Heat Pumps and Electric Heating - Electric wall heaters in basement

I'm finishing my basement and want to add some extra heat for the winters. I live in southeastern Wisconsin so winters can get cold from 30 degrees down to below 0. I have two 4 X 10 forced air heating ducts in the ceiling and one 12 X 12 cold air return just off the floor on one side of the room. I don't think the 2 ceiling registers will be enough to make the room comfortable all year round.

The room is approximately 600sq ft. I have Kraft faced R11 insulation from floor to ceiling on all outside walls between studs. Also the builders sprayed the hard foam insulation between the foundation and where the structure sits on the foundation. Ceiling and walls will all be dry walled.

I would like to add a few 2000w 240v wall heaters spread out in the room to help supplement the heat in the winter. The ones I'm looking at are the Broan 128 models which are 2000w at 240v.
If I add three of them my calculations are 6000w/240v = 25amps. I know I've read that electric heating should have a circuit rated to 125% of max amps used, so that comes to 31.5 amps. Would I still be safe using a 30amp 240v double pole breaker with 10/2 romex? Or would I need to go with a 40amp 240v double pole breaker with 8/2 romex?

3 of these would give me around 20400 Btu.
If I went with 2 instead I would get around 13600 Btu and use fewer amps.

Sorry this thread is so long. I would love to hear your advice on this. Also all heaters would be wired to a single thermostat.
My goal is to make the basement when done just as comfortable or close to the upstairs.

Also, should I put the heaters near the floor or closer to the ceiling since I have a cold air return near the floor? My thoughts are floor level but I may be wrong.

Thanks

Dennis

Mount them on the floor. You might want one unit to be a wall mounted unit with blower. That will help warm the room quicker if you set back your thermostats when not using the space.

I would have to check on the circuit rating to be sure. Hopefully someone will chime in by then. Or you could try posting on an electrical forum.

The units I'm buying (Broan 128 register heaters) are fan blown. So they should heat the room up pretty good. I'm actually leaning more towards 2 instead of 3. It is a basement which is easier to heat from what I hear. Two of these would give me 13,600 BTUs. Like I said, I do have two 4" X 10" registers in the ceiling from the furnace as well plus the 12" X 12" cold air return near the floor.
I was planning on mounting the two electric ones on the outside wall pointing towards the inside of the room. One on each end of the wall should give good coverage.
My calculations for that come out to 20.875amps for 125% of max amps from both heaters combined. Each unit pulls 8.3 amps when wired in 240V. I would think a single 240V 20amp double breaker would work wouldn't it? Maybe that's cutting it too close?

Maybe I'll post this question in the electrical forum.

Thanks for replying so far.

This (http://www.ezdiyelectricity.com/?p=687) should help answer your circuit rating question.

This (http://www.ezdiyelectricity.com/?p=687) should help answer your circuit rating question.

Thank you, it does answer my question sort of. I know how to figure out amps when I know the volts and wattage. I also know which gauge wire to use for the size of the circuit. It just sucks that it's so little over that I need to use a 30amp circuit and 10/2 wire vs. a 20amp circuit and 12/2 wire because of the difference in price. Oh well, better safe than sorry right.
Those two heaters would equal 16.7 watts together. 80% of a 20amp circuit which is required for continual use is 16amps. That’s only 0.7amps to many! But, I would rather spend a little more money to be safe than risk starting a fire.

Thanks for the link; it helps me with figuring out the average for watts needed per sq ft. According to that article you need roughly 10 watts per sq ft. That means I need a minimum of 6000 watts. The two heaters combined are 4000 watts. With the two registers I already have in the ceiling coming from the furnace and the fact that the whole room except for the top 18" is underground should be more than enough to heat the room even on the coldest days. I would think a majority of the year I wouldn't even need to run the wall heaters.

Thanks