earth bonding

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Every time I write something about bathrooms I also learn something. When you try to give advice you keep thinking about all the ifs and buts and well thats not exactly rights.

Regulations talk about showers and baths, and the zones around them. Not about bathrooms. Bathrooms tend to be small so often they are completely filled by zones, but they may not be. Strictly, the bonding applies to equipment inside the zones. The idea is that it affects the space within reach of the bath. I do not myself see why a soaking wet person would not wander around his extra large bathroom, so from that point of view I think it is probably better to consider the whole bathroom from the point of view of bonding.

As I said, if your ceiling is high enough (2.25m) and the light is at least 60 cm away from the bath or shower, then lighting is considered out of reach and thus not included in requirement to bond. Also ceiling mounted heaters, or anything. No part of this should be below the 2.25m.

So in the case of your friend's bathroom, it depends on how high the ceiling is and how close sideways from the bath. If the lamp is within the zones then it may also require an IP waterproofness rating, depending on which zone it is in. Do not panic if it turns out the lamp is just within zones. There are lots and lots of bathrooms with no bonding. People do not generally go round touching light fittings when having a bath. Also, if the lamp fitting is completely insulating and enclosed, then there may not be much which could cause any problem.

As to bonding to the CU. If you have metal pipework then your bathroom already has a connection indirectly to the CU. Introducing extra paths to earth in a bathroom is generally not a good thing. On the other hand, it is not necessarily a bad thing either. My view would be not to install it, but not to rip it out either.

The important thing is that any sources of earth going into the bathroom must be connected together so there can never be any question of e.g. towel rail being earthed but tap being live....and you touch both at once. The bonding shorts everything out. But also you do not bond isolated metal objects. So if it is just a metail rail screwed to the wall, do not bond it. It is just conductors coming in which are important.

Any circuit coming in must be protected by its appropriate CPC (Earth).
This is to make sure fuses/breakers work effectively and turn things off if there is a fault. Otherwise, introducing extra earths adds extra possibilities of things which could be at different voltages.

Yes, there must be restrictions on length. But if you use 4mm then any reasonable route would be ok. As to route, On site guide says "the supplementary bonding may be provided in close proximity to the location". How close is your airing cupboard? (no I don't want to know! )That is a judgement call on what the regulation says. Close proximity to an atom bomb explosion might be a mile. If it is just outside, then fine. If right across the hall, then I would be thinking about finding a closer route.
 
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josey said:
if the supplementary bonding has to be connected to the other equipment earths, what size wire to use as the light fitting is 1.5mm, do i need to connect the 4mm wire to this aswell

If the terminals of the light fitting are too small for 4mm fit a junction box near to the light fitting, run the 4mm earth conductor to the junction box then run a short length of 1.5mm to the light fitting.
 
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Remember - it is the cpc of circuits supplying Class I and Class II appliances within the Zones that need to be bonded - that does not mean that you have to carry out the bonding at the appliances...
 
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