earth bonding copper pipes


Postby cemhlm » Sun Jan 13, 2008 11:52 am

2 Questions on Earth Bonding.

1. My house is a late 60's construction, the copper pipes to the bath - hand basins are not earthed, the pipes are easy to get to, how do I bond these? can I use earth clamps from say the bath hot supply pipe, dasiy chain it to the cold, then onto the hand basins. There is a 40 amp junction box in the loft space that is adjacent to the rear of the toilet hand basin, can I attach the end of the earth cable onto the earth terminal in the junction box.

2. The lighting circuit is the older 2 cable type (no earth), I want to instal a light fitting that requires earthing, I think I can run an earth cable from the light fitting into the loft space (chalet bunglaow) to an easy to get at socket, can I attach the earth cable to the earth terminal in the socket.
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Postby kbrownie » Sun Jan 13, 2008 3:18 pm

Hi cemhlm
Before we start running away with things,
1) do you need to supplementary bond anything? Do you have electrical equipment that are within the specified Zones in the bathroom
2) and if you do, this will come under part p of buildimg regs and needs to comply
Don't want sound unhelpful, but you may not need to supp. bond anything as long as out side the zones
Regards
KB
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Postby ericmark » Sun Jan 13, 2008 6:23 pm

There are 4 types of earth. Circuit protective conductor (Normally built into supply cables) Main equipotential bonding conductors (Independent of supply cables connects gas and water to main incoming earth) Earthing conductor (This connects your whole system to earth rod or supply authority earth) and Supplementary equipotential bonding conductor (These connect exposed conductive parts together and don’t have to return to main incoming earth but often do as they will link items to ones which also have a circuit protective conductor).

Your bathroom comes under the last type of earth and you only connect metal bits together and if you have electric items in the bathroom these will link it back to incoming earth.

As to your second question your lights however come under the first category.
“544-01-01 When overcurrent protective devices are used for protection against electric shock, the protective conductor shall be incorporated in the same wiring system as the live conductors or in their immediate proximity.â€
ericmark

Postby cemhlm » Sun Jan 13, 2008 6:59 pm

KB thanks for info. The only item in bathroom is a low voltage power shower, that is nearing the end of its life and will be replaced with another low voltage power shower. Will I need to supplemntary bond? if yes will the method I mentioned earleir be adequate.
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Postby ericmark » Sun Jan 13, 2008 7:31 pm

What do you mean by Low Voltage? The 16th edition shows that as between 50 volts and 1000 volts AC and is what we think of as normal house supply. Often people think of low volts as extra low volts and this could be up to 50 volts but for bathrooms it needs to be separated (SELV) that is special transformer with a shield with two interlinked circles inside and less than 12 volts. If it is SELV then to earth would be against the rules but if low voltage you must earth and if 12 volt it would have quite heavy cables about 60 amps or so. I know 230volt is about 3 amp so times 20 = 60 seems a little high? The 230volt one I fitted was very hard to physical fit I would recommend remote pump in future in loft or under bath depending on design of house of course. And if the pump is in loft than no need to worry about earth bonding I would expect.
ericmark

Postby kbrownie » Sun Jan 13, 2008 8:37 pm

Ho cemhlm,
what I suggest you do is wait untill you buy your new shower, depending which kind you buy it may not need bonding as RCD may be supplied with it, if not it's the earth on the shower that needs to supplementary bonding.
If you can find a convenient water/radiator pipe, do have cistern in the bathroom?
Bond to that then cross bond all others Rads, sink pipes etc. This only applies if your pipes are conductive(not PVC).
But remember Part P.
KB
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Postby 333rocky333 » Sun Jan 13, 2008 9:48 pm

While your at it I would check the Main bonding at the supply for the water and gas (if any).
Judging by the rest of it this is proberly wrong or non existent
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Postby 333rocky333 » Sun Jan 13, 2008 10:33 pm

To the best of my knowledge and the 16th regs.
May be different with new regs now.
You would need supplementary bonding in your bathroom.
Usually 4mm or 6mm is used linked between copper hot, copper cold, copper waste's , metal bath ,and any copper central heating pipes,with proper b/standard earth clamps .

Also any structural metal in the bathroom

If all sinks etc are the same solid joined pipe you should only need to bond that pipe once.
These bonds can as far as I know go under the floor.

The regs as far as I am aware do NOT actually specify bonding a metal sink !!!


You may also need to bond to the shower pump spur , but unsure what you have .
You should not really join to the j/b .

AS far as I know
The point of cross bonding is NOT to provide an earth but to sort of balance the metal to prevent voltage between the metal.
THAT IS why you need to check the MAIN bonding also

All to conform to iee regs and is part p related
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