Understanding how to wire a thermostat is essential knowledge for every homeowner. If your thermostat fails, you may be able to repair it yourself to save time and money. If you would prefer to use a professional, then this information will help familiarize you with the wiring process. Wiring a thermostat is basically connecting the correct-colored wires to the correct terminal. Understanding what each wire is for is critical to complete the procedure successfully.
If you are unsure of any of the thermostat wiring, it is safer to contact a qualified professional. The wiring for thermostats can be configured in a variety of ways. So now what? Should I remove the switch from the furnace? Bill lee is incorrect. If you only have a single red wire the jumper between Rh and Rc are required for some heating and cooling hybrid systems depending on your thermostat.
Nathan, if you only have red and white wires, your system is only set up for heat. The cool switch on the furnace is manual for a reason, and it is for running the fan when the furnace is off. Hello guys. Great info here. I have a question, I want to install the ecobee4 and I have just 2 cables from my old mercury thermostat. For what I understand, please correct me if wrong, Rh has 24V and close the circuit with the W correct?
Then the thermostat act like a dimmer? Then C will power my thermostat with 24v too, correct? Then, can I jump or Feed my C connector from my Rh cable? Is this possible? Thanks Marcelo. Great site and good questions! Better yet you can buy a thermostat that uses battery to switch the contacts and thus no second transformer the only downfall is the battery changes every couple years on that.
Good luck to the DIY folks just remember not all appliances or thermostats work the same so take time to read the product literature. The device must be sent back to the factory to have the smoke put back in:. Small clarification. The power coming into your house has two phases and a neutral.
From phase A to phase B is vac. This is used to power your electric oven, electric dryer, etc. Phase A to neutral is vac. Phase B to neutral is vac. What he calls Factory Smoke is normally referred to as Blue Smoke in these parts.
If you fry a circuit, the blue smoke escapes. Sorry Dave but residential power here in Canada is single phase. I have a hunch that this is true through out North America. Power comes from a single phase transformer with a center tapped ground and is referred to as the neutral. The power is supplied over two legs. Can anyone please tell me where I need to connect my wires on this chart? Any help wold be greatly appreciated.
Thank you!! It IS confusing when everything I read talks about the C wire providing power to the thermostat. Very helpful information! Outstanding comment. Thank you! But yes, I know what you are saying. Thanx for setting the record straight. This is not correct. Many others output AC. All depends on the appliance to be powered. There is no conversion from AC to DC. The voltage is stepped down from to 24 volts. Just like the transformer on the pole outside your house steps down from 7, volts to volts for your house panel.
Not on my Rheem furnace. Thanks for this info, adding my comment because Google brought me here and this might help others. So I got my multimeter out and touched the red lead to the blue wire and black lead to ground and got 0 vac, so I was really bummed out.
Then my Google foo kicked in and brought me here! So I tested again, this time touching the red lead of my multimeter to the red wire and the black lead to the blue wire and what do you know, I got 24vac! John, there is no polarity in measuring AC voltages.
Or perhaps you accidentally had the meter in the DC range. The only way you can measure a 24 vac output is across the two secondary terminals. Household wiring is not floating, but rather, is considered to be earth referenced. My furnace bonds all common leads to the furnace frame assembly. I know this thread is old, but important since people including me still visit this site. Many people have that misconception about electricity.
The neutral on your home wiring will kill you faster than the hot wire if you find yourself in the circuit. Only saying this so DIY folks always put safety first. In the right conditions—heat, humidity, the amount you sweat—6 milliamps will kill you.
There is no way 24 volts will kill you. Why scare DIY s? A neutral wire will not kill you either. Yes, 6 milliamp at 10, volt can give you a thrill. I have experienced that on an old picture tube type TV. I am still here. As a qualified electrician, I heartily agree. The voltage applied to the circuit forces current through the device, and the entire supplied voltage will appear across all device s in the circuit that are in parallel. As long as the neutral is tied to ground and is intact there will be no significant voltage on it.
If, however, a break appears in the neutral before the point where it is tied to ground, that entire applied voltage will now appear across the break. In a typical four-wire system the 24vac is supplied by the R wire. If the thermostat says heat is required, it allows the 24vac to go back on the W wire. If cooling is needed, 24vac is sent back on the Y wire. If the fan should be running, 24vac is sent back on the G wire.
If no heat, cooling, or fan are required, there is no power flowing through the thermostat. If you have a five-wire cable, the C wire of whatever color is a usually a common that allows 24vac to be flowing therefore used by most smart thermostats. Can I splice into 1 of the white wires? Nothing to do with white t-stat wire which connects to a brown wire at unit.
My Goodman furnace has a control board with no C terminal. All I did was connect the unused blue wire from the thermostat control wire bundle to the blue bundle at the 24V transformer be aware, there is another similar looking wire bundle next to the thermostat control wire bundle, but only 2 wires are used, black and white.
