Discuss Underfloor Heating Drilled Through!?! in the Electric Underfloor Heating Wiring area at ElectriciansForums.net

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peterc2609

Hi all,

I had underfloor heating fitted in my bathroom, tiled over and seemed to be working ok.

Bathroom fitter came to finish off today, and when he left, the circuit for upstairs had tripped.

Couldn't work out what it was but think I've tracked it down to UFH.

It is wired into a fused spare. On the thermostat, there is the LIVE from spare IN, Neutral from spare IN, LIVE from Heating Mat IN, NEUTRAL from Heating mat IN, the earth from each are choc-blocked together.


It seems, that even when the fuse is out of the spare, the circuit can still trip. When it does work, it seems to trip once the thermostat tells the mat to heat up.


Does this sound like the fitter has possibly drilled through the heating cable?


thanks
 
Yeah, from a non-spark. my fuseboard is split into 2. upstairs and downstairs. 2 seperate RCDs. The upstairs one totally goes - not just the switch for the upstairs sockets - everything.
 
Get the fitter back and batter him around the head with something blunt and heavy.
It’s his problem, to drill a floor knowing there’s heating under there takes a special type of idiot! Or just you’re average bathroom / kitchen fitter.
 
Since Mr Bathroom Fitter has been in there.

He's fitted a few things today, namely the toilet. But where he put the screws I thought was too far away from the cable... and the cable is 3mm thick.. so its a one in a million chance that he's hit it. But maybe, the weight of things on the tiles etc has done something.

I expected that if he went through the heating cable then it simply wouldnt heat up... not trip the electricity.

Although, its been a very short space of time between ufh fitting, tiling and bathroom... I only tested the ufh once...
 
I've got a very cheap multimeter, but mate is on way round with an expensive thing. What can i do with it?

To be honest, I told the fitter there was no ufh round the toilet, but forgot that i had a back to wall toilet which screwed in at the back of the floor! So he's not really to blame.

Just find it weird that that part of the ufh could cause an issue... the fused spare, yes. But the heating element?!
 
Get the fitter back and batter him around the head with something blunt and heavy.
It’s his problem, to drill a floor knowing there’s heating under there takes a special type of idiot! Or just you’re average bathroom / kitchen fitter.
Well..i was thinking either that or....a borrowed neutral...
 
Get the fitter back DONT Pay him and possibly charge him for the refitting,retiling renewing the heating mat as I dont think thede can be "repaired" as such
 
We havent established whether he has drilled through it yet. If he has it was a great shot.

I'm just asking what the outcome would be of drilling through the cable....

If its broke, then its staying like that... too much work gone into the bathroom... its took ages ha ha
 
I used my rubbish multimeter to test resistance. Set it to 200 ohms, and got 135 on the screen. I think the mats resistance should be around 150... so 10% aint too bad.

dunno whether that proves anything though
 
The UFH cable has an earthed screen and damage will cause an earth fault which will trip an RCD.
Only way is an insulation test @500v to establish whether the cable is sound.
 
Mate just tested it. Reckons neutral has been shorted to the earth.

What does he do on the insulation test?

a screw through a 3mm cable... madness!
 
Have you had the whole bathroom area fitted with under floor heating.
If you have, did you inform your bath room fitter of the same.
 
Mate just tested it. Reckons neutral has been shorted to the earth.

What does he do on the insulation test?

a screw through a 3mm cable... madness!

A multimeter wont be much use,you need a 500v insulation tester,and test between the live core and the earthed screen of the cable..you should expect a reading of hundreds of megohms if the cable is sound...<1 megohm would be a worry....if damaged you may get a dead short,ie 0.00 megohms. If the IR is OK test the continuity of the cable using your multimeter....the reading will be in ohms and should match the manufacturers declared resistance for the legnth/rating cable you have.
 
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