earthing and bonding

[IRB]

When using a dual rcd CU what needs to be bonded in the bathroom etc? I'm a bit rusty at this
. I'm waiting to do the 17th edition course.

 

[piccollo]

Are you meaning Main Protective / Equipotential Bonding or Supplementary Bonding. Main Bonding / Equipotential Bonding is the safety connection from the MET [ Main Earth Terminal to the Incoming Services [ Gas, Water, Oil, ] & possible any main ductwork or steel. The sizes depend on your Earth system / Supply [ TNCS, TNS or TT] although there are minmum sizes. The Supplementary Bonding [ additional protection] me be ommitted if certain requirements are met. ie earth path from piework or metal work is below 0.5ohms from the point to the MET. Just because you have a dual RCD [ 17th Edition board] doesn't mean you can lapse. If I'm getting to Technical I apologise. piccollo

 

[IRB]

Supplementary bonding is what I was wondering about, thanks.

 

[Sparky Ninja]

There is a regulation which covers this. I havn't got the book but I think it's 701.415

 

[piccollo]

Sorry, got wrong jest. Bathroom installation earthing , Any supplies/ circuits need crossbonding [ same as 16th] i.e. shower, lighting, heater etc. Supplementary bonding as mentioned in previous may not be necessary if the earth parth is below 0.5ohms. A long lead test will prove this, connect long lead between Main Earth Terminal & meter [set on ohms]connect short / meter lead to meter & touch other end to pipework & earth terminals etc . piccollo

 

[Sparky Ninja]

I thought we had to take 415.2.2 into account for supplementary bonding.

R<50V/Ia

This is where that figure 1667ohms comes from.

 

[martysparky]

Supplementary bonding may be omitted when all of below are met:

(i) All final circuits of the location comply with the requirements for automatic disconnection in accordance with reg: 411.3.2
(ii) All final circuits of the location have additional protection by means of 30mA RCD in accordance with reg: 701.411.3.3
(iii) All extraneous - conductive - parts of the location are effectively connected to the equipotential bonding in accordance to reg: 411.3.1.2

Note effectiveness of the connection of extraneous conductive parts to the earthing terminal may be assessed applying reg: 415.2.2 = resistance between exposed and extraneous conductive parts meet R<50 V/Ia in an a.c. system.

 

[sjm]

The tests piccollo suggests will prove that all extraneous-conductive parts are effectively connected via the main protective equipotential bonding to the main earthing terminal. As the earth terminals are not extraneous parts you don't need to bother testing them.
However the other requirements of 701.415.2 must also be met in order to not require supplementary bonding.
1/ All circuits in the bath/shower room must meet the required disconnection times.
2/ All circuits in the bath/shower room must be protected by 30mA RCDs.

 

[Sparky Ninja]

Hey martysparky, any chance in telling me reg no please?

 

[IRB]

The shower is a power shower, so do I need to cross bond this?

 

[pushrod]

Hey martysparky, any chance in telling me reg no please?

701.415.2 mentions it. Basically if you have rcd protection, as you do with a 17th ed board, you are very unlikely to need supplementary bonding is my understanding.

 

[pushrod]

The shower is a power shower, so do I need to cross bond this?

not if you have an rcd and your main protective bonding - unless you have an oil pipe or a strange bit of structural steel running through the bathroom

 

[sjm]

Cross bond???
If the installation doesn't meet all the requirements of reg no 701.415.2 then SUPPLEMENTARY BONDING will be rquired between the extraneous-conductive parts and the earth terminals of all electrical equipment within the bath/shower room.

 

[martysparky]

Hey martysparky, any chance in telling me reg no please?

Its as you stated m8.

 

[piccollo]

sjm, Fair do's, As IRB stated it was a dual RCD board so all circuits would be protected by RCD, also I took it his highest Zs readings for lighting & other applicable circuits would be lower than 80% Max so disconnect times should be met. Sorry if I did not complete but as he only asked about bonding [ & I read the thread wrong to start with] other conditions were ommitted. piccollo