old water main protective bond -

[pushrod]

Was a water MPB ever allowed to be incorporated onto a cpc? I found a 10mm water bond connected to a nearby 10mm cpc single that was serving a dedicated cooker circuit in a small purpose built flat from 1960s approx. Oven is only 2kW. Was just wondering if it was ever a recognised way of doing things. cheers

 

[Deleted member 9648]

Perhaps it was the main earth at the time...rather than a bond?

 

[pushrod]

Main earth now seems to be what looks like 6mm aluminium disappearing behind a wooden board with a copper 10mm just twisted onto it. Didn't investigate it properly but somewhere there is a pretty effective earth as a couple Zs figure were very low. lol

 

[Knobhead]

Before the 60’s separate earths to sockets weren’t uncommon. It could be a hangover from then.
My first house had a collection of 6” long “earth spikes” each connected to a separate socket with bare 3/.029’s. First job was to throw the lot out.
Don’t forget it was perfectly normal to use water and gas services as the only earth.

 

[johnboy6083]

its still permitted to use extraneous metalwork as CPC. So in other words in an industrial situation with steel everywhere, you could completely do away with conventional CPC's. Obviously certain conditions need to be met, but not difficult.

 

[Engineer54]

It was a long time before i came into the industry that water and gas services were allowed to be your sole means of earthing to a property. What you may be finding, is examples of those bygone years. Far more likely your seeing unauthorised connections to service pipework!! ...lol!! It's still allowed on privately derived water systems, if they meet the criteria....

Supplementary bonding has never been a problem to incorporate but again, not as your sole means of earthing. Structural steelwork also can't be your CPC, it can however be your bonding conductor connection to equipment etc. All normal circuits need to incorporate a CPC from the installations MET/MET be it a TT, TN-S, TNC-S earthing system. That has been the rule from early 13th edition Reg's, where a CPC has been required. (not required on lighting circuits till late 13th early 14th ed Regs, late 50's ish lol!!)

 

[telectrix]

(not required on lighting circuits till late 13th early 14th ed Regs, late 50's ish lol!!)

bit later than that, mate. 70's.

 

[needasparks]

Totally Agree with the above comments, very common to find a socket bonded to the lead water pipe then that circuit would backfeed the board. each earth would then be twisted together in a linetap or similar conector. The guy i trained with used to wire them in the late 50's like that. This formed the main earthing to the house.

 

[Engineer54]

(not required on lighting circuits till late 13th early 14th ed Regs, late 50's ish lol!!)

bit later than that, mate. 70's.

Are you sure?? As the council estates in my old area of UK started off with no CPC in the lighting circuits, but by the time the estates were completed, they were incorporating CPC's in the lighting circuits.
And the last ones were around the late 50's early 60's era, certainly not as late as the 70's when i came into the industry.

 

[johnboy6083]

See 543.2.1 (vii) and 543.2.6

What is considered common practice is often different to what is allowed according to BS 7671

 

[Engineer54]

See 543.2.1 (vii) and 543.2.6

What is considered common practice is often different to what is allowed according to BS 7671

I don't have the Reg's with me right now, so what does it say??

 

[needasparks]

I thought cpc's on lighting never came in till 72, although it was being installed 2yrs before.

 

[Knobhead]

1973 was the first rewire I did, my own house. Lighting CPC’s in there then. My house was the only one on the road that didn’t have the water and gas as the only earthing method, all TT supplies.

 

[Engineer54]

All i can say, is that those council houses that were completed at the very latest early 60's had lighting earthing conductors. Though i'm not totally sure, they were still using the black TRS T&E too. So when did they start using PVC T&E, as i was in the industrial side of things in those early years, where you never saw T&E in any form...lol!!

But i certainly saw these T&E lighting circuits while helping my uncle in his local electrical business before i even started my training years.... so somewhere along the line there's a bit of discrepancy in when we saw CPC's being used in lighting circuits...lol!!!

 

[johnboy6083]

The regs I was referring to basically say that extraneous metalwork can be used as CPC, as long as it is an equivelant CSA to cu, it's not under stress, it's it an oil or gas pipe, and precautions are taken against its removal.