Consumer units -how do they work?

[TobyParticipant @toby]

Posted by Emgee on 08/01/2017 11:30:48:

Posted by Rick Kirkland 1 on 08/01/2017 09:49:29:
And before ANYBODY starts shouting about the onsite guide, that is ALL it is, , a guide. I look at certificates where the column asking for the " max Zs permitted under BS7671" is put down as one of the figures from a table in the onsite guide. TOTALLY WRONG.

Edited By Rick Kirkland 1 on 08/01/2017 09:51:16

Hi Rick

If the Zs table (A41.1to A41.6?) in the on-site guide is copied from and the same as that included in BS7671 why is it wrong to enter the Max Zs permitted for the cct by reference to a table of values ? provided of course the correct part of the table is selected for the type and rating of the protective device and maximum disconnection time for the cct.

The cct measured Zs value will be written in the relevant column in the test readings to check compliance.

Emgee

I have to admit I am not clear what Rick means, the on site guide tables are not the same as BS7671 as the on-site has a 0.8 correction factor to take into account conductor temperature. I wonder if he is referring to Cmin, I don't have the latest copy of the guide to check if that is now included in the tables.

Or maybe Rick is refering to circuits with RCDs where Zs can exceed this figures (but Zln should not….). Actually that is something that has always annoyed me, the certs (and hence what most people test) concentrates on Zs, completely ignoring that it still needs to work with a Line-Neutral fault.

EDIT: but yes, Rick's post above mine and Russell before that are right, I am also going to shut up now

Edited By Toby on 08/01/2017 12:00:05

[EmgeeParticipant @emgee]

Posted by Rick Kirkland 1 on 08/01/2017 11:44:36:
Toby. . I'm giving up now. You on the other hand could go on for ever answering comebacks from people with just enough dangerous knowledge in their possession to keep making comebacks. This is one of the reasons I've not (and many others that have made themselves known to me) have not posted here for a couple of years.I'm in no way painting everyone with the same brush, but the term 'babies playing with loaded guns" springs to mind.

Hi Rik

The solution to the problem you describe is to use the "Ignore member" button at the bottom of the posting, then you don't have to see any of the mainly misinformed rubbish the most prolific writer (on all subjects) keeps posting.

Emgee

[AjohnwParticipant @ajohnw51620]

Posted by Russell Eberhardt on 08/01/2017 11:40:24:

This thread is getting silly!

Russell.

They often do. In some ways it keeps the forum going. This sort of area can be more of a problem. The guide has getting on for 400 pages. Posts can only be so long. Best advice really is buy it and read it if it's of interest.

Frankly though I would be rather surprised if anyone reading threads like this here or anywhere else really thought that it would give them all of the information they need to do jobs like this. The other point of cause is that essentially what people can actually do themselves is severely limited. I would have thought every one was well aware of that.

John

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[Mark CParticipant @markc]

So that poses the question; Are you just typing things for the sake of an argument or are you actually doing the stuff?

Mark

[AjohnwParticipant @ajohnw51620]

Neither Mark. No aim concerning arguments here. I've already mentioned why I bought the guide. Current levels an deaths weren't based on starting any arguments just based on info I received from people who are specialists in that area. It really wouldn't be a good idea for people to assume that rcd's fully protect people. They wont.

John

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[Robin GrahamParticipant @robingraham42208]

Extractor now working fine. I really only needed to know if it was an over current or earth leak that was tripping the box. Armed with the info that it was an earth leak, I tracked it down to a live wire which must have been trapped between the entry box and the casing, perhaps when the previous owner had fiddled with it. Squashed, but no bare wire so probably a capacitative leak. Rewire without replacing components seems to have sorted it.

End of thread?

Rob.

