How to Replace the Thermostat on a Hydronic Heating System

What You'll Need
Wire cutter
New thermostat
Flat blade screwdriver
Hand or power drill
Protective overalls
Working gloves

The thermostat on a hydronic heating system provides accurate temperature control. If there are problems in the heating system in regard to the amount of heat being passed to the room, inspect the thermometer to diagnose the fault. Commonly, it might be a simple problem that requires turning on the thermostat or making temperature adjustment. If this does not work, however, then it is necessary to replace the thermostat.

Step 1 – Inspect Old Thermostat

To find out if the old thermostat is working properly, turn on the heating system and adjust the thermostat above room temperature; the system should start heating. Wait a few minutes and adjust the temperature below room temperature. The heating system should stop operating. If this does not work on the equipment, buy a replacement part that will work with your system.

Step 2 – Remove Old Thermostat

Make sure that the power is disconnected to the heating system at the main fuse. Be careful when working around the system as electrical components can be dangerous. Carefully lift the front cover of the thermostat. With the wires still in place, remove the wall plate from the wall. Be sure to note how wires are connected in the old thermostat.

Step 3 – Disconnect Wires

Before disconnecting the wires from the thermostat, note how they are connected in the old device and compare them with the new one. Disconnect each wire one at a time, and make sure they do not touch the wall and or each other.

Step 4 – Install New Thermostat

Remove the thermostat from its packaging material. Pull the body off the base, but do not use too much force as this can easily spoil the thermostat. Use a screwdriver to connect wires at the terminals screws. Make sure the connection is exactly as it was in the old connection or the equipment might not function properly.

Position the base of the thermostat on the mounting surface on the heating system. If the surface does not provide a good mount, find a different location to mount the thermostat.

Outline the base of the device on the new surface. Use chalk to mark mounting holes, and then open them with a drill.

Step 5 – Secure Thermostat

Use mounting screws to fasten the base to the wall, making sure it is even and leveled on the surface. Tighten the device in place with a screwdriver. Secure excess wire into the wall, and make sure they are safe. It is advisable to place an insulating material underneath the thermostat to prevent drafts from interfering with its operation.