Can't see supplementary bonding in bathroom

[silure130]

Hi
What happens when you guys are testing and you can't see if there is any supplementary bonding in the bathroom, and cannot see the clamps on any pipe work.

The shower is rcd protected but the lighting is not. Would you code it C2 for the bonding and C3 for the lighting not being on the RCD.

Would then fitting a RCBO for the lights or moving them to the the RCD side of the board meet the requirements.

My line of work is industrial, motors, plcs etc. I'm starting to get interested in the testing side and have a few books, the above scenario is my own bathroom so I'm using it as a bit of a practice.

thanks

 

[Geoffsd]

Hi
What happens when you guys are testing and you can't see if there is any supplementary bonding in the bathroom, and cannot see the clamps on any pipe work.

It could be elsewhere.
Are the parts extraneous?
Measurements need to be taken.

The shower is rcd protected but the lighting is not. Would you code it C2 for the bonding and C3 for the lighting not being on the RCD.

That depends which, if anything is wrong or missing.

Would then fitting a RCBO for the lights or moving them to the the RCD side of the board meet the requirements.

It could but may it not be necessary.



You need to test to determine if supplementary bonding is required.

 

[D Skelton]

^^^^^ What he said!

 

[silure130]

Thanks for the reply.
There is definately no connections elsewhere. I've looked in the airing cupboard which is next to the bathroom.
Extraneous parts, are these the copper pipes coming into the bathroom. The whole house is copper, no plastic anywhere.

"You need to test to determine if supplementary bonding is required. "

This is the bit im not sure on. I'm thinking its maybe to late in life for me to start trying to get my head around this because I'm usualy pretty good but I cant grasp this.

ta

It could be elsewhere.
Are the parts extraneous?
Measurements need to be taken.


That depends which, if anything is wrong or missing.


It could but may it not be necessary.



You need to test to determine if supplementary bonding is required.

 

[Geoffsd]

Main Protective Bonding must be correct.

Supplementary bonding in the bathroom is applied to extraneous-conductive-parts and exposed-conductive-parts to reduce the potential difference between them to a level that is deemed safe in fault conditions - 50V.

To determine this, firstly, measure the resistance between all parts which may be extraneous and the Main Earthing Terminal.
If greater than 23kΩ (some prefer 46kΩ) then the part is considered not extraneous and no supplementary bonding is required.

Next, measure the resistance between all the parts which are extraneous and between these parts and the CPCs of the circuits in the bathroom.
If less than 50V/Ia then supplementary bonding is not required.
Ia being that for the highest rated OPD of the circuits in the bathroom.

If, for example, there is only a 6A lighting circuit in the bathroom then resistances between parts can be less than 50/30, that is 1.66Ω
Only above that is supplementary bonding required.
With a 40A shower circuit in the bathroom the figure is 50/200, i.e. 0.25Ω.

RCDs on ALL the circuits can with other criteria allow supplementary bonding to be omitted altogether.


So depending on your situation supplementary bonding may or may not be required.
You cannot tell by looking.

As you say yours is all copper it is likely that the pipes will be extraneous but very short runs may be of low enough impedance that no supplementary bonding is needed.



Edit - figures are for B type MCBs.

 

[KAS1]

Very well explained

 

[D Skelton]

Me and Geoff have smashed out supplementary bonding debates on many occasions! I can't think of anyone more suitable to explain it in such an effective yet simple way

 

[KAS1]

I'm afraid I tend to think with how bonding has changed over the years too many find it hard to understand, that it either gets missed out or bonded when not required, in a way bonding all pipes in bathrooms required or not used to ensure everything was covered, but money seems to be the driving force now.

 

[KAS1]

Yeah I've read several of your posts (both of you) on earthing /bonding all very good

 

[silure130]

Thanks very much Geoff, I appreciate you taking the time to explain it.

Main Protective Bonding must be correct.

Supplementary bonding in the bathroom is applied to extraneous-conductive-parts and exposed-conductive-parts to reduce the potential difference between them to a level that is deemed safe in fault conditions - 50V.

To determine this, firstly, measure the resistance between all parts which may be extraneous and the Main Earthing Terminal.
If greater than 23kΩ (some prefer 46kΩ) then the part is considered not extraneous and no supplementary bonding is required.

Next, measure the resistance between all the parts which are extraneous and between these parts and the CPCs of the circuits in the bathroom.
If less than 50V/Ia then supplementary bonding is not required.
Ia being that for the highest rated OPD of the circuits in the bathroom.

If, for example, there is only a 6A lighting circuit in the bathroom then resistances between parts can be less than 50/30, that is 1.66Ω
Only above that is supplementary bonding required.
With a 40A shower circuit in the bathroom the figure is 50/200, i.e. 0.25Ω.

RCDs on ALL the circuits can with other criteria allow supplementary bonding to be omitted altogether.


So depending on your situation supplementary bonding may or may not be required.
You cannot tell by looking.

As you say yours is all copper it is likely that the pipes will be extraneous but very short runs may be of low enough impedance that no supplementary bonding is needed.



Edit - figures are for B type MCBs.