This has me mystified!

[Octopus]

Ok. based on another recent thread I hope we can get to some sensible suggestions to this conundrum I have due to a visit on my way home today!

Underfloor heating (recent install) is tripping the RCD - the CU has all socket circuits and lighting circuits on the RCD so when it trips pretty much everything goes off.

Underfloor mat is this stuff:

Floor Heating | Underfloor Heating Foil - https://www.magnumheating.co.uk/products/32-1-floor+heating+/p-226-MAGNUM+foil+set

There is only the L & N running from the controller to the mat, so no CPC and thus its not possible to IR the system

An IR test from the L of the mat, (L & N both disconnected from the controller) to the CPC of the socket circuit its connected to via a FCU only gives just over 1 meg ohms.

End to end reading is OK.

I did a direct connection from the FCU to the mats and it tripped immediately .

The installers put this down about 6 weeks ago and its not worked properly since then.

The mats are laid side by side and with 5 mats connected the RCD goes immediately, with only 2 connected, the RCD holds. Which points at one of the 3 disconnected units having an issue but the installer says it has worked with all 5 connected.

What was interesting is that when the mat is on, there is a distinct "hum" from part of the floor.

Having read the manufacturers website and checked with the installer, they didn't use the damp proofing foil!


Any comments, sensible or off topic please - I've never seen this stuff before and hope some of you have!

thanks

 

[static zap]

See if any mats more lively with a volt stick !
(design sounds -iffy + situation makes worst - Till it dries ?)

 

[Octopus]

possible that he has nick it on the cable and a dead short .and has it some damp.

The live and neutral cables are singles .....

 

[telectrix]

sounds strange to me.all the ufh elements i have ever come across are a coax cable. the inner is the element L-N (end to end), and the outer is cpc.

 

[Christopher Bernard]

Did you test both the neutral and live against the cpc of the sockets? also I wouldn't go by what the installer says.

 

[Wilko]

Hi - I've not used that foil, it looks fragile for flooring installer use (sorry to be blunt). My 20p is one of "the 3" has been punctured and is in contact with the original concrete floor (?), but you'd think IR would be lower ... And the buzzing is the mat vibrating in the space between new flooring and original floor (not properly secured?).

 

[Octopus]

sounds strange to me.all the ufh elements i have ever come across are a coax cable. the inner is the element L-N (end to end), and the outer is cpc.

Likewise and thats why I posted this...... hoping somebody else had installed it!

 

[Octopus]

Did you test both the neutral and live against the cpc of the sockets? also I wouldn't go by what the installer says.

Hum - the ends of the mat were both tested to CPC at the sockets

 

[telectrix]

what's the end-end continuity of each?

 

[Octopus]

They were linked in parallel so the reading was 64 ohms - the connections are very rough IMHO and I didn't want to undo them.

 

[Darkwood]

I take it they used the polystyrene insulation plates?

Given they haven't followed manufacturers instructions and now have a earth leakage fault then I suggest damp has got into the insulation plates if fitted, my advice is be blunt and tell them it will have to come up and be done properly if you are to try repair it and put your name to it.
The humming does sound like tracking or arcing so suggest the mat is damaged or badly terminated.

 

[AJshep]

I've not seen or used this heat mat, however I've used a similar looking product years ago when I was still learning. It was supplied by a conservatory company, I can't remember the make but it came on transparent plastic laminate it only had a L & N connection that that pushed onto a terminal on the mat, it looks very similar to your product.

Had a few issues all had the same problem it was where the push-on L&N connector didnt quite make a solid connection on the mat, it got hot around the connector and damaged the mat.

Not saying this is the problem here, and it was about 17 years ago so but it was similar symptoms to what you have described.
I remember it well because I got the blame !

 

[Richard Burns]

Perhaps an IR test from the mat leads to the floor itself (perhaps with water on it) to see if there is a connection to the floor, there may be an alternative route through the ground rod back to the RCD.

 

[Octopus]

Perhaps an IR test from the mat leads to the floor itself (perhaps with water on it) to see if there is a connection to the floor, there may be an alternative route through the ground rod back to the RCD.

???

 

[Richard Burns]

???

Through the ground, like an earth rod,

error in editing!