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robj · Oct 27, 2006, 09:57 PM

Mayby you gyes know this one. I have a nice sized room that is heated in the winter by 3 220 volt 20 amp heaters that are set in the wall and each one is on there own circuit. The problem is that all they have for controlling them is low, medium, and, high. I would like to put them all on a thermostat. I was think about perhaps installing 4 relays or 1 relay if they make one big enough for this at the circuit breaker box and then running a low volage wire into the room from there and connecting on it a heat only thermostat. Any help. Thanks

tkrussell · Oct 28, 2006, 04:43 AM

What you are proposing is possible and practical. First a quick lesson on words, a relay is a small switching device that usually is intended to switch or control low voltage or low amp control circuits, the contacts will be rated for no more than 10 amps.

A contactor is a larger "relay" that has contacts rated for line voltage and higher amps, 20,30,40,50 amps, etc. These will be called a "definite purpose" contactor.

Without knowing the details, say for example, each heater is 1500 watts at 240 volts, and you want to use a 24 volt thermostat. Then for each heater, insert into the circuit a 2 pole contactor with contacts that are 20 amp 240 volt rated and a 24 volt coil.

Each contactor can be at the heater, or at the panel. If you have several then all the 2 pole contactors can be in a large junction box, next to the panle, where all the branch circuits begin, and each branch circuit can be wired through each contactor.

To control the contactors, install a 24 volt t'stat, with a 24 volt transformer for power, to control all the contactor coils at one time. The transformer needs to be a VA rating that can handle the total load of all the coils.

If this sounds like what you would like, then provide more detail of the heaters, wattages, voltages, and we can go from there.

robj · Oct 28, 2006, 02:27 PM

I think it be easiest to install the three 2 pole contactors at the panel. Suppose I'd have to install them in a junction box. The transformer will be near the panel too with a 120 volt line in it and then obviously 24 volts out to the t-stat. The 24 volt line will be run in the walls to a place that is generally in the middle of the room and away from a heater where the t-stat will be installed on the wall. I would like a progammable t-stat too. The heaters themselves have there own separate circuits and have there own 20 amp 240 volt circuit breaker. I removed a cover on the heaters and I think that they pull around 13 amps when installed on a 240 v.a.c line cause it says 25 amps when installed as 120 volts. The heaters are also 2 hp when installed as a 240 v.a.c line. Thanks

tkrussell · Oct 28, 2006, 03:02 PM

OK then since the heater is rated in HP, then the contactor must be rated to handle at least 2 HP,the heater must have a fan motor also.

robj · Oct 28, 2006, 03:17 PM

Yes it does have a fan motor. I don't know if you were asking for information regarding this but I really couldn't find too much on the fan. So it looks like I need a transformer, three 2 pole contactors rated at 240 volt 2hp and has a 24 volt coil, a 24 volt programmable thermostat, and a junction box. Where can I find all this stuff and/or you wouldn't happen to have model numbers or internet links to all this stuff. Thanks

tkrussell · Oct 28, 2006, 05:46 PM

No,no, I wasn't looking for fan info, you have what you need already, the 2HP rating at 240 volt. Very important.

Try www.grainger.com. I am sure you can find everything there. If you have a problem , let me know.