UFH mat blowing fuse.

[Sean Kelly]

The dread strikes when the number of a customer appears on your phone several months after you have done work for them.

This happened to me yesterday when a customer stated that her UFH is now blowing the fuses in her house.

I completed the job in May’14 and had a continuity test running on the mat from start to completion of job. I also took resistance readings before/during/after installation. These readings matched the mats documentation. I left the readings for the electrician. The usual spiel about turning it on gradually etc was given to the customer.

To be fair, the customer was ringing me for the name & number of the mats makers.

The mat was stuck to 18mm ply, then SLC, then 60x60 porcs in the kitchen.

Just by chance, the electrician was there and he stated that the continuity test was fine, but when he put a high volt through the cable it showed a possible crack in the insulation.

I’m not a sparky, but what else can I do at installation stage when all the readings are fine.

I believe that they tested the mat in May and it was fine.

Strangely enough their previous ufh mat did the same thing. It was down for 5 years then developed a fault where it kept blowing the fuse – possible connection?

Has anyone else come across this scenario?

 

[radim]

who is manufacturer? warm up offers lifetime guarantee so I would giv them a call.
you say that it blows fuses in the house - there ishould be a fuse box below thermostat. On houses I work is anyway...

 

[Sean Kelly]

'Prowarm' from the Underfloor Heating Store. As far as I remember there was a spur that the cables went into, but I did not touch that part of the system. Lifetime guarantee is a bit sketchy when it comes to an already installed system. Will let the customer deal with the company as I don't know exactly what the electrician has done.

 

[White Room]

I'd be getting a sparky in...

 

[Time's Ran Out]

How big was the mat in respect of amps and the load it would have put on the ring main ?
Was the plywood acclimatised to the room before it was fixed?
Did the customer send off the documentation for their guarantee?

 

[Sean Kelly]

How big was the mat in respect of amps and the load it would have put on the ring main ?
Was the plywood acclimatised to the room before it was fixed?
Did the customer send off the documentation for their guarantee?

200w 6 mtr mat. Ply down for About 10 years. Don't know if customer sent off docs.

 

[Diggy]

Is it blowing the fuse on the fused switch spur or the main fuse board?

Just interested to know , not a sparky , but nice to know of diffo scenarios for anything in the future.

Diggy

 

[Sean Kelly]

Don't know Diggy, but I've given the customer contact details etc of the UFH company . I've also asked her to keep me posted because if the resistance is good and the continuity is good there is nothing more I can check.

 

[Sean Kelly]

It's blowing the fuse on the main board.

The story so far. I spoke with the Underfloor heating store and they said that the cable could have had a very slight nick (a hairline crack). This crack would not show up on the resistance test nor the continuity test. It would however show up on a megger tester (250v).

When the cable heats up it expands. It makes the hairline crack open slightly, and it could be this that is causing problems.

I've put a call into Steve Ashby (he appears on several threads within this forum). He is an independent fault finder/fixer. If it is a fault with the mat then the Underfloor heating store will pay. If it is an installation fault then I will pay.

One thing that the UFH Store said to me was that the customer must fill in the lifetime guarantee form and send it back.

The only thing that is nagging me is that the main consumer board is blowing. Is this normal? I would have thought that only the spur fuse would blow.

 

[Time's Ran Out]

200w 6 mtr mat. Ply down for About 10 years. Don't know if customer sent off docs.

200w mat is for concrete not wood. Expansion in the heating up may open the joints in the plywood and split the cable. Without the guarantee being sent off there is no recourse.
But then again the shop may accept responsibility!