A lot of people are familiar with a thermostat simply because these things regulate the temperature (either hot or cold) of their appliances. Common appliances that have thermostat readings are refrigerators, air conditioning units, heaters, and other heating or cooling devices. Thermostats are quite crucial in keeping your appliances running, but are you familiar with the wires that make them work?
The RH and the RC wires are found in every thermostat. If you need to change the wires, basic knowledge of them will be very helpful. Here’s the difference between the two.
Why Are Thermostat Wirings Important?
If you aren’t a mechanic, why do you need to know about wirings? Face it, there will be times that your appliances will break down and there won’t be any available mechanics. During times like this, it’s useful to know a bit about these wires for you to understand where the problem is.
In a heating or a cooling unit, a thermostat is powered by a heating system and a cooling system. These systems work together in order to regulate the desired temperature inside the unit. This means that the cooling system will automatically turn on when the temperature is going up. The same goes for the opposite.
What are RH and RC?
If you’re worried that this is too technical for you, don’t be. The RH and the RC wires are actually pretty easy to understand because they’re straightforward.
The RH wire refers to “red heating” which means that this is the connection you need in order to power the heating system of your air conditioning unit. Yes, even your air conditioning unit has a heating system to keep the temperature in balance. While the ‘red’ term is universally used to signify a live electrical wire, it isn’t dangerous, and it doesn’t need to be red. In fact, it only utilizes 24 volts which aren’t enough to shock you. To add to that, the wire is not always red. There is no standard for the color of the RH wire, but most units use a red one.
The RC wire, on the other hand, refers to “red cooling”. It’s the same with the RH wire in that it powers the thermostat. For the RC, it powers the cooling system.
How Do the RH and the RC Work?
The thermostat that you see on your air conditioning unit is wired to a furnace. This furnace houses the heating and the cooling systems. To operate those systems, specific wires connect both the thermostat and the heater. This is where you’ll see the RH and the RC wires.
Usually, these wires are powered with 24 volts. Even though you won’t get any electric shock from operating them, you should always make it a habit to turn off the unit before working or replacing the wires. Some units don’t have an RH wire, but instead, they have an R wire. An R wire is similar to either the RC or the RH, so if you don’t have an RH wire, the R wire will be in place to control the heating system.
What color wire powers the Nest thermostat?
To wire up your Nest Thermostat, simply: Connect the Red wire from the transformer to either the RC or RH terminals (as they are connected internally) Run the White wire from the furnace on the W terminal. Connect the Yellow wire from the compressor to the Y terminal.
What is the O/B wire on the thermostat?
O, B, O/B: These wires are responsible for switching the changeover valve in a heat pump system. The O wire reverses the valve from heating to cooling, and the B wire switches the valve from cooling to heating.
What are the 4 wires on a thermostat?
4 Wire Thermostat Wiring (Heat Pumps, HVAC)
- Red wire for power (24V)
- White wire for heating (connected to W or W1 terminal).
- Green wire for fans
- Blue or yellow wire for cooling (connected to Y)
Does red wire go to RC or RH?
There is no standard for the color of the RH wire, but most units use a red one. The RC wire, on the other hand, refers to “red cooling”. It’s the same with the RH wire in that it powers the thermostat. For the RC, it powers the cooling system.
Where does the R wire go on a nest?
An R wire can go into a Nest Learning Thermostat’s Rc or Rh connector. The Nest Thermostat E only has an R connector, which is typically where an R wire would go.
Does Nest require common wire?
With a Nest Thermostat E or Nest Learning Thermostat, you’ll need to install a C wire if the thermostat has power issues or its battery often drains.
What do the different color wires mean on a thermostat?
This is the most typical thermostat wiring style, and it applies to systems that regulate both heat and air conditioning. The wires are typically arranged as follows: red for 24-volt hot, white for heat, yellow for cooling, green for the fan, and blue for common (although the common wire may be a different color).
How many wires does a Nest thermostat need?
The procedure to install the Nest thermostat with 2 wires is the same for both thermostats. Remove the existing thermostat and mark the wires. If you have a heat-only system you should connect your thermostat wires to the W terminal and Rh terminals.
Other Relevant Wires You Need to Know
Aside from the RH and the RC wires, there are other wires that you will find in your cooling or heating system. Here are some of the most common wires and what they signify.
The G wire is probably the safest wire in the unit. It’s not a live wire, but it does operate the blower fan. The blower fan pushes the warm or cool air outside the vent, so without the G wire, there won’t be any air going out of your unit.
The C wire is not always present in every unit. In fact, some units can work without it because they get power from the wires already existing. The C wire’s primary purpose is to give power to operate the thermostat itself. No, they’re not like the RH and RC wires because these two power the systems and not the thermostat. If your unit doesn’t have any, this is nothing to be worried about.
Wires that have ‘Y’ in them pertain to wires that connect to the cooling system. They’re the ones responsible for increasing the air that is being pushed out. Some units just have one Y wire, while some have two; hence, the Y1 and Y2 codes.
Similar to the Y wires, the W wires are the ones responsible for the heating system. If your thermostat is too cold and you wish to lower it down, these W wires are the ones that signal the heating mechanism. They can also be found in two’s or in single wires.
Wire E is found in heat pumps, and they are usually activated when the surroundings are too cold. Let’s say your room is cold because of the winter and you want to fire up the heater. If your heating unit doesn’t have an auxiliary heat pump, then the E wire is used to increase the heat. Ideally, you don’t ever have to use this emergency heat pump if your heating system is working well.
The L terminal is more of a port than an actual wire. This terminal is used for the indicator lights you see on the thermostat. This terminal will light up if your heating or cooling system has a problem.
And then you have the X wire. The X wire stands for auxiliary heat which was already mentioned a while ago. Not all units have auxiliary heat pumps, but that shouldn’t be a problem. Just like the E wire, auxiliary heat pumps are there to give additional heating whenever the system cannot keep up with the cold surroundings outside.
And there you have it! While these wires can be a little bit confusing at first, you’ll get the hang of it the more you tinker with your cooling system. If it’s still confusing to you, then you need to consult the manual and the wire instructions.
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