UK Bathroom scenario, what's your opinion.

[Daniel Oake]

Condition report for a house, no RCD protection on the lighting in the bathroom so Code 3; the bathroom had the radiator and sink earth clamped.

Long lead back to the MET and got a reading of 0.04ohms... brilliant right?
I submitted my report and got a phone call later and my boss told me because it's not bonded to a circuit within the bathroom the regs say it's not good enough.

Is this correct and if so are you seriously telling me that 0.04ohms back to the MET isn't sufficient enough?

If I'm wrong in any of this let me know and explain it please as I really do prefer a good discussion

 

[Pete999]

Condition report for a house, no RCD protection on the lighting in the bathroom so Code 3; the bathroom had the radiator and sink earth clamped.

Long lead back to the MET and got a reading of 0.04ohms... brilliant right?
I submitted my report and got a phone call later and my boss told me because it's not bonded to a circuit within the bathroom the regs say it's not good enough.

Is this correct and if so are you seriously telling me that 0.04ohms back to the MET isn't sufficient enough?

If I'm wrong in any of this let me know and explain it please as I really do prefer a good discussion

Is your Boss an Electrician Dan? Did you carry out any tests to see if the extraneous parts neededbonding
'

 

[Daniel Oake]

Is your Boss an Electrician Dan? Did you carry out any tests to see if the extraneous parts neededbonding
'

Yes Pete he's an electrician, big respect for him aswell so go easy lol

I didn't do any tests to see if they needed bonding, let's imagine they did need bonding though for this instance what would you say with my readings back to the MET.

Would you agree with my boss and say that the bathroom earth clamps should be connected to say the light fitting for example or would you argue that being bonded back to the MET is okay?

 

[Pretty Mouth]

What circuits and electrical equipment are there in the bathroom?

 

[Daniel Oake]

What circuits and electrical equipment are there in the bathroom?

Light and shower only

 

[Pretty Mouth]

Any class 1's?

 

[Daniel Oake]

Any class 1's?

Sorry I'm not 100% sure what your asking, the light fitting is plastic and so is shower both with suitable Zs values

 

[Pretty Mouth]

Class I equipment. Equipment in which protection against electric shock does not rely on basic insulation only, but which includes means for the connection of exposed-conductive-parts to a protective conductor in the fixed wiring of the installation (see BS EN 61140).

 

[ChrisElectrical88]

Mainly copper or plastic pipe in the house? I’d say with a reading of 0.04Ohms it was reading through the meal pipework and back down the main bonding unless you disconnected the clamps?

 

[Pretty Mouth]

From best practice guide 4:

Non-compliances with the current edition of BS 7671 that do not give rise to danger and do not require reporting
• 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

However, I don't think an electric shower is class II. While they're usually all plastic casing, every one I've worked on has had an earth terminal and required earthing. So IMO it's either:

C3 – Improvement recommended
• Absence of RCD protection for circuits of a location containing a bath or shower where satisfactory supplementary bonding is present

or
C2 – Potentially dangerous
• 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 have additional protection by means of a 30 mA RCD
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So I would say you need to test between the shower cpc and the extraneous parts to see if they meet the requirements of 415.2.2. From there you can decide C2 or C3

 

[Wilko]

Hi - the supplementary bonding is in addition to the protective bonding that you’ve likely measured, if I’ve understood correctly. The light circuit cpc and shower circuit cpc should be locally linked to the radiator etc for supplementary bonding.

 

[Ian1981]

If supplementary bonding in a bathroom is applicable then Bathroom supplementary bonding needs to connect together the terminals of the protective conductor of each circuit supplying class 1 and class 2 equipment and to the accessible extraneous conductive parts (water pipes etc) or if there’s no extraneous parts then each circuit only that serves the location.

 

[littlespark]

The wording is "equipotential" meaning everything inside the bathroom needs to be bonded together with as short a length of cable as possible.... not via the MET.

Sometime in the future, a length of heating pipe may be replaced with a plastic fitting. There goes any continuity back to the MET

 

[Daniel Oake]

Mainly copper or plastic pipe in the house? I’d say with a reading of 0.04Ohms it was reading through the meal pipework and back down the main bonding unless you disconnected the clamps?

I didn't disconnect the clamps so i see your point there, i'll keep that in mind for future Chris
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After reading the replies iv'e come to understand what is meant now, essentially even though we create the House as one big potential zone as we earth everything back to the MET, we also create another equipotential zone within the house i.e the bathroom to further reduce the risk of shock.

My understanding was that if its bonded back to the MET with such a low reading then in the event of a potential it would be fine but i can see that its a box within a box to further reduce the risks.

I'll bear it in mind for future
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The wording is "equipotential" meaning everything inside the bathroom needs to be bonded together with as short a length of cable as possible.... not via the MET.

Sometime in the future, a length of heating pipe may be replaced with a plastic fitting. There goes any continuity back to the MET

Yeah thats a fair point, parallel paths arn't going to always be available essentially, which is why we perform R1+R2
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If supplementary bonding in a bathroom is applicable then Bathroom supplementary bonding needs to connect together the terminals of the protective conductor of each circuit supplying class 1 and class 2 equipment and to the accessible extraneous conductive parts (water pipes etc) or if there’s no extraneous parts then each circuit only that serves the location.

Ian, would that mean that the shower circuit and the lighting circuit would need to have their CPCs connected with a single earth between the two as to create the above diagram Wilko posted?

meaning the fact they go to the MET is not good enough and need to be connected within the equipotential zone aswell?

 

[Ian1981]

I didn't disconnect the clamps so i see your point there, i'll keep that in mind for future Chris
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After reading the replies iv'e come to understand what is meant now, essentially even though we create the House as one big potential zone as we earth everything back to the MET, we also create another equipotential zone within the house i.e the bathroom to further reduce the risk of shock.

My understanding was that if its bonded back to the MET with such a low reading then in the event of a potential it would be fine but i can see that its a box within a box to further reduce the risks.

I'll bear it in mind for future
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Yeah thats a fair point, parallel paths arn't going to always be available essentially, which is why we perform R1+R2
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Ian, would that mean that the shower circuit and the lighting circuit would need to have their CPCs connected with a single earth between the two as to create the above diagram Wilko posted?

meaning the fact they go to the MET is not good enough and need to be connected within the equipotential zone aswell?

Yes each circuit is required to connected together