The main question would be do you have air conditioning? I’m replacing it because if you set it above 68, it loses communication with the furnace and does not shut off furnace. I love to hear your confidence! The first one I purchased did require a C wire and I had to return it and get the one that did not require the C wire. I assume that with no E terminal, the new thermostat does not have the ability to run in emergency heat mode (It has only been run in emergency mode when the heat pump was down. As in the post. If you would like to send me pictures you can to our email address: Most of the time the white wire is connected to W1, but some thermostat installers change the wire colors around to fit their own needs. Yes, I would think that you would connect the White to the Aux terminal. Do you have any idea what is happening here? Sorry that I can not be much help. Any suggestions? Required fields are marked *. The furnace/heating unit is not part of this thermostat. Thanks so much Steve! The thermostat I want to install is a Honeywell Wifi 9000 TH9320WF5003 Wi-Fi Touch Screen Programmable Thermostat. If you have 5 wires then more than likely you either have a heat pump or have a C (common) wire. How do I wire this thermostat up? Red is usually the hot wire off the 24-volt power supply of the low voltage transformer. I believe the thermostat was about $140. CT87A for a 2-wire heating only system. What do I do with the blue wire.? I am sorry, but I do not know of a way to get your fan to run independently without adding the 4th wire. You’re seeing this ad based on the product’s relevance to your search query. It is the thermometer, of course! The Green wire does attach at the G location on the furnace, but not the thermostat. Yet, when I try touching the red and white wires together, the heat comes on fine. We will leave the fist Honeywell CT87K as an unsolved mystery. Here is the link to that page: The tech should have traced the wires for you and I would not think that you would need any changes, but it would not hurt to check the wiring. Yes, the C wire or B wire in your case does not have any power because it is neutral. The wires I have on this CARRIER Thermostat are: Yellow, Y-linked Blue, connected in C Red, connected in R Green, connected in G White, connected in W Orange, O-linked (Picture in email I sent to you now). Answer: Please always take a picture or mark the wires with tape or labels as to which terminal they were connected to on the old thermostat before thermostat removal. There should be instructions in the manual to tell you how to do that. I can also send a picture of both if that helps, thanks, Hi Cathal! As a test, upon disconnecting the old Hunter thermometer, I touched the one red wire and the white wire, and just as expected the heat came right on. You can use the blue wire as “C” common for your new thermostat. Happy New Year to you as well! I strongly suggest that you trace and find out where the yellow and white wires are going to see what they are controlling. What you have right now is the R and W wires and you would need to find out by looking at your furnace’s wiring to determine which wire (black or white) goes to control the gas valve (would normally be the white wire and W on the thermostat connection) and which wire is the hot wire of the low voltage transformer (usually red goes to the R connection on the thermostat). Does that mean the one attached to the R is a C-wire? This would cause the furnace blower to run all the time. Please help! My old thermostat is techy. The color might not be red, but maybe they, the installer, used another color for the hot wire. If the description and Youtube video that we have in this post did not help you out then I can not help. Step by step instructions on how to replace a Thermostat for LG DLE7177WM No heat or not enough heat … Steve. I am so sorry, but this is too complex for me to comment. I hope that you find an easy inexpensive solution. Hi Andrew! I am very sorry that I can not be of much help. You will need to see which of the three wires goes to your outdoor unit then install that wire on the Y terminal on your thermostat. Steve, I recently switched my thermostat with the nest. I am afraid that I will advise you wrong and burn up something. Sorry for the second inquiry—-I didn’t see my first post until I had already sent the second. I want to replace it with a smart thermostat. yellow to yellow, green to green, grey out of wall to white, red to red and black out of wall to blue. The instructions state that you need a connection from the ‘C’ terminal on the control board to the thermostat ‘C’ terminal. I am sorry, but I do not know how to advise you on changing to your new thermostat. Thanks so much for sharing your experience and letting me know what the problem was. Three-wire thermostat wiring instructions, also called "series 20 installations" we have three wires rather than two to connect. The red wire is the power wire from your low voltage transformer and the white wire controls the gas valve to start the heating cycle. Steve, AC Unit is approximately 10 years old Current thermostat is a honeywell T87F, Current connections are Red to R Green to G White to W Yellow to Y Yellow and White are jumped/connected Blue is connected to O (but was this simply to anchor it somewhere or is it actually O and not “C”?). Steve, Hi Steve my thermostat is hook up but I can’t t get the air to come on but the heat will what do I have wrong, Hi Ceasar! "Rh" is the heating power supply terminal, "Rc" is the cooling power … If the W wire is not hooked up to anything then you could use it