Supplementary Bonding Query

[ibruceuk]

Hi,

I'm in the process of putting in a new bathroom suite and there is no bonding in the bathroom. The new bath is steel.

To carry out bonding am I correct in thinking 4mm earth from steel bath to both pipes, to towel radiator and earth for shower circuit. It isn't possible to access the lighting circuit as walls are concrete. But the light switch and shower switch are next to each other just outside the bathroom door. Can I join the earth cables between the light switch and shower switch to acheive the connection between the circuits?

 

[fidom]

The earth wire on the lighting circuit is too thin to use for bonding. I would run an earth wire from the CU to the bath then daisy chain from there to the pipes etc. If the shower is wired in singles through conduit you could get the earth from there but if it's wired with twin & earth I think you would be better to run your bonding to the CU.

 

[JohnD]

* fidom is completely wrong **

sorry.

You do not bond to the CU

You do not bond to the bath.

You bond all the metal pipes entering the bathroom (usually hot and cold water, radiator flow and return, sometimes also pipes to cylinder, iron soil pipe, metal waste pipes) to the earth wire of every circuit entering the bathroom (lighting, sometimes also electric heater, shower, shaver socket, immersion heater, CH pump)

it is explained in the Wiki

//www.diynot.com/wiki/electric...l_bonding:supplementary_equipotential_bonding

 

[jockspark]

fidom before you give advice look in the 17th edition
page 166
701.415.2
the 17th comes in on 1st july not that far away 16th also would tell you you do not bond back to the cu

 

[fidom]

Why do you not bond to the bath? In my bathroom all the pipework is plastic but I have an earth bond wire on the steel bath. You could not rely on the pipes to earth the bath anyway as there are plastic nuts/washers on the taps. If it can be explained to me why my setup is unsafe I will change it.

 

[ibruceuk]

Thanks for your replies.

I cannot access the CPC for the lighting circuit, except for at the switch. The building is concrete prefab flats and accessing the rose would involve demolishing half the ceiling (which is concrete).

Would it be ok to join this to the shower CPC at the switch with 4mm then onto the hot/cold pipework and finally to the towel radiator (which is electric)?

Cheers

 

[GaryMo]

601-04-01 states that local supplementary equipotential bonding should connect together the terminal of the protective conductor supplying class I and II equipment in zones 1, 2 and 3 and extraneous-conductive-parts in these zones including (i), (ii), (iii) and (iv), (iv) being a metallic bath or shower basin.

See 601-04-01 for full list of items (i), (ii) and (iii).

You need to access if your metal bath is an extraneous-conductive-part.
Can it introduce a potential into the bathroom?

 

[GaryMo]

I cannot access the CPC for the lighting circuit, except for at the switch. The building is concrete prefab flats and accessing the rose would involve demolishing half the ceiling (which is concrete).

Would it be ok to join this to the shower CPC at the switch with 4mm then onto the hot/cold pipework and finally to the towel radiator (which is electric)?

Cheers

Yes, the switch is fine.

 

[Spark123]

Why do you not bond to the bath? In my bathroom all the pipework is plastic but I have an earth bond wire on the steel bath. You could not rely on the pipes to earth the bath anyway as there are plastic nuts/washers on the taps. If it can be explained to me why my setup is unsafe I will change it.

If all the pipework is plastic and the bathtub is not in contact with a metallic building structure then it isn't extraneous and cannot therefore introduce a potential into the equipotential zone. The idea of supplementary equipotential bonding is to keep everything in the location at or about the same potential. It is done locally and does not need to connect to the MET.
What you have effectively done is made it into an extraneous conductive part by bonding to the MET.