Ufh Cable Might Be Damaged.

[Sean Kelly]

Today I had to replace a cracked tile.

The customer said there was UFH under the tiles.

I carefully smashed the tile out and had to excavate the adhesive from around the cable. I slightly nicked the casing from around the cable but covered it up with insulating tape to protect it against moisture

Before I started I asked the question about SLC over the cable. Yes, there was SLC said the customer. I did warn her that the cable could be damaged if it was not protected.

When I removed the thermostat I found that there 3 mats attached to it. I did a reading and got 16.9 off my multimeter. There was no room to separate the individual cables to test them.

The question is: If one of the mats (the one I nicked) was faulty, would I still get a reading off the multimeter?

I have no idea the size of the individual mats and I haven't the foggiest idea of what readings they should have.

 

[Old Mod]

You may find you'll have to isolate each individual Matt and take individual readings.
If that's a warm up cable their helpline is very good in my experience Sean
Is that whole floor covered in tape Sean?

 

[Sean Kelly]

You may find you'll have to isolate each individual Matt and take individual readings.
If that's a warm up cable their helpline is very good in my experience Sean
Is that whole floor covered in tape Sean?

Thats what i thought.

I can only guess that the whole floor is just like pic 1 above. Im surprised it hasn't already failed as there is trapped air between the cable and the tape.

I've suggested she turn on the mat in a couple of weeks to test it out.

 

[Old Mod]

I'd be more concerned about the tiles failing mate.
If that whole floor is taped you're relying on the tape staying firmly adhered to the floor.
If the tape fails, the floor fails!
Prob why tile cracked in first place.

 

[Sean Kelly]

I'd be more concerned about the tiles failing mate.
If that whole floor is taped you're relying on the tape staying firmly adhered to the floor.
If the tape fails, the floor fails!
Prob why tile cracked in first place.

Oh, The tiles have been down for years.
Somebody dropped a glass on the tile.
The tiles are hollow all over the place!

I was lucky that I only had to replace 1 tile. The others will go soon enough. The grout is cracked everywhere.

 

[Old Mod]

Oh, The tiles have been down for years.
Somebody dropped a glass on the tile.
The tiles are hollow all over the place!

I was lucky that I only had to replace 1 tile. The others will go soon enough. The grout is cracked everywhere.

I wonder why?

haha

 

[Flintstone]

Not looking good ! That tape is no good at all, quote them for renewing it all. Whenever I'm asked to repair a tile or remove one over wires, I always explain its a risk and I can't guarantee the wires not getting damaged.

 

[Diggy]

Did you try just turning it on before you retiled? I doubt a slight nick would be much prob , as I recall Devimat uses a kevlar coating so its pretty tough stuff in general.

Diggy

 

[Sean Kelly]

Did you try just turning it on before you retiled? I doubt a slight nick would be much prob , as I recall Devimat uses a kevlar coating so its pretty tough stuff in general.

Diggy

I thought about that, but because the cable was exposed I thought I had better not. It's a conservatory attached to a room. About 40sqm.

I did explain about the hollow tiles and the chance that the UFH may not work afterwards. They still have 2 other mats!

I just nicked the cable and got to a silver wire..........It was the one of the very last bits of adhesive I was chipping out.

 

[SJPurdy]

If it's like the cables I've used the heating cable(s) are in the centre surrounded by an insulator, around this is an earth braid and then the final outer insulator. If you have just nicked the outer insulator then you may have only just exposed a bit of the earth braid which I would think can just be recovered with insulating tape. However if you have cut deeper and reached the inner heating cable(s) then this will be more of a problem and a repair kit will be required (usually quite cheap) but this probably needs to be fitted by a certified electrician. Always check the resistance between the heater wires and the earth, it should be open circuit otherwise you have a problem. Please check with the tech help of the wire manufacturer, my notes are just to help understand the likely construction.
In addition to the no SLC I would inform the customer about the dubious use of tape and the poor fixing which looks from the photo to be dot and dab over a thin notched bed of adhesive rather than solid bed.

 

[Sean Kelly]

Thanks Mr Purdy. I think you are right. I only just nicked the plastic coating of the cable to expose a bit of the metal earth. I would have checked the resistance but when I unscrewed the thermostat there was no play on the cables. All I saw was 3 mats connected. There was no way I was going to unscrew the wires and test them, i'd never get them back again!

 

[dynamictiling]

Even if the cable has snapped it can be fixed. Ever warm do a joining kit for it. Get a spark to do it obviously. My spark took £70, takes roughly 3 hours.

Hardest part of it is trying to get a decent spark who is willing to undertake the task in hand

 

[Stef]

I carried out my own repair, shrink tubbing from Maplin so no moisture gets into it.
It was only the outer earth I exposed also.

 

[Marvo]

You'd need to continuity test the heating wire and the outer earth wire if there is one then you'd need to insulation test the wire using a 1000v mega tester. You might need to get a bit creative to mega test the insulation if the heater doesn't have an earth wire running inside it, the damaged area would need to be exposed.

Problem with heat shrink tubing is you'd need to cut the wire completely to get it on then rejoin afterwards.

If you damage UFH wires my best advice would be to get a sparky in who specialises or has lots of experience with UFH systems. This especially goes with UFH in a bathroom which is far more likely to give people a fatal shock if it's faulty.

 

[Stef]

I phoned the company I buy my Mats from & they put me on to the technical man from Ireland where the Mats are made & he talked me through it.
The mat is still going strong after 3-4 years.

 

[dynamictiling]

You'd need to continuity test the heating wire and the outer earth wire if there is one then you'd need to insulation test the wire using a 1000v mega tester. You might need to get a bit creative to mega test the insulation if the heater doesn't have an earth wire running inside it, the damaged area would need to be exposed.

Problem with heat shrink tubing is you'd need to cut the wire completely to get it on then rejoin afterwards.

If you damage UFH wires my best advice would be to get a sparky in who specialises or has lots of experience with UFH systems. This especially goes with UFH in a bathroom which is far more likely to give people a fatal shock if it's faulty.

If the rcd detected any irregularities it would trip the power. If there is anything problems with the ufh, this is far more likely to happen than someone meeting a shocking death (no pun intended) ufh controllers also monitor this and again will trip the power if there is a problem. It is highly unlikely for anyone to get an electric shock from ufh.

Even older fuse box's are likely to trip with irregular currents from ufh running through them.

 

[Marvo]

RCD's save lives but there's no guarantee, some people die from shocks of less that 30mA, it's just a numbers game where most will survive but some won't.

Older fuse boxes often don't have RCD protection, only overload protection. The fuses in them only protect the circuits from overload damage, they don't protect people from getting fatal shocks.

All the UFH controllers I've experienced are just a temperature control, they don't include shock protection or earth leakage protection. Technology progresses and systems are constantly made safer so I'd be interested to read up on the controllers you refer to if you can give me a link.

People getting shocks in a bathroom are far more likely to be killed than in other locations. The electrical regs recognize this and address it by declaring bathrooms 'special locations' that require extra protection measures.

It probably is statistically unlikely to get a shock from an undamaged UFH system as you say but if the wire is damaged under the floor and there's moisture around the damaged area it's highly likely it would cause someone in bare feet to get a shock. There's many variables involved so it might just be an occasional tingling or 'static' sensation when touching taps or a towel rail or it might be worse.

My advice still stands, if the UFH heater tape or wire is damaged I'd strongly advise an official repair by someone with experience who can test the system afterwards.