Tech Tips: Wiring 2 Heating Systems to a Thermostat

Today we're going to talk about hooking two heating rolls or two heating mats to a single thermostat. If you look in the back of the thermostat you have four wires coming out of the back. These two wires, the top and the bottom, will be attached to the power coming from the circuit breaker box. What we're going to do is we're going to be attaching these two heating mats or heating rolls to the load wires that are sticking out of the back of the thermostat. The thermostat load wires are the ones in the center.

To attach two systems to one controller you would take these two yellow wires, and if this were a 240 system these would be red. You can see that we also have two black wires, and we also have two green wires. We're going to tie the two yellow wires together because this is a 120 mat. We're going to attach them to the red wire coming out of the back of the thermostat. This one is labeled "load."

Next thing we want to do is we want to hook up the black wire, the black load wire in the back of the thermostat. We take the two black wires from the heating system - or from the rolls or from the mats, whichever one you have - and you tie the black wires together. Then you tie those wires to the black wire coming from the back of the thermostat that's labeled load.

That leaves you two green wires. These two green wires will attach to the ground that is going to be inside the junction box that the thermostat is in. That's how you hook up two mats or two rolls to one controller.