Underfloor heating help

[orbital]

Never installed underfloor heating, but was asked to look at a system that had been part installed by the homeowner.

The matting has been laid and tiled over.

Both connections are to short to reach FCU

One cable is a black two core cable, which i presume is power

The other is a blue single core cable which appears to have a copper core and a copper shield. I thought this must be the temp probe.

However the home owner then brought out the temperature probe which he did not bury under the floor.

He plans to try to push it a couple of cm under the tiles.

So thats three cables!

So I am unsure what the blue cable will be, any ideas

Is it possible / advisable to join cables

Is not using a temp probe and putting it on a timer a complete no no

I am very reluctant to touch any of this, but any guidance would be great, so I can better advise the customer.

Thanks

 

[Andy™]

you can join the cable - its only the actual heating cable that cannot be joined

form the instructions of some i recently connected, the probe is recommended, but it would work without

depending on the heating mat, some have a 2 core & earth to control, some are a loop with a concentric type cable, and there are probably other variations

 

[Theorysparky]

Hiya

First of all are there any instructions ????

next..

before you do anything to this you must check the continuity of the floor mat.

if the readings are not per the guidlines set in the instructions then walk away as its knackered and you dont want to be the one accused of it not working

it sounds like hes messed it up already...

do a searchg on the forum as this has been covered before

 

[Apache]

The other is a blue single core cable which appears to have a copper core and a copper shield. I thought this must be the temp probe.

So I am unsure what the blue cable will be, any ideas

Wasn't there some talk of a temporary circuit that could be used to show if any damaged was done to the mat during installation??

 

[a1spark]

Orbital .bear in mind underflor heating is notifiable work and as the homeownerers have part installed it themselves this will produce a bit of a dilemma as far as issuing an EIC and with complying with the building regs.

 

[sparkytim]

Hi

Is the "Black 2 core" cable also a single core with outer screen?

If so this is the LIVE tail and the other Blue one is the Nuetral

You should be able to measure the resistence of the Heating element between these two conductors and also test Insulation Reistence to earth between the core conductors and the screen earth.

You will need a CONTROL unit to connect to BEFORE the FCU, this is a room thermostat and timer control that can also have Floor temp sensor connection to it.

 

[wozz]

is this in a bathroom? if so a room stat may be out of the question.

 

[NozSpark]

TBH it sounds like the blue cable is the heating mat which they've brought back and cut..

If that is the case the mat is toast

 

[orbital]

SparkyTim

I think you will be right, thinking about it. The black cable was stripped back a little so it looked like two separate stranded cables, but one still had an outer insulation sheath.

 

[kme]

Regarding the comment about ignoring the floor probe...

Be aware that, even if everything else is as is should be, some UFH timer/controllers will not work at all/correctly/limited functions without a correctly operational floor probe.

Before burying the floor probe, test its resistance with a multimeter (NOT megger) - you would normally expect 14-20Kohms

Testing the mat - continuity test between the two ends - dependant on mat size, reading should be in the low (<100) ohms, IIRC. However, you also need to megger between the screen & element wiring.

HTH

KME