Earthing and bonding arrangements

[Ken77]

Hi,

I have done a E.I.C.R report on an installation with 16mm meter tails and 6mm Earth conductor. Whilst this is undersized and should be 10mm, using the adiabatic equations the 6mm is fine to carry the fault current. My question is this, the bonding is also 6mm and whilst I would recommend for this to be upgrade to 10mm, would you class this as unsatisfactory and fail an installation? As the bonding is present (albeit undersized) would you code this as C2 or C3?

Thanks

 

[telectrix]

what earthing system is it? if it's TT or TN_S then a code C3 would be appropriate as long as no signs of thermal damage.

 

[Ken77]

Thanks. Should of said TNS so I dont have to worry about the relationship with earth and neutral conductor.

 

[telectrix]

you do. with TN-S the bonding conductor needs to be 50% of the csa of the main earthing conductor with a min. of 6mm. as long as the adiabatic confirms that the MEC is adequate, you're OK. however, i'd be inclined to upgrade the MEC to 10mm or 16mm if it was an easy job.

 

[D Skelton]

Ken, if you've confirmed the MEC is ok at 6mm then it's not undersized is it? If a TN-S then the main bonding is also ok at 6mm. No code is warranted, not sure why you would reccommend unneccesary work?

 

[odawire]

Hi,

I have done a E.I.C.R report on an installation with 16mm meter tails and 6mm Earth conductor. Whilst this is undersized and should be 10mm, using the adiabatic equations the 6mm is fine to carry the fault current. My question is this, the bonding is also 6mm and whilst I would recommend for this to be upgrade to 10mm, would you class this as unsatisfactory and fail an installation? As the bonding is present (albeit undersized) would you code this as C2 or C3?

Thanks

As long as the adiabatic equation says 6mm is ok then its fine, but I agree with telectrix in regards the MEC, unless its a hard job, change to a 16mm, no question

 

[johnboy6083]

I agree, if the tails are adequately protected by the suppliers fuse, then they are ok, no code despite what people say.
on a TT or TNS the earthing conductor can be sized using the adiabatic, and the bonding is half of that, with a minimum of 6mm.
again no code.
the problem is that other sparks who follow will almost certainly slate it. A little knowledge and all that.

 

[D Skelton]

change to a 16mm, no question

Why???

 

[odawire]

Why???

Belt and braces, how long is it gonna take? how much will it cost? I know its not required to be upgraded but that's the way I work and that's what ird always recommend

 

[D Skelton]

Belt and braces, how long is it gonna take? how much will it cost? I know its not required to be upgraded but that's the way I work and that's what ird always recommend

Fair enough, I'm not 'avvin a pop but I just don't understand why you'd fix something that aint broke.

What would you explain to the customer if you were to reccommend upgrading a perfectly adequate 6mm earthing conductor to a 16mm one and they asked why? What if they were to ask you why you were reccommending fixing something that aint broke?

 

[odawire]

Fair enough, I'm not 'avvin a pop but I just don't understand why you'd fix something that aint broke.

What would you explain to the customer if you were to reccommend upgrading a perfectly adequate 6mm earthing conductor to a 16mm one and they asked why? What if they were to ask you why you were reccommending fixing something that aint broke?

It wouldn't be a job ird quote and charge for, ive done things like this before and not even mentioned it to the client, it wouldn't even require a conversation but if it did and if someone's paying me for my professional opinion im gonna tell them exactly what I think, regardless of what the "regs" say, they're only for guidance, they way I carry out my work is based on a combination of what the regs say, my experience and the kind of organisation I want to be proud of running. that is of course assuming its a basic short length of cable that just needs replacing which lets be honest, it usually is.

 

[D Skelton]

It wouldn't be a job ird quote and charge for, ive done things like this before and not even mentioned it to the client, it wouldn't even require a conversation but if it did and if someone's paying me for my professional opinion im gonna tell them exactly what I think, regardless of what the "regs" say, they're only for guidance, they way I carry out my work is based on a combination of what the regs say, my experience and the kind of organisation I want to be proud of running. that is of course assuming its a basic short length of cable that just needs replacing which lets be honest, it usually is.

Fair enough, I still don't understand why but I accept what you're saying and I'm not going to condemn it.

 

[Geoffsd]

The trouble is that if you replace the EC with 16 - 'just because you do' - someone else is going to come in and state that the MPB should be 10 and that could be a pita to fit costing the customer.

It's the same as replacing tails with 25 - 'just because you do'.

It isn't necessary and achieves nothing.