radiant heat calculation

[bobbymari]

load calcs radiant heat(cieling)

question. anyone familiar with the old 70's style cieling radiant heat. I am working on load calcs for a multifamily and trying to figure va for radiant heat . first calc i've had to do with this style heating. each thermostat is on its own 15amp/240 volt breaker. any ideas on what these style heating elements actually pull? I sure dont want to figure them at 15 amps each. calcs would be sky high... any knowledge on this would be hugely appreciated​

 

[ptonsparky]

Any chance you could measure the current for each area?

As a rule of thumb, we used 10 watts per sq ft here. Most likely high for you.

 

[Smart $]

... any knowledge on this would be hugely appreciated

Turn 'em on. Measure current (should drop as they heat up... so allow settle time).


Oh yeh... Multiply by voltage.

 

[bobbymari]

thanks fellas yea ill just take a reading...
oh yea and multiply by voltage lol thanks this forum really is helpful and appreciated

 

[K8MHZ]

My dad built one of these homes for us to live in when I was in school.

Each room will be different as they followed a pattern with the element wiring in the ceiling. The larger the room, the more element wire.

That type of heat is grossly inefficient. We ended up heating with wood. The house was built with money borrowed from the bank in 1967. By 1971 our winter electric bills were more than the house payment.

In order to properly evaluate the amount of current the heating system will draw, you will have to turn on ALL the room thermostats to high at the same time and then check current at the panel.

Using the 'rule of thumb' given, 10 watts per sq. foot, our 3,200 sq foot home would need 32kW to heat the house or 133 1/3 amps at 240 volts just for heat.

Breaking that down by room, a 12 x 12 foot room would need 1440 watts, or 12 amps at 120 volts, which sounds about right.

I think you should sell them a furnace.