Temp Continuity bonding for non electricians...

[dooper]

OK i kick started a discussion on this over on the plumbing forum but i guess this is the best [place to get the expert view.

I work in the gas industry and i get the feeling that a lot of stuff is trotted out which might be slightly inaccurate/not fully understood.

Electricians may know that when disturbing any metallic fittings or cutting through pipe/doing alternations, it is a requirement to fit a temporary continuity bond to bridge the gap. You then do the work and remove the bond.

My understanding is that the temp bond performs two functions..
a)With Gas,it prevents the possibility of spark and subsequent ignition of gas left in pipe..a remote possibility
b)it maintains an equipotential zone in the working area.

Am i right?

So,picture this...person fits temp bond and cuts into pipework. One side runs back to gas meter to which there is fitted a mains earth bonding cable. The other side goes under the floor and round the house somewhere.

The bit that comes from the gas meter is to be extended and re routed elsewhere.

The other bit is to be abandoned but just left in the structure of the house because it is too difficjult to remove.

So work done..we then remove the temp bond.

Have we created a hazard because surely the abandoned pipe is no longer earthed?

Ta

 

[telectrix]

no, because the abandoned pipe is no longer an extraneous conductive part. it cannot introduce an earth potential into the building.

 

[dooper]

no, because the abandoned pipe is no longer an extraneous conductive part. it cannot introduce an earth potential into the building.

I was thinking that at some time in future it could become live by some means or other,eg accident/interference damage to a cable etc and then presumably there might be no protection mechanism??

 

[telectrix]

it is a false belief that everything metal has to be earthed. it's exposed metal that is likely to be at earth potential that must be earthed. the test would be to use an insulation tester ( megger ) and test between the old pipe and the main earth terminal. if the reading is above 22kohms, then it should not be earthed.

 

[IQ Electrical]

it is a false belief that everything metal has to be earthed. it's exposed metal that is likely to be at earth potential that must be earthed. the test would be to use an insulation tester ( megger ) and test between the old pipe and the main earth terminal. if the reading is above 22kohms, then it should not be earthed.

Bonded

How many times do you hear guys saying "you should just bond it, it's good practice" but by distributed fault voltages atc. you are actually introducing danger into the installation by bonding non-extraneous conductive parts.

The test that Telectrix describes is spot on to determine bonding requirements.

I'd make Guidance Note 8 compulsory for scheme membership.

 

[dooper]

OK so put simply, if its an orphaned section of pipe which isnt at earth potential then there is no need to bond.

I guess that as you say,the only way to check if it is at earth potential or close is to measure,something which is outside the remit/skillset of plumbers etc.

I guess the answer is that the plumber wouldnt know whether or not it was at or close to earth potential...in fact it wouldnt even be on his radar.

I know that for example, if someone permanently removes a gas meter,and lets say there is a metallic incoming gas service,they are required to either bond from the installation to the incoming service..or more likely since they are not electrically qualified, fit an insulation sleeve to the metallic service so that it isnt possible to contact it.

 

[SPARTYKUS]

Bonded

How many times do you hear guys saying "you should just bond it, it's good practice" but by distributed fault voltages atc. you are actually introducing danger into the installation by bonding non-extraneous conductive parts.

The test that Telectrix describes is spot on to determine bonding requirements.

I'd make Guidance Note 8 compulsory for scheme membership.

LOVE it

 

[telectrix]

Bonded

How many times do you hear guys saying "you should just bond it, it's good practice" but by distributed fault voltages atc. you are actually introducing danger into the installation by bonding non-extraneous conductive parts.

The test that Telectrix describes is spot on to determine bonding requirements.

I'd make Guidance Note 8 compulsory for scheme membership.

sorry IQ, i used the incorrect term thinking it would be easier for him to take on board. bit like saying twin and earth, instead of twin and cpc.LOL.

 

[millwall ken]

sorry IQ, i used the incorrect term thinking it would be easier for him to take on board. bit like saying twin and earth, instead of twin and cpc.LOL.

F***s sake Tel, don't beat yaself up over it mate.

 

[telectrix]

F***s sake Tel, don't beat yaself up over it mate.

i'm not, mate. no worries. plenty of beer in stock. just about to sample an OWD Rodger. mmmmm.

 

[Geordie Spark]

I suppose you could make up a temporary earth bond kit out of 10mm ( a bit like a wander lead made off onto earth bond clamps at both ends) which you could coil up or wind onto a suitable reel which you keep in the van for when you need it. It would encourage safe practice if you have it with you at all times on site........

We should have these things with us at all times as they are part of our standard kit - along with a manometer & can of leak detecting fluid.

They are usually a length of 10mm green/yellow - about 2 metres long - with a big croc clip on each end and are readily available at most of the plumbing suppliers.

 

[sparc]

What are the chances .... ?

I read telectrix comment about 22Kohms thinking ... I've seen that before on the forum but never met it in the regs. Then I remember I bought myself a copy of GN8 the other week, opened it up randomly - page 57 - there it is "Rcp is above the threshold of 22 KOhms ... etc" - right at the top page 57. I wish it were always that easy!

BTW, don't make my mistake with GN8 - not checking the edition before clicking 'buy' on Amazon (£22). It's still BS7671: 2001, with amendments to 2004. I should have waited until they updated it.