Im lost now,
whotafock was it that was trying to say it wasnt needed?!!!!!!
headbang
whotafock was it that was trying to say it wasnt needed?!!!!!!
headbang
Main protective bonding conductors
- Thread starter gselectrical
- Start date
Help Support Talk Electrician Forum:
so,
are we now saying,
and Im not making anyone guilty here,
well I hope not anyway,
we should always bond a metal service pipe on the consumers side unless we can prove beyond doubt that it is not and is very unlikely to not become an extraneous conductive part ?
is that the question I need to ask?
cos Im so confused now.......
are we now saying,
and Im not making anyone guilty here,
well I hope not anyway,
we should always bond a metal service pipe on the consumers side unless we can prove beyond doubt that it is not and is very unlikely to not become an extraneous conductive part ?
is that the question I need to ask?
cos Im so confused now.......
I think quite a few people will work on the same basis as me..............
If it's a straight forward job to bond both gas and water services at the correct positions (as per the regs
), then I will do so, regardless of whether it's metal or PVC coming in - if the stop-tap and continuing pipework is metal, I'll bond.
BUT, if say the water intake was really hard to get to and would cause a lot of disruption to the property to get a 'bond' to it, then I might question (if PVC), whether it is actually extraneous and whether it requires bonding.
My house was dead easy, see, so I bonded the water, even though it's PVC coming in.
If it's a straight forward job to bond both gas and water services at the correct positions (as per the regs
), then I will do so, regardless of whether it's metal or PVC coming in - if the stop-tap and continuing pipework is metal, I'll bond.BUT, if say the water intake was really hard to get to and would cause a lot of disruption to the property to get a 'bond' to it, then I might question (if PVC), whether it is actually extraneous and whether it requires bonding.
My house was dead easy, see, so I bonded the water, even though it's PVC coming in.
or is it just easier to deviate from the regs and put a note in the box?
Is this acceptable? - I haven't done it before.
I'm doing a CU swap now, (under the stairs), the water intake is at the back of the house, by the kitchen sink - no bonding at present! - and it's all metal.
I'm looking at a 20 metre run around the outside of the house to get a Main Bond to it.
If I can find somewhere nearer, can I bond there and make a note of it??
I suppose if I took a 'wander lead' reading at the 'incommer' after I 'd bonded, and it was within requirements, then this would be okay?
bond where practical,
cylinder cupboard?
and yes, put a note at CU and on cert,
certs I use actually have a box beside bonding to use , "location when not obvious" or something like that.
oh,
and no, I dont think you can put it down as a deviation,
cylinder cupboard?
and yes, put a note at CU and on cert,
certs I use actually have a box beside bonding to use , "location when not obvious" or something like that.
oh,
and no, I dont think you can put it down as a deviation,
Manator
©Honorary Essex Boy™
We have to look at the history of main bonding to understand a little more about why we do it. Pre 1970 almost all supply pipes were metal, the main problems with rigid gas pipes as you can imagine is the fact that they can easily be damaged, the flexible pipes (still of metal construction) was developed in Japan, and mainly to help prevent ruptures in the event of earthquakes. Shortly after plastics high grade plastics were used for the supply of gas. Water was traditionally supplied in lead, lead is very flexible and would not suffer from the same stresses that a rigid steel pipe would, however the health implications of drinking water with high lead content meant that this too had to be changed to plastic.
From an electrical point of view we have to look at the history of supply and distribution, the main earthing arrangements were TNS and TT. Both these supply arrangements had problems, there was even some experiments in the early days to supply a main earth with the distribution cable, and then wire the home without any earthing, this obviously failed and was considered far too dangerous. The supply companies (well it was only one back then), soon realised that problems with having different potentials to earth reference in one equipotential zone (the home) had to be dealt with. The supply pipes were sometimes used as earth electrodes, this was a safe and normal practice up to the introduction of plastic pipes being used for the supply of gas and water, when it soon became apparent that should the pipe be replaced, the property would be left without a suitable earth. TNS supplies were also bonded to the water and gas, one reason was to equalise any potential differences within the building, and secondly to at least give a direct path to earth in the event of any failure.
It is conceivable to wire a property without any bonding to any internal pipe work, and under any fault conditions it could be argued that without any electrical contact the pipe will never become a problem. However this is not the case, no electrical cable will, under normal use come into contact with the pipes, but us humans will, and in the event of any fault occurring were contact between two different earth potentials exists we are going to try and equalise this difference through our bodies.
