How to replace a thermostat controlling an elelectric baseboard heater?
Hi,
I giving my finished basement a tune up and as a part of that I would like to replace the electric baseboard heat thermostats. I thought I could just buy something similar, take out the old ones, and intall the new ones, similar to a light switch. Nothing is ever that easy though is it. The current ones have 3 wires. Every new thermostat I have seen so far has either 2 or 4 wires. I am a homeowner, not a professional, so go easy if this question is as dumb as I think it might be! Thnks in advance!
Tom
Replies
You need a 120/240V thermostat. These are special units, different from your standard low voltage (18-24V) units. The high voltage thermostats will have two active connections -- hot in and hot out -- a ground connection, and possibly a doubled dummy terminal to allow the neutral/other hot of the incoming/outgoing lines to be joined.
(Be absolutely sure to turn off the breaker before working on one of these. Unlike with the low voltage units the voltage is lethal.)
Are these line voltage thermostats on the wall?
or low voltage controls?
Line voltage on the wall.
There are several different ways these things are done. I strongly reccomend that you hire this out if you are the least bit confused. I will describe the two most common methods.
First off, baseboard heat can come in either 120v or 240v versions. You need to know which version you have. If you don't understand 240v, and KNOW how to kill the power, don't play with it.
Secoond, there are two common ways these things use thermostats.
Is the thermostat mounted on the heater itself? If so, replacing the 120v version is pretty straightforward. If it is the 240v version, things can get tricky.
If you have the 240v version, the replacement thermostat probably will not have the inside connections arranged the same way as the old one. Oh, it will LOOK the same, but the internals will be different. USE A METER beforehand, to identify exactly which screw are opened and closed by the thermostat. Fail to do this, and you will make a direct short circuit the first time you turn it on.
If you don't have a meter, don't even try.
The other way has the thermostat on the wall. If that's the case, the thermostat is probably powered by a low voltage - 24vac is common - and actually controls a thermal relay in the baseboard unit. In these systems, it is usually the relay that goes bad with age. If you do want to replace the thermostat, take it to a heating supply shop; the usual ones at the hardware store won't work. Nor will the fancy electronic ones.
The thermostat on the wall is apt to be 120/240V as well.