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Discuss Bonding water services when plastic pipes are present in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

A

ashlec

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Hi All,
ive been working in a old 50's/60's property which has a black pvc/almost rubber water pipe incoming to the stopcock, then it leaves the sc in the same type of pipe
then disappears into a box section going upstairs under the floor . Now the other end could be anywhere but i can't find it, we all know it should be within 600mm & before the first branch etc
but in this case its not going to happen.

My question is there is a 6mm earth going from the MET to the cold ( everywhere else is copper pipe ) in the bathroom linked to the hot & all the 4mm sup bonding is in
position ( Allready there ) & a new 17th edition board is fitted, it is a TNS system so this should be exceptable according to reg 544.1.1 , do we agree ?
I quizzed the NIC tech about it, he was saying i needed to use the adiabatic equation to work it out to see if it is sufficient enough, i've done this for main earth before
where the earth is sweated on the incoming cable but never for a services bond any ideas ?

All help will be much appreciated
 
Your telling me the NIC tech desk as advised you to use the Adiabatic for protective Bonding conductors or for a protective conductor ................... if he was referring to protective bonding conductors then words fail me

You need to tell us why we are bonding metal work, can I ask why do you think we bond metalwork/services?
 

Amp David

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Mentor
Arms
The NIC tech boy doesn't know what he's on about then, as the adiabatic is not to be used for sizing bonding conductors.

If there is a new CU with all circuits protected by RCD then forget about the supp bonding.

If needed the bonding should go ideally within 600mm of the service entering the building or within 600mm from where it is copper.

Test the service first to see if you require it in the first pace.
 

DNS1

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Arms
Esteemed
If all the metal pipework is internal, it's completely isolated from earth so doesn't need bonding at all does it?

That's my understanding of it.

I'd check to make sure the copper pipework doesn't earth at any point though (eg: buried in the garden for outside tap)
 
E

Edd

  • Thread Starter Thread Starter
  • #5
This question is gona become asked more and more as plastic is becoming more popular. Basicly if the incoming is in pvc then no bond is required.
we are trying to stop an external Earth path being brought into the house that is diffrent from the Electrical earth. No external Earth path No bond required. (I know theres more to it than that, please feel free too go indepth)
 
Any internal metal pipe work can produce an earth potential inside a building ( see G3 ) witch advises/recommends bonding regardless of incoming services being plastic , A bond will be present on the water pipe via gas connection ,, the problem is when the boiler is removed braking the connection
 
E

Engineer54

  • Thread Starter Thread Starter
  • #11
Any internal metal pipe work can produce an earth potential inside a building ( see G3 ) witch advises/recommends bonding regardless of incoming services being plastic , A bond will be present on the water pipe via gas connection ,, the problem is when the boiler is removed braking the connection
I wouldn't take that GN3 advise as gospel, it is unlikely that pipework would meet extraneous conductive part criteria. What this GN is indicating, is earthing rather than bonding, which in a domestic situation i wouldn't find at all necessary. The boiler will be earthed anyway, via it's electrical connection...

However, (without opening a can of worms again) there are going to be situations where bonding metal service pipework etc, WILL be necessary, even when the service supply to the building is in plastic, so it's not a hard and fast rule across the board. Consider apartment blocks for example. But generally, for individual houses etc, plastic service incomers won't require any internal metal pipework being bonded.

The very best solution if in any doubt at all, is to Always conduct your own tests, better still make those tests mandatory on every job you undertake. ...Can't really go too far wrong then, can you!! lol!!!
 
O

oldtimer

  • Thread Starter Thread Starter
  • #12
Also in this can of worms say you have earthed the water and the gas incomers and the DNOs turn up 2 years later and change the supply pipes to plastic . Or say you are doing a CU change and the gas or the water pipe is plastic but internal to the house is metal so say you do not earth bond the gas because its supply pipe is plastic yet this pipe will still be earthed through the bonded water pipe via the CH boiler ie "Electrically & Mechanically sound" from the 14th
 
D

Deleted member 9648

  • Thread Starter Thread Starter
  • #13
One point about testing to find out if metal pipework fed by a plastic incomer is extraneous is that it's not that easy in practice. There are liable to be loads of parallel paths in practice which may be very hard to isolate......chances are an unbonded service will be at the same potential as the electrical earthing system anyway due to these parallel paths.
 
R

Rauer

  • Thread Starter Thread Starter
  • #14
The minimum size is also stated in table 54.8
 

rich.250

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Arms
One point about testing to find out if metal pipework fed by a plastic incomer is extraneous is that it's not that easy in practice. There are liable to be loads of parallel paths in practice which may be very hard to isolate......chances are an unbonded service will be at the same potential as the electrical earthing system anyway due to these parallel paths.
I would isolate supply and remove main earth as for a Ze test. In turn removes all parallel paths from
Within the building, continuity test from this removed earth to the service.
Job done. :)
 

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