10mm Earth From shower to Earth Block

[marnerbird]

Hi All,

Hopefully just a quick question. Currently I have a 10mm earth coming from my shower to the earth block next to the cut out (TN-S). The cable also has an earth clip connected to the cold water feed to the shower. Is this ok or should it be a 4mm earth from shower connecting to the cold water feed and then to the bathroom light CPC.

Thanks for your help

 

[securespark]

This was done a lot under the 15th, never quite sure why...

All you need under the 17th is PEB's to gas & water & RCD-protection to all circuits within the bathroom, assuming your pipework is electrically continuous.

 

[Taylortwocities]

Umm. That's raised a question in my Merlotized brain.
Its not correct to bring an 'earthy' lead into the bathroom and it should be removed.

This then means we need to arrange protection for the bathroom.
As SS says, all circuits to the bathroom could be RCD protected and the MEBs brought up to scratch. Then we do not need supplementary equipotential bonding (per 17th).

Alternatively, if RCD protecting all circuits is not desireable/practical, is it still OK to carry out supplementary equipotential bonding?

 

[dingbat]

Umm. That's raised a question in my Merlotized brain.
Its not correct to bring an 'earthy' lead into the bathroom and it should be removed.

But, on the other hand, if the pipwork is already introducing earth potential you have changed nothing.

Alternatively, if RCD protecting all circuits is not desireable/practical, is it still OK to carry out supplementary equipotential bonding?

RCDs provide additional protection. So does supplementary bonding.

RCDs provide a means of automatic disconnection. Supplementary bonding eliminates dangerous potential differences.

Sadly, very few electricians understand the principles of earthing and bonding, so this is an area that will continue to be needlessly debated... and poorly executed. The newly introduced ubiquitous use of 30mA RCDs provides some degree of protection from incompetence as well as carelessness.

 

[securespark]

Sadly, very few electricians understand the principles of earthing and bonding, so this is an area that will continue to be needlessly debated... and poorly executed.

So for the benefit of us confused electricians & even more confused DIYers, could you please enlighten us in your definitive guide to this area of electrical installation?

 

[dingbat]

What ho, Simon.

GN8 is Gr8.

 

[securespark]

Ding, I can see it is frustrating for users of this site to see posters telling them they're getting it wrong, or are confused about something, but not then offering their wisdom.

Can you share GN8 with us?

As for the earth to shower pipe back to the MET, it is uneccesary & is a parallel earth path.

As long as the PEB's are in place, there is no need for any earthing conductors (unless supplying circuits) to be installed within the bathroom that go directly back to the MET.

 

[dingbat]

It's a real problem, I agree, but there is no easy way of getting through to people with a quick post.

I daily meet dozens of electricians, supervisors, designers, engineers, etc and it is rare indeed to find any of them completely comfortable with the subject - and bear in mind that at least they are attending courses - who knows what the ignorant masses are up to?... but here goes.

1. Earthing is the provision of an earth fault path to ensure disconnection of overcurrent protective devices.

2. Bonding connects together any conductive parts which may either become live in the event of a fault or independently introduce a different potential.

3. In a real situation it is important to determine what, if any, extraneous conductive parts exist and whether or not they require additional bonding to supplement bonding that already exists via the main protective bonding conductors. This often requires measurements to be taken and maybe even (quelle horreur!) some rudimentary calculations...

... and that's where the average spark gets confused.

 

[dingbat]

As for the earth to shower pipe back to the MET, it is uneccesary & is a parallel earth path.

As long as the PEB's are in place, there is no need for any earthing conductors (unless supplying circuits) to be installed within the bathroom that go directly back to the MET.

Quite right, supplementary bonding is only used to locally supplement the main bonding, if required. But if, as I said, the [much larger cross-sectional-area of] copper pipework is already at or near earth potential then the unnecessary 10 sq mm is merely a useless waste of wire.

If, however, the pipes it connects to are not earthy in themselves the ten-mill introduces an earth path where there was none before. In the event of contact with intentionally live parts, this does introduce a hazard.

Either way, what needs to be done (or not) can only be decided by an assessment of the actual conditions on site.

 

[securespark]

I assume the calculations you mention are to check electrical continuity of the pipework within the bathroom to the cold water pipe.

The 17th says you can do away with supplementary IF:

PEB's are in place

All circuits feeding the bathroom are protected by 30mA RCD

pipework is effectively connected to incoming water pipe (and therefore to the PEB to that pipe)

You would have to check with a flying lead that all pipework within the bathroom has a reading of 0.05 Ohm or less when referenced against the cold water pipe.

 

[dingbat]

Ah, but read 415.2 to see a better way of determining whether additional bonding conductors actually need be added.

 

[marnerbird]

Wow, what a lot of info.

The reason for my question was I dont have any RCD protection or supplementary bonding in the bathroom. I've been re-wiring the house to the 16th (why have done to the 16th has already been debated in another post) all registered with LABC and have started to do the bonding.

I've had a new gas supply, which I've now bonded to the earth block. I've also main bonded the Soil Vent Pipe (Cast Iron) and upgraded the mains water (was 6mm2), all using 10mm2 straight back to the earth block.

In the bathroom, I've bonded the pipework to the bath and sink taps and the towel rail using 4mm2. I've now got to connect that into the flex outlet for the towel rail and then from there to the immersion heater switch into the shower pull switch and then onto the bathroom light.

I'm assuming I should use 4mm2 from my shower, clipping onto the cold water feed for the shower and then into the nearest point, which will be the immersion heater switch, removing the 10mm2 to the earth block in the process.

All this will obviously be tested by building control, but i wanted to make sure i'd got everything correct before they come out.

Does the above all sound ok, or is their other info you would need to comment ?

Thanks for all your replies so far.

 

[ban-all-sheds]

If the towel rail has an earth connection then it is not an extraneous-conductive-part and therefore doesn't need supplementary bonding, which might make things easier and/or more attractive.