How to Install a Heater Thermostat

What You'll Need
New thermostat
Slotted screwdriver
Phillips head screwdriver
Masking tape
Paper and pencil

Learning how to install a heater thermostat is essential to maintain the proper hot water temperature. Most experts say water should be kept at between 120 to 125 degrees. If your thermostat cannot maintain this temperature, replace it with a new installation


Step 1 – Select the New Thermostat

Check with any indication on your hot water heater for a replacement number to secure a new thermostat. These should be available at the retailer offering the brand of water heater you have installed. Check the manufacturer’s website to find an authorized parts dealer if you do not know one nearby.

Step 2 – Power Off

Make sure you throw the hot water heater circuit breaker off. Place a piece of masking tape over the breaker switch to make sure no one turns it on while working to replace the thermostat.

Step 3 – Remove Access Cover

Remove the hot water thermostat access panel with a slotted screwdriver releasing the screw holding it in place. Remove any insulation found surrounding the old thermostat.

Step 4 - Mark Wires

Make sure to mark all wires for easier identification when installing the new thermostat. There should be three to five wires attached to terminal screws. It’s a good idea to draw a wiring diagram locating all the connectors with an identifying number marked on a piece of tape that you wrap on the end of each wire.

Step 5 – Disconnect All Wires

Use a Phillips head screwdriver to loosen all terminal set screws. Once loosened, extract all wires pulling them out of the way.

Step 6 – Remove Mounting Screws

Remove the mounting screws with a Phillips head screwdriver and take the old thermostat out.

Step 7 – Insert the New Thermostat

Place the new thermostat next to the tank and secure it by tightening the attachment screw securely.

Step 8 – Connect Wires

Connect the power wires using the diagram you created when removing the old one following the number directions you earlier established. Make sure to wrap the exposed ends of the wires in a clockwise direction around each terminal screw.

Step 9 – Set Temperature

Using a slotted screwdriver, turn the temperature adjustment screw to your desire setting. A recommended setting would be between 110 to 125 degrees. You may need to locate and push a reset button after you have set the temperature.

Step 10 – Replace the Cover

Replace the thermostat cover plate and replace the insulation. Replace the access panel and tighten it in place with the attachment screws.

Step 11 – Power On

Switch the power on and wait about 30 minutes to check the temperature of the water and adjust the temperature control if necessary.

Make sure to wear work gloves when handling the hot water heater insulation material.