Those are the basics of why we bond, but what about how?
Well the first thing we have to remember is that as the pipes were originally used as electrodes (to some extent) then we need to bond them as close to the point of entry to the ground as possible. As the pipe belongs to the supply company, this had to be done on the customers side. It was also an agreed normal practice, to aid inspection and for maintenance to have a distance were this could be achieved. 600mm from entry, and preferably before any branches or joints. Again the reason for this is the added resistance through any mechanical joint. To aid in compliance of this ruling, as always, we do have a caveat, meaning that if you can not get a bond within this distance you can bond where you decide is as close as possible.
I am sure that the topic of main bonding will become more and more subjective given the fact that with the introduction of plastic, the functions of any extra earthing to true earth is almost defunct, and the main bond could in reality be bonded at any point within the metal piping in the home.
Having said that, even when you note the position on the EIC, the fact still remains that out of 100 PIRs that I do I only ever see about two previous certificates.
At least with the 600mm rule, I know where to start looking.
Sorry for the long reply.
From an electrical point of view we have to look at the history of supply and distribution, the main earthing arrangements were TNS and TT. Both these supply arrangements had problems, there was even some experiments in the early days to supply a main earth with the distribution cable, and then wire the home without any earthing, this obviously failed and was considered far too dangerous. The supply companies (well it was only one back then), soon realised that problems with having different potentials to earth reference in one equipotential zone (the home) had to be dealt with. The supply pipes were sometimes used as earth electrodes, this was a safe and normal practice up to the introduction of plastic pipes being used for the supply of gas and water, when it soon became apparent that should the pipe be replaced, the property would be left without a suitable earth. TNS supplies were also bonded to the water and gas, one reason was to equalise any potential differences within the building, and secondly to at least give a direct path to earth in the event of any failure.
It is conceivable to wire a property without any bonding to any internal pipe work, and under any fault conditions it could be argued that without any electrical contact the pipe will never become a problem. However this is not the case, no electrical cable will, under normal use come into contact with the pipes, but us humans will, and in the event of any fault occurring were contact between two different earth potentials exists we are going to try and equalise this difference through our bodies.
Those are the basics of why we bond, but what about how?
Well the first thing we have to remember is that as the pipes were originally used as electrodes (to some extent) then we need to bond them as close to the point of entry to the ground as possible. As the pipe belongs to the supply company, this had to be done on the customers side. It was also an agreed normal practice, to aid inspection and for maintenance to have a distance were this could be achieved. 600mm from entry, and preferably before any branches or joints. Again the reason for this is the added resistance through any mechanical joint. To aid in compliance of this ruling, as always, we do have a caveat, meaning that if you can not get a bond within this distance you can bond where you decide is as close as possible.
I am sure that the topic of main bonding will become more and more subjective given the fact that with the introduction of plastic, the functions of any extra earthing to true earth is almost defunct, and the main bond could in reality be bonded at any point within the metal piping in the home.
Having said that, even when you note the position on the EIC, the fact still remains that out of 100 PIRs that I do I only ever see about two previous certificates.
At least with the 600mm rule, I know where to start looking.
Sorry for the long reply.
thebantam
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This is a good thread guys, it's good to see how others interpret the regs as this is a real grey area.
A while back I was working for a company who only did new builds. The incoming water and gas was always plastic. From the stop tap it was then done in bit of copper under the sink then back to plastic again for the whole house (including central heating).
We always bonded the water and gas as standard, but when I asked my supervisor why (in a similar way of the original question from gselectrical) he just looked at me daft and said it's a requirement and didn't elaborate!
My own conclusion was to always bond water and gas as surely it's better to have a fault path than nothing at all?
A while back I was working for a company who only did new builds. The incoming water and gas was always plastic. From the stop tap it was then done in bit of copper under the sink then back to plastic again for the whole house (including central heating).
We always bonded the water and gas as standard, but when I asked my supervisor why (in a similar way of the original question from gselectrical) he just looked at me daft and said it's a requirement and didn't elaborate!
My own conclusion was to always bond water and gas as surely it's better to have a fault path than nothing at all?
Manator
©Honorary Essex Boy™
There was a practice a while back to install a 6" length of copper for the electricians to bond to. This is obviously wrong, and is not done or is rarely done these days. The problem with this practice is to introduce a potential where there was none previously.
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