Discuss EICR Coding Confusion wrt Supplementary Bonding in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

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Dartlec

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Yes, it's another EICR coding question - hurrah! :blush:

Inspecting a small 1 bed 70s ex-council flat that was going well. Main Bonding had been put in place in advance and most of the tests were as perfect as you could get. Seriously, if you wanted to set up a 'perfect' test rig I don't think you could have done better.

Then I got to the bathroom, which proved more interesting.

Electric shower, with 30mA RCD protection.
Class 2 light, and Class 2 Ceiling Fan not RCD protected.
Supp(?) bonding in place and verified to pipes under the sink, where a passive descaler device had been fitted to the cold pipe that then ran up at nice head height to the shower. (Some of you may see where this is going)
Unable to verify Supp bonding conductor at the light.

Some of the shower feed was in nice chrome pipe, with the last bit in copper, though it had all been painted.

Tested near the shower (not through paint!), and sure enough - no continuity to the pipe, though a very low IR test. And of course the descaler magnetic thing had nice insulated plastic push fittings.

Fortunately there was enough slack on the bonding to bridge the device, and then the pipework near the shower had perfect continuity and overall well under 0.05 back to the MET which was in a cupboard adjacent.

While trying to work out coding, I ran into a possible contradiction in the Best Practise Guide.

On the one hand it suggests under situations for Code 2:

Absence of supplementary bonding where required (such as in a location containing a bath or shower), where any of the following three conditions are not satisfied:
- All final circuits of the location comply with the requirements of Regulation 411.3.2 for automatic disconnection, and
- All final circuits of the location have additional protection by means of a 30 mA RCD, and
- All extraneous-conductive-parts of the location are effectively connected to the protective equipotential bonding (main earthing terminal)

Which is fair enough and what I already had in my head.

However, it then later has a section for "non compliances that do not give rise to danger and do not require reporting"

Which includes:

Absence of supplementary bonding for installed Class II equipment where required (such as in a location containing a bath or shower), in case the equipment is replaced with Class I equipment in the future.

Which left me a little confused, since BS7671 (701.415.2) states supp bonding should be connected to Class 1 AND Class 2 fittings.

Given that the shower in this case was RCD protected, and the pipework bonding verified after adjustment, I did not consider this was a case for a C2 on Supp Bonding. But the BPG seems to suggest not coding or even reporting the lack of it at the light, which seems counter intuitive - and ticking the box without reporting would make it appear that it was in place.

I will certainly be noting it in the comments, but wondering what other people's views are on situations like this that are in a grey area? Would you put it as a C3, or just note it, or C2 regardless due to lack of RCD on the Class 2 light? Anyone with a copy of Codebreakers want to see if it makes things any clearer?

Clearly in terms of safety the practical end purpose of supplementary bonding is to bring all extraneous-conductive-parts within the area to the same potential and that was met.

In this case, since the CU and MET were literally in a cupboard beside the bathroom, there is even an argument that effective supp bonding existed within the CU, since the feed to each circuit was so short, but obviously that isn't normally the case.

Pic of the shower feed pipe in case you haven't seen a pipe before...

EICR Coding Confusion wrt Supplementary Bonding Shower Pipe - EletriciansForums.net
 
All circuits serving the location require additional protection, the shower has it the lighting circuit does not.
if there’s supplementary bonding in place between all circuits in the location ( shower included) and to the extraneous pipework then it is a C3 for no additional protection to the lighting circuit, no supplementary bonding, then a C2.
 
All circuits serving the location require additional protection, the shower has it the lighting circuit does not.
if there’s supplementary bonding in place between all circuits in the location ( shower included) and to the extraneous pipework then it is a C3 for no additional protection to the lighting circuit, no supplementary bonding, then a C2.
That's a consistent viewpoint, but then what is the thinking behind the BPG saying that " Absence of supplementary bonding for installed Class II equipment where required " should not be coded? I assume it's not a mistake, though I dont know if it's always been in the previous versions.

I always prefer to understand coding rather than just follow a checklist approach. For the purposes of discussion, in a situation where extraneous pipework is effectively bonded back to the MET, but supplementary bonding is not in place between all circuits as specified in BS7671 what is the potential danger that would necessitate a C2 code?
 
The supplementary bonding is there to reduce the voltage between exposed conductive parts and extraneous conductive parts in the event of an earth fault.

The class II light fitting has no exposed conductive parts, so no voltage possible - there is no immediate safety benefit by sup bonding its CPC to the other conductive parts in the bathroom.

Presumably regs require sup bonding to class II's in case the light is changed for a class I at a later time.

