Could it actually be the nest display unit that's malfunctioning? But that yellow wire was removable. If the A/C unit and the Heater functions are reversed then the connections of two wires need to be reversed. Thank you again for your guidance. Thanks. On the furnace should I hook them up the same way? Bad batteries may also be a contributing factor when your thermostat is getting no power. In the case of a low voltage (24 volts) 2 wire thermostat, there will be a ‘red’ and ‘white’ color wire coming into its back. Things like nicotine, dirt, dust, and other filth can build up on the inside and will need to be cleaned on a regular basis to properly function. I have replaced the one in my current home and used the old thermostat wiring set up to do the new one and it works fine. I flipped it back on and it worked….for a little bit and then tripped the breaker again in a couple of hours. On the other hand, the display and the controls on some thermostats are not powered by batteries. Sure, 15 minutes to install! Adjusting this to the correct temperature can sometimes solve the ignition problem. It is not stuck in the cooling mode all the time. However my upstairs unit will turn on but it works backwards when the heat is turned on it will cool and when it is set to cool heat comes out. I did on the other one pull the deal off and reset the R wire to see if it was that. Another thing youâll want to check is to see if your thermostat is wired correctly into the control board. When I went to configure the thermostat as Geothermal Heat Pump, it asked for O/B Changeover on Heat or Cool, which neither applies to me. The red wire is connected to terminals beginning with the letter R, which include R, RH, and RC units, depending upon how the thermostat is being used. If you find that your wires are damaged, or your transformer is bad, youâll need to hire professional help unless you have the knowledge to complete the job yourself. When I removed the old thermostat, the wires were connected to W1, Rh and G. The Nest would not stay charged, so I read enough to realize I would need a common wire. If you need additional information on this, youâll want to refer to the reference guide. This electrical wiring question came from Sylvester, a Homeowner in Cumming, Georgia. I tried switching the wires on the thermostat but it didnt change. I need help to connect a Honeywell programmable thermostat. The wiring diagram on the HVAC unit will be helpful as well. I replaced my old thermostat with a Honeywell RTH25 10B. The reason is because your home’s electrical system is what runs the thermostat. Thus modern thermostats require a continuous power supply and the C wire or Common wire is required for most thermostats to ensure 24 volts AC supply continuously. Compare the wiring to the tables provided above, and most of all the instructions and wiring diagrams that came with the new thermostat. The circuit breaker is Okay and was On. I purchased a lyric thermostat and followed the instructions to install. Hi Raynald, For instance, a bad relay coil or a direct short between a 24 v AC wire and Common or GroundÂ can cause a lot of current to flow through the fuses. For your convenience, use this simply checklist: Â Inspect the breaker box to see if a breaker has been tripped. I have electric heat with a outside AC unit. On the other hand, if this didnât solve your problem, go downstairs to your sump pump, if you have one, and see if the outlet that your sump pump is plugged into has been tripped. If you want to check your fuse and other circuit components, simply inspect it or hook it up to a multimeter (Testing for a blown fuse).Â However, if you don’t have any experience with electrical components, you will need to call a professional to have a look. Transposing the wire connections from the old thermostat to the new thermostat should be correct. I traced the wires back and they seem to go from red and white then in basement red goes to black and then back to red. The controls in addition to the display on most thermostats is run by batteries. Ensure air flows across both brushes at the same time like a football through a field goal post. If the Nest doesn’t turn on after installation and the Red LED is blinking on front, the Nest thermostat battery is low and needs to be charged. Wait for few seconds and check the RH wire status on the Nest Thermostat display. Dave. I then unhooked the wires that were hooked up to the furnace but recorded where they had been connected. Green LED will illuminate when powered and there are no faults. I will never be able to convince my wife to pay a professional $150 to install a $150 thermostat – It may be best to simply return the unit. Page top photo: a basic room thermostat showing the red and white wires being switched by the thermostat and a place where it's easy to check for voltage at those terminals. Dave. Okay I got 27 volts at sec 1 and 2. (Fan), Y terminal will use the yellow wire. I again did some trouble shooting and found that when I checked voltage across the contacts coil it read 0 VAC. All these wires will need to be plugged into the corresponding terminals on the inside of your thermostat. Â If your thermostat is powered by batteries, check them to see if theyâre still good. Also, the blower unit may be in need of lubrication. My AC was out randomly, which I didn’t realize until the temperature had climbed 7 degrees. Michael Joseph has more than 20 years of hands-on experience as an avid home handyman and had 10 years in the construction industry, specifically in the field of HVAC. Dave. Pulled out my multimeter and sure enough, there