earth bonding

J

josey

hi, with regards to earth bonding in a bathroom, is 4mm earth cable ok, or should i use 6mm.

The loop of cable to each item being earthed should be unbroken,YES ?, but if the proper crimps are used is it ok to not have the earth wire continuous.
I was wondering how to connect to our steel bath and radiator, both would be easier if they were at the end of the cable run. Also the radiator is a chrome towel type, are radiator connections available for this type ?

also main earth cable should be 10mm ?, when i put this in for the kitchen, i only had 6mm, so i ran two lengths to the water and gas, is this ok or should i replace it with 10mm, thanks
 
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josey said:
hi, with regards to earth bonding in a bathroom, is 4mm earth cable ok, or should i use 6mm.

First, it's not 'earth' bonding. it's supplementary equipotential bonding. You use 4 sq mm yellow/green pvc insulated cable and you connect together all the exposed extraneous conductive parts (pipes, rads, bath, etc) along with the protective conductors of any electrical circuits in the bathroom. In practice this usually means running your supplementary bonding cable to the 'earth' connection on the light fitting and shower (if fitted).

josey said:
The loop of cable to each item being earthed should be unbroken,YES ?, but if the proper crimps are used is it ok to not have the earth wire continuous.
In an ideal world the bonding cable would be continuous. But' let's face it' most bathrooms have no bonding whatsoever anyway, so do the best job you can to maintain a low resistance path.

josey said:
I was wondering how to connect to our steel bath and radiator, both would be easier if they were at the end of the cable run. Also the radiator is a chrome towel type, are radiator connections available for this type ?
There are clamps on the market specifically designed to attach to radiators and other non-pipe metalwork, but all such connections are unsightly. As before, do the best job you can to obtain a sound electrical connection. You can even solder your bonding conductor to the pipes beneath the floorboards if you wish

josey said:
also main earth cable should be 10mm ?, when i put this in for the kitchen, i only had 6mm, so i ran two lengths to the water and gas, is this ok or should i replace it with 10mm, thanks

The main earth conductor for TN-S and TN-C-S systems should be 16 sq mm (assuming you have 25 sq mm live and neutral tails) connecting the suppliers earth terminal to the Main Earth Terminal of your consumer unit (or to a separate MET)

Main equipotential bonding (10 sq mm) connects the incoming gas and water supplies (and oil and structural metalwork, if appropriate) to the MET.

Hope that helps.
 
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dingbat said:
In practice this usually means running your supplementary bonding cable to the 'earth' connection on the light fitting and shower (if fitted).


Just to clarify: Or any other circuit's earth within the room, ie Shaver socket, wall heater, shower pump, immersion heater, etc......
 
J

josey

let me get this straight , i am about to fit a power shower, this needs a 3amp supply, (not decided how to run the supply yet, that's another post), i will have a 2.5mm t&e cable going to the shower.
1) Are you both saying that the supplementary equipotential bonding should be connected to the earth of the shower.
2) should the supplementary equipotential bonding be connected to the main earth terminal at the cu, or just to the earth of the shower (or other equipment)
3) is it wrong, against the regs, if say a bathroom with only a light fitting (no other electrical equipment) has an 4mm earth wire run from the main earth terminal at the cu and is connected to all metal work in the bathroom but NOT the earth at the light fitting, and likewise the earth in the light fitting is on connected to the earth rail at the cu by its lighting circuit, because i have seen this in a relatives house.
 
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josey said:
do i have to also run the end of my supplementary equipotential bonding to the earth terminal on the shower
Yes.

The supplementary bonding does not have to be run back to the cu. Its purpose is to make sure that all exposed metalwork in the bathroom is at the same potential. The function of the circuit protective conductor (your circuit earth) is to provide a means of operating the circuit protective device (fuse or circuit breaker) in the event of a live-to-earth fault.
 
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I fancy it is not actually necessary to bond a metal bath provided all the metal pipework connected to it is bonded. Or if all the plumbing is plastic, then none including the bath need to be bonded. It is acceptable to use lengths of permanently conductively jointed metal pipework as part of the bonding circuit, so the cable does not have to be continuous.