It's possible that the lighting circuit was effectively sup bonded anyway, the MET being so close to the location. To determine this, you need to apply reg 415.2.2:

R <= 50V/Ia

From the OSG 4.8:
Supplementary bonding is not required to metallic parts supplied by plastic pipes, for example, radiators, kitchen sinks or bathroom taps.

This in mind, I would say your shower head likely didn't need bonding past the plastic descaler.
 
Just to muddy the waters a little.

How do we feel about 12V down lights and 12V fans powered from a non RCD circuit in a bathroom.

If all other circuits were RCD protected, would this mitigate the need for supplementary bonding?
 
The supplementary bonding is there to reduce the voltage between exposed conductive parts and extraneous conductive parts in the event of an earth fault.

The class II light fitting has no exposed conductive parts, so no voltage possible - there is no immediate safety benefit by sup bonding its CPC to the other conductive parts in the bathroom.

That's how I understood things, but wondered if I was missing something.

Presumably regs require sup bonding to class II's in case the light is changed for a class I at a later time.

Makes sense - but then I would have thought the BPG would suggest recording it at least, in the same way that one would record the absence of cpc in circuits with Class 2 fittings.

It's possible that the lighting circuit was effectively sup bonded anyway, the MET being so close to the location. To determine this, you need to apply reg 415.2.2:

R <= 50V/Ia

I assume in cases where there is more than one protective device, one would take the higher value? So in this case, the 6A for the lights (since the shower is RCD protected and would be taken as 0.03 under part (i)) would allow up to 8.333 Ohms between the parts. That was easily met in this case.

From the OSG 4.8:
Supplementary bonding is not required to metallic parts supplied by plastic pipes, for example, radiators, kitchen sinks or bathroom taps.

This in mind, I would say your shower head likely didn't need bonding past the plastic descaler.

I did wonder about that. My concern was the potential for a voltage to be introduced from the shower end. That circuit was RCD protected though so perhaps it was over caution. I don't know if the descaler device would count as a 'plastic pipe' either? The body looked to be metal, but the push fit inserts were obviously plastic.

Although I got no continuity between the parts before the adjustment, I did get 0.01MOhm on an IT test (at 500V) which suggests there was some continuity.

For the additional cost of one clamp it probably wasn't worth worrying too much about.

Thanks for the reply - I do appreciate being able to have discussions on subjects like this and adding to my knowledge/experience
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Just to muddy the waters a little.

How do we feel about 12V down lights and 12V fans powered from a non RCD circuit in a bathroom.

If all other circuits were RCD protected, would this mitigate the need for supplementary bonding?
An interesting additional scenario!

I am even less sure about that - On one viewing, you could view them as equivalent to a Class 2 fitting since there is (usually) no earth provided to the final fitting?

12V fans are usually Class 2 anyway aren't they? - since they usually provide the feed from transformer to fan as a 2 wire flex - at least in the ones I've come across. In fact fans in general are mostly Class 2 in my experience, even mains voltage ones.

However, a lot of the standard chrome 12V downlights were the same as the 230V fittings, with a different lamp holder.

414.4.4 says exposed-conductive-parts of SELV circuits shall not be connected to Earth.

However, it then notes that if the e-c-p is liable to come into contact with e-c-p of other circuits, then protection against electric show no longer depends solely on SELV.

If the transformer feed was badly terminated (or jammed in around insulation etc), then there is a higher chance of the metal body becoming live at mains voltage so maybe the body should then be considered as an exposed-conductive-part for the purpose of Supp Bonding?

If you were installing Supp Bonding in a new installation to meet BS7671, I imagine you should be running it to the transformer in those cases to comply. In an EICR, its a case of deciding if there is a potential risk in ongoing usage.

Very interested to hear more thoughts though as I'm far from certain I have that fully clear in my own mind.
 
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I did wonder about that. My concern was the potential for a voltage to be introduced from the shower end. That circuit was RCD protected though so perhaps it was over caution. I don't know if the descaler device would count as a 'plastic pipe' either? The body looked to be metal, but the push fit inserts were obviously plastic.

Although I got no continuity between the parts before the adjustment, I did get 0.01MOhm on an IT test (at 500V) which suggests there was some continuity.

For the additional cost of one clamp it probably wasn't worth worrying too much about.

Thanks for the reply - I do appreciate being able to have discussions on subjects like this and adding to my knowledge/experience
No worries matey, it's a tricky one to get the head around isn't it, this bonding malarkey.

Are there any branches on the pipework between the descaler and the shower? If not, then this is how I see it:

The shower CPC is sup bonded to the pipework on the far side of the descaler. Any earth fault occurs, and the shower CPC and that pipework are at pretty much the same potential.

