UFH question for a tiler..

Andystiletiling · Apr 21, 2019

Morning all, nipped over from The tiling forum to run a question by you regarding electric ufh, so I'm happy to install the mat and run a continuity test before leveling over and laying tiles, a registered electrician is then usually sourced by my customers to connect up and sort the power out ...but my question is, is it ok for a 9sqm 200watt mat to be wired up to a spur nicked off a socket run or should it have its own feed direct from fuse box and whilst we're on the subject out of interest what would the maximum size 200w mat this is ok to do?

Note; I am not getting involved with messing with any electrics its just something ive witnessed recently and would like peace of mind for my customer it has been done correctly.. Thanks all..

Charlie_ · Apr 21, 2019

200w/sqm = 1800 w
That load is ok to take off a fused spur as you describe..
But, what needs to be checked is that the socket circuit that you propose to spur off is actually ok..- correct size cable, fuse/mcb, RCD protection..
If everything is ok with that circuit then yes just spur out from an existing socket to a fused outlet

Andystiletiling · Apr 21, 2019

Many thanks Charlie, I presume he checked all was ok.. Just for future reference what would be the maximum size mat presuming all was ok?

Charlie_ · Apr 21, 2019

I would recommend no more than 2 kw permanently connected to a fused outlet..
You can go more, all the way to 13amp but ufh tends to be on for quite a long time so wouldn’t advise loading it to the max

Andystiletiling · Apr 21, 2019

Thanks again, appreciate your reply's..

Charlie_ · Apr 21, 2019

Also, as well as testing the resistance of the ufh to make sure there is continuity, an ‘insulation resistance’ test needs to be done from the ufh LN to the ufh earth, this is something that usually goes untested by non sparky trades.. due to specialist kit being needed

Strima · Apr 21, 2019

TBH it would be a worthwhile investment if you're doing this sort of installation quite often to invest in a cheap and basic tester to do some testing before you install the mat and once you've finished tiling.

This way you can confirm the mat works from the factory and was not damaged when you did the tiling.

All you would need then is your sparky mate to test, connect and certify as you're doing now comfortable in the knowledge that the UFH will work.

We know how expensive things can get when a UFH system doesn't work.

Something like this: Electrical Insulation Tester - Electrical Cable Insulation Test Meter - https://www.test-meter.co.uk/electrical-insulation-tester/

Andystiletiling · Apr 21, 2019

I have no electrical training or knowledge but ive got a multi meter, no idea what the different settings on it are for.. A sparky once put it on the right setting for testing resistance for me and that's where its stayed.. To be honest the numbers mean nothing to me. I just check the mat before laying it, after laying and and before I leave the job after tiling..

Charlie_ · Apr 21, 2019

That’s ok for the functional side of the mat but for safety reasons the integrity of the wiring to earth needs to be checked too..
worst case scenario would be naked homeowner doing the moonwalk and tap dance across the bathroom floor

Andystiletiling · Apr 21, 2019

Oh ok, never knew about that and I've fitted a lot of ufh..bit of a worry!! I take it that test should be done before instillation? Is that something this meter I have can check and if so how?

[ElectriciansForums.net] UFH question for a tiler..

Charlie_ · Apr 21, 2019

Unfortunately that meter can’t do the necessary test..
Strima posted a link to what you need..
May should be tested before and after installation..
I would also test it once you have laid it and prior to fixing tiles down