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Topic Title: Test Cert ?
Topic Summary: Meter & board install ?
Created On: 11 January 2015 06:06 PM
Status: Read Only
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 13 January 2015 12:08 PM
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Posts: 996
Joined: 23 November 2006

Sorry all, I had to bring this one back to the top of the pile, as I don't think anybody has actually helped Ampman yet

I for one, empathise with Ampman keenly.

I think everyone on here can understand him.

We all know what we are supposed to do, and if we're with a governing body (as I am), we probably do do.
If the electrician is employed in a big company, he probably don't do - because that's someone else's job. (I know it shouldn't be but that's the reality I think)

I'd suggest in Ampmans case, he do the following as a minimum:


IR - of the whole DB or identify the circuit(s) that do not comply and recommend remedial action.
Best to check each circuit IR before termination though.

Zs of each circuit at one point (This will confirm that you have reconnected earth, Neutral and live correctly at the DB) I would not recheck every point on the whole circuit, unless given good reason to do so.

Check the size of cables and the MCB that supply them seem to correspond (don't worry about volt drop for example)

Identify the supply that is supplying your new tails and ensure your new tails are sized correctly

Issue a certificate with the above details on it - use the box wisely that says "extent of the installation covered by this certificate" and hightlight that you are reconnecting existing circuits without addition or alteration. Use the LIM or N/A those bits that you don't know or cannot answer. (I'm sure to get some grief for that statement) EG: (R1+R2) or R2 - IMO Zs will suffice for this certificate. I wouldn't even try to subtract Ze to come up with a stupid figure for R1+R2.

If, in ampmans scenario if there is a low IR on a circuit with who knows how many old florry lights running through the basement of an office block in Oxford street - is it the circuit or the lights that are at fault? If they have old wire wound ballasts on them - it's very likely to be the lights themselves (as opposed to the circuit conductors). Is there a light hiding in some basement storeroom that has been lost under some stairs or at the back of the switch room?

The point being that fault finding can be very onerous. If you were to allow for 2 hours fault finding for every circuit you moved, you would probably find that you will soon price your self out of a job.

I know I've been in Ampmans shoes - I dont want to find faults that are related to other work - on old florescent lights especially.

I think I can understand why he asked the question. He knows he has to do the testing I'm sure, he's just trying to find out why and ask on here to see what everyone else does.

I'll bet almost anything that nine tenths of electricians under the same scenario, on a commercial install, would not do the testing and would not issue a certificate unless the facilities management pressed them for it.

You've been given a little bit of a hard time Ampman. Take it as good advice, because I think we all understand.
You still have to test the circuits though, sorry.

 13 January 2015 12:38 PM
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Posts: 16202
Joined: 13 August 2003

I might even be tempted to do a few tests before dismantling the old - in order to have something to compare with the new results. E.g. if an insulation test shows 0.7 Meg both before & after then you've got some pretty good evidence that you've not introduced a fault on that score. (OK, there's a theoretical possibility that your work does have a fault and it happens to exhibit exactly the same resistance as an original fault that you've eliminated - but I think the likelihood of that is so small that it can be totally ignored).
- Andy.
IET » Wiring and the regulations » Test Cert ?

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