was no current in any of the wires. Note: You might be thinking the R wire (Red wire) from furnace is already a power line and why a C wire is required! Heat pumps are used for heating and cooling. it’s an HVAC unit. Technically, power flows to the thermostat from the R (red) wire. Effectively there isn't a second RH wire, although there is an RH terminal. ), Â G terminal will use the green wire. Press Esc to cancel. Is it safe to place the BLUE WIRE over or under the existing Y wire currently there without causing harm? This electrical question came from: Sid, a Homeowner in St. Lucie, Florida. Power flows from the red wire, but not continuously so the common wire is necessary to complete the process. But the is no yellow wire that comes out of the wall. I purchased a Honeywell thermostat a couple years ago, and it took some splicing and rewiring at the furnace to get it working. Youâll want to start by removing the cover and looking for the fuse. On the Carrier, the Yellow wire is connected to terminal RS-, the Red to RS+, the Blue to V+ and the White to VG. Hi Dan, The problem is that after a while, the temperature inside goes very cold but the thermostat is not sending any cooling command. Usually the issue is contained to the cooling side. The wiring is as described and double checked. On a sheet of paper, make a 2 column table. The thermostat which I am wanting to install is a Honeywell programmable. If you see thick, black or red wires then you have a line voltage system. Double check the wiring to the Nest compared to the configurations described in the owners manual. First, inspect your homeâs circuit breaker. I have a CR2032 battery in this which has just over 3 volts, checked it. Here are common uses and preferred colorsÂ for these wires: R terminal will use the red wire. Hi Alex, Remove Rh and G and connect them together with a wire nut or simply twisting together. On the thermostat there was no manual or auto fan switch. If there is no power to the thermostat then you will need to call a professional electrician to run a new wire from the HVAC unit to the thermostat. Additional Comments: Your website has great articles for the homeowner and the novice. I can reboot with a 10sec hold and turn on and off the a/c just fine. From what you have described, your new Honeywell thermostat does not require the C terminal connection, therefore cap off the black wire with a small wire nut or wrap it with electrical tape and keep it as spare. This wire connects to your heat pump (if applicable). When I flip the heat switch on, the a/c and condenser turns on. If the heat pump is stuck in the cooling mode all the time, then the control wiring to the heat pump will need to be verified. I'm at my wits end !!!!! The fan was working, but the condenser unit outside was not turned on. When inspecting the fuse, look for the filament running through the length of it. You have discovered that your thermostat wiring has been spliced and the color sequence changed, therefore it may be helpful to chart out the wiring to understand the actual purpose of each individual wire. I have a lennox G61MPV, which is giving me problems. So 10 C is 50 F… pretty cold for an office environment. Although this may sound a little goofy, youâd probably be a little surprised to find out how many people actually bump into their thermostats when passing by and accidentally turn them off. Any ideas what else the problem could be? If you donât have a sump pump, then youâll still want to see if the outlet that your HVAC equipment is plugged into has been tripped, and just like mentioned above, simply flip the switch to turn it back on. This type of wiring requires a line voltage thermostat and is not compatible with low voltage thermostats If you see wires connected to terminals labeled G1,G2,G3, you will need a thermostat capable of controlling multiple fan speeds, none of our retail thermostats are compatible with this system type. Tools Required: Basic Electrical Hand Tools including a small screw driver and small wire strippers. I did at one point have it to when the A/C was supposed to be on, it was just the fan blowing, no heat, no cool. This electrical wiring question came from Robert in Dallas, Texas. I again checked wiring at the t/stat and it looks correct, especially when I compare it to the diagrams on this web page. The two wire bundle are white and black The four wire bundle are white, black, red, and green. I can certainly connect the free floating BLUE wire to the new thermostat. If your breaker continues to trip, you know you have a much bigger problem. Push back your thermostat wires to allow the thermostat pins to insert completely into the backplate. The most essential colors are red, green, and yellow, although you may find up to eight different wires in a heat pump thermostat, or as few as five in a more common hot water system. The task is to test the integrity of the wires and their colors. The 5 wire cable has red, green, white, blue, and yellow. Why would it start to make this noise right after replacing the thermostat? First of all, you will need your old thermostat and the label information you created before removing the original wiring. I took a picture of the connection (red to Rh, white to W, blue to C). Test. I am purchasing a home which I noticed the thermostat is missing and the wiring is there but no thermostat. Double check the thermostat wiring. Red/R* – power wire for your heating and cooling system. A green wire goes to G, a red wire goes to R, and a white wire goes to W. (I do not have air conditioning.) When the colors of the thermostat wires are not standard then a conversion chart or diagram will need to be made to identify the wire colors that you have and how they will be connected. Keep in mind that for the heating and cooling cycles there are actually three wires involved, the Power Supply, the Heating Cycle, and the Cooling Cycle. 