Heated floor calculations requirements

Merry Christmas
E

electricladyland

New User
Location
Colorado
Occupation
Maintenance
60sf heated floor
720 watts
12w sf

120v / 720w= 6a

15 amp GFCI thermostat

Everywhere I look it says use a 20amp breaker.
Why wouldn't you use a 15amp breaker if there's only a 6 amp load.
 
There is no reason that I can think of that would require a 20 amp breaker. I am guessing they want a larger wire than a 14 feeding the extra length. I don't believe they require a separate circuit so that may be one of the reasons. IDK
 
Is this hard wired or cord and plug? Regardless, if you put this on a circuit with other things, and they treat heating as a load that requires a 125% factor, a 6A load becomes 7.5A. A 15A circuit with other general use receptacles on it is limited to 50% of the circuit being used for equipment fastened in place. So a general use 15A circuit would be marginal to have 7.5A of heat load on it and still used for other purposes.

If this is a dedicated circuit with no general use receptacles on it, I don't know why they would say 20A circuit. So many times instructions don't make sense. Could this floor heat system possible be larger so it could get up to 16A and they are just telling you the max limit?
 
I've wired for a lot of floor heat thermostats, never seen higher than 8 amps on one cable, and every one says 20 amps as far as I know.

I think there's some misunderstanding, where a "generally speaking" philosophy is employed.

Generally speaking, bathroom lighting is ok on 15a, but "everything else" is 20 amps. I've heard it said like that lots of times, and that can guide manufacturers sometimes.
 
James L said:
Generally speaking, bathroom lighting is ok on 15a, but "everything else" is 20 amps. I've heard it said like that lots of times, and that can guide manufacturers sometimes.
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There is no "generally speaking" rule in the NEC that would require this floor heating to be on a 20 amp circuit but to your point manufacturer's have proven time and time again that they're pretty dumb when applying the code to their products.
 
infinity said:
There is no "generally speaking" rule in the NEC that would require this floor heating to be on a 20 amp circuit but to your point manufacturer's have proven time and time again that they're pretty dumb when applying the code to their products.
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I know there's no "generally speaking" rule in the NEC. But there is certainly a "generally speaking" frame of mind within the trade.

And that mindset can trickle back upstream and affect engineers, product designers, and all kinds of people who should know better.

It's the same kind of thinking as an inspector seeing plywood behind a breaker panel on a concrete wall, over and over and over, then suddenly he sees somebody mount a panel on unistrut and he thinks he needs to fail it because "you have to have plywood behind it" - generally speaking, people use plywood. To the point that some people think it's mandatory

I'm just saying it wouldn't surprise me if that kind of mentality has led to floor heat manufacturers wanting to see a 20 amp circuit for 6 amps worth of heat
 
The floor heating systems have so many options and frequently require more that a single mat or "cable type" system. Its easier for the manufactures to just state use a 20 amp circuit since that is what the T-stat is rated for.

I don't see the 20 amp circuit as a requirement if the load can be supported by a 15 amp circuit.
 
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