Wiring Thermostat

[charlesg]

For those who read the other post, I dropped the recessed wall heaters idea.

I am planning an addition where I would indstall two plain 4 ft. electric baseboard heaters controlled by their own thermostat (one thermostat for both). The rest of the house has hot water radiators. I figured I would by two 750W 3' units from QMark or Comet (the room is a little over 100 sq. ft.)

First, I am wondering what the big difference is between 120V vs. 240V (beside the obvious). What would make me pick one over the other?

I am also having a hard time figuring out the wiring. On the wall, I should have one wire going to the unit #1 and one wire down to the basement. Do I need a relay box of some kind down there? I was also gonna put both units on one breaker, daisy chained together if you will. Is that a bad plan?

Since we're contracting the work out ourselves, I am trying to be as prepared as possible when the electrician comes by to quote me on the work.

Thanks.

[RBM]

There is no functional difference between 120 volt and 240 volt heaters and if all you want to run is a total of 1500 watts, the size of the wire is pretty much the same as well. You can run a 20 amp 120 volt cable from your panel to the wall thermostat (single pole line voltage), then run a twenty amp cable from the stat to each heater

[Mikepier]

If I am reading your post correctly, you want to put 2 electric baseboards with their own T-stat in a 10' by 10" room. Why not just put a single 6 foot or 8 foot baseboard with one T-stat? If you go this route, then you will probably need 220V. There is no relay needed since the T-stats you will be using are line voltage types. But you definately have to run a new circuit to the breaker panel for the electric heat.

[Paul Franklin]

If you use a line voltage thermostat (common for this situation) you would just run the feed from the panel into the junction box of the heater, and two wires from the thermostat there as well, and make the proper connections in the junction box.

If you use a low voltage thermostat you will need a control transformer and a relay.

Most baseboard units have a chase so you can run extra wires along the unit to daisy chain them together.

Are you sure you will need 1500 watts to heat 100 square feet? Sounds like a lot...guess it won't hurt though, will just cycle faster if you have more watts than you need.

If you go with 240 units the current will be half (doh!). For your application it won't make much difference since one 12 ga circuit will be enough for the two heaters. Half the current will be a little easier on the thermostat if you go the line voltage tstat route. 240 is a tad more efficient since you get less voltage drop in the wire due to half current...but unless you've got a really long run it won't be much.

HTH,

Paul

[Mikepier]

I guess I did not read your post correctly, sorry. You just want to put

1 T-stat. I thought you wanted to put 2 T-stats.

[charlesg]

Thanks everyone for the replies. Very helpful. Just to double-check one thing, heaters should always be in parallel when on the same 20amp line correct? So the thermostat goes in series on the feed, and than both thermostat in parallel with that. Correct?

[RBM]

I think you mean both heaters in parallel. Yes that is correct. You can either run individual lines off the thermostat to the heaters or one line and bounce it from heater to heater, but definitely connect them in parallel