99. I have run into similar thermostat installations, and here is what typically helps me: Batteries generally need to be replaced on average every 6 to 8 months. I hope this helps, I believe the instructions for the Honeywell thermostat are accurate under ideal installations where the wiring has not been altered or spliced. Dave, I am attempting to replace my older thermostat with a Programmable WIFI Thermostat. I would first check to make sure the thermostat is switched over to Cooling mode, and that it is not in the Heating mode. My Y at the thermostat is connected to the C terminal at my furnace. I double checked that I tightened the C connection tight again in the furnace box. Thanks, Red wires, specifically Rc wires, are responsible for 24-hour volt AC power from your transformer. We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need. However, the only way to positively identify all of the wires of each cable would be to find the other end and note each wire connection, and this information could actually be used for a 3rd column of information in your table. IMPORTANT! I bought a new thermostat because my old one’s display was no longer working. If you notice that the filament is broken, then youâll know that the fuse will need to be replaced. 0:15.3. out the thermostat before I go jumping into the wiring. Make sure of the jumper connections as they may be interfering with the new thermostat. 8. There are several possible reasons why your thermostat may have no power. Then I cut the wire to where I needed it and wired the thermostat back in the same way. On the other column of the table record any known labels that are identified on the new thermostat which logically match the original thermostat. Thermostat: Make sure that the thermostat is set properly; often, the issue is that the thermostat is set lower than the temperature in the room. I can make it heating by activating the heat/cool mode and raising the target temperature over the ambient. The house was back down to a really cool setting again. Red or “Rc” Wires. Leaving it with this connection and circuit breaker off and back on still didn’t change a thing. Hi Roger, I hope this helps, I don’t want to damage anything. Should I hook a wire to the c post? The Rh wire connects to the heating system. Dave. Can anyone help me. Clip the red lead to the power wire and the black lead to the negative wire. I hope this helps, When you find yourself in this position, again check your fuse box to make sure you didnât trip a breaker. The office building is over 20 years old and the heat pump is a Carrier 38YKC. Red/Rc – i… [ATTACH]78511[/ATTACH] My wiring has both a B wire and an O wire, but does not have a C wire. Rc wires are only for air conditioning systems or dual transformer systems. Although diagnosing the problem may seem like a complicated issue, if you follow the steps below, youâll be able to pinpoint the issue in to time at all. Temperature settings are normal (cooling only mode set at 22 C). CB did not shut off at all. I know that sounds simple, but these basic settings are often overlooked. It causes issues with the Nest thermostat’s operation. Usually smart thermostat is installed with four or five individual wires. By doing it yourself instead of calling a professional, youâll also save yourself a little cash too. Hi Brandon, The fuse will literally pop out when this happens. Like mentioned already, when you have no power to your thermostat, there are several reasons why this could be happening. These wires only connect to your cooling system. Rh: Power for heating, Â C terminal will use the blue or black wire (Common wire, It enables the continuous flow of 24 v AC from the Red wire. However, the fan/blower is vibrating all the time now. Do you think this will solve my problem? Dave. Save my name, email, and website in this browser for the next time I comment. Like mentioned already, when you have no power to your thermostat, there are several reasons why this could be happening. From what you have described, the serviceman made the right corrections to enable the thermostat to work properly. You can purchase new fuses at most home improvement stores for a very reasonable price. I have tried messing with the settings and reconfiguring the software, but only heat. While youâre inspecting the wires, youâll also want to make sure that none of the wires are damaged, corroded, or have been chewed through by a pest. Get it as soon as Tue, Dec 15. An electric failure in the thermostat unit may be at fault. Now I really dont know what to do. As once I pop on the Thermostat face/ screen, I get nothing at all but a blank screen. The red wire is connected to terminals beginning with the letter R, which include R, RH, and RC units, depending upon how the thermostat is being used. Also, the furnace is a Carrier 59SP5A. Hang on to the old thermostat just in case you need to compare the old connections and functions with the new thermostat. On the old thermostat, the orange wire went to the “Y” terminal. If theyâre dead, replace them. Usually the issue is contained to the cooling side. Blue – This is your common or “C” wire. It is suppose to come on the screen with a white screen with Honeywell name first, then go to next screen. I hope this helps, 5. 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