How do I Install a Fireplace Thermostat? | Hunker Step 1. Refer to the fireplace owner's manual to check the voltage of your current thermostat. Electric fireplaces already have a pre-installed thermostat. Match your replacement thermostat to the fireplace's original thermostat, since incompatible thermostats will cause other operational issues and could prove unsafe. How To Install A Gas Fireplace Thermostat - Fireplace Thermostat For Gas Fireplace Install Wiring Scientificredcards Org. Gas Fireplaces At Com. Natural Gas Fireplace Wiring Diagram Third Level. Emberglow 24 In Timber Creek Vent Free Dual Fuel Gas Log Set With. Wiring A Gas Fireplace To Thermostat Data Diagram Schema.