UFH Electric - Instant trip

[DrizzyDanny]

Hi everyone

Been scouring the Forum looking a miracle I think

So Iv got a house that had already installed underfloor heating that was working fine. Had some things done in the house and when cutting an only laminate piece out that was stuck the flooring guy has damaged the UFH. The damage was clear to see. So twisted the wires back together with a hope of putting the system on checking its working fine problem is the second the UFH turns on it immediately trips the electric

Tried soldering the wires together and wrapping in electrical tape but see getting same result, abit lost on why its not working, im no electrician so I know the obvious answer is get one in, but getting one in on short notice is no easy feat

I have attached a picture of the type of wire thats been cut

Thanks in advance for any ideas

 

[Alec_t]

Welcome to DIYnot.
Is that bare wire we're looking at? Where's the insulation?

 

[DrizzyDanny]

Welcome to DIYnot.
Is that bare wire we're looking at? Where's the insulation?

Thats the wire thats contained within the foil sheets, iv peeled them back to get to the damaged wire. The damaged wire is at the top of the loop, you can’t really tell from the picture but the wire is costed in like a clear plastic

 

[oldbutnotdead]

Lets have a look at your mend. Specifically, how many wires did matey cut and are you sure there is no other damage

 

[DrizzyDanny]

Lets have a look at your mend. Specifically, how many wires did matey cut and are you sure there is no other damage

my mend looks shocking (excuse the pun) Theres two wires per loop and he’s cut through x4 ( top of two loops).

Iv only done the bodge job on it now to test the circuits working. I will get a repair kit and do a ‘proper’ job on it if ai manage to get it on without the fuse tripping out

Im fairly certain theres no damage elsewhere, iv pulled some laminate up but it came straight up, no visible damage to any other foil and no tools or cutting was done anywhere else apart from here at the bottom step

 

[mikeyd]

Questions that might help.

What is tripping - A fuse or MCB or RCD or RCBO etc?
How did you know which wire went with which?

 

[oldbutnotdead]

First question is what exactly is tripping? Is it a MCB (will have a small lever and a marking like B6 or C32 or similar) or an RCD or RCBO (will have a small lever and a test button).
Second, how have you determined which wire connects to which (given you have 4 ends to play with).
Third, why hasn't the floor fitter called an electrician in to sort his spectacular potential FUBAR?

 

[DrizzyDanny]

First question is what exactly is tripping? Is it a MCB (will have a small lever and a marking like B6 or C32 or similar) or an RCD or RCBO (will have a small lever and a test button).
Second, how have you determined which wire connects to which (given you have 4 ends to play with).
Third, why hasn't the floor fitter called an electrician in to sort his spectacular potential FUBAR?

Questions that might help.

What is tripping - A fuse or MCB or RCD or RCBO etc?
How did you know which wire went with which?

With the B32 switched off the circuit doesn’t trip but when I switch it on as soon as the panel activates the heating it trips the both RCDs, the one its on and the separate one

The wires are in pairs so its a 50/50 on both but have tried both ways on each side, process of elimination attempt's

In regards to the fitters whatever it costs me I’ll work it at the backend with them

 

[bernardgreen]

You need four repair kits. The type of kit will depend on the type of cable.

For single conductor cable https://www.cli-mate.co.uk/product/devi-heating-cable-repair-kit/
For twin conductor cable https://www.plumbworld.co.uk/prowarm-electric-underfloor-heating-cable-repair-kit-101755-1273841

( other sources are available )

It is not a task for an inexperienced DIYer

 

[ericmark]

I am sure one can with epoxy lined shrink sleeve repair the non heated bits of UFH, but the element if extra insulation is added may over heat, so in the main if damaged only option is to renew it.

I had same problem with mothers wet room, no option lift tiles and fit new mat.

But not all electric UFH is the same, some use resistive cable, the cheap type, and some use a resistive chemical which increases resistance when heated so self regulates, unfortunately when I was laying it, that type needed a earthed mat fitting above it, so not as easy to fit, so used the cheap stuff.

I can see the silver cover, which may be the earthed mat, but there are so many types, some is in sections and there are cutting points, and as shown there are repair kits for some types, but really this is not a DIY job.

 

[DrizzyDanny]

Yeah, so had electrician out today to look at it, looks like I need to replace the lot, luckily only cost £200 for materials. Had a week and half honestly

Thanks to everyone for the help and advice

 

[DrizzyDanny]

So, riddle me this. I have installed completely new undamaged mats as pictured. Tested the wires, reads the rights Ohms as per manufacturer and no shorts.

So when I hook it up to the power, its instantly trips still???

If I leave the wires unattached from the mains, separated and turn the power on the thermostat comes on and doesn’t trip so can’t be anything but the mat tripped it.

I have even attached another mat which is unfitted, its still on the roll, instant trip

Feel like im losing my mind

 

[bernardgreen]

If the RCD is tripping then you may have connected the Neutral wire to the wrong Neutral bus bar in the consumer unit.

 

[DrizzyDanny]

If the RCD is tripping then you may have connected the Neutral wire to the wrong Neutral bus bar in the consumer unit.

As in to the mat? The wiring for the thermostat and to the box was already installed and worked fine.

As for the mat it has coloured wires so cant really mismatch it.

Upon further investigation I have found that any load trips the RCD, remembered that there is a set of plugs in the attic and one plug socket upstairs that wern’t working. So unhooked all the underfloor heating, and plugged in a led light (newly installed on steps, works fine in other sockect) and as soon as I switched it on via the socket that wasnt working it tripped the RCDs.

Thinking now it may be a faulty B32, as seems to overload under any stress, it must have some sort of capaicity as without anything hooked to it, or the said socket been on it managed to power the thermostat, but seems any further load than this trips it.

Got an electrician to come out to check, just thought id give an update

 

[ericmark]

I think you have a neutral - earth fault.

The neutral with no load is same voltage as earth, so if there is a low resistance between the two, nothing will trip, as no imbalance. But as the load increases the voltage between earth and neutral also increases, not by much, but enough to cause current to flow.

We use this meter to test, and it puts 500 volt between the wires to be tested, it can destroy electronics, so care is required in its use, and the cheapest will cost around £35, it is always used when laying electric under floor heating, so the person laying it should have one.

I have seen it where a bit of damp toast in a toaster has caused a RCD to trip when kettle is used, as often we don't switch the neutral.