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Installing a new 32a circuit for cooker


 
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rizla01

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Location: London,
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PostPosted: Wed Mar 20, 2013 9:52 pm Reply with quote

Hi,

Can someone tell me if a leccy is meant to test a 6mm 30a circuit before connecting and if so what tests should have been carried out?

Installation was a 32a RCD, 6mm run of cable (4Mtrs) to isolater switch, then connection to outlet and then to cooker.
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ricicle

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PostPosted: Wed Mar 20, 2013 10:13 pm Reply with quote

If it was a new circuit then you should have received an EIC which will include test results as well as a schedule of inspection. Also signature responsibility for design and construction
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rizla01 (20 Mar 2013)
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rizla01

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PostPosted: Wed Mar 20, 2013 10:25 pm Reply with quote

Leccy has't finished the job yet as he has a mains circuit to extend for the kitchen.

Just that I watched the whole install of the 30a circuit right through to connecting the cooker which was then switched on. That was that.

Perhaps he has done so many and as it was all new wiring, he didn't feel the need to test anything.

Can you tell me (So that I sound like I know what I am talking about) just what tests should be done on the extended ring main?

I realise that I will get a certificate but I would like to know and it doesn't feel right asking him.
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Taylortwocities

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PostPosted: Wed Mar 20, 2013 11:55 pm Reply with quote

Table 8.5 - Correct sequence for safe testing
BEFORE CONNECTION OF THE SUPPLY
1 Continuity of protective conductors
2 Main and supplementary bonding continuity
3 Continuity of ring final circuit conductors
4 Insulation resistance
5 Connect ring in 'figure of 8' configuration and carry out R1+R2 measurements at CU and at every socket outlet
6 Polarity

WITH THE SUPPLY CONNECTED
7 Confirm correct polarity
8 Earth-fault loop impedance
9 Correct operation of residual current devices
10 Correct operation of switches and isolators / functional testing

There may be other tests needed, depending on the supply type.
The results of the above tests will be recorded on the Installation Certificate
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rizla01 (21 Mar 2013)
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ericmark

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PostPosted: Thu Mar 21, 2013 2:44 am Reply with quote

What Taylortwocities says is correct but it is quite common to miss some tests out however to be able to fill in the paperwork he will need to use a loop impedance meter.

Some firms don't provide all their electricians with the test gear and have an electrician who calls in at each site and does inspection and testing.

Fudging up results for the paperwork can really cause problems latter on. What we should do is before testing look at previous test results and then compare with new results to see if the circuit is degrading.

The RCD should also be tested with a special meter which not only tests that it works but measures the time it takes to work which should in most cases be under 40ms.

Maybe you should ask him if he can show you what a loop impedance tester looks like as you have heard about them but never seen one. Then see what he says?
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rizla01 (21 Mar 2013)
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rizla01

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PostPosted: Thu Mar 21, 2013 11:37 am Reply with quote

Thanks all, for the advice and info. Good to know what I am paying for and to know what to look out for.


Last edited by rizla01 on Fri Mar 22, 2013 11:29 am, edited 1 time in total
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rizla01

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PostPosted: Fri Mar 22, 2013 11:27 am Reply with quote



Just as an aside, do many installations actually fail? (Poor cable, insulation, Sockets, Etc) on a new install?

Al that testing seems to be overkill when compared to days of yore when it wasn't done.

I agree entirely with the correct routing of cables, earthing Etc etc but how necessary is all the rest, in true reality?

NOT asking for a lecture here, just inquisitive. icon_smile.gif


Anyone?
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EFLImpudence

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PostPosted: Fri Mar 22, 2013 11:36 am Reply with quote

rizla01 wrote:
Just as an aside, do many installations actually fail? (Poor cable, insulation, Sockets, Etc) on a new install?

They may not 'fail' but it shows up mistakes or that none has been made.
Quote:
Al that testing seems to be overkill when compared to days of yore when it wasn't done.

Perhaps it is for one cable.
Quote:
I agree entirely with the correct routing of cables, earthing Etc etc but how necessary is all the rest, in true reality?

So which test(s) would you omit?

If testing is not done, you wouldn't know it didn't really need doing, would you?
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rizla01

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PostPosted: Fri Mar 22, 2013 11:46 am Reply with quote

So would you say that the majority of these tests are checking human error more than product failure?
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EFLImpudence

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PostPosted: Fri Mar 22, 2013 12:04 pm Reply with quote

rizla01 wrote:
So would you say that the majority of these tests are checking human error more than product failure?

Not the majority - no. Some are both.

The list may look daunting (I don't know your experience) but they don't take long to do.
It's good to know that all is well and you haven't made a mistake.

I ask again, which would you omit?
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rizla01

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PostPosted: Fri Mar 22, 2013 12:19 pm Reply with quote

Well, I would have thought a lot of the faults tested for would show themselves up pretty quick (Blue flash, Smoke, CU tripping) but I am sure that a few could show up only under certain , fairly unlikely, conditions, but that they have to be tested for regardless

Not being a Leccy I wouldn't know quite which ones.
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EFLImpudence

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PostPosted: Fri Mar 22, 2013 12:32 pm Reply with quote

Ah, but that's the point.

Blue smoke, flashing and cu tripping are not a good way to test and are to be avoided.

By testing with a meter before energising these events can be predicted and prevented.

Wires melting and the need to redo the circuit are not desirable so a quick test will show that it won't happen.
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rizla01

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PostPosted: Fri Mar 22, 2013 2:16 pm Reply with quote

But my point is that once connected and switched on. assuming there are no obvious faults showing within 2 mins, the likelyhood of any faults are extremely thin, surely.

The only checks that are likely to be needed in most cases are earth faults and rev polarity checks Etc - both of which may not show immediately but that a basic test rig (Mains socket tester) would show up.

Other than these easily noticeable faults, other failings would surely be almost unheard of.
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EFLImpudence

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PostPosted: Fri Mar 22, 2013 2:55 pm Reply with quote

rizla01 wrote:
But my point is that once connected and switched on. assuming there are no obvious faults showing within 2 mins, the likelyhood of any faults are extremely thin, surely.

But my point is that switching on and waiting two minutes to see if anything goes BANG or melts is not a good way to verify the safety of electrical circuits.

Quote:
The only checks that are likely to be needed in most cases are earth faults and rev polarity checks Etc

But that is what should be done.
How many other of the tests do you include in 'etc.'.

Quote:
both of which may not show immediately but that a basic test rig (Mains socket tester) would show up.

Socket testers are used when the circuit is energised so it may be too late and they cannot distinguish between Neutral and Earth so earth faults and reversed N and E would not be noticed.
That is why tests are done prior to energising with something that can?
Nor can socket testers be used at a cooker connection point.

Also, your original post seemed to be complaining that the electrician had not carried out any tests which he should have done.
Perhaps he 'just knew' everything was alright.

Quote:
Other than these easily noticeable faults, other failings would surely be almost unheard of.

But they are not easily noticeable and would not affect the operation of an appliance.
Yet when something goes wrong they would be dangerous.
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rizla01 (22 Mar 2013)
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