bonding


Postby ajax » Sat Feb 16, 2008 1:21 pm

I am having a new bathroom put in at the moment, and the issue of bonding has come up. Several electricians and plumbers have given me confusion, by all saying different things. my questions are:

1) do i need to bond
2) there is two type of bonding, which do i do, if i have to.
3) how is the bonding done ?

The work will be certified by an electrician once all completed.

Any advice ?

many thanks
ajax
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Joined: Sat Feb 16, 2008 1:13 pm

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Postby ericmark » Sat Feb 16, 2008 9:41 pm

Regulations wise many of the requirements for bonding have been removed but at the end of the day the electrician who is signing the cert is the one who decides what is required so your only option is to do as he says.
There are two types of bonding as you say "Main protective bonding conductor" is often not in the bathroom but connects water and gas pipe etc. to the earthing conductor. The "Supplementary protective bonding conductor" is most likely to be in bathroom and does not have to return to the earthing conductor although often does and may not be required at all. With plastic pipes it has been realized that sometimes earths can do more harm than good which is why there have been some changes and not all electricians will agree unless they are on site and can see exactly what is in the bathroom.
ericmark


Postby ajax » Sun Feb 17, 2008 8:52 am

many thanks,

the bathroom has just had all new copper pipes installed, so there is no plastic. The plumber who installed, said yes, I must use 10mm earth bonding between the pipes, and join it to the lighting circuit, or some other main earthing "return". A friend who is an electrician, says you dont have to now, but becasue I am doing the work, and having it certified, I would rather get it ll cleared up, so I dont have to open anything up for corrections at the end.
Would it be wise just to join the pipes together ? i have seen in the garage, that the gas pipe has a "stamped and sealed" earth bonding on it, going to the consumer unit, but thts all i see.

many thanks for your help.
ajax
Posts: 25
Joined: Sat Feb 16, 2008 1:13 pm


Postby ericmark » Mon Feb 18, 2008 8:47 am

The "Supplementary protective bonding conductor" connects all metal parts but does not have to return to the "Main protective bonding conductor" if one of the metal parts were connected to the "Main protective bonding conductor" because it was electric i.e. an electric towel rail then it would through that. The idea is everything stays at the same voltage so if for example an immersion heater went faulty and its own earth was missing then everything would be at that voltage so no shock. But to earth through the for example the lighting earth if there were no metal parts on the lights could on that scenario overload the earth wire to the lights so weighing up the dangers both ways unless the lamp is metal it should not be connected to the "Supplementary protective bonding conductor"
415.2.1 Supplementary equipotential bonding shall include all simultaneously accessible exposed ¬conductive-parts of fixed equipment and extraneous-conductive-parts including, where practicable, the main
metallic reinforcement of constructional reinforced concrete. The equipotential bonding system shall be connected to the protective conductors of all equipment including those of socked-outlets.
701.415.2 Supplementary equipotential bonding
Local supplementary equipotential bonding according to Regulation 415.2 shall be established connecting together the terminals of the protective e conductor of each circuit supplying Class I and Class I I equipment to the accessible extraneous-conductive-Parts, within a room containing a bath or shower, including the following:
(i) metallic pipes supplying services and metallic waste pipes (e.g. water. gas) (ii) metallic central heating pipes and air conditioning systems
(iii) accessible metallic structural parts of the building (metallic door architraves. window frames and similar parts are not considered to be extraneous-conductive-parts unless they are connected to metallic structural parts of the building).
Supplementary equipotential bonding may be installed outside or inside rooms containing a bath or shower, preferably close to the point of entry of extraneous-conductive-parts into such rooms.
Where the location containing a bath or shower is in a building with a protective equipotential bonding system in accordance with Regulation 411.3.1.2, supplementary equipotential bonding may be omitted where all of the following conditions are met:
(i) All final circuits of the location comply with the requirements for automatic disconnection according to Regulation 411.3.2
(ii) All final circuits of the location have additional protection by means of an RCD in accordance with Regulation 701.41 1.3.3
(iii) All extraneous-conductive-parts of the location are effectively connected to the protective equipotential bonding according to Regulation 411.3.1.2.
Reading that I would say it is unlikely that you need any bonding. As you can see though not as easy as saying yes and no it depends on what other conditions are met.
ericmark


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