps generally require more wires than a gas furnace AC combo. You can read all about tstat wiring here.
Thank you, you have been a lot of help!
I have a Ruud RP1560AJ1NA unit that is run by a Honeywell TH320R1003. Well technically WAS run by the Honeywell. This spring I switched out the Honeywell for a Nest and l must not have checked the heating side because now that the temps are lower, I am not getting heat. The nest only used 6 of the 8 wires that came from the unit when I hooked it up. I used only 6 because the Nest peeps said the other 2 wires (orange & black) are for an outside temp sensor. Well, I took the Nest off today because I don’t have any heat and want the Honeywell back but I can’t find the picture I took of the Honeywell wires before I removed it. No, heat and I’d love to get a little heat back. FWIW the Nest worked perfectly on air conditioning. Now I’m not sure anything is working.
It’s heatpump with LPG back up or the other way around.
Nest setup
I had the yellow wire in Y1
Green wire in G
Red wire in RC
White wire in W1
Brown wire in W2/AUx
Blue wire in C
I currently have the Honeywell wire setup
Blue wire in C
Red wire in RC
Orange wire in S1
Black wire in another S1
White wire in W or O/B
Green wire in G
Brown wire in W2 or Aux/E
I think you need to call for service as this seems a little out of whack for the wiring colors. Someone who knows what they are doing needs to confirm the wiring colors at the other end where they are terminated in the air handler and the condenser. You have a heat pump with LP back up heat known as dual fuel. This problem does not necessarily mean the problem of no heat was because the NEST was wired wrong but it could be something wrong with the heat pump itself. With the NEST wiring you had no control for the reversing valve which is most likely the orange wire (don’t take my word for it…………..it needs to be confirmed absolutely at the termination point). In Rheem and Ruud the reversing valve energizes in heat mode (as noted above). It is likely the orange wire but I have seen others use the blue wire in Rheem and Ruuds. This is why I told you the wire colors need to be absolutely determined correct by someone who knows what they are looking at lest you blow a transformer.
Not sure the NEST has a jumper inside the thermostat but the RH or RC or R needs power and with the red terminated at RC you only had the cooling side powered. So from my perspective based on the information you provided it was definitely wired wrong (NEST). Additionally, whenever you change out a thermostat all modes of operation should be tested before considering it a job well done.
Lastly, the outside air temperature sensor needs to have two wires terminated at S1 and S2 and are dedicated directly to a thermistor located outside somewhere. With Honeywell, depending on how it is set up in the program, this temperature sensor could be read only and have no control functions what-so-ever. If it is set up for control then it will turn the condenser off when the outdoor ambient temperature is below the programmed set point and you will run exclusively on LP gas heat.
Thank you! I recently installed a new thermostat and would not have been able to do so without this resource. The instructions that came with the new tstat were not helpful because the old tstat had different terminals. Your explanation helped me figure out what went where.
No problem…..your welcome!! Don’t forget to share us on social media………..we appreciate the kind comments and the sharing on social media. It helps so other people can get help also.
Good Morning, I went in to the attic. found my models my Condenser ASXC160601BC serial #1307225441 Is a two stage scroll compressor cooling. my furnace is model AMVC950905CXBA serial #1307131781 gas furnace two stage burner variable speed blowers… this is how is wired at this moment:
From Condencer
Red-Red, Blue-Com, Purple-y1, yellow-y2 those are the wires in the condencer.
the way the cables were connected are as followed.
to air handler
R to R, blue to common, now Y1 was used as green cable and is connected to Y1, then Y2 is yellow cable and connected to y2 in the air handler.
from the air handler: to thermostat
R to R, C to C, G to G, w1 to w1, w2 to w2, y1 to y1, and y2 to y2,
i feel this is not correct how is the two stage going to kick in.
I feel cool stays in first stage for ever, and my heat throws too much air… i hope you can help me, because no one cant.
i was wondering do i need jumpers in order for the two stage to work… either for furnace or cooling?
Boris, I will properly reply to this this weekend. I am working on a large project and have an important deadline to meet. Thank you for your patience. Richard
Thank you forgot to include my thermostat info Braeburn 5220 here are my plugs s1, s2, G, o/b/v3, y1, y2, l, c, w1/e/w3, w2, rh, rc
Boris, I just finished working on your answer. I wrote a whole article about it. Hope it solves your problem. Two-Stage Furnace Air Conditioner Thermostat Control Problem. By the Way, the S1 and S2 plugs are for an outside air temperature sensor for outside temperature display. Some thermostats also use the outside air temperature for a control point if you have a heat pump.
I want to thank you, not by saying but by donating some money is there a way I can do that. Not a lot of people take their time to help others. Once I get home I will check on my thermostat and check the settings.
No Boris, its okay. Just share the site on social media ie Facebook, Twitter, Reddit and others. I simply hope your problem is resolved!. At least now you understand how it works.
Boris, I just updated the new article to include more information about your blower issue you mentioned.
hi I was wondering if you can help me with a two thermostat… because I don’t think my condencer is using the second stage…. I open the thermostat and see that they jumpers,, but is there away you can illustrate my brain and the correct set up I have an amana 16 seer 2 stage 5 ton units and no one seem to understand this unit,
Is this 2 stage for heating or two stage for cooling? Is it a heat pump or is it just a straight air conditioner? Or is it an an air conditioner with a gas furnace for heat? It is really important to know this information. For a second stage cooling you need need a Y-2 terminal in the thermostat and it needs to be properly connected in the air handler and condenser. For second stage heating you need a W-2 terminal in the thermostat and it too needs to be properly connected in the air handler. One last note, Amana also uses a control system called Comfortnet and this means it is a communicating thermostat. This is completely different than a conventional thermostat. It communicated through a small wire to the air handler and the condenser. You can download a program and hook the thermostat up to your computer through a USB port for customization. However, I do not know what you have there Boris except your basic description of a 16 SEER 2-stage 5-ton. You can find all the information here if you have the communicating thermostat. удача Boris!
Hey my AC is acting up and for some reason the condenser shuts off and the inside fan and induction fan stays running causing the house to heat up. Any suggestions I would greatly appreciate.
Oh and by the way the logic board is blinking 6 times which in translation says open rollout if that means anything. Thanks.
This needs the attention of an HVAC Tech. Roll out is a safety feature that is used in the heating cycle. Whenever the rollout pops it is possible something serious is going there which requires the attention of a professional to ensure there is nothing dangerous going on that would cause the roll out to pop.
So I’m running air conditioner and its calling for heat? Must be a bad logic board?
No, that would be making an assumption and without looking at it there really can be no definitive answer. When it comes to anything safety related, especially a gas furnace, it needs the attention of a professional as I recommended to you. The fix could be something very simple or it could something very complex. No one knows until its gone through troubleshooting.