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Old 03-09-2010, 11:03 AM   #1
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Electric radiant heat in the shower?


I posted about this in the HVAC forum too, but I wanted to get the electrical take on it.

Watts SunTouch matts are UL approved (according to their site) for use inside a shower. It's 120v, and the heating coils are encased in Pex tubing. I will also be installing a schluter kerdi waterproofing membrane between the heating elements and the tile.

This will obviously be on a GFCI circuit. I assume also, this should be on a 15 amp circuit, since the line-voltage thermostat is only rated for 15.

Thoughts? Should I do the shower or not?

Here's the proposed layout of my bathroom, the shaded areas would be heated.


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Old 03-09-2010, 10:10 PM   #2
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Electric radiant heat in the shower?


Are you connecting those different shaded areas together on one thermostat?

I'd keep the shower area separate, with maybe an aux switch to turn it on and off .....

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Old 03-09-2010, 10:14 PM   #3
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Electric radiant heat in the shower?


I was planning to do it all on one zone. The bathroom is only 40 sq feet including the shower, and it will only run a few hours a day max.

Why do you suggest I separate, just for $$ reasons?
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Old 03-10-2010, 06:57 AM   #4
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Electric radiant heat in the shower?


If the bathroom is slab-on-grade, I would heat the shower pan.
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Old 03-10-2010, 07:24 AM   #5
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Electric radiant heat in the shower?


It's over a basement, wood framing.

I think I'm going to do it...the idea of a warm floor in the shower sounded really nice this morning
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Old 03-10-2010, 10:45 AM   #6
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Electric radiant heat in the shower?


Check on that "120v" again, please. I worked on a major home reno project and part of that was the installation of a radiant heat electric flooring in the new bath and entrance foyer. The Master Electrician I was working with told me that "NEC requires these electric heating elements in wet locations to be 24 v DC". We did install a transformer, furnished with the heating material, and a thermostat clearly I.D.'d as "Low Voltage", in the bath area. The foyer got the full 120v system. These were a "mat" type material. They could be cut to size, and multiple mats connected. The mats then had to be connected per manufacturer's recommendations. One circuit with the transformer sized accordingly. Darn stuff worked great. David
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Old 03-10-2010, 11:14 AM   #7
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Electric radiant heat in the shower?


The book definitely says it's safe in showers:

http://www.suntouch.com/literature/d...N-20071121.pdf

Even some of the examples show it being installed in the shower. When I called to ask about it, they said you can run the mat right over the curb and into the shower.
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Old 03-10-2010, 11:18 AM   #8
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Electric radiant heat in the shower?


IF safety is in question, I can skip the shower....but if it's safe...I want to do it!
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Old 03-10-2010, 11:38 AM   #9
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Electric radiant heat in the shower?


I take hot showers....
So I don't see much of a benefit as the floor warms up pretty fast
New shower has steam generator...so not needed there either
I think any electric inside a shower/tub enclosure is a risk
Might be a very low risk
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Old 03-10-2010, 11:41 AM   #10
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Electric radiant heat in the shower?


True. If it were low voltage I wouldn't be so concerned.

I'll probably worry about it constantly if I put it in the shower. Guess that means I should skip it
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Old 03-10-2010, 07:15 PM   #11
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Electric radiant heat in the shower?


Quote:
Originally Posted by secutanudu View Post
I was planning to do it all on one zone. The bathroom is only 40 sq feet including the shower, and it will only run a few hours a day max.

Why do you suggest I separate, just for $$ reasons?
My point in asking was you had different colors shown on your map representing the different areas to be heated.

We did a job for a customer a few years ago similar to yours. The system worked great for about 2 years, then started tripping out the GFCI built into the thermostat.

We installed an isolation transformer in the crawl space between the thermostat and the heating elements. That solved the problem, and it has been working fine ever since. BTW, they did install it in the shower stall.
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Old 03-10-2010, 10:49 PM   #12
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Electric radiant heat in the shower?


You can run a 120v sytstem through a transformer to lower the voltage? Does that reduce the effectiveness?

Can I reduce the voltage just for the shower portion, if I do it on a separate mat?
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Old 03-11-2010, 12:43 AM   #13
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Electric radiant heat in the shower?


he's refering to an isolation transformer, not a step up/down transformer. an isolation transformer is wound 1-to-1, it decouples the device from the earth ground, basically you could touch the "live wire" out of the isolation transformer's secondary and touch earth ground and not get shocked... the secondary is your new hot/neutral, isolated from the home side.


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Old 03-11-2010, 04:21 AM   #14
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Electric radiant heat in the shower?


Correct. However, we did use a 480/240 primary --> 240/120 secondary transformer on this particular application. Since the thermostat was capable of being installed on either a 240 Volt or 120 Volt floor heating system, we opted to feed it with a 240 Volt circuit, then we connected that into the transformer primary windings.

With the isolated output of 120 Volts for the floor heating element, there was no further problems with any leakage tripping out the GFI device. Its the same principle that is commonly used in hospitals for operating rooms, etc.
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Old 03-11-2010, 05:56 AM   #15
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Electric radiant heat in the shower?


Wow...I'm confused....not really understanding how that works.

In any case...is it costly?

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