Push fit plumbing, even with metal casing, may not be a good electrical joint. Taps or short lengths of metal pipe on the ends of long plastic pipes need not be bonded.
 
J

josey

let me get this straight , i am about to fit a power shower, this needs a 3amp supply, (not decided how to run the supply yet, that's another post), i will have a 2.5mm t&e cable going to the shower.
1) Are you both saying that the supplementary equipotential bonding should be connected to the earth of the shower.
2) should the supplementary equipotential bonding be connected to the main earth terminal at the cu, or just to the earth of the shower (or other equipment)
3) is it wrong, against the regs, if say a bathroom with only a light fitting (no other electrical equipment) has an 4mm earth wire run from the main earth terminal at the cu and is connected to all metal work in the bathroom but NOT the earth at the light fitting, and likewise the earth in the light fitting is on connected to the earth rail at the cu by its lighting circuit, because i have seen this in a relatives house.
 
J

josey

please see post above,posted again for dingbat, is it wrong to only conect the supplementary bonding at the cu and not to the earths of the other equipment in the bathroom.

and 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
 
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josey said:
let me get this straight , i am about to fit a power shower, this needs a 3amp supply, (not decided how to run the supply yet, that's another post), i will have a 2.5mm t&e cable going to the shower.
1) Are you both saying that the supplementary equipotential bonding should be connected to the earth of the shower.
3 of us now. Yes.

2) should the supplementary equipotential bonding be connected to the main earth terminal at the cu, or just to the earth of the shower (or other equipment)
No need. This is not about earthing per se, it's about getting the relevant stuff in the bathroom to the same potential.

3) is it wrong, against the regs, if say a bathroom with only a light fitting (no other electrical equipment) has an 4mm earth wire run from the main earth terminal at the cu and is connected to all metal work in the bathroom but NOT the earth at the light fitting, and likewise the earth in the light fitting is on connected to the earth rail at the cu by its lighting circuit, because i have seen this in a relatives house.
No - that is not right.
 
J

josey

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
 
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If you start poking around people's bathrooms I expect you will see just about everything. Bathroom bonding is actually extraordinarily complicated.

For electrical purposes a bathroom is not so much a bathroom as a set of zones. As you get further away from the bath, the rules relax. If your bathroom is big enough or tall enough then you get to be outside the zones.

If the shower pump is in the bathroom zones, then its earth should be connected to the supplementary bonding.

If the pump is outside the zones (i.e. inaccessible to a person using the bathroom), then its earth need not be connected.

The supplementary bonding should connect to the earth of every circuit which enters the bathroom zones. You only need connect once, so if the fan,switch and light are all part of the same circuit, only one of these points needs to connect. If the ceiling is more than 2.25m high and all these are 60cm away from the bath sideways, then lighting would be outside the zones and need not be connected.

You do not need to run a separate cable back to the consumer unit, or anywhere outside the bathroom. It is permissable to run the bonding a short distance outside the bathroom to help with making the connection. (but not desirable).

It is permissable to use 2.5mm earth cable where this is mechanically protected. All pipe connections should use a proper pipe clamp with warning label about not disconnecting a safety earth.
 
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Damocles said:
It is permissable to use 2.5mm earth cable where this is mechanically protected. All pipe connections should use a proper pipe clamp with warning label about not disconnecting a safety earth.

im pretty sure soldering to pipes is acceptable and has the advantage that soldered joints are exempt from accesibility rules
 
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Just remember 'a little knowledge is a dangerous thing

And it is 1 o'clock in the morning.
 
J

josey

just another quick question i forgot last night, is there any restriction on the length of the earth bond, if i have to bond all pipes to the light and shower earth, it would best if i can run the wire from the bathroom, under the landing floor and up through the airing cupboard to the attic, is this acceptable ?

Also been worrying about my relations wiring, the supplementary bonding in that house goes from the bathroom and is connected at the cu earth, i now know this is not right, but until i can put it right, is it dangerous to leave it this way, and would it be better to disconnect it from the cu for the time being until i can reroute it to the light fitting earth in the bathroom, thanks.
 

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