Heat mat fault, neutral earth reading...

[SSE]

A neighbours underfloor bathroom heating mat stopped working a while back, she asked me to look at it today. Turns out when it was installed the joiner had accidentally burst the cable for it. It's a small thin blue cable that heats up that has two conductors & an earth. Someone has done a repair on it underneath floor which looks like they have used proper kit, crimps, heat shrink etc. I've just took a voltage reading at the programmer which is fine going in & out & Ive peeled off the heat shrink & took a reading between each of the conductors & earth & on one I'm getting 150v & the other I'm getting 90v. Any ideas? Mat just needing replaced I'm guessing.

 

[Pete999]

A neighbours underfloor bathroom heating mat stopped working a while back, she asked me to look at it today. Turns out when it was installed the joiner had accidentally burst the cable for it. It's a small thin blue cable that heats up that has two conductors & an earth. Someone has done a repair on it underneath floor which looks like they have used proper kit, crimps, heat shrink etc. I've just took a voltage reading at the programmer which is fine going in & out & Ive peeled off the heat shrink & took a reading between each of the conductors & earth & on one I'm getting 150v & the other I'm getting 90v. Any ideas? Mat just needing replaced I'm guessing.

Have you carried out any other tests other than checking voltages at various points, IR as an example.

 

[SSE]

Have you carried out any other tests other than checking voltages at various points, IR as an example.

Yes. Checked the resistance & it was fine & so was the IR from conductors to earth. Strange.

 

[Pete999]

Yes. Checked the resistance & it was fine & so was the IR from conductors to earth. Strange.

Thanks SSE is the fault the heating not working, tripping the RCD or CB, or what, sorry to be blunt but without knowing the exact fault it's hard to suggest what the problem might be.

 

[Pete999]

Thanks SSE is the fault the heating not working, tripping the RCD or CB, or what, sorry to be blunt but without knowing the exact fault it's hard to suggest what the problem might be.

Sorry Mte read the thread , no mention of exact fault, but title says Nto E fault, could the chippy have damaged the cable you mentioned elsewhere?

 

[Deleted member 9648]

Yes. Checked the resistance & it was fine & so was the IR from conductors to earth. Strange.

If you've checked the resistance of the conductors and it's 'fine', and IR to earth is good, and there is full voltage at the cold tails then it'll work. As it doesn't one of the above is clearly amiss.

 

[KEV 1 N]

What was the resistance between L and N? If it's high, the heating cable may be damaged (but not a clean break) and not touching the earth, hence good IR readings

 

[PEG]

Hi,where were your voltages measured,and with what?
Has it got a temp sensor?
Has the joiner been water-boarded?

 

[SSE]

What was the resistance between L and N? If it's high, the heating cable may be damaged (but not a clean break) and not touching the earth, hence good IR readings

Resistance was about 58 ohms which was pretty much bang on for the size of mat.

Hi,where were your voltages measured,and with what?
Has it got a temp sensor?
Has the joiner been water-boarded?

Correct voltages measured at cable that leaves programmer, odd voltages taken at the cable repair crimps. The cable that leaves the programmer is obviously not the same cable/wires that heats the mat, they obviously join at some point. Would be good to be able to get a reading where the cable changes but it's buried under the tiles somewhere! It has a floor sensor. Haha, joiner waterboarding is a great shout!

Thanks SSE is the fault the heating not working, tripping the RCD or CB, or what, sorry to be blunt but without knowing the exact fault it's hard to suggest what the problem might be.

She said it wasn't working but it seemed to me to be working ok but when she mentioned the repair that's when I noticed the odd voltage readings.

Sorry Mte read the thread , no mention of exact fault, but title says Nto E fault, could the chippy have damaged the cable you mentioned elsewhere?

Possibly yes but will never know now unless tiles are lifted!

If you've checked the resistance of the conductors and it's 'fine', and IR to earth is good, and there is full voltage at the cold tails then it'll work. As it doesn't one of the above is clearly amiss.

Apparently it works intermittently. Why the strange voltages at the repair crimps though?

 

[Octopus]

I would remove the controller and see if it works ........

 

[PEG]

Also,120V with a MFT,is not necessarily the same as 120V with an AVO Mk8...

 

[dmxtothemax]

Have you tried lifting both power connections,
Then re checking those resisitance measurements to ground ?

 

[marc8]

you say IR value reading is good but no mention of the value, could you supply the IR value for L/E & N/E on the mat & test voltage used to measure.
sorry not saying you have not carried out correctly but would like to know the values.

 

[Octopus]

I would remove the controller and see if it works ........

This has too be the next step if the ir and end to end is ok.

Controllers fail.

Remove it, link feed directly to Matt and see what happens

 

[Octopus]

Deleted, duplicate post

 

[SSE]

Ok. Update, she doesn't seem to think it's working correctly as there's one area where a tile is cold, then one where a tile is a lot warmer than the rest. I redid all the tests today, resistance between the two conductors is as it should be, around the 58 ohms mark, I done an IR again live to earth >299, neutral >299. Reading at the programmer is still the same, 230v leaving programmer but still voltage between both conductors & earth at the join. A friend who is also an electrician looked at it today & he thinks it's ok, possibly something to do with the type of mat or the actual cable/wires that heat up but I'm not so sure. It's like the voltage (240ish) is split exactly over the two conductors, judging by readings at join. I also bypassed the programmer & results are still the same.

 

[Deleted member 9648]

Ever heard of volt drop across a resistor?

 

[dmxtothemax]

Do you know how the mat is laid out ?
And how its's wired.
Is it just one continues run ?
Or are there several area's all coming together somewhere ?

 

[marc8]

well if your readings are correct & the programmer is working, check the Resistance of the sensor with multi meter just to make sure.
next thing get the mat up hot for couple of hours & use IR camera then should be able to trace the heat pattern around the floor, this should show if any of the heat mat has been laid under the cold spot or not, same with the hot spot might have been the spare if any & have a more dense area of the heat mat in that area.
IR camera will tell you also you can check the joint same time.

 

[SSE]

Ever heard of volt drop across a resistor?

You think this is why I'm getting those readings?

Do you know how the mat is laid out ?
And how its's wired.
Is it just one continues run ?
Or are there several area's all coming together somewhere ?

Spoke to joiner today, says it's one big continuous run, one mat. It's only an area of 6m squared. He says hotter & colder tiles are common due to density of tile adhesive.

well if your readings are correct & the programmer is working, check the Resistance of the sensor with multi meter just to make sure.
next thing get the mat up hot for couple of hours & use IR camera then should be able to trace the heat pattern around the floor, this should show if any of the heat mat has been laid under the cold spot or not, same with the hot spot might have been the spare if any & have a more dense area of the heat mat in that area.
IR camera will tell you also you can check the joint same time.

Can I ask why I've to test the sensor? Afraid I've not got an IR camera. Thanks for the suggestion though, would have been ideal.