Does underfloor heating need an earth?

[Grant M]

Must underfloor heating always have an earth?

I was under the impression that it always needed an earth, but a builder I sometimes do work for has already put it down and there are only two wires and no earth at all.I know that normally the earth is the metal sheathing that comes with the live and neutral. He says it doesn't come with an earth nor does it need one.

Regards.

 

[SirKit Breaker]

Generally no, but the fused spur to it does.
Read the installation instructions that come with the kit.

 

[pennywise]

It may be the matting type were the conductors are enclosed in a plastic sheath rather than a metal element type.

 

[telectrix]

as both previous posts.some types are earthed, some are class 2. depends. if you only got 2 wires, then just earth to the FCU.

 

[Pat Tester]

The Matt and Cable underfloor heating I have used always has an earth, It may be that you can't see it untill you strip back the insulation on the leads.

 

[Deleted member 9648]

753.411.3.2.....where heating units are supplied without exposed conductive parts,an earthed grid shall be installed above the floor heating elements.....also see 701.753 for installations in bathrooms where the same applies.

 

[Clark3169]

What's the best way to connect the earthed metal sheathing stuff? Drives me up the wall.

 

[Stroppy]

If its the braided wire type of sheathing then you unbraid it down to the plastic sheath, then twist it all together so its looks like flex then pop it in some earth sleeving and earth as normal.

 

[Clark3169]

Yeah that's what I've been doing but it's really fiddly right?

 

[44ALLAN]

Yeah that's what I've been doing but it's really fiddly right?

I do this on heat trace cable for off shore hoses that we manufacture.
Manufacturers instructions tell you to open a gap in the braiding and pull the inner sheath through it then sleeve and terminate................rough as a badgers tbh.

I meticulously separate every strand then twist it all together to get a 4mm size core which is then crimped with a 4mm terminal then sleeved and glue impregnated heat shrink applied to the joint............beautiful earth it makes and looks lol

Fiddly..........yes.
Worth the effort...........hell yes

 

[Darkwood]

2 and a half year old thread here boys would have been better as a new thread..... but as a answer use SY glands with a banjo to ensure the braiding is earthed at the supply end.... although it shouldn't be used as an earth you should have a separate earth core. If you are using it from an inverter for a motor then ensure you follow the manufacturers instructions on how to earth the braiding up and where as RF interference may be generated if done incorrectly.

 

[Stroppy]

I'm afraid I've never found it too fiddly, a bit time consuming unbraiding without breaking too many strands, but straightforward enough. I like the idea of pulling the cable through a gap in the braid, as that would save unlaying it all and risking breaking strands. I've never seen an SY gland, but if its made for this you may as well use it.

Twisting SWA armour into an earth and sleeving it is a real pain in the botty!

 

[44ALLAN]

I'm afraid I've never found it too fiddly, a bit time consuming unbraiding without breaking too many strands, but straightforward enough. I like the idea of pulling the cable through a gap in the braid, as that would save unlaying it all and risking breaking strands. I've never seen an SY gland, but if its made for this you may as well use it.

Twisting SWA armour into an earth and sleeving it is a real pain in the botty!

Sy glands have a slot either side of the thread entry where the braiding fits into so you have to half it basically.
Not easy to do if you haven't separated the wires lol

 

[telectrix]

yep, and then your thumbs and fingers resemble pin cushions. awful stuff.

 

[44ALLAN]

yep, and then your thumbs and fingers resemble pin cushions. awful stuff.

Stuffing gland then sleeve the braiding and terminate inside the enclosure lol

 

[markythesparky]

Think you'll find that there is something in the regs about it. It must be covered in an earthed sheath or grid or something.

 

[Darkwood]

Sy glands have a slot either side of the thread entry where the braiding fits into so you have to half it basically.
Not easy to do if you haven't separated the wires lol

yes but your only playing with an inch of braiding so shouldnt be the biggest of tasks

 

[44ALLAN]

yes but your only playing with an inch of braiding so shouldnt be the biggest of tasks

Very true but I was just explaining to him what they looked like as he hadn't seen them before.
Hardly a task separating the wires for those glands,as you say,as I normally snip all the excess off first when using them.

 

[Stroppy]

I looked 'em up now. I don't really see the advantage of them over separating and twisting into a single earth. Maybe I'm missing something.