6mm

[cbw]

Ok, C.U. Change,

60A main fuse 16mm tails, pme @ 6mm main earth and 6mm main bonding to gas and water.

I know the 6mm main earth needs upgrading by DNO to 16mm, however just need putting straight on the following....

1. I will upgrade the water main bond to 10mm, however the gas is a nightmare, can I leave it at 6mm? I know it should be 60% of main earth so in theory not but how 'naughty' is it to leave it???

2. Can I leave the tails at 16mm given the 60A fuse? (Fairly sure I can)

Fairly basic questions I know but adibatic equation does my head in!

 

[Sintra]

Adiabatic can't be used for calculating bonding conductors. Use reg 544.1.1 and table 54.8 for selection.

16mm tails fine on 60A supply.

Before an addition or alteration can be made to an existing installation it must be ascertained that the earthing and bonding arrangements comply with the current version of BS7671 and any existing equipment including the incoming supply is adequate for the proposed addition or alteration. reg 131.8, So imo should be upgraded to 10mm.

 

[PC Electrics]

Check the ESCs 17th edition 'forum'. You can leave the 6mm bonding in place as long as it is good condition. EDQ12:
Alterations and Additions in Domestic and Similar Premises

 

[Sintra]

Contradicts EDQ5.

 

[PC Electrics]

Contradicts EDQ5.

No it doesn't. EDQ5 is about inadequate bonding. EDQ12 is saying that existing, good condition 6mm is adequate.

 

[cbw]

I have read all sorts of bits and bobs on this, get more and more confused as various bits contradict each other.

Have decided to advise customer to request upgrade to PME, I will upgrade tails to 25mm and put a 10mm water bond in, the 6mm gas will have to stay, looks in good condition and I will cont test it to confirm!

Common sense to prevail!!!

 

[Des 56]

I believe the earthing and bonding should be upgraded, where possible
Where it cant be done,we explain the situation to the customer and if rejected, we can fall back on the check and inspect for thermal damage advise by the esc

Not sure about whether the tails upgrade should be done though

 

[ezzzekiel]

although 16mm will be fine on a 60a how much additional work is involved changing them to 25mm.
6mm bonding can be left if proved adequate, except on pme.

 

[Deleted member 9648]

6.0mm can be left,even on pme.You should carefully inspect the cable for any signs of thermal damage and justify the decision to leave it at 6.0mm on the cert. Yes,99 times out of 100 you would upgrade,but if i'ts nigh on impossible, as long as you are prepared to justify on the cert and ultimately take responsibility if anything happens in the future which is attributed to an undersized main bond....Unlikely.....I have to say in 30 odd years I have never seen any thermal damage to a 6.0mm on a pme.....

 

[cbw]

Will be no problem changing the tails or upgrading the water bond, however the customer will not accept the added cost of changing the existing 6mm gas bond.

It will be a lot of work and upheaval so I think he would choose to either have John Wayne in or just stick with the rewirables.

At the end of the day he will be getting a safer installation than he has at present, but I have always been a bit of a stickler for regs!!!

 

[JonAW]

If I was doing the install I would not bother with changing the mains tails as I believe 16mm to be adequate for a 60A main fuse. It would be different if the mains fuse was 80A. The main earth and bonding should be upgraded to 10mm as well.