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BS 7671 Regulation 132.16 – Existing Main Protective Bonding and EIC of an Addition/Alteration

Prasoon Raghavan
I am seeking technical guidance regarding the application of BS 7671 Regulation 132.16 to an addition/alteration at an existing electrical installation.
As part of electrical works at an existing LUL station, an addition/alteration has been carried out. During the certification process, it has not been possible to verify the presence of main protective bonding conductor to the incoming mains water service, but test shows that they are continues.
The electrical contractor has advised that they are unable to issue the Electrical Installation Certificate (EIC) for the completed addition/alteration until either:
  1. Written confirmation is provided confirming the existing main protective bonding connection and conductor size to the mains water service; or
  2. A new main protective bonding conductor is installed to the mains water service, where such bonding is required.
I understand that Regulation 132.16 requires consideration of the adequacy of the existing installation, including the earthing and bonding arrangements where these are necessary for the protective measures associated with the addition or alteration.
I have also referred to IET Guidance Note 3, Inspection & Testing, under the section 1.4  covering Additions and alterations. I understand  that the relevant parts of the existing installation should be inspected and tested to establish the safety and compliance of the addition/alteration.
Importantly, GN3 also  states that
“Whilst there is no obligation to inspect and test any part of the existing installation that does not affect and is not affected by the addition or alteration, any departures or non-compliances observed are required to be noted in the ‘Comments on existing installation’ section…”
In this particular case, the electrical alteration does not directly interact with, modify or alter the incoming water service or its existing bonding arrangement.
On the basis of the above GN3 guidance, my interpretation is that, provided the existing water bonding arrangement does not affect the protective measures relied upon for the new addition/alteration, and the alteration does not adversely affect that existing arrangement, an inability to verify the water bond would not necessarily prevent certification of the addition/alteration.
Instead, any observed existing non-compliance could be appropriately recorded in the “Comments on existing installation” within Form 2.
I  would be grateful if somene could confirm whether my interpretation is correct and provide guidance on the following:
  1. Does Regulation 132.16 prevent an EIC from being issued for an addition/alteration solely because the presence or adequacy of an existing main protective bonding conductor to the water service cannot be verified, where that part of the existing installation does not affect and is not affected by the addition/alteration?
  2. How should it be established whether the existing water bonding arrangement is relevant to the protective measures applicable to the addition/alteration for the purposes of Regulation 132.16?
  3. Where the lack of required main protective bonding is an existing-installation deficiency but does not affect the safety of the new work, can the existing deficiency be recorded in the “Comments on existing installation”on Form 2 while still issuing the EIC for the compliant addition/alteration?
  4. Separately, if an Electrical Installation Condition Report (EICR) is undertaken and the inspector determines that required main protective bonding is absent and constitutes a potentially dangerous condition, can this be classified as C2, where technically justified, resulting in an overall “Unsatisfactory” assessment?
  5. Is there any other  caluse in BS 7671 Regulations and/or IET Guidance Note references that should be taken into consideration?
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  • +1

    Could you clarify "but test shows that they are continues." 

    In general you don't need to see the full length of the wire - a quick test with a meter  showing a nice low impedance tells you it is continuous, and if that is what you mean, then it has been confirmed , and that can be written down. 'verified by continuity tests' or something, (same applies to bonds to structural steels and all sorts of things that would require impractical levels of demolition to expose) if that helps.
    (though on large systems its common to require a larger than normal test current, partly as measuring milli-ohms is hard, and partly to fail anything hanging by a single strand..)

    To your questions more specifically, but these are my initial thoughts, and do realise that of course I'm not there and I can't see it, and in any case wait, because others will probably disagree and add a bit.

    1) Does Regulation 132.16 prevent an EIC from being issued.. 

    On its own no, but see above, and there are not many installations where a total absence of bonding can be argued to not make the installation less safe, perhaps all plastic pipes, or buildings with no water supply! 

    2) How should it be established.. if it is relevant to the ... addition/alteration
    there are not many installations where an absence of bonding can be argued to not affect touch voltages during fault conditions and so make the installation slightly less safe, again perhaps all plastic pipes, or buildings with no water supply. The "exam question" is could a person receive a shock between  an un-bonded pipe and something exposed attached to the CPC of the new work? Classic would be filling a kettle at a sink, in a domestic setting. Considering credible faults both on the old and new side when thinking about this.

    3) can the existing deficiency be recorded  Yes !! certainly should at the very least be noted, ideally also raised as requiring correction if there was actually any  credible danger.

    4)  .. can (missing bonding) be classified as C2? Yes, but unlikely  if the rest of the earthing and RCDs etc are in order - in general C1 is dangerous now, C2 could be dangerous in the event of a single event of further damage or fault. In a good system, no single fault leaves the system in a dangerous state, and two at least are required ('defence in depth' or 'double fault to danger' are the old mantras)
    5) not sure - this will depend on the location and details of the rest of the installation.


    I re-iterate these are just first personal thoughts and only  based on what you have typed - it may be that this situation is more complicated than it appears or that I have mis-understood the situation - from an online post this can happen. 
    It also reads like you are pretty sure that you don't have an unbonded installation - you just don't know the cable route, which is a much less worrying situation (and quite common apparently).
    Mike

Reply
  • +1

    Could you clarify "but test shows that they are continues." 

    In general you don't need to see the full length of the wire - a quick test with a meter  showing a nice low impedance tells you it is continuous, and if that is what you mean, then it has been confirmed , and that can be written down. 'verified by continuity tests' or something, (same applies to bonds to structural steels and all sorts of things that would require impractical levels of demolition to expose) if that helps.
    (though on large systems its common to require a larger than normal test current, partly as measuring milli-ohms is hard, and partly to fail anything hanging by a single strand..)

    To your questions more specifically, but these are my initial thoughts, and do realise that of course I'm not there and I can't see it, and in any case wait, because others will probably disagree and add a bit.

    1) Does Regulation 132.16 prevent an EIC from being issued.. 

    On its own no, but see above, and there are not many installations where a total absence of bonding can be argued to not make the installation less safe, perhaps all plastic pipes, or buildings with no water supply! 

    2) How should it be established.. if it is relevant to the ... addition/alteration
    there are not many installations where an absence of bonding can be argued to not affect touch voltages during fault conditions and so make the installation slightly less safe, again perhaps all plastic pipes, or buildings with no water supply. The "exam question" is could a person receive a shock between  an un-bonded pipe and something exposed attached to the CPC of the new work? Classic would be filling a kettle at a sink, in a domestic setting. Considering credible faults both on the old and new side when thinking about this.

    3) can the existing deficiency be recorded  Yes !! certainly should at the very least be noted, ideally also raised as requiring correction if there was actually any  credible danger.

    4)  .. can (missing bonding) be classified as C2? Yes, but unlikely  if the rest of the earthing and RCDs etc are in order - in general C1 is dangerous now, C2 could be dangerous in the event of a single event of further damage or fault. In a good system, no single fault leaves the system in a dangerous state, and two at least are required ('defence in depth' or 'double fault to danger' are the old mantras)
    5) not sure - this will depend on the location and details of the rest of the installation.


    I re-iterate these are just first personal thoughts and only  based on what you have typed - it may be that this situation is more complicated than it appears or that I have mis-understood the situation - from an online post this can happen. 
    It also reads like you are pretty sure that you don't have an unbonded installation - you just don't know the cable route, which is a much less worrying situation (and quite common apparently).
    Mike

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