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.
The placement of the R wire, also known as the power or 24-volt wire, depends on the specific HVAC system and thermostat setup. In most cases, the R wire is connected to either the RC (cooling) terminal or the RH (heating) terminal on the thermostat.
For heating and cooling systems, it will have a red Rc and a red Rh wire. Though both wires are red, they are not interchangeable. For the thermostat to work properly, the red wires must be connected to the correct corresponding terminal. The C, or common wire, provides smart thermostats with continual power.
Putting more than one wire into a Nest thermostat connector can damage your system and your thermostat. Instead of using jumper wires, Nest Learning Thermostats use an internal jumper between the Rh and Rc connectors. A Nest Learning Thermostat will automatically use this internal jumper if your system needs it.
The Rc wires on your thermostat are for air conditioning systems or dual transformer systems. Dual transformer systems refer to a setup with a cooling and heating transformer. Rc wires connect to the RC terminals on your thermostat.
Note: If you have an R, Rc or Rh wire, you can put it into the R connector on the Nest Thermostat. If you have a W2, Y2 or O/B wire, you can put it into the *O/B connector, if needed. Gently tug each wire to check they're secure, and make sure each connector that has a wire stays down.
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).
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.
The orange wire (O) is essential for heat pump systems. When your thermostat calls for cooling, the orange wire activates the reversing valve, allowing your heat pump to switch into cooling mode. In heating mode, this wire reverses the refrigerant flow, enabling your heat pump to provide warmth.
A jumper is a short wire or staple connecting two connectors (usually Rc and Rh). If your current thermostat has jumper wires, do not connect them to your ecobee thermostat. ecobee thermostats will automatically use an internal jumper between Rc and Rh if your system requires it.
If you put wires into the wrong thermostat connectors during setup can, this can cause your system to malfunction or possibly damage it.
If there is no hidden C-wire, you can use a G-wire instead. However, you will not be able to use your fan independently when the heating or cooling isn't running. Also, many HVAC systems are incompatible with this solution, including: HVAC systems using electric heat.
A C-wire, or a common wire, runs from your low-voltage heating system (24v) and carries continuous power to your thermostat. In today's electric market, most newer heating and cooling systems have C-wires, which guarantees compatibility for the installation of all smart thermostats.
RC: The RC terminal is the 24-volt cooling power supply. RH: The RH terminal is the 24-volt heating power supply. (Note: The RC and RH terminals are jumpered together in a four-wire heat/cool system and a single-stage heat pump system but not in a five-wire heating/cooling system.)
The blue wire on a thermostat typically connects to the C (common) terminal on the HVAC system or furnace control board. The C terminal is used to provide power to the thermostat, and it helps to complete the circuit for the thermostat's operation.
For example, in the US 120/208V 3-Phase systems, the hot can be black, red, or blue if they're following normal convention, while in 480/277V 3-Phase systems, it's orange, brown, yellow. White is normally reserved for the neutral, and green or bare copper isfor the ground wire.
O/B: This option selects the type of reversing valve for heat pump systems. An “O” reversing valve is energized when cooling and a “B” reversing valve is energized when heating. Most systems use an O type reversing valve.
In this case, you'll want to check for the following: Tripped Circuit Breaker: The main issue here is not with the thermostat itself but with the electrical panel. Go to the breaker panel and locate the circuit breaker for your thermostat. If it's off, try to reset the breaker switch.
If you have two wires, R or RH go into the R terminal and RC into the RC terminal. If you have more than one wire (for example, you have a wire labeled R and another wire labeled Rc), remove any jumpers between the R and Rc terminals or push the switch to open the RC terminal to insert a wire.
Again, If your heat pump has electric backup, install the aux heat wire to W2 for NEXT and W1 for EcoBee. Then in setup wizard, you can set backup heat to electric. Check the CEC website for more heat pump information.
As you examine the wiring, you will probably see two wire jackets, also called wire bundles. One of them, with Rc, G, and Y, comes from the cooling system. The other one, with Rh and W1, comes from the heating system.
2 Thermostat Wire System
A 2-wire thermostat is almost always for a system with heat but without air conditioning, controlled by a digital thermostat. The two wires are most often red for power and white for heat.
Typically blue is used as C wire. But that needs to be confirmed on the control board. You have two spare wires: blue and brown. Either can be used as C wire as long as it is connected to the C terminal on the control board.