Electric UFH melted

[hudster]

Recently bought this house which has electric underfloor mats downstairs. Been using them all without any problem.

Noticed that the engineered wood floor in the lounge had a bit of a dip in it, so I pulled up the floor thinking I'd probably find a failed joist. However the dip was caused by the underfloor electric mat having got too hot and melting the insulation below it. This has only happened in one strip - the rest of the room was absolutely fine.

The system was a foil mat on the purple budget insulation you see sold online a lot. Engineered wood flooring on top. Final photo shows it flipped upside down.

The whole lot is in the skip now so it's no danger to anyone. But it looked well installed.

I'm wondering what causes this to happen, and shouldn't there be some safety cut-out?

 

[ericmark]

Two types of electric underfloor heating, one uses a special chemical heating element which increases resistance as it warms up, so reasonably self regulation. The other has pockets (bits of pipe built into the floor) and sensors in them to limit the floor temperature to 27ºC but one the one I fitted if disconnected the temperature can be exceeded in other words it does not fail safe.

 

[bernardgreen]

Localised over heating of thermostat controlled UHF can be caused by rugs or other items that thermally insulate an area of the floor preventing heat from moving from the element and into the room. A sofa can have the same effect.