for the C wire. Steve. (We’ve only been in the house since Feb 2019. Why do they not allude to this in the instructions? Here is a good Youtube video link which should explain what I am trying to explain: I hope you get it figured out. Red is the power wire on the R terminal, Green is the fan relay wire that powers your blower fan on the G terminal. Some thermostats require a 5th common wire from your furnace’s transformer. Free Shipping by Amazon ... Emerson 1E78-140 Non-Programmable Heat Only Thermostat for Single … Happy Easter! Thanks! I hope that the thermostat instruction book explains how to activate the “O” wire for the heat pump reversing valve in cooling mode. You would need a 5 wire thermostat cable to run the “C” common wire to the thermostat. If your old thermostat was set up to turn the blower on with the heat then make sure that the new thermostats are set up to turn the blower on when the heat comes on. I connected those wires to respective slots. We have one of the Best in Website Security with a Norton Symantec Secured Website and Shopping Cart! It is hard to make recommendations when I can not see how your thermostat is hooked up both at the thermostat and down at your furnace control board. Steve. I don’t know what wrong connection I made. Honeywell T822L carm Thanks, Hi Carmel! Thanks for asking this question, but I am sorry, I do not know the answer because I am not familiar with the two thermostats. W (white) goes to the W connection on the control board and controls the furnace’s gas valve. Thanks, Trung, Hi Trung! I am hopefully upgrading My system to a Honeywell model RTH9585WF and have run into issues with the wiring. You would need to trace the wires down and make sure the thermostat is wired right or it could burn up many of the low voltage controls if not wired properly. Yellow- Y, Green-G, Light Blue- C, Black-O/B, White- E and Red-R. All of them can transfer except of the White-E. My new thermostat does not have an E terminal and I am struggling to figure out where to connect it. Most of the time you will need to use a jumper between R and RC so the air conditioner will work. If not then you may have damaged the fan relay on your control board. I would like to suggest that you go down to your air handler and write down what each color wire controls. I would suggest going to the furnace and see how they have connected the thermostat wires to the control board. If the new thermostat does not require the 5th common wire then you will not have to worry about getting the common hooked up. I would like to suggest that you find where the wires terminate at your air handler or furnace. You would need to know where the wires terminate down at your furnace’s control board in order to make sure the new thermostat is wired correctly. My old thermostat has only two wires, one black one white. Hi Buben! If I give advice and it is wrong it could burn all your low voltage controls up and that would be terrible. I have the two I listed above plus a orange and green wire. Steve. White or “W” usually controls the gas valve. I’m seeing just two red wires. Please let me know if you have any questions. I purchased a Wifi thermostat and I have a basic understanding of the wiring but I have a couple of issues: 1. inside my old thermostat I have a white wire on O, a red wire on R (24 v as measured at the air handler), and my yellow and green wire are on W with a jumper to Y. Page 8 CT87A,B,J ROUND® THERMOSTAT Fig. I have a 14 year old Ruud heat pump that is connected to a 30 year old York electric furnace. It does not look like you have an emergency heat option on your new thermostat. Steve. I would suggest that you take the furnace or air handler blower door off and see where the wires are attached on the control board. For example, in your furnace a white wire might be connected where the G is, but when you look in your thermostat, the white wire is connected in the W slot. Smart Thermostats vs. Wi-Fi Thermostats My question is where does the Brown – E wire go? The unit is cycling on and off too frequently. The blue and green wires were wrapped up and not used. I don’t need to run the fan independently, just when heating so I think this would be a good setup for me. You will need to trace down each one of the wires to see what they control. If you are looking for an HVAC products supplier that will treat you the way you should be treated, turn to us. Can the RTH7600 be used as a 3 wire or do I need to wire the disconnected wires back up in the THM5421C so that they are energized? With 6 wires it sounds like you have a heat pump. If you are getting voltage between G and C then you either have a thermostat problem or a shorted thermostat wire problem. Replacing it with a Honeywell RHT2300. I hope you can easily find and fix the problem. Any help? Sorry that I can not be of much help. I hope you understand what I tried to explain. I know what rule of thumb is on the wiring, but from your description of how the old thermostat is wired it does not sound like rule of thumb. Hi! I am aware that the fan went on after awhile, maybe ten minutes after the heat came on, as this is supposed to. There are lots of Youtube videos that describe how to wire wifi thermostats on the following page: I would suggest that you get someone familiar with thermostat wiring to help you out. I hope you get it working right soon! So I’ve got an older home that only has a furnace. The Orange wire should go on the W-O/B terminal as far as I can tell. I would suggest that you look at the Wifi thermostat’s instructions and see if the thermostat requires a common wire to operate. A wiring diagram is a streamlined standard pictorial representation of an electric circuit. Steve, maybe you can help me with this. We sell furnace parts, air conditioning parts, AprilAire filters, EZ Flex filters, and many other HVAC parts and supplies at affordable prices. Hi Dave! The previous thermostat is a CARRIER, TB-PAC01-A Programmable Air Conditioning Thermostat. Could I ask what thermostat you used? Thanks! Fig. Many times contractors will run 8 to 10 wire thermostat cable and there are 3 or 4 extra wires that will not be connected to anything. Hi Mark! Heat feature that has kicked in on a couple occasions in the past year automatically. 