How to Replace a Thermostat
Why does my new thermostat not work? What to Check When Replacing a Thermostat.
Electrical Question: Why does my new thermostat not work?
I am installing a thermostat. The original thermostat worked correctly and there was no issue. I removed the original thermostat yesterday and installed the new one, but it did not work. I put the old thermostat back on within 20 minutes but it did not work either. I reinstalled the new one today and called the manufacturer and I verified that it was wired correctly, but I found that the red wire was not sending power to anything. The red wire appears to be issue. It sent power yesterday, but as soon as I tool the old thermostat off nothing has worked since.
Thanks for the Help!
This electrical wiring question came from Dan, in Summerville, South Carolina.
Thanks for your electrical wiring question Dan.
Problems when Replacing a Thermostat
Application: Thermostat for Controlling HVAC Heating Ventilation and Air Conditioning.
Skill Level: Beginner to Intermediate – Best if wired by a Licensed Electrical Contractor.
Tools Required: Basic Electrical Hand Tools including a small screw driver and small wire strippers.
Estimated Time: Depends on personal level experience and ability to work with tools and the small thermostat wires.
Precaution: Identify the circuit for the furnace or heat pump, turn it OFF and Tag it with a Note before working with the thermostat wiring.
Troubleshooting and Testing: Most thermostats may be tested using a Volt/Ohm Meter. The thermostat battery should be tested and replaced as needed.
Notice: Make sure to get the exact replacement thermostat or or one that is a compatible replacement, such as a fully programmable thermostat.
What to Check if a New Thermostat is not Working
- A thermostat that is used for cooling or heating typically gets it’s power from the unit that it is controlling, therefore it is best to turn the heating or cooling unit OFF before replacing the thermostat.
- If the power remains ON while replacing the thermostat then there is a possibility of shorting the wiring which may damage the power supply and the thermostat.
- The voltage that is used for the thermostat will depend on the exact equipment and application.
- After replacing the thermostat the power source should be restored and turned back on so the thermostat may be set and tested.
More about Replacing and Wiring a Thermostat
- Furnace Thermostat Wiring and Settings
- I put in a new thermostat the old one was removed without labeling the wires
Troubleshooting Thermostat Wiring Connections
Troubleshooting and Repairing Electrical Wiring
Electrical Troubleshooting Methods used to solve the majority of the home electrical problems and wiring failures encountered.
Be Careful and Be Safe - Never Work on Energized Circuits!
Consult your Local Building Department about Permits and Inspections for all Electric Wiring Projects.
The Safest Way to Test Electrical Devices and Identify Electric Wiring!The Non-Contact Electrical Tester
This is a testing tool that I have had in my personal electrical tool pouch for years, and is the first test tool I grab to help identify electrical wiring. It is a Non-contact tester, [amazon.com], I use for the detection of Standard Voltage in Cables, Cords, Circuit Breakers, Lighting Fixtures, Switches, Outlets and Wires. Simply insert the end of the tester into an outlet, lamp socket, or hold the end of the tester against the wire you wish to test. Very handy and easy to use.
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