What happens if you wire a 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.

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.


How do you wire a thermostat to a furnace?

Quote from the video:
Quote from Youtube video: And a separate air conditioning system something where there would be two 24 volt transformers powering in you would remove that jumper. Right in this case it's a gas furnace.

What color wire goes where 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).

Why is my thermostat not communicating with AC unit?

Loose connections, frayed wires, and aged wires all can cause your thermostat to eventually lose its connection to your A/C and heating system. Inspect your wiring thoroughly, making sure the connections are tight, and replace any wires as deemed necessary by you or an HVAC professional.

How do I know if I installed my thermostat correctly?

How to test if the thermostat is properly installed?

  1. Step 1 – Turn off HVAC power. …
  2. Step 2 – Remove the thermostat cover. …
  3. Step 3 – Remove wires from terminals. …
  4. Step 4 – Turn HVAC power back on. …
  5. Step 5 – Test other wires. …
  6. The display. …
  7. Incorrect temperature. …
  8. Strange behavior.

Is RC and C wire the same?

The C and Rc wires are not the same. To install this thermostat you should follow the exact same wiring of the previous thermostat.

What does RC and RH mean on a thermostat?

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.)

How do you read a thermostat wiring diagram?

Quote from the video:
Quote from Youtube video: And it's going to look like this whenever you see a switch like this on a wiring diagram that is a temperature switch which means this switch goes up and down depending on the temperature.

What does C wire mean on thermostat?

common wire

What is a C-Wire? A common wire (C-Wire) provides Wi-Fi thermostats continuous power by connecting it to a heating and cooling system (e.g. furnace). C-Wires are required on most Honeywell Wi-Fi thermostats, with the exception of the Smart Round Thermostat (formerly known as the Lyric Round).

What wire controls AC on thermostat?

Yellow Wires

Yellow Wires



They control your air conditioning system. The yellow wires terminate at your compressor contactor via an air handler. The yellow wires connect to the Y terminals on your thermostat.

Do I need to connect the blue wire on my thermostat?

The Blue or 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.

Why is my thermostat not communicating with furnace?

When a furnace is not responding to a thermostat, there is either a problem with the heating unit or the actual thermostat. Lack of power to the thermostat, wrong settings, and outdated software might be to blame, as well as faulty wiring, a tripped breaker, and a dirty furnace filter.

How do you fix a thermostat that is not communicating?

Common Fixes When Your Thermostat Cannot Connect To Anything

  1. Reinstall The App And Reconnect The Thermostat To Your WiFi.
  2. Reset Your Thermostat To Factory Settings.
  3. Replace Batteries And Clean The Inside Of The Thermostat Housing.
  4. Check Connections And Wiring.
  5. Contact Honeywell Support If All Of This Doesn’t Work.

What could be the problem if the HVAC is not responding to the thermostat?

HVAC System Suddenly Quits Working



If the thermostat’s display is dark, a lack of power may be the issue. Try replacing the batteries, then check for a blown fuse or tripped breaker in the electrical panel. If the thermostat is still unresponsive, make sure the breaker is shut off and remove the cover.

Why does my thermostat setting not match my home’s temperature?

Poor air flow, bad sensors, or other broken components can also cause room temperatures to be different than your thermostat setting. The biggest clue that your furnace is the culprit is your heating bill.

How do you know a thermostat is bad?

7 Ways to Tell Your Thermostat Is Broken

  1. Thermostat Has No Power. …
  2. AC or Furnace Won’t Turn On. …
  3. Heater or AC Won’t Turn Off. …
  4. Thermostat Doesn’t Match Room Temperature. …
  5. Thermostat Doesn’t Respond. …
  6. Short Cycling. …
  7. Thermostat Forgets Programmed Settings. …
  8. Thermostat Replacement Services.


What would cause a thermostat to stop working?

There simply may not be any power going to your thermostat. This could be caused by a poor connection, blown fuse, dead batteries, or a tripped circuit breaker. If all of these areas look good and your unit should be receiving power, the issue lies elsewhere.

How do I test my furnace thermostat?

How to Test an Old Thermostat

  1. Step 1: Turn off HVAC power. This can be done by switching the furnace to the off position if your system has an on/off switch. …
  2. Step 2: Remove thermostat cover. …
  3. Step 3: Remove wires from terminals. …
  4. Step 4: Turn the HVAC power back on. …
  5. Step 5: Test other wires.