Floor heat quit working

  rlswan 22:30 PM 09 Nov 11
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Floor heating cable was installed a little over 3 years ago. Last March the GFIC code came on the thermostat and the instructions said to reset it and if it would not reset to replace it. We did replace it but the same happened with the new one. Installer has worked on it for 8 months now with no success to find cause. It is a Warm Tiles system and their tech haven't been of any help either.

  Forum Editor 22:55 PM 09 Nov 11

Specifically which system do you have? There are various cable mat versions - under carpet, under laminate or wood flooring, etc.

Tell me which system you're using and I'll try to offer some advice.

  rlswan 23:14 PM 09 Nov 11

It is a heating cable system not a mat. It is a Warm Tiles system manufactured in Indiana. It is a Kit number 38261, 240 volt 860 foot kit. Thermostat # 29050.

  rlswan 23:16 PM 09 Nov 11

It is installed under a tile kitchen floor.

  Forum Editor 23:35 PM 09 Nov 11

Thank you.

Cable kits work on exactly the same principle as mats, the difference being that the cable is manually laid out and fixed to the floor using adhesive tape, prior to fixing. This system is primarily designed for use in areas where a mat would be difficult to lay - such as in a complex shaped floor area.

A common problem with cable kits is faulty installation - the cable runs are too close together, or even touching in some places - or the cable has been damaged by subsequent tiling work. If a tiler doesn't take proper care when trowelling the tile adhesive its possible to cut the cable insulation with a trowel edge.

Problems can also occur if the floor screed on which the cable was laid is damp in places, or if air pockets exist because of a rough, uneven surface. A GFIC code is not something to ignore. GFIC stands for 'Ground Fault Circuit Interrupter'. It's an American standard, and equates to our Earth Leakage Circuit Breaker - a device that stops current flowing the instant it detects a leakage to earth. The fact that you are getting this error code is indicative of a fault in the wiring at the mains connection. Get your installer to carefully check the way that the heating cable is connected to the mains power.

Did the installer lay insulation boards on the floor surface before laying out the cable?

  rlswan 01:39 AM 10 Nov 11

Are you saying to check at the point where the cold cable connects to the heating cable? No, the installer did not lay any insulation boards on the concrete floor prior to installation, but there was leveling material put on the floor before the heat cable was installed. The system worked just fine for 3 years and 4 months so am confused by that. Also, the installer laid the cable out on the floor area where there were there to be two built-ins installed, one an island and one against a wall. He was well aware of these two built-ins but put wire under them anyway. One built in was secured to the wall (a book cabinet) and the island was secured by glue and a heavy granite top on it. Should we take up the tile where the connection is between the cold and the heat cable and replace the connection. We have a repair kit.

  rlswan 01:42 AM 10 Nov 11

I have pictures taken of the entire floor wiring before the tile was installed and there are no wires touching. The wires are secured with metal strips supplied with the cable. The tile installer is a very, very careful individual so feel good that he did not damage any cable.

  wiz-king 13:15 PM 10 Nov 11

I would suggest that you get an electrician to disconnect the mains lead from the heating cable, then check the heating cable for any faults especially earth leakage. Then get him to wire a load across the output of the controller and test that.

Heating the concrete floor is not a good idea - you should have had an thermal insulation layer on the floor then put down the heating cable.

  Forum Editor 23:53 PM 10 Nov 11

wiz-king's advice is sound

It's a simple matter to check for earth leakage in the way he suggests.

If your kitchen sub-floor was constructed fairly recently there would be no need for insulation boards - current building regulations require that rigid foam insulation is incorporated in all solid floor constructions. Otherwise, electric underfloor heating should never be installed without a layer of insulating board (specially manufactured for the purpose) under the heating element. If that isn't done you are paying out good money for heat that will dissipate into the concrete floor slab, and from there into the ground beneath. Your installer should have recommended insulation - the self-levelling latex screed has no insulating properties.

Installing a heating grid underneath fixed kitchen units isn't usually a problem because most units are supported on plastic legs - there's air movement beneath the units.

  rlswan 00:45 AM 11 Nov 11

The home was built in 1970. No insulating board was used when the heating system was installed. The built-ins are an island that is built with cabinets with four legs supporting a heavy granite top. It appears as if about 1 inch of air space may between the floor and the bottom of the drawers but it is enclosed by wood and trim so no space is seen. The other cabinet is enclosed on the floor and no space can be seen although the bottom of the shelves is about 2 inches from the floor. The instructions from the manufacturer says DO NOT PUT HEAT CABLE UNDER ANY BUILT INS AS DAMAGE MAY OCURR. I just want the floor heating system fixed. The installer won't even come back because they can't figure out what is wrong. I have initiated legal action.

  Forum Editor 18:43 PM 11 Nov 11

As I said earlier, installing a heating grid underneath kitchen cabinets isn't usually a problem - the legs ensure that the base of the unit is raised above the floor.

The manufacturer's concern is that nothing with a large 'footprint' should be placed permanently on the floor above a heating grid because of the danger that heat will not dissipate so readily, causing the conductor wire to overheat.

A house built in 1970 will not have any insulating foam incorporated into the floor slab. A competent installer should know this, and should advise that a heating grid is installed over insulating boards. These are made for the purpose, and are widely available.

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