Poor IR results on electric UFH... options?

[HappyHippyDad]

Carried out an EICR and am now doing the remedials.

Poor IR results on conservatory ring which I have now identified as the electric UFH.

The UFH has 2 x line and 2 x neutral conductors on the load side of control panel (same terminal). I'm not sure why as the conservatory is only 4m x 3m so not sure why it needed two separate feeds.

Both cables of the UFH show faults. Side 1 N-E 0.24Mohms, side 2 N-E 0.75Mohms.

There is no earth conductor going to the mat/cable (whatever it is), just 2 x line and 2 x neutral plus the 2 core cable for the floor thermostat.

I have disconnected, but I was wondering if there is absolutely anything you can do to remedy this? I'm guessing moisture has got into the conservatory floor, and there is nothing you can do about it, but thought I'd ask.

Cheers all.

 

[HappyHippyDad]

Might not even be mats, they may have used heating cable, in 2 runs for convenience?
Either way, it should probably be disconnected if they're not wanting to have the floor up to have it fixed...

Yep, I left it disconnected as per last paragraph in first post

As you are talking N-E, and the mat connections don't have earth, I'm assuming the low IR is on the supply side of the control box?
If so I wondered if is it possible to disconnect the two underfloor loop circuits and re-test, to prove whether the fault is control box side or not.
Sorry if I've completely misunderstood your post!

The Low IR is between the neutral of the heating mat (both neutrals, as 2 mats/cables) and earth. Even though there is no earth going to the heating mat, there is an earth in the control panel, the earth is from the FCU that is feeding it.

Thread seems to be a bit drifty. As I understand from HHD's description, there are two cables / mats. Both have continuity, are functional and have been in regular use. When tested separately, both have been found to have sub-1MΩ IR to the mass of earth.

There is a way to stop leakage from joints in underground pipes without excavating, by pressure-grouting them with epoxy. I wonder whether a similar process could be invented for underground cables, by pumping in electricity coated with silicone or even just some plastic electrons followed by applying a potential to earth to attract them towards any cracks in the insulation.

I'll give that a go tomorrow Lucien ?

 

[mattg4321]

If both mats have gone bad it almost certainly means any combination of the below.

1. Cheap poor quality materials failing
2. Incorrectly installed
3. Damaged by water ingress etc.

I don’t see that 2 good quality separate mats would go bad just by chance giving a similar result.

I must’ve fitted hundreds of heat mat brand ufh mats over a 15 year plus period with zero failures except when some idiot tiler thought the ‘end cap’ was in his way and pushed it under the skirting board where it wasn’t encapsulated in tile adhesive/self levelling compound.

 

[brianmoooore]

The Low IR is between the neutral of the heating mat (both neutrals, as 2 mats/cables) and earth.

You should get (practically) the same reading between the mat lives and earth. The few ohms of the mat's heating cable shouldn't affect the IR to earth, if the cable has continuity and heats up when powered.