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gaz1000gaz · 6 Dec 2010

Can anyone help who is either an exprienced electrian or underfloor heating specialist.

We have just finished laying 17 sq mts of porceline floor tiles over 15 meters of loose wire heating cable. It would appear that the cable used is too industrial for a typical kitchen floor and is to have at least a 50mm screed above it - EVEN THOUGH WE CHECKED WITH THE SUPPLIER FIRST !! They are now saying they do not have the recording of the call when we sought advice. So options are - rip up a £2000 floor - Live with a cold floor - or maybe supress the power ? Devi say the floor heat will be too powerful and that it will be patchy at best - but will heat up the adhesive !

Any help please as wife in tears !!

Many thanks

Gary

londonboy · 6 Dec 2010

I have no experience in underfloor heating.

If you have just laid the tiles could you possibly prise them back up again?

How long does the adhesive take to set fully??

gaz1000gaz · 6 Dec 2010

londonboy said:
I have no experience in underfloor heating.

If you have just laid the tiles could you possibly prise them back up again?

How long does the adhesive take to set fully??

Hi Londonboy,

No, unfortuantley the tiles will be wrecked when taking them up along with the underfloor heating, oh and £300 of 10mm insualtion board !

Nice thought though.

All the best

Gary

ricicle · 6 Dec 2010

What exactly is the problem then - is it too close to the surface so it will be too hot ? Which system is it ie make/type

There may be a solution if you can tell me the wattage and/or resistance of the wire.

flameport · 6 Dec 2010

What is the actual cable you have installed? If it is Deviflex, then there are several different types, some of which are for thin floors (i.e. under tiles) and others which are designed for installation under several inches of concrete.

gaz1000gaz · 6 Dec 2010

ricicle said:
What exactly is the problem then - is it too close to the surface so it will be too hot ? Which system is it ie make/type

There may be a solution if you can tell me the wattage and/or resistance of the wire.

Hi Ricicle,

Its a Devi Deviflex DSIG-20 sinlgle conductor loosewire floor. The spec sheet says the following

Voltage 400v AC
Effect 20 W/m
Max temp 65 degrees
We have run it directly into the fuse board

The general problem appears to be the floor adhesive will get very hot (and i imagine crack etc). The cable should have 50-60mm of screed above it before a tile or slab etc - we only have 10-15 mm of adhesive above it then the 8mm floor tile.

We were hoping perhaps we could harness some of the power/heat so it would produce less heat / normal stregnth !

Does this help you ?

Many thanks

Gary

ban-all-sheds · 6 Dec 2010

gaz - clearly the electrician you used to install the heating was an incompetent buffoon, and you need to get him to sort out the mess of his making.

This work was notifiable, so he would have had to inform Building Control of it, and he would therefore have had to say how he complied with P1. The chances of it being anything other than "compliance with BS 7671:2008" are so small that they can be ignored, so he would also have been bound to provide you with an EIC certifying that he did comply with that.

And one of the aspects of compliance is following manufacturer's installation instructions.

gaz1000gaz · 6 Dec 2010

flameport said:
What is the actual cable you have installed? If it is Deviflex, then there are several different types, some of which are for thin floors (i.e. under tiles) and others which are designed for installation under several inches of concrete.

Hi Flameport- yes it was deviflex - and it would appear one that is suitable for concrete / steps / pavements etc. When my tiler saw the cable - he rang Devi to ask if it was sutiable for a normal floor tile with 10mm insu board and 10mm adhesive - yes was the response. Only now, it would appear it isnt.

ban-all-sheds · 6 Dec 2010

gaz1000gaz said:
The spec sheet says the following

Voltage 400v AC

If that's true then you need have no worries about it getting too warm.

Probably quite the reverse.

ban-all-sheds · 6 Dec 2010

ban-all-sheds said:
gaz - clearly the electrician you used to install the heating was an incompetent buffoon, and you need to get him to sort out the mess of his making.

Would the **** who voted my post down care to explain why he disagrees with that?

This work was notifiable, so he would have had to inform Building Control of it, and he would therefore have had to say how he complied with P1. The chances of it being anything other than "compliance with BS 7671:2008" are so small that they can be ignored, so he would also have been bound to provide you with an EIC certifying that he did comply with that.

Or explain why that is incorrect?

And one of the aspects of compliance is following manufacturer's installation instructions.

Or that?

flameport · 6 Dec 2010

Simple answer - the product chosen is the wrong one, and therefore has been installed incorrectly.
Your options are limited - remove the floor and fit the correct product, or don't use the heating.

Hopefully this isn't what you mean either:

gaz1000gaz said:
We have run it directly into the fuse board

since there must be a thermostat/controller fitted as well, and some means of isolation.

ricicle · 6 Dec 2010

Hmm - instructions say 230V

gaz1000gaz · 6 Dec 2010

ricicle said:
Hmm - instructions say 230V

Hi Ricicle

Sorry yes 230v. Cable spec says 400V.

Can you help me with any suggestions ?

Thanks

Gary

ricicle · 6 Dec 2010

I still think you should chase whoever installed it for you. One question though - please tell me you fitted the temp. probe ?

gaz1000gaz · 6 Dec 2010

ricicle said:
I still think you should chase whoever installed it for you. One question though - please tell me you fitted the temp. probe ?

Yes it was fitted and tested. The chap who layed the floor is a professional tiler and a good friend of mine. He telephoned the cable company whilst i was there and they said it was ok to use it. What more can you do.

Is there anyway we can use some form of suppressor ?

Thanks

Gary

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