radiant floor heater thermostat


Old 03-26-08, 09:27 PM
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radiant floor heater thermostat

I've got a SunTouch radiant heat mat installed under a tile floor. Yet to be wired up into a live circuit because I'm not sure if I should put it on a 15 or 20 amp breaker. #12 wire was pulled to the bathroom during a remodel so we can have the outlets on a dedicated 20 amp circuit...and the way we roughed in the electrical for the floor mat, it will be on the same circuit. I'm just a bit confused about the wording for the installation manual for the thermostat.

"The circuit breaker in the main circuit panel should be 15 amps maximum
for a floor warming system totaling 12 amps or less. For larger systems up to

15 amps, use a 20 amp maximum circuit breaker. Never exceed 15 amps on
this thermostat."

My "floor warming system" is 12 amps or less, it's just a small mat. I should never exceed 15 amps on the thermostat... meaning what? I can't run it on a 20 amp circuit, or not overload it with 15 amps worth of mats?

I'd like to run the circuit at 20 amps rather than waste a #12 circuit by limiting it to 15 amps.
Old 03-27-08, 04:29 AM
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Most tile heater are not super high wattage type however it depending on how big the area you going to be heated and follow the manufacter instruction very carefull [ it don't take much to get all screw up ]

and the other thing if this heater thermosast do not have GFCI protection then you have to install the GFCI breaker for this unless the termostast do have included a CFCI

however most bathroom i done some before most are 800 w or less but larger one useally split in two grids.

for wiresize i useally run #12-2 romex you can use either 15 or 20 amp breaker

Old 03-27-08, 08:55 AM
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Originally Posted by kornbln View Post
I should never exceed 15 amps on the thermostat... meaning what? I can't run it on a 20 amp circuit, or not overload it with 15 amps worth of mats?
That means you cannot load it with more than 15A worth of mats. It is okay to be installed on a 20A circuit.
Old 03-30-08, 03:15 AM
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If I read your post correctly, you ran one cable for both the bathroom outlets and the heater. Using a hairdryer which pulls up to 15 amps while the heater is running will pop even a twenty amp breaker. You need two dedicated circuits.
The manufacter's instructions seem perfectly clear to me. If your mat draws 12 amps, use a 15 amp breaker. If it draws between 12 & 15 amps, use a 20 amp breaker. If it draws more than 15 amps, get a different thermostat. The physical size of the mat is not consideration in wiring the heater, only the current draw.
"waste" or economy is a minor consideration in electrical wiring - function and safety come first.
Old 04-03-08, 07:21 AM
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SunTouch heating floor

#1. A dedicated circuit is preferred, and likely the way you have yours run, with outlets sharing, will cause tripping problems. There is a GFCI built in to the Suntouch Thermostat, so if there are any other GFCI's on the circuit, they will conflict with each other. Electricians call this, "Cross-Talk".

#2. Here is a simple formula for calculating breaker amperage: exceed the load by 25%.
So, if you have a load of 15 amps, use a 20 amp breaker. Suntouch products are made to be used (If you are using a Suntouch Thermostat) without a GFI breaker.
So, you have a 12 amp system, requiring a 20 amp breaker. It would probably work O.K. with a 15, but a 20 wont hurt and doesnt cost much more and will not give any problems.
If you have any further questions, please feel free to contact me
Old 04-03-08, 10:51 AM
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Just a bit of clarification on 15a breaker vs 20a. The breaker protects the wiring not the device. Think of the #18 wire on a lamp or a wall wart plugged into a 20a circuit. You can fry either with a lot less then 20a but it is ok to use them on a 20a circuit. If they do cause an absolute short not just an overload in excess of their limit then the breaker protects the wiring by tripping but they are probably fried by then.

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