Mismatched MCBs C2 or C3?

[Jurassicspark]

Londoners warned of potential fire hazard lurking under the stairs

Londoners warned of potential fire hazard lurking under the stairs

www.london-fire.gov.uk

I wonder why the cause of fires started to increase gradually and after 2012 the numbers significantly increased.

 

[JohnW2]

Try these

Thanks - but in that case your reply to EFLI should have been "No mate" (rather than "Yes mate"), shouldn't it, since if one changed a device to a non-approved one, then one has to repeat the 'type testing'.

Unless I misunderstand, EFLI is suggesting that if one CU tests satisfactorily whilst containing"Device X", that device therefore should be OK in any CU, without any further testing - which is not what you and I believe (in terms of standards/'rules' etc.)

 

[ericmark]

However, as I've said, despite often asking, I have yet to come across anyone who has seen a problem which was probably due to a (satisfactorily fitting and 'properly installed') device being of the 'wrong brand'.

The 'satisfactorily' is the main point, some clamp down on the bus bar, and some up, and I have seen where the bus bar tag went the wrong side of the clamp, so connection only by light pressure. However, seen this where the proper MCB was used as well as with wrong one. As to 'properly installed' it can't be properly installed if not type tested to fit that consumer unit.

There is of course the point DIN is a German standard, so if a device uses DIN rail, can any device designed to fit on DIN rail be wrong? We know it is because the terminals don't always match, and the cut-out for operation don't always match.

But the EICR does not any longer have a code "does not comply with current edition" code 4 was removed. We are looking for danger and potential danger, the latter is a bit stupid, as 230 volts is always potentially dangerous, but some MCB's are identical other than the name on the device, so we can't say in all cases it is C2, as clearly there are times when it's not, but there are also times when it is, so people who do EICR need to be trained to use their judgement as to which it is.

Since in a distribution unit, the devices do not need to be on the type list, in fact in a non-domestic there is nothing to stop me making my own units, which I have done many times, with PLC's, contactors, and overloads all in the same box, the question only arises with domestic, and I fail to see how something allowed in commercial becomes potentially dangerous when used in a domestic environment. There was a plastic cover over much seen, to allow the door to be opened to program the PLC, however I got a rap on hand from HSE for leaving the key in a door, he said the key could be used with any other door, so must be removed.

So if using the wrong make of MCB results in a potential danger, yes code C2, but it is not an automatic thing, there must be a potential danger, and that is a personal decision, not one made by a committee.

If the device fitted is not on the list, then the enclosure is no longer a consumer unit, it is only a distrubution unit, I have not found the rule to say domestic installations must use a consumer unit, since a CU has a max of 125 amp and single phase, to have a rule saying must be a CU would cause some problems with larger homes, and EV charging etc.

 

[JohnW2]

I wonder why the cause of fires started to increase gradually and after 2012 the numbers significantly increased.

Quite so - and the claimed "five-fold" increase in house fires allegedly originating in CUs between 2009 and 2014 makes absolutely no sense, does it? The only interpretation that makes any sense to me is that over those 5 years, the LFB for whatever reason became 5 times more likely to claim that a fire started in a CU!

There is also the more general point thgat it seems that 'electrical origin' may have become (maybe increasingly, hence some of these figures?) a 'scape goat' when LFB can't determine any other cause of a fire!

That article is, of course, a prelude to the (in my view pretty crazy) introduction of the requirement for 'non-combustible' CUs which was seemingly forced upon BS7671 by the LFB. OK,it's 'just me', but I personally regard the change as not only potentially dangerous but also plain daft in how it has been implemented in BS7671 - quite apart from all the debate about 'non-combustible', there is absolutely no requirement for 'fire containment' - a CU would today e it acceptable to BS7671 if it were covered on front, sides and bottom in half-inch diameter holes, provided only that what little material was left was 'non-combustible'

 

[JohnW2]

If the device fitted is not on the list, then the enclosure is no longer a consumer unit, it is only a distrubution unit, I have not found the rule to say domestic installations must use a consumer unit ...

