electric under tile heat?

[bmxdukie]

Hi folks.
Thinking about using electric infloor under tiles.
What is the largest space that could be done?
And what would the cheapest solution be?

 

[Hpozzuoli]

I am starting a job just now that is a master bath gut and remodel. Building a custom shower stall and heating the floor. I bought a kit off eBay because I have used them before. Comes with wire, sensor, thermostat, wire guides, tester, etc. I believe it was 60sqft for $324ish.

I just got all the tile up so I will begin at some point this week running the wire. This is a second floor master on a wood sub floor.

 

[sublimate]

Is a kit like that good for outdoors (snowmelt) as well? I've got a area just in front of my door (about 60 sqft) that's shaded and tends to ice up. It would be under flagstone.

 

[Jess]

I use Nuheat mats under tile for baths and kitchen floors. They are made in stock sizes and easy to thinset down before tiling over. No loose wires in the field to worry about. Thermostat and floor sensor are an easy install. Available in 240V or 120V so you can replace small baseboards in bathrooms.

http://www.nuheat.com/

 

[Voi]

Hi folks.
Thinking about using electric infloor under tiles.
What is the largest space that could be done?
And what would the cheapest solution be?

We put them in at our house and I did the math on how large of an area could be ran on a single, 20 amp dedicated circuit but I can't remember the numbers.

Quick Google search found this:

What are the Voltage and Amperage requirements for floor heating?
Both 110/120 & 220/240 systems are available. Mats are 12 watts per Sq Ft, which means you can control up to 150 Sq Ft of floor warming at 120v (and twice that (300 SF) for 240v) per circuit. Each circuit has a 15 amp maximum, and 1 thermostat control is required per 15 amp circuit. A dedicated circuit is recommended, but very small systems of 20 SF only require approx. 2 amps, so you may be able to add on to an existing circuit; a licensed electrician will know the answer for your project.

http://www.warmyourfloor.com/cms/faq#usage

150 square feet per circuit sounds about right based on my faint memory.

I've seen an entire basement heated with these which I assume took a few to several circuits.

 

[BellyUpFish]

Good timing on this thread.

I'd like to heat the floor in the bathroom of the house we are getting ready to build.

 

[1969]

Interested in this also.

 

[matt_i]

I did a bathroom about 10 years ago in metro Atlanta. It was SunTouch. I forget how many mats, want to say 4-5 but it was 120vac full 15A draw.

A couple of limitations (which may have changed). I had to put in a lot of junction boxes in the walls, I think one for almost every mat. The braided pigtail from the mat was nowhere near long enough to reach the attic. I didn't like this but it was necessary.

The mat can be carefully cut apart if needed and the heater element stuck in a custom place with hot glue to the backerboard. A careful tile guy can work around it.

It shouldn't be put under the cabinets (I had tile set all the way to the wall to raise the cabinet height). I put it near the front of toilet for warm feet but didn't put enough mat there on the sides and it had hot and cold spots in the same 18" sq tile.

It took quite awhile to warmup. I ended up putting in a 7-day timer to give about 3 hours lead time before the floor was actually warm....when it was...awesome. Floor mats not needed except to soak up water/traction from wet feet.

So at that point, I took the "relay output" from the Suntouch controller and sent this to control a 120vac-coil contactor, I left the Suntouch controller always on (thermostat was calling for heat around 20 hours per day), and used the 7-day timer to inhibit the contactor when it was not needed. Thermostat was always in control and internal to the controller it was tied to the "relay output" from the controller. Contactor output went thru a standalong GFCI module to duplicate that function built into the controller which I had eliminated with my custom controls.

I ended up putting in a selector switch in a closet for "normal" = 7 day timer, "vacation/off" = always inhibit, and "on" = always on.

If you are familiar with relay/ladder logic you could design this pretty easily. Hopefully nobody will ever have to fix it . I did leave instructions and a wiring diagram with the next buyer/owner but not my name or contact info due to the contentious due diligence period with the buyer, and concerns over liability due to their nature of employment. Theoretically they could use the closing documents but....I digress...

I plan to put it in again for the next bathroom redo which is future planning at this point.

I think it would get expensive in startup and electric running costs for a basement. One also has to account for the thermal inertia...it takes some time to get up to temp.

 

[Voi]

Is a kit like that good for outdoors (snowmelt) as well? I've got a area just in front of my door (about 60 sqft) that's shaded and tends to ice up. It would be under flagstone.

The electricians who installed our under tile heat also do electric ice melt installations and said they use some sort of thick, PVC coated cable in a sand bed for under driveways, etc.

 

[thammel]

Check out delta therm and their MI wire/cable. I actually did a heated driveway in m prior house. This drew four(4) 40 amp 240 circuits. Used it only a few times a year but it was great. One heck of a pain in the **** job! Put this in under asphalt.

Tom

 

[75gmck25]

Last year I renovated my basement bathroom, and I installed a heated electric floor grid from Warmly Yours. I sent them a scale layout of the bathroom and they sent back a specific list of how much grid was needed, and the choices for thermostats and other items.

