I have PME system For main equipotential bonding I need:
16mm² earth 10mm² lead water mains and bridge plastic leadloc to copper 10mm² gas with 600mm of gas meter downstream 10mm² central heating flow and/or return (both or pick one?)Each of above should be separate runs to earth block on dist. board.
Is this correct?
The 16mm connection should be the left hand earth connection in the photo (don't laugh!)
Also is there an easy way to measure my exisiting earth cable sizes?
-- Mike W
Are you sure? See below.
For the main earthing (not bonding) conductor - yes :-)
No need to bond on the lead side of the lead-lok coupler, provided the lead section is short and reasonably inaccessible.
Yes.
Not required unless your heating pipes qualify as extraneous-conductive-parts, e.g. if they are running underground at some point.
Not necessarily - you can daisy-chain them as required to save copper. Intermediate connection points on a chain should use a unbroken conductor, i.e. not cut the wire, just remove some insulation and form a U-loop round the terminal screw of the earth clamp.
That appears to be a sealed DNO's connection. You may need to provide a new earthing block, or you can use the earth bar in the consumer unit if it has enough capacity.
- but then there's an earth wire coming out of the top of the cut-out next to the neutral, suggesting it's PME. Is this an official conversion to PME or has someone been taking liberties? And just why is there a GLS bulb wedged behind the tails?
I'd have thought extra earthing would be good - belt and braces.
Really??? What if they become live? Or you mean flow AND return not required. But I still connect at one point? and does it matter where?
Okay fine.
Can you confirm, you see the left hand connection I've just stuffed in there as it was not even connected!! It is sealed by electic board, but I'll unseal an connect properly. When I sell I'll have them certify it, but I'm sure I read the earthing/bonding can be DIY'd without inspection.
Yes the earth bar in the consumer unit is where that left hand earth cable goes.
The green label on the earth connection block states 'PME' The card stuffed behind dates from 1945 The lightbulb was hurridly stuffed there about 8 years ago. It worked, I haven't broken it yet. Thanks Andy.
Do it if you like, it will do no harm, but don't bridge any insulating insert they you may find in the gas service - Transco put those in deliberately to prevent circulating currents in their mains.
Yes.
Why should that happen? Electrical parts of the heating system such as pump, boiler and motorised valves will either be earthed via their own circuit protective conductors, to ensure disconnection of the supply if they become faulty, or will be of Class 2 ('double insulated') construction to prevent them becoming live at all. A faulty component should never be able to make the whole system live (other than very briefly during the permitted disconnection time).
No, you don't need any main bonding to your heating pipework unless it can import a potential, i.e. the local earth potential, by dint of being in contact with the ground in some way. Structural steelwork in contact with the ground should be bonded for the same reason.
You do of course need to provide local supplementary bonding (generally
4 mm^2) to any heating pipework in the bathroom.
No I can't confirm anything as the service has some odd-looking features. If you need a new earthing conductor connected you should contact the DNO. If you tell them that there's doubt about the earth connection they'll usually come out very quickly, particularly if you can quote an abnormally high Ze reading.
Adding or upgrading main or supplementary bonding is not notifiable under Part P, but altering the installation earthing surely is. "Not notifiable" only concerns building regs and does not give you a licence to interfere with the DNO's equipment or to cut their seals.
Surely by that argument why bother with earth at all? Thanks for your help Andy. Earth straps and cable shopping time.
BTW, anyone know of the cheapest source for by the metre cable, always seems such a rip off wherever you go.
-- Mike W
I explained that. You do bother with earthing, or else use Class 2 equipment.
Oh so you are saying that a live CH system relies on earthing arrangements supplied by the boiler ie its manufacturer? So if you do have plastic fittings surely you must provide your own earthing? Not that I do, just interested.
-- Mike W
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