This wire bundle goes to the outside compressor to control it. After hooking up the new thermostat, connecting the same blue wire now at the thermostat end to the C connector of the thermostat. Works perfectly. Hi, have you ever encountered old thermostats functioning with a 1 single wire?
Any ideas? Have you tried the compatibility checkers on the manufacturer websites? Do you just have a heating system? If you do resolve this, either through adding more wires or choosing a particular thermostat that works with your 1-wire setup, come back and let us know how it goes!
Good luck. My house was built in and still has the original furnace. As far as I know there is no control panel. Online compatibility checkers: Ecobee3 compatibility checker Nest compatibility checker. If you have typical wires behind your thermostat, those wires must go somewhere. Sorry to be of such limited help. If you do figure it out — or find out that your system is simply incompatible with C-wire needing WiFi thermostats — do come back and give us an update! Thanks for the quick response.
I think your suggestions are a good starting points. I recently got married and we purchased our first house this year. I attempted to hire an hvac company to come clean the furnace and the guy took one look on the furnace and was completely baffled. He had never seen one before and had no idea how to clean it. We have a more knowledgeable tech coming in a couple weeks.
I never actually pulled the cover off my thermostat to check whether it had a c-wire or not. To my pleasant surprise, the hvac tech looked the furnace over and said it already has a c-wire. Now I just need to figure out which wifi thermstat to get. My thermostat has 3 wires red white and green am I missing wires? The only way I can use furnace is to combine red wire with white help!!!!!!
Sorry about the slow response, sounds like you have a simple heating thermostat with a fan function, for ease of future conversations use the marked letter designations rather then colors as not everyone uses standard colors. I suspect I can simply move the free green wire over to the common side of the 24V transformer to make it a C-wire with heat only function for an ecobee?
I have a boiler with two wires, R and C coming from the transformer inside the boiler. I ran a new wire with 5 wires. Just seeing if and how I can wire the thermostat so it functions. I need a constant 24v circut and one to switch the boiler on an off…. There is nowhere to attach a C wire to on the boiler side.
Any suggestions on how to proceed? Could I install a v to 24v transformer and if so how would it be wired? Any help would be appreciated. Like Bill, I have the very same situation. And it seems there is no answer anywhere online. I have managed to get the thermostat to power on, since there is 24vac existing in the 2 wires at the thermostat. I jumped the W wire to the C terminal on the new TS. I programmed my new thermostat but as soon as the boiler fires up, the TS shuts off and power resets.
So, close but no cigar. Well, I installed a v to 24v transformer which has a R and a C terminal an ran an additional thermostat wire from the transformer to Rc and C on the thermostat. I removed the jumper between Rc and Rh and the transformer powers the thermostat without problems.
I then wired TT on the aquastat on the boiler to Rh and W on the thermostat. Unfortunately the thermostat is not sending a heat call to the aquastat when the heat is turned up.
I assume the thermostat may be bad. What color is AC wire? Y wire yellow, for air conditioning. W wire white, for heat. C wire blue or black, common for volt power to the thermostat. What is R and RC on thermostat? RC is no different and simply means red cooling. The wire is generally red, although there is no color standardization -- but more importantly, the "R" really means that the wire and terminal are hot; it's a live electrical wire.
The RC wire connects to the RC terminal, which controls the cooling system. What does the blue wire go to on a thermostat? The blue wire, or C-wire, is known as the common wire. It's there to provide power to the thermostat. Power comes into the thermostat on a wire connected to the transformer, which is usually red, and returns to the transformer on the C-wire, which is usually blue, but it can be black.
What does a blue wire mean? Many smart home kits come with their own adapters, but you can also buy a separate one online or at a home improvement store. They come with a diode that splits the current from one of your existing wires into two new wires and a box containing new wires that you will mount on your furnace control panel.
Start by taking a photo of the current wire connections inside your thermostat and on your furnace circuit board. This will come in handy if you get confused while disconnecting and reconnecting wires. For best results, follow the instructions that come in your kit or an online tutorial. Of course, you always have the option to install new wires altogether so you have a functioning C-wire without making modifications or sacrificing the use of your fan.
While you can attempt this on your own, you may feel most comfortable leaving this job to a professional. If you want to make sure your thermostat is hooked up correctly the first time and avoid any risk of damaging your system or new thermostat, you can trust the technicians at Malek Service Company to install a new C-wire and get your HVAC system up and running in no time. Our well-trained team has been providing HVAC service to Central Texas for nearly 30 years, so you can rely on us to do the job right.
Call us at today or request an appointment. What Is a C-Wire? Some of the other wires powering your thermostat include: R-wire — Power, usually red G-wire — Fan, usually green Y-wire — Cooling, usually yellow W-wire — Heat, usually white The easiest way to know if your system already uses a common wire is to remove the faceplate of your thermostat and check if any wire is connected to the C-terminal.
Option 1: Do Nothing There are a lot of thermostats on the market that do not require a C-wire, including older models and some smart thermostats.
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