Advice for first ever post. DB change.

[Newinthegame]

Hello there,
Newly registered with Elecsa and raring to go.
My first 'official' job. DB change in customers house. One slight concern i am not sure on. There is one 6mm bonding cable going to both the gas and water. The termination at the gas is complete (ie not cut, but looped through the clamp)
Have done a continuity test and has come out fine 0.04 ohm. Visually looks in good nick too.
My thought was that it would be ok to reconnect into my new board.? TN-S supply (earth sweated onto main incomer) Not sure on main fuse size though!
Any help would be grateful.

 

[Farmelectrics]

how much do elesca charge now make sure you do some pre testing to see if instalation takes new dual rcd board good luck your water and gas should be 10mm but im sure others will say you can use 6mmm using the adabatic rule good luck

 

[kingeri]

It's OK to have the main earth 'daisy-chained' from MET to gas to water, but if it's not too far I would replace with two seperate earths, it is generally accepted as 'better', especially with some of the scam inspectors. It really 'should' be 10mm too!

 

[Farmelectrics]

i agree kingeri theres no req i no of that states you cant daisy chain earth but if it were me i like to run seperate 10mm earths

 

[Newinthegame]

Elecsa charge was £380 + the dreaded VAT!! Got to be done though. I though Adiabatic was not used for bonding?
Ok so the distance to gas is about 3 mts and to water a further 2. Will speak to the customer and recommend upgrade to 10mm.
If they refuse i presume i write this on the EIC just to cover my big arse?

 

[Octopus]

Elecsa charge was £380 + the dreaded VAT!! Got to be done though. I though Adiabatic was not used for bonding?
Ok so the distance to gas is about 3 mts and to water a further 2. Will speak to the customer and recommend upgrade to 10mm.
If they refuse i presume i write this on the EIC just to cover my big arse?

Yes, can't remember the reg number but if 6mm is under 0.05 ohms and in good condition it can be retained. However, if the run is only a few meters and easy to do I'd be inclined to change it.

 

[Geoffsd]

It's OK to have the main earth 'daisy-chained' from MET to gas to water

It's main bond, not main earth - important distinction.


On TN-S the main bonding conductor csa shall be not less than half of the earthing conductor.

So, in this case, it depends whether the earthing conductor is replaced with 16mm² with the CU change.

The earthing conductor can be sized using the adiabatic equation.

 

[IQ Electrical]

Yes, can't remember the reg number but if 6mm is under 0.05 ohms and in good condition it can be retained. However, if the run is only a few meters and easy to do I'd be inclined to change it.

Just to clarify, after a long thread on here, I got clarification from the IET that there is no limit for main protective bonding resistance values and the 0.05 Ohm value only applies to bonding connections between extraneous-conductive parts ie 2 metallic pipes between which a bonding connection would be required.

The earting conductor (on TN-S, TT and PNB) can be sized from the adiabatic equation and the main protective bonding conductors can then be half the size of the earthing conductor with a minimum size of 6mm.

 

[sedgy34]

10mm all the time for me

 

[Geoffsd]

As a point of interest.

If, by the adiabatic equation, a 10mm² earthing conductor would comply but you fit a 16mm² one (because you do), would you then have to fit a 10mm² main bond ?

 

[IQ Electrical]

As a point of interest.

If, by the adiabatic equation, a 10mm² earthing conductor would comply but you fit a 16mm² one (because you do), would you then have to fit a 10mm² main bond ?

Interesting point- 544.1.1 uses the terminology 'not less than half the cross sectional area required for the earthing conductor' so if the requirement is 10mm but you install at 16mm then the requirement is still 10mm!

 

[telectrix]

as IQ. said.

 

[Geoffsd]

Yes, I had overlooked the 'required' but probably not worth the OP having to argue the point on his first assessment

 

[EIPM]

When I price for a board change I always recommend that the main bonding conductors should be 10 mm. I think you should upgrade.