Unipotential bonding - have the regulations changed?


Postby enigma » Mon Mar 29, 2010 9:06 pm

We moved into out present house in 1997, and had an electrician bring all the electrics up to date, including a new CU.

At that time the electrician installed some earth bonding sections that run as follows:

section 1:
From external electricity meter box
to CU
From CU
to copper water main pipe at the point of entry to the house

section 2:
From copper cold water pipe that feeds the plastic cold water storage tank in the roof
to the three copper pipes running from this tank to various destinations

The effect of this arrangement appears to be to provide a path to the CU earth from every copper pipe in the house.

I have been reading recently that metal pipework should not be connected back to earth in this way.
The present intent of bonding appears to be to bond together every metal object in a bathroom (say),
without connecting back to the CU or the water main.

Have the regulations changed since 1997?

Is my bonding in accordance with current regulations?

Is it safe? If not, what do I need to do?
enigma
Rank: Labourer
Progress to next rank:
25%
Posts: 2
Joined: Mon Mar 29, 2010 8:42 pm

Sponsor

Simply Build It

Postby ericmark » Tue Mar 30, 2010 10:45 am

In 2001 and 2008 there were major changes to BS7671. The whole idea of equipotential bonding as the name surgests is to have all metal parts at the same voltage. This has not changed. However the idea of earthing door handles and window frames has gone and in the main items likely to transport a fault from one room to another is what is looked at. Pipes in the main.

One problem is the use of plastic and specially where very short. A one meter lenght of plastic pipe with water in is a very high resistance and where in the main plastic is used there is no problem and where for show plastic pipe are changed to copper or chrome these do not need earthing. However where two copper pipes are joined with a plastic connector then it would require a link.

In real terms it is impossible to know where plastic connectors have been used so with lattest regulations the idea of using loads of interconnecting earth cables has been replaced with the requirement for RCD protection and now other than the main incomming connections the earthing of every bit of pipe has been replaced with very tight regulations on the use of RCD protection.

However there is no need to remove any earths and you can't comply bit by bit it is all or nothing so there has been a move in last couple of years to renew consumer units to types able to give RCD protection on all circuits.

The rules are a little hard to follow as to when RCD's must be fitted. As a result I do not think it is really something for the DIY man. But as long as you have RCD's on all circuits there is very little to worry about only where RCD's are not fitted does one have to be very careful as to what is earthed.
ericmark
Rank: Project Manager
Posts: 1796
Joined: Fri Oct 02, 2009 8:49 pm
Location: Mold, North Wales.

Postby enigma » Tue Mar 30, 2010 9:00 pm

ericmark,

Thanks for your very comprehensive reply.

I am pretty sure there are no plastic joints or pipes anywhere in the house. All the pipework under the floor is 1970 vintage copper with soldered joints, and everything visible is the same, or newer all-copper.

There is 30ma RCD protection on every circuit, including one of the three lighting circuits.

The only thing holding me back on RCDs for the remaining two lighting circuits is the nuisance of an RCD tripping when a bulb fails, and plunging the house into darkness.

However, once LED bulbs get down to a reasonable price, this shouldn't be a problem!
enigma
Rank: Labourer
Progress to next rank:
25%
Posts: 2
Joined: Mon Mar 29, 2010 8:42 pm

Postby ericmark » Wed Mar 31, 2010 5:07 am

I also had the problem of being plunged into darkness. Cure emergancy lights top of stairs and in garage where consumer unit is. No longer a real problem.
ericmark
Rank: Project Manager
Posts: 1796
Joined: Fri Oct 02, 2009 8:49 pm
Location: Mold, North Wales.

Display posts from previous
Sort by
Order by



  • DIY How to Project Guides

  • DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!



 


  • Related Topics