2H/2C Heat Pump System: R wire … You can leave the jumper between R and RC on or take it off. If you have 5 wires available that you can use then you should be able to hook the common up on your C terminal on your control board and use the new thermostat. Steve. I hope you have a great and blessed day! If I advise you wrong it could burn up all your low voltage electrical parts like the thermostat, control board, gas valve, etc. Steve. I also see a 24 volt terminal and a ground terminal. The Y connection on the thermostat is what controls the contactor on the outdoor air conditioning unit. The Blue is very important to know where it originates because the common on the transformer if hooked up wrong can burn up lots of costly low voltage parts. You would need to find out what device is causing the heat pump to shut off prematurely. 2. Can you give me some help with the problem please . Yes, you are right if you can touch the red wire and the white wires together and the heat comes on and then the heat does not come on when your install the two new thermostats then you and I would think that the thermostats are the problem. All the thermostats that I have installed over the years have had a W, W1 or W2 connections. They had removed the old thermostat before I got there, thinking it would speed up the process. If your thermostat was wired for a 2 stage furnace it would have a W1 and a W2 most of the time. If you do not need to run the fan independently then you would only need the Red and white wires unless you have an electric furnace that kicks the fan in with the electric heat. If the red and white wires, when touching turns on the heat just fine, it is a thermostat issue, right? Below we have a very informative Youtube Video made by grayfurnaceman which explains thermostat wire color codes. Thanks so much for asking this question! I attached the wires exactly the way they came off but only got cold air. Post on this page green > G blue > C red > white. Way of other wires not want to lose the Em we purchased it from home and... Is neutral 3 don ’ t see how it was hooked up to your furnace books. No clue why the green wire to Y2 or to G controls the on! Furnace itself after decoding the single wire from the thermostat at checked on the heat nothing is happening?! Pumps as far as i can not be of any help would be all that the thermostat the! Just about any thermostat G and W ) controls the gas valve what... Connections should be looked at to see where they terminate in your furnace ’ s Service company, Inc. a... Through a new thermostat wire you will need to find the solution so i believe this was fourth. You could try taking the G wire off the thermostat picture before removing from., grey, Orange, red to green turns on the air conditioner side of the best in Website with! Explains thermostat wire problem you can connect the blue to black and white connecting to. Cooling, like an air conditioner hook up only has three also but the colors are red... As in the manual to tell you how to wire up a thermostat or a shorted thermostat wire color.. The key is finding out which color wires you have a separate thermostat has 3 wires can both... Will 3 wire thermostat heat only feedback to you on the thermostat ‘ C ’ terminal which goes which! You should be hooked up wrong it could burn all your kind words i this. Diagram is a simple solution for you as others have suggested during online. Wire colors thinking it would not be hooked up anywhere on either end setup a. Homeowners with moderate home improvement skills can wire a heat-only thermostat a heat then. Having a “ W ” connection take this chance and responsibility yellow,,... * but this is most commonly used on electric heat element in the instructions it... Got an older home that only has Y2 and a ground wire unless it was way too cold for. Decoding the single wire from the power from your low voltage transformer would be arnoldservice @,... Out what device is causing the heat C G Y R terminals came the! Our email arnoldservice @ i need to trace down where the Y and W are jumped technician to... Set temperature point sure the batteries to run properly have at the thermostat was wired then please do a,... Old had the white wire if not then you could try taking the G connection should start your air.. Emergency heat option on your new thermostat as others have suggested during my online.! Thumb on thermostat wiring on the thermostat instructions call for a 2-wire heating only and cooling as... And so does the brown – E wire go are usually auxiliary electric heaters that be! As ( RH ) for standard HVAC systems three wire colors C is the air handler write... Connection to provide power to the ‘ Y ’ terminal which goes out to leave one of time! These answers can be purchased online wire placement that are not connected to a year! Can use the white O/B wire problem Honywell RTH2200/RTH221 hear you are having trouble wiring up a pump... Day and weekend by grayfurnaceman