pir code for undersizes water bond

[sid578]

hi .doing a test on a complex where the tails are 25mm ..main bond 16mm ..but the cable bonding main water is only 6mm..think the tails have been upgraded from original but not water bond (not a easy run) .there are 30 flats in complex ..what pir code would i put fo this

 

[Octopus]

Potentially no code. Can't remember the new reg number but it was 131.8 in the BRB!

 

[telectrix]

what is the earthing? is it TNC-S?

 

[Eco Chap]

What's the resistance of the conductor. Worst case scenario c3...

 

[telectrix]

use adiabatic equation to determine the min. reqd. size for main earthing conductor. ( irrespective of the fact that the re is a 16mm there). then the main bonding conductor/s need to be at least 50% of that size.

 

[sid578]

what is the earthing? is it TNC-S?

hi tnc-s

 

[sid578]

its a tnc-s supplied from 60a bs 88 fuse

 

[topquark]

As there's existing bonding, assuming it's metal and extraneous. TNC-S = minimum of 10mm, it is potentially dangerous, so code 2.

 

[telectrix]

code C3, if any, IMO.

 

[topquark]

The reason for the minimum sizes (and why they must be updated before any work is done) is to ensure that fault current can be handed in the event of a fault. It would depend on where the fault was (which circuit/ocpd etc) to actually cause a real issue.

If it isn't potentially dangerous, why would it need to be upgraded before any work was done?

 

[ferg]

6mm, If no sign of thermal damage then no code. Or just doesn't comply with current regs but is not unsafe.

 

[Octopus]

The reason for the minimum sizes (and why they must be updated before any work is done) is to ensure that fault current can be handed in the event of a fault. It would depend on where the fault was (which circuit/ocpd etc) to actually cause a real issue.

If it isn't potentially dangerous, why would it need to be upgraded before any work was done?

Not picking a fight BUT if it was this important why don't those who make the rules, make any attempt to educate the public. More often than not Joe Public thinks that the sparkie is trying it on with unnecessary work.

Joe Public would say his cables on his final ring have 1.5mm earth so what's wrong with his 6mm bonding.

 

[sid578]

many thanks guys .the ze was 0.11. just worked it out to 4.6 .. prob put as a c4 just to cover my self

 

[telectrix]

that's 4.62 for the main earthing conductor. you can divide that by 2 for bonding. for pme, though 10mm is specxified, so a C3, IMO. there's no code 4 now.

 

[Guest55]

In comment to telex and top quark i'd split the difference
C3 if undamaged and soundly connected , C2 if heat damaged and badly connected.
This is new diplomatic biff.
;-)

 

[telectrix]

agreed. but if clipped onto pipework with a rusty croc clip, i might go as far as a C1.

 

[Farmelectrics]

code 3 for me

 

[oldtimer]

Me thinks there has to be a bit flexability here and they realise this so say you go to a 25 yo installation in a flat the DNO fuse is 60A it is a TNS with 6mm to the water and gas and the customer wants a new CU fine but you aint going to rip the flat up to put 10mm in and when I moved into my house there was a bit of stranded 1.5 unsheathed wrapped around the main stop cock so me thinks we need to get real here as I think 10mm is fine for a 100A supply with 25mm tails.

 

[Engineer54]

25mm tails and a 16mm earth for a service supply of 60A?? Bit of an overkill to say the least!! ...lol!!!

 

[telectrix]

considering that i've had 16mm tails running at 95A for an hour and just managing to reach 40deg.C.