furnace wiring

Here are common uses for wire colors:
Blue or Black – C – Common wire, may be unused by your existing thermostat. Red – R – 24VAC power from the furnace’s transformer.Red – Rc – 24VAC (dedicated to heat call)Red – Rc – 24VAC (dedicated to cooling call)Green – G – Fan.White – W – Heat.Yellow – Y – Air conditioner.

What are the 5 thermostat wires?

5 Wire Thermostat Wiring (Any HVAC Device – Air Conditioners, Heat Pumps, Furnaces, etc.)
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).Black wire for “C” or “Common” wire.

What are common wires?

The common wire is normally the white wire, at least in the United States, and is often called the neutral wire. It’s also called common because all circuits in the house typically have the white wires tied together, which means every circuit has that wire in common.

Does your heat pump use an O wire or B wire?

If you have a heat pump and your thermostat doesn’t have a separate wire labeled O, then the wire labeled B should be connected to the Nest thermostat’s O/B connector.

Do I need a jumper from R to RC?

If you have a wire in the R terminal, and another wire (not a jumper) in the RC terminal, you will not need to connect the R and RC terminals. See our Basic Wiring article for more info here.

What happens if you wire thermostat wrong?

Potential consequences of improper installation could include: Electric shock. Blowing a circuit breaker. Damaging the thermostat unit, the electrical system or even the AC/furnace unit itself.

Where does blue wire go on furnace?

The Blue or “C” Wire

C wires or varying colors apply to every thermostat, but blue C wires belong to thermostats attached to a heat pump. Blue wires are for heat pumps, like orange wires. This wire connects to terminal B on your thermostat.

What color is C wire?

Blue wires are also called C wires because they are the Common wire. C wires are necessary for any smart thermostat that needs to be connected to a power source 24/7, regardless of your heat pump type.

What kind of wire does a furnace thermostat use?

The most common thermostat cabling is 18/5 (18 gauge, 5 conductor), because 5 conductors typically offer enough functions for a modern thermostat/low voltage device.

Does thermostat get power from furnace?

Most room thermostats on heating and cooling systems receive their 24V AC electrical power from a low voltage transformer that itself is usually found at the boiler or furnace (blue arrow in our photo at left).

What does R and C mean on transformer?

In the case of HVAC/R systems, the power source is a low-voltage transformer (usually a 24 VAC transformer) and the two wires supplying the power are labeled C (common) and R.

How is a gas furnace wired?

Modern gas furnace wiring includes a single-pole on-off switch. The blower and control circuit for a modern gas furnace uses its own 110 to 125 volt circuit breaker. A single sheathed cable runs from the circuit breaker to a single-pole light switch located next to the furnace.