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Recommended checks before CU change

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Recommended checks before CU change

Posted by Fitzy71 on May 4, 2019 8:00 pm

As most of you know I’ve only been qualified for just over a year and I’ve got a quote to do for a cu upgrade.

I know I’m nowhere experienced enough to do EICR’s yet, but what would you guys recommend I check/test before doing the cu upgrade and should I do these checks/tests at the quote stage?

Re: Recommended checks before CU change

Posted by Chris Pearson on May 16, 2019 6:30 pm

Fitzy71:
This is with the main cover removed, then I removed the little grey cover from the centre switch to do my Ze.

And then?

Re: Recommended checks before CU change

Posted by Fitzy71 on May 16, 2019 6:49 pm

Then I forgot to put it back on when I was doing my rfc continuity tests to the circuits on the right of main switch and little finger brushed the live tail. 

The big big question now though is:

As the IR figures were really low (0.42mohms), do I quote not to get the job, quote to get the job and hope the IR is good after all or quite and include extra for the extra remedial work and if not needed, don’t charge?

As I need this job for my reassessment, I’m thinking quite with a few extra hours included for potential remedial works, or even bite the bullet and quote for just the cu replacement.

Luckily, I have a full time job, so by just doing any remedial work won’t actually lose me any money, just my time. 
 

Re: Recommended checks before CU change

Posted by Chris Pearson on May 16, 2019 9:04 pm

Fitzy71:
Then I forgot to put it back on when I was doing my rfc continuity tests to the circuits on the right of main switch and little finger brushed the live tail. 

That's why you should do dead tests before live tests!

Re: Recommended checks before CU change

Posted by Alan Capon on May 16, 2019 9:13 pm

Fitzy71:
. . . As the IR figures were really low (0.42mohms), do I quote not to get the job, quote to get the job and hope the IR is good after all or quite and include extra for the extra remedial work and if not needed, don’t charge? . . . 

The whole idea of the pre-tests is so that you can give your customer a reasonably accurate quote. Whether or not you choose to ignore / believe the figures you have is a business decision by you. What is your contingency for example if you do just a board change, then are unable to get the rcds to stay closed, so your customer is without light and / or power? 

Regards,

Alan. 

Re: Recommended checks before CU change

Posted by sparkiemike on May 16, 2019 9:33 pm

Fitzy71:
Then I forgot to put it back on when I was doing my rfc continuity tests to the circuits on the right of main switch and little finger brushed the live tail. 

Fitzy, hopefully you realise you made a mistake, this time you got lucky! There is a sequence for tests, had you followed them you it is quite likely you would not have put yourself in danger. For a quick refresher look at this https://youtu.be/Sc0tJGl4Oas

The big big question now though is:

As the IR figures were really low (0.42mohms), do I quote not to get the job, quote to get the job and hope the IR is good after all or quite and include extra for the extra remedial work and if not needed, don’t charge?

As I need this job for my reassessment, I’m thinking quite with a few extra hours included for potential remedial works, or even bite the bullet and quote for just the cu replacement.

Luckily, I have a full time job, so by just doing any remedial work won’t actually lose me any money, just my time. 

As as already been said, you need to make a business decision is it worthwhile for you do the repairs and what to charge. It could be a full rewire or simply fixing a nicked cable in a backbox. Had it been my job, I would have taken time to identify which circuit(s) was giving the low reading. Then I would have had a discussion with the customer about my recommendations and costs. This may not be the job for your reassessment?

Re: Recommended checks before CU change

Posted by Fitzy71 on May 17, 2019 6:55 pm

I’ve made a decision to quote this job competitively to try and win it, as I need the experience, plus it’s for my reassessment.  I can use it as a learning experience too.  I’ll factor in a few extra hours for any remedial works in the quote and if they’re not need I won’t charge for them. 

