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Mike G.
Mike G., Master Electrician
Category: Electrical
Satisfied Customers: 7494
Experience:  Proven Professional 48 years Experience
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I obtained a quote for installing electric radiant heat when

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I obtained a quote for installing electric radiant heat when I install my tile bath/hallway floors. The system I was quoted totals 1772 watts. I pre-wired a dedicated 20amp GFCI circuit for 110/120V. The quote is for a 240V system - although 220V thermostat/controller is available.
Question: I understand the watts are the same regardless and I understand that with 240V the idea is you half(sp?) the amperage per wire. Is there a good reason (or justifiable reason) to try to re-run 12-3 romex to accommodate the quote/system? All the home's walls are closed up and finished as well as the panel/breakers installed.
Hi, I'm Mike and I'll be glad to assist you. If the system requires a neutral when using the 240V application, you'll need 3 wire from the panel. Otherwise the 2 wire may be used for the system by putting a 2 pole GFCI breaker with the black and white on the hot terminations and not having a neutral connected on the load.
Customer: replied 3 years ago.

Hello Mike

I'm sorry for not responding back sooner. I wanted to give some thought to how I worded my original inquiry and to re-think why I proceeded in the first place. This was the first time I've used such a service and my recollection is that the site presented me with a professional profile of an electrical engineer living in my area of California. That is what sold me on proceeding. I have a basic understanding of line voltage wiring. Although poorly worded and with typo's my inquiry concerned the specific application the manufacturer (Warmly Yours) is suggesting for wiring radiant floor heating in my home. They market their "SmartStat" thermostat as GFCI and specify the panel breaker as either single pole (110V) or double pole (220V). The same thermostat is used for both voltages. There are only two line in connection points - 110V using a single line in hot and single line in neutral or 220V connecting one line to the same line in hot as above and the second line in hot to the neutral position indicated above. The ground connects the same for both configurations . I understand that if used as 220V I would "color" my white jacket "neutral" either black or red at both panel and thermostat J box to indicate it is a "hot" lead. The question is will this pass California code if the GFCI is relying on the ground wire to accomplish its goal. The other question and one in which I was hoping to obtain an electrical engineer opinion on was the value a 220V system would have in my application. I understand balanced load, I understand more amperage/wattage (larger capability of system). The manufacturer also states there is no difference in function between the two voltage systems ie. same wattage used and same time to bring system to and maintain temperature.

You have the choice of voltage and 240V would be the one to use. A 2 poleGFCI doesn't need a load neutral if it is on a 240V circuit. That meets all code requirements.
Customer: replied 3 years ago.


I understand your choice of 220V but don't have a clue as to the factors you considered in finding your decision as it relates to my application. For me to change to 220V would require the purchase of a new two pole "standard" 220V breaker at approx $90. I understand that the line neutral associated with a GFCI breaker facilitates the "test" button and that the "ground" wire (from application) to the ground bus is what facilitates the GFCI working properly. Warmly Yours staff have told me to not use a GCFI breaker for their system as the thermostat has that function built in - hence the wiring similar to that which we have been discussing. So I am back to my original inquiry which prompted my contact - why 220V (other than load balance and greater system wattage potential)?

If the t-stat has its own GFCI a 2 pole breaker is all that is needed. The lesser amperage for the size of the wire and load is why I suggested it. The white wire should be identified as being a hot wire by black tape.
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