Edited By Robin Graham on 09/01/2017 23:36:04

[David Standing 1Participant @davidstanding1]

Posted by Robin Graham on 09/01/2017 23:33:06:

Extractor now working fine. I really only needed to know if it was an over current or earth leak that was tripping the box. Armed with the info that it was an earth leak, I tracked it down to a live wire which must have been trapped between the entry box and the casing, perhaps when the previous owner had fiddled with it. Squashed, but no bare wire so probably a capacitative leak. Rewire without replacing components seems to have sorted it.

End of thread?

Rob.

Edited By Robin Graham on 09/01/2017 23:36:04

Well Rob, that's taken all the fun out of it! .

[TobyParticipant @toby]

Posted by David Standing 1 on 10/01/2017 01:44:58:

Posted by Robin Graham on 09/01/2017 23:33:06:

Extractor now working fine. I really only needed to know if it was an over current or earth leak that was tripping the box. Armed with the info that it was an earth leak, I tracked it down to a live wire which must have been trapped between the entry box and the casing, perhaps when the previous owner had fiddled with it. Squashed, but no bare wire so probably a capacitative leak. Rewire without replacing components seems to have sorted it.

End of thread?

Rob.

Edited By Robin Graham on 09/01/2017 23:36:04

Well Rob, that's taken all the fun out of it! .

but good news it was a easy fix

[Les Jones 1Participant @lesjones1]

One thing I have wondered is if it had been fed from an RCBO if there is a way of knowing if it was tripped by over current or earth leakage.

Les.

[EmgeeParticipant @emgee]

Les, the 40Mohms resistance reading motor case to live conductor (with an ohmeter) it would have been interesting to see the test result with a 500v insulation tester.

Emgee

[TobyParticipant @toby]

Posted by Les Jones 1 on 10/01/2017 08:43:33:

One thing I have wondered is if it had been fed from an RCBO if there is a way of knowing if it was tripped by over current or earth leakage.

Les.

Not easily. You would have to test the circuit/equipment to find the fault. The other disadvantage of RCBOs is they are single pole (mostly in the uk domestic market anyway) so will not interrupt a neutral to earth leakage. Depends on what is energising the neutral of course.

[Les Jones 1Participant @lesjones1]

Thanks Toby for your quick reply. That was my own view. I was thinking of a situation with an intermitant fault were any clue is a great help. It is like trying to get the OP on threads like this to tell us if it is an MCB or RCD that tripped when all they say is that it tripped the power.

Les.

[David Standing 1Participant @davidstanding1]

Posted by Toby on 10/01/2017 07:46:21:

Posted by David Standing 1 on 10/01/2017 01:44:58:

Posted by Robin Graham on 09/01/2017 23:33:06:

Extractor now working fine. I really only needed to know if it was an over current or earth leak that was tripping the box. Armed with the info that it was an earth leak, I tracked it down to a live wire which must have been trapped between the entry box and the casing, perhaps when the previous owner had fiddled with it. Squashed, but no bare wire so probably a capacitative leak. Rewire without replacing components seems to have sorted it.

End of thread?

Rob.

Edited By Robin Graham on 09/01/2017 23:36:04

Well Rob, that's taken all the fun out of it! .

but good news it was a easy fix

Indeed .

[EmgeeParticipant @emgee]

post deleted
 

Edited By Emgee on 10/01/2017 15:32:55

Edited By Emgee on 10/01/2017 15:33:31

[TobyParticipant @toby]

post deleted as Emgee deleted his post that I was replying to…..

Edited By Toby on 10/01/2017 15:38:12

Edited By Toby on 10/01/2017 15:38:25

[TobyParticipant @toby]

Posted by Les Jones 1 on 10/01/2017 10:21:59:

Thanks Toby for your quick reply. That was my own view. I was thinking of a situation with an intermitant fault were any clue is a great help. It is like trying to get the OP on threads like this to tell us if it is an MCB or RCD that tripped when all they say is that it tripped the power.

Les.

yes indeed, in this case having a separate MCB and RCD was helpful, although he might not have thought so when the RCD took out all the other circuits connected to it

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