A couple more questions though:

Both gas & water were bonded albeit in 4/6mm², gas is a pretty easy job to replace as I can run the cable externally to the gas cupboard in the utility room, kitchen stop c*** on the other hand is a bit more difficult as the stop c*** backs on to the conservatory, but in the garage is a water pipe coming up through the concrete garage floor at the back and this is where the water has been bonded.  Would this water bonding be suitable for the whole water installation?

Are Lewden RCBO boards ok?  Found out today that the plumbcentre are selling both lewden & bg populated rcbo boards at brilliant prices.  

Do you have to use C type rcbo’s if there are fluorescent lights in use, or should you always use C type rcbo/mcb on lighting circuits?

 

Re: Recommended checks before CU change

Posted by Zoomup on May 17, 2019 8:10 pm

Is the incoming water pipe metal?

I have always found for domestic lights, even fluorescent types, a B6 M.C.B. is fine. I normally use B types of M.C.B.s for all circuits in a house, unless there is a big electric welder or similar load.

Z.

Re: Recommended checks before CU change

Posted by Fitzy71 on May 17, 2019 8:20 pm

Zoomup:
Is the incoming water pipe metal?

I have always found for domestic lights, even fluorescent types, a B6 M.C.B. is fine. I normally use B types of M.C.B.s for all circuits in a house, unless there is a big electric welder or similar load.

Z.

The pipe for this standpipe in the garage is copper tube, along with the stopcock supply under the sink, they don’t know where their water meter is either. 

Re: Recommended checks before CU change

Posted by Chris Pearson on May 17, 2019 11:13 pm

Fitzy71:
The pipe for this standpipe in the garage is copper tube, along with the stopcock supply under the sink, they don’t know where their water meter is either.

Some of us have never had a water meter.

Re: Recommended checks before CU change

Posted by geoffsd on May 18, 2019 12:57 am

Fitzy71:
kitchen stop c*** on the other hand is a bit more difficult as the stop c*** backs on to the conservatory, but in the garage is a water pipe coming up through the concrete garage floor at the back and this is where the water has been bonded.  Would this water bonding be suitable for the whole water installation?
 

 
Stop cocks are irrelevant.

The water supply pipe - if an extraneous-conductive-part which it will be as it comes out of the ground - should be (main) bonded where it enters the premises where practicable.

If it is the same pipe as the one in an attached garage (not clear from the description), then that would suffice..

 

Re: Recommended checks before CU change

Posted by Fitzy71 on May 18, 2019 5:05 pm

Sorry, only mentioned the stopcock (pipework above) as that’s were you bond the water 9 times out of 10.

i would assume the garage stand pipe is connected to the same house water supply, they said they do have a water meter, no idea were it is at the front of the property. 

Re: Recommended checks before CU change

Posted by Zoomup on May 18, 2019 5:58 pm

Fitzy71:
Sorry, only mentioned the stopcock (pipework above) as that’s were you bond the water 9 times out of 10.

i would assume the garage stand pipe is connected to the same house water supply, they said they do have a water meter, no idea were it is at the front of the property. 

Under a black circular cover in the pavement or drive perhaps.

Z.

Re: Recommended checks before CU change

Posted by AJJewsbury on May 18, 2019 6:53 pm

As the IR figures were really low (0.42mohms)

It's not that low - 20% higher and it would have actually have been acceptable under the 16th. That sort of value is quite normal where there's mineral insulation involved - e.g. traditional electric cooker heating elements or perhaps an immersion heater or two. Even if the elements aren't switched on at the time they'll still show on a N-PE test, and most likely on a L-PE test too if there's anything to bridge L to N - such as a timer or some other connected load.

The other common culprit for low IR is outside lighting or similar where water can get in.

The other gotcha for older installations is borrowed neutrals - especially on lighting. Lights were commonly wired in sheathed singles so N (and sometimes L) would be picked up from anywhere convenient rather than necessarily the correct circuit - landing light being fed from the downstairs lighting L (at the hall switch) but returning through the upstair's lighting's N was a common kludge - similarly wall lights (and occasionally outside lights) using a handy socket circuit for N.

  - Andy.

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