Protective bonding conductors in a flat?

[alanl]

I've just been to a flat tonight to look at some potential work, but there is no bonding conductor to the incoming water pipe inside the flat.
I had a quick look in the main distribution board cupboard of the flats, but could see no evidence of bonding to the water, and the main water incomer to the flats is hidden away anyway.
So, should there be protective bonding to the water in each flat?
Or, is one bond enough between the main block of flats Dist. Board and the water incomer for the flats?
I'm presuming not, and it will need some 10mm put in, but would like others thoughts on this.

Thanks
Alan.

 

[Deleted member 26818]

If the water is bonded to the main Distribution Board, then there would be no need to bond again at each flat.

 

[Engineer54]

If the water is bonded to the main Distribution Board, then there would be no need to bond again at each flat.

I disagree with that, Every CU of each separate dwelling unit needs to have it's EMT bonded to any extraneous metalwork such as water and gas pipework entering that flat. Reliance on a single point for a block of several dwelling units isn't something i've ever seen, either in the UK or else where. Not particually a very sensible thing to have either!!!

 

[Guest123]

If the water is bonded to the main Distribution Board, then there would be no need to bond again at each flat.

Sorry spin, I disagree too. As does GN8.

I recommends bonding at point of entry to the building & point of entry to each seperate flat.

 

[topquark]

Unless of course, it's non metallic

 

[Deleted member 26818]

The purpose of equipotential bonding, is to prevent extraneous-conductive-parts from introducing a diference in potential.
We are required to connect to a point as close to the point of entry and before any branches, in order to prevent the pipework being disconnected and continuity being lost.
Once bonded, what purpose would further bonding achieve?
To my mind, it would be no different to bonding pipework in every room of a single dwelling.

 

[johnboy6083]

i agree with you in principle mate, but i suppose that we are tying to acheive as near a fardays cage as possible in the flats. Is probably more accurate to call it supplementary bonding.
It also helps to ensure that when you are testing an individual flat, you can ensure that it meets all of the regs.
Each flat would be its own instalation.

 

[Engineer54]

I haven't got GN 8 to verify or not, but commonsense tells me that if as an example were talking about a high rise block of apartments/flats, reliance on a single bonding point isn't a particually safe or secure situation to have. At anytime Mr wet pipe, the plumber or Mr Gas Man could bring in a plastic main for the water/gas and that service single point bonding is lost.

Now these high rise blocks are going to be constructed using reinforced concrete so there is no way that the existing metallic pipework is not going to remain extraneous and will still need bonding. Far better to have each apartment bond this and other pipework as it enters the apartment, there is then no doubt whatsoever that any pipework etc, within the apartments are at the same potential as the electrical earthing conductor...

 

[i=p/u]

id say it is plastic pipe in this situation...

 

[johnboy6083]

i see your point E54, and its a very valid 1.

 

[Chr!s]

Several issues spring to mind.

1, Energy network association guidance would view each individual flat as an installation in its own right, therefore requiring a Met, this being metered or not.

2, It may be prudent, although in the 17th not required, if circuits with 5 sec disconnection time exist the voltages will appear within each flat, bonding each individual flat reestablishes the equipotential zone lowering touch voltages.

3, In general local bonding will lower touch voltages and allow futures extraneous parts which may be brought into the flats be easily bonded.

It could also be argued BS7671 sees it this way too.

 

[radosparks]

I have come across a similar situation to this in an old house which has been converted into flats many years ago. The main intake has been split into separate fuses for each flat, concentric up to the flat, main fuse, meter then board.

I had wrongly assumed the main intake MET would have the main bonding to services. I phoned the NIC tech line and based on my assumption they said bonding in each flat was recommended but not essential if bonding was present at the intake.

I have since installed a RCBO board, all circuits covered.

I know a 10mm earth in the flat to gas and water would be the obvious answer but routing is an absolute nightmare. Of course if its needed it will be done, but just wondered what others thoughts are.

Isn't RCD protection enough? I'm trying to think of instances were it wouldn't be;

- Fault in flat circuit to water/gas pipes and RCD would trip
- Service pipes made live from another flat without RCD and bonding and metal pipes not entering ground, shock? Nothing for RCD in flat to trip because that is not the origin of the current.

Any thoughts.... Cheers.

 

[Engineer54]

The NIC making up it's own rules again i see!! lol!! Each separate dwelling unit needs it's own bonding arrangement, to any extraneous service entering that unit!!

 

[Guest123]

The NIC making up it's own rules again i see

Not only that but wholly contradicting themselves too.

Their 'snags & solutions' book indicates bonding of services at point of entry to the overall building AND point of entry to each individual dwelling.

No mention of anyway of circumvention at all.

 

[radosparks]

Ok, thought as much. The routing is a nightmare as I said and phoned them to check, and went with it. I know that if I got the main bonding done at the incoming to the block and anyone picked up on it I would on my own so should have done it to start with. So it will be done.

Just while I'm thinking of it out of interest, what is it preventing if RCD's are used on every circuit? Faults introduced by other flat installations?

Thanks.