4000w of heat on the same circuit

[HamElec]

So I have a customer that wants electric heat in her movie room that is being built in her basement. I took the dimensions of the room and its 408 Sq Ft at 10 watts per sq ft comes out to 4080w of heat. She would like to use the in wall fan forced heaters. I was going to get two, 2000w heaters and put one on either side of the room. I know this is too much to put on a 20a circuit, so I would like to run 10/2 and put it on a 25a breaker. My main area of concern is the thermostat. I see that both Honeywell and Marley 4 wire stats are only rated for 22amps. These are the two brands carried by my local supply house. Does it pose a risk to put the thermostat on a 25a or 30a breaker? Every house that Ive wired that was to be heated with electric, was tiny and only needed a couple circuits. Ive only done a handful of houses that needed electric heat in my 13 year career, so if there may be a better solution or product I'm all ears and appreciate the help.

 

[OldSparks]

I would use two 'stats. In cases where only a small amount of heat is needed, one heater can supply the demand. Set the two stats a few degrees apart so that both heaters are energized only when there is adequate demand.

 

[electrofelon]

I'll say it. I put 4000 Watts of electric heat on a 20 amp circuit all the time. After VD they'll draw less than 3840.

 

[tom baker]

How about a heat relay on each heater? Control both with one T stat via lv wires

 

[petersonra]

Get a couple heaters rated for 230 volts. Only 9 amps per circuit

 

[Besoeker3]

I think 4kW seems like an awful lot heat for something like a 20 ft by 20 ft room. How high is the ceiling?

 

[Frank DuVal]

I think 4kW seems like an awful lot heat for something like a 20 ft by 20 ft room. How high is the ceiling?

I agree since it is a basement room. But, this is a I want it hot now, not keep it hot for days, so extra KW is good.

A line voltage thermostat is 22 amps. 22 x 120 = 2640 watts. Two of those circuits is 5280 watts. What's the question?

I would go with 240 volt heaters, and baseboard at that. Who wants FAN NOISE in a movie room??????

Two baseboard heaters total of 4 to 5 KW, each on a thermostat, should heat it up nice and quiet too.

 

[Frank DuVal]

Does it pose a risk to put the thermostat on a 25a or 30a breaker?

Does it pose a risk to use a 15 amp wall switch on a 20 amp breaker to feed a ceiling light? No! Control device needs to be rated for the load, not the feed.

 

[Besoeker3]

A line voltage thermostat is 22 amps. 22 x 120 = 2640 watts. Two of those circuits is 5280 watts. What's the question?

Not my question - the OP wanted 4040W. I rounded it to 4kW.

 

[tom baker]

I like King Pic-A-Watt heaters, can easily adjust heater wattage. Use a quality digital T-stat, the old knob T stats have a wide deadband on temp. Some t stats from King have Bluetooth and cell phone app

 

[drcampbell]

... the dimensions of the room ... 408 Sq Ft at 10 watts per sq ft comes out to 4080w of heat. ...

1) Heating equipment should be sized according to the area and conductivity of the wall(s) exposed to the outdoors, not the floor area.

2) Where did 10 W/ft² come from? Somebody's rectal research?

 

[Eddie702]

I would use baseboard as well.

 

[winnie]

I agree that the sizing of heating equipment should be based on the heat loss through the envelope, however the 10 W/ft² rule of thumb seems to be very very common.

On the other hand post #7 makes a very good point. It is very likely that this room will be cold except when in use, and you probably want something oversized that will heat the room quickly.

-Jon

 

[drcampbell]

the 10 W/ft² rule of thumb seems to be very very common.

It may be common, but it doesn't take the thermal insulative properties of the walls & windows into consideration.
And if it's applied to floor area, it's not just incomplete, it's completely wrong.

 

[retirede]

It may be common, but it doesn't take the thermal insulative properties of the walls & windows into consideration.
And if it's applied to floor area, it's not just incomplete, it's completely wrong.

Like most “rules of thumb”, the person using it needs to be aware of its limitations, lest they get bitten in the proverbial behind!

 

[petersonra]

Like most “rules of thumb”, the person using it needs to be aware of its limitations, lest they get bitten in the proverbial behind!

It's not like he's going to get bit in this case. The worst that would happen is he has more heat than he needs.

 

[Frank DuVal]

Where did 10 W/ft2 come from? Somebody's rectal research?

This rule of thumb for baseboard heat works for most every case. Thermostats will make sure the room is not overheated. Sure, a real Manual J or using the loadcalc.net site will get a closer answer*. Then when the power is off for an extended time, the house takes way longer to heat back to temperature. What savings is that? The extra few feet of baseboard heat is minimal in price.

Now, installing HVAC systems, yep, be more on the mark.

* then one has to convert BTUs to watts....

 

[drcampbell]

... The worst that would happen is he has more heat than he needs.

... or not enough.

 

[tortuga]

So I have a customer that wants electric heat in her movie room that is being built in her basement. I took the dimensions of the room and its 408 Sq Ft at 10 watts per sq ft comes out to 4080w of heat. She would like to use the in wall fan forced heaters. I was going to get two, 2000w heaters and put one on either side of the room. I know this is too much to put on a 20a circuit, so I would like to run 10/2 and put it on a 25a breaker. My main area of concern is the thermostat. I see that both Honeywell and Marley 4 wire stats are only rated for 22amps.

I dont see a issue with the 22 amp stat, not a NEC issue. I believe the stat or relay just needs to be sized for the load. Look a t most dimmers rated 300 Watts.