The grid does not go under my shower, commode or under the vanity, so its smaller than the square footage of the bathroom. After I talked to them on the phone I decided to also install cork mat underneath the electric grid, since there is no insulation under my slab (house built in 1940). I don't know how much that little bit of insulation helps, but it was relatively inexpensive.

I prepped the floor with the recommended coating, and then glued down the cork in a layer of thinset. I then embedded the grid and temp sensor in a thin layer of thinset on top of the cork and let it dry. The tile guys laid the ceramic tile in thinset on top of the grid. I had to let the tile set up for 30 days before I turned on the heating element.

The thermostat I bought is programmable (nighttime, daytime, vacation settings, etc.) and its switching 120 volts in the grid based on the low voltage temp sensor I installed in the floor next to the grid. You have to install the thermostat in a double box with a mud ring for a single device. I think it requires the larger box volume because of the 120v switching. The thermostat has a built in GFCI, and is supposed to have a very low current draw.

I leave the thermostat set for 78 degrees, but it can be set higher. I find that 78 degrees does not feel warm in bare feet, but also does not feel cold in the winter. That works out very well for comfort when standing on the tile after getting out of the shower.

Bruce

 

[Showkey]

Heated bath floors are awesome ........I have done 6 bathrooms in our last two homes. I agree with 75gmc on temp setting 78-82* is a sweet spot on heat vs cost. Some will operate 85-90* and the floor will be warm to the foot.

The last bath I purchased mats that go in the joist space in the basement, which allows an install without putting a new floor down. I have used the mats and the cables with clips in other baths. Both have there merits and compromises.

As far as doing large spaces...........anything is possible with enough circuits.........BUT.........it's still electric heat and will NOT be cheap to operate. There is no way I would do a room larger than the a bath. Install cost will be too high and do the power calculation it's going to High as well.

 

[theoldwizard1]

Any type of electric (resistance) heat is expensive to operate.

I have heard that you folks in Ontario have some really low "hydro" (electricity) rates, but you should check into this first.

 

[greenbikemike]

Best thing ever for a bathroom,glad I did it. I used the SunTouch from HD and it was a very easy install. I have the programmable system,80 in the morning and after 5 PM then drops down to 72 after 11.PM You can feel right where the mat ends, if you stand on the first tile as you enter,half your foot would be warm and you'll feel the difference. As for what it costs to run,I have no clue,but I think its worth it....and women LOVE IT!

Greenbikemike

 

[bmxdukie]

Thanks guys.
I have it in my master bath and shower.
But was thinking of doing a couple of zones when I do the basement.
Ie. Around pool table, and anywhere our feet would touch the floor for any long time.
But yes, in Ontario we are getting screwed for hydro... just make sure you guys in the US vote Republican.

 

[rebelranger]

I did my whole kitchen 300 sqft is heated, large island and side cabinets are not heated and my master bath 180sqft. My floors go up to 109 degrees f. At 90 they are very warm and feel amazing on a 10d day. Now there is no insulation in the joists below right now, as they are above an unfinished basement. My units are 240v. the 300sqft mats use 9amps an hour so my electric rate of .08 means I pay .72 per hour to run them. which is nothing for the comfort they provide.

My bathroom includes my stand shower so it holds water without problem. The mats were installed over fiberrock and thinset.

 

[Charles (in GA)]

If you are familiar with relay/ladder logic you could design this pretty easily. Hopefully nobody will ever have to fix it . I did leave instructions and a wiring diagram with the next buyer/owner but not my name or contact info due to the contentious due diligence period with the buyer, and concerns over liability due to their nature of employment. Theoretically they could use the closing documents but....I digress....

So you are saying an attorney bought your house?

Neighbor advertised a very nice, very expensive Mooney aircraft for sale years ago (he was an airline pilot). The guy who showed up wanting to buy it (and had the money) was an attorney. The seller (a worry wart if there ever was one) fretted for years after... that he would get sued by the new owner/attorney for something......

Charles

 

[Showkey]

I did my whole kitchen 300 sqft is heated, large island and side cabinets are not heated and my master bath 180sqft. My floors go up to 109 degrees f. At 90 they are very warm and feel amazing on a 10d day. Now there is no insulation in the joists below right now, as they are above an unfinished basement. My units are 240v. the 300sqft mats use 9amps an hour so my electric rate of .08 means I pay .72 per hour to run them. which is nothing for the comfort they provide.

My bathroom includes my stand shower so it holds water without problem. The mats were installed over fiberrock and thinset.

^^^^^^^^^^^^^^^^^^
At 50% duty cycle that's $8.64 per day or $260 for month

 

[slickgt1]

I installed them in 2007, under every tiles surface. So my bathrooms, and kitchen got it.

I remember the most expensive part about it was the thermostat. Otherwise it is pretty cool, and the wife enjoys it. Thermostat heats is up fairly quick, I would say it gets to where it needs to in about an hour.

I also noticed that with big areas, it essentially heats the tile, and then the tile becomes a huge radiator. I realized what was happening when my normal steam heat wasn't kicking in all day at all. The tile - heated floor, gets the air around my thermostat warm enough to keep it from kicking in. Had to actually lower the heated floor in one bathroom enough to make the temp drop in the hallway. We keep the bathroom doors open by the way.