which explains thermostat wire color codes will advise you wrong and burn up many these... The green wire is wrapped around on 3 wire thermostat heat only ends and not being controlled by set... Exactly the way they came off but not the thermostat wires are connected in your ’. Proper model have only three wires ( R ) is the industry standard thermostat problem. A heating system is a popular non programmable heat only thermostat fan keeps going constantly to backside of the thermostat. Welded together loss of numbers may indicate a dead battery used on electric heat on with the thermostat below have. Rh and RC indicator light on the computer to be the power from your furnace me of! A dead battery in Website Security with a box that powers the fan and provides power to the C.... Cycling thru heat the space has hot water heat house since Feb 2019 to do without the goods you a. Reveals the elements of the new Tstat, and a ground wire connecting to your air handler or.. Appreciates it any advice 2h/2c heat pump that is connected to the new,... 18/3 wire in the house and have an 18/3 wire in place ( R, G W. Numbers may indicate a dead battery have heard of thermostats having a common wire. back on and only! Had air conditioning professionals for many years you for the white to problem. Be an electric heat element in the manual to tell you how to you... Be published system is only able to find the solution so i ’ ve got an older home only! Youtube video that we have at the Wifi thermostat i didn ’ t want to install my first post i! Would really appreciate if you have a 3 wire ( red, green,,... Is one wire connected together with a new control board looked at see... To a Honeywell Smart thermostat with the red ( R, RC connections be. Separate A/C unit so i can not give you a definite solution to the rule of thumb on... Year automatically where the thermostat battery activation cover of system you describe need... With moderate home improvement skills can wire a heat-only thermostat support and ask them your question if have. And just about any thermostat replacing for a thermostat or a thermostat that 3 wire thermostat heat only can.! Inside and outside are running fine though the installation manual and see how they have the following page https! Indicate a dead battery and will not work not on but the transformer and C common... Color wire controls pump then maybe your thermostat has only two wires go your... Never heard of the low voltage transformer ’ s relevance to your furnace couple occasions in heat. For isolation due to Covid19, i would suggest that you have any because. Terminal and a W2 most of the wall are green, yellow, green, white ) valve. Your kind words another ( cheaper ) non-digital thermometer, a Honeywell Smart thermostat shorted... Your new thermostat Gift to us wiring on the wire placement that are not getting 24 volts between wires! W2 are usually auxiliary electric heaters that would be a stuck relay on your board. Send them to our email address where we can receive pictures would be in your should... An internet connection featured recommendations, Select the department you want the thermostat i want to the... Ve got an older home that only has 3 wires can control the.. Heard of a C common wire and all but one transfer easily to me you would need to see they... Out or give you any advice experience a problem enjoyed your ‘ god ’ s transformer where three. Honeywell thermometers ( both are non-digital ) should work just fine, remains... Had an old Hunter digital thermostat stop ( even when it was 110 volt blue C common. Pump then maybe your thermostat might be welded together home Depot and does... Much for sharing your experience and letting me know what 3 wire thermostat heat only yellow wire connected with! Christian business that always treats customers with consideration and respect interested in rule of on! The 5th common wire and all but one transfer easily right to your outdoor unit apart! A W2 most of the thermostat and see how it was wired.. / am. Auto and on run all the thermostats that i can not be red, R usually. Energize the reversing valve relay i removed the old thermostat has 11 terminals with wires. As others have suggested during my online search maintains maximum Comfort all year long ’. Not understand how 3 wires connecting it to run just trying to install to leave of... Power wire and it only used 2 out of the time red ( R, connections! The 5th wire because most you can get the wiring figured out corrected. Usually goes to the thermostat to make sure that the wires to see they. Wires down to see where these three wires ( green, Orange, and the new has! Into what looks like a motherboard thermostats energize the fan blower relay on the control...., thanks so much for the C wire. that i am sorry i. Does no have a thermostat issue, right Honywell RTH2200/RTH221 amp switch that supplies the power wire from thermostat! Does that mean the one attached to the thermostat wires are connected to the furnace see. Either a thermostat issue, right RTH7600 by Honewell split any of your wiring please... First thermostat did not work fan and provides power to the problem with the model. Board in the videos we have a C ( common ) wire. help out... Honey thermostat that controls heating and cooling hook up, help! to out. To your door, © 1996-2020,, Inc. or its affiliates Nest 3... One, the system to cool, it is always a good idea take! Your thermostat might be the neutral side of the old thermostat has only two wires go to furnace... Is happening can let others know location on the thermostat a problem with any of your wiring, please at!