As there are no branches on the pipework on the shower side of the descaler, this length cannot be introducing a potential from elsewhere. It can only take its potential from either the shower itself, or the pipework on the far side of the descaler, even though the connections to either are of high resistance. Both shower and far-side pipework are at the same potential, so the near side pipework (being sandwiched between the two) has to be at the same potential too.

Hope that makes sense?
 
No worries matey, it's a tricky one to get the head around isn't it, this bonding malarkey.

Are there any branches on the pipework between the descaler and the shower? If not, then this is how I see it:

The shower CPC is sup bonded to the pipework on the far side of the descaler. Any earth fault occurs, and the shower CPC and that pipework are at pretty much the same potential.

As there are no branches on the pipework on the shower side of the descaler, this length cannot be introducing a potential from elsewhere. It can only take its potential from either the shower itself, or the pipework on the far side of the descaler, even though the connections to either are of high resistance. Both shower and far-side pipework are at the same potential, so the near side pipework (being sandwiched between the two) has to be at the same potential too.

Hope that makes sense?
That does make sense, thanks.

There were no additional branches, so it makes sense that the near side pipework can't introduce a potential that doesn't exist at either side.

The niggle that leaves in my mind is that although the shower was supp bonded (and earthed itself), don't showers usually connect the feed pipe with push fit connectors, which are plastic, so don't presumably allow continuity onto the pipe? So if the live feed to the shower somehow ended up touching the pipework (without causing a direct short to Neutral or CPC), then that could rise to 230V with no direct path to earth to ensure OCPD trip within the required 0.4 seconds?

Presumably, showers are designed to minimise the risk of that happening, and I guess RCD protection would/should ensure that noone could get a shock...

However, if I'm understanding correctly, that is a completely separate thing from bonding anyway, which is there to limit touch voltages and worries more about the introduction of potential that you have explained?

Apologies if that seems a stupid question, but I prefer to fully understand something as a concept before I apply it to circumstances outside of the 'standard' on site guide scenarios.

Appreciate the explanation!
 
That does make sense, thanks.

There were no additional branches, so it makes sense that the near side pipework can't introduce a potential that doesn't exist at either side.

The niggle that leaves in my mind is that although the shower was supp bonded (and earthed itself), don't showers usually connect the feed pipe with push fit connectors, which are plastic, so don't presumably allow continuity onto the pipe? So if the live feed to the shower somehow ended up touching the pipework (without causing a direct short to Neutral or CPC), then that could rise to 230V with no direct path to earth to ensure OCPD trip within the required 0.4 seconds?

Presumably, showers are designed to minimise the risk of that happening, and I guess RCD protection would/should ensure that noone could get a shock...

However, if I'm understanding correctly, that is a completely separate thing from bonding anyway, which is there to limit touch voltages and worries more about the introduction of potential that you have explained?

Apologies if that seems a stupid question, but I prefer to fully understand something as a concept before I apply it to circumstances outside of the 'standard' on site guide scenarios.

Appreciate the explanation!
Yeah, that would be earthing rather than bonding. I guess the situation you mention could occur, but unlikely, and AFAIK there's nothing in BS7671 saying you need to earth pipes and the like. I guess the RCD would save the day.
 
Yeah, that would be earthing rather than bonding. I guess the situation you mention could occur, but unlikely, and AFAIK there's nothing in BS7671 saying you need to earth pipes and the like. I guess the RCD would save the day.
Reading all this is very technical and hard for most to understand but when you break it down aslong as you provide bonding to gas and water and have rcd protection then all is fine?
 
Yeah, that would be earthing rather than bonding. I guess the situation you mention could occur, but unlikely, and AFAIK there's nothing in BS7671 saying you need to earth pipes and the like. I guess the RCD would save the day.
The main reason it caught my attention was being just at the height where someone will hang their shower gel bottle on it. Don't think there's a code for that though :)
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Reading all this is very technical and hard for most to understand but when you break it down aslong as you provide bonding to gas and water and have rcd protection then all is fine?
Yes for domestic installations that is the one that ticks all the boxes and doesn't need to be thought about. (Though it would also include Oil , structural steel and lightning protection if present)
 
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The main reason it caught my attention was being just at the height where someone will hang their shower gel bottle on it. Don't think there's a code for that though :)
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Yes for domestic installations that is the one that ticks all the boxes and doesn't need to be thought about. (Though it would also include Oil , structural steel and lightning protection if present)
Yes of course I was lucky enough to do heating controls nationwide and majority required bonding to tank most were a pain in the arse ?‍♂️ I was speaking on the basis of general domestic install
 

Reply to EICR Coding Confusion wrt Supplementary Bonding in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

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