I made that point early on since, like you, I cannot think of anything in BS7671 that says that domestic premises must have a CU (as opposed to a DB). However, Bazza then brought our attention to 536.4.203 of BS7671 which addresses the issue of non-approved devices in both CUs and DBs.

.... since a CU has a max of 125 amp and single phase, to have a rule saying must be a CU would cause some problems with larger homes, and EV charging etc.

As above, that's rather moot, given 536.4.203. IN any event, there are workarounds. Although I don't have EV charging, I have a very big house, but multiple CUs. Whilst it is literally true that the supply to the house is 3-phase, the three pahses are used separately, so each CU is only single-phase, hence probably does qualify as a 'CU'!

 

[JohnW2]

Yes, but if my theory is correct there will be no adverse effect.

You're almost certainly right - but you could only be certain if you undertook the entire battery of 'type testing tests' on a CU of a different brand it which you had installed the device (to confirm that there was no 'adverse effect') - but no installer is going to do that.

 

[Deleted member 142255]

You're almost certainly right - but you could only be certain if you undertook the entire battery of 'type testing tests' on a CU of a different brand it which you had installed the device (to confirm that there was no 'adverse effect') - but no installer is going to do that.

Correct. As I said, an individual or small business wouldn't have the knowledge and resources to carry out the tests or the finances to employ a test house.

I have taken part in compliance testing and it isn't straightforward.

 

[EFLImpudence]

Correct. As I said, an individual or small business wouldn't have the knowledge and resources to carry out the tests or the finances to employ a test house.

They wouldn't need any such knowledge if it was stated that all makes are subject to the same criteria when tested.
How can they not be?

I have taken part in compliance testing and it isn't straightforward.

Compliance with what?

 

[Deleted member 142255]

They wouldn't need any such knowledge if it was stated that all makes are subject to the same criteria when tested.
How can they not be?

All makes are subject to testing in their own units, not as a general any unit.

Compliance with what?

EMC Regulations. We built a machine for the Atomic Weapons Establishment in Aldermaston and had to certify for EMC emmissions.

 

[JohnW2]

They wouldn't need any such knowledge if it was stated that all makes are subject to the same criteria when tested.
How can they not be?

I'm not sure whether it's deliberate or not, but you seem to be repeatedly missing/overlooking the point I have made several times ....

... the devices are not tested 'in isolation', nor even in some sort of 'generic enclosure', but in the specific enclosure (accompanied by other specific devices) in which their use is to be approved.

You, I and lots of other people may regard it as fairly 'far fetched' but there are clearly some people who believe that a device may behave differently (hence with different test results) in different enclosures and/or in the company of other devices.

I've been trying to think of analogies to help you understand, but I have yet to think of any others which are anythiung like as apparently 'silly' than this one appears (to me) to be.

 

[ebee]

Again, that's the question I keep asking. We know that, laws or no laws, manufacturers will only supply CUs/DBs populated with their own (tested and approved) devices, and undoubtedly would still do that even if there were not laws stopping them selling it in the UK if they didn't. As you and I (but not necessarily everyone) understand, thge whole discussion relates to the situatioin when which someone puts a 'non-approved' device in it after it has been (legally) sold by the manufacturer.

You may not want to answer, but .... have you never 'done it'?

Yes I have never done it, I have never had the need to.
If an emergency repair such as Bazza mentioned, presented itself then I would make the judgement call on a temporary basis and mitigate as far as I could, example siting one as far as possible from the correct ones and making sure the busbar is exactly the same dimension or can be fitted with no extra strain on the existing. I would only do it for an emergency not purely to make life easier.

 

[ebee]

I will not argue with that one but what makes you or I or anyone else fitting any old make of MCB into any make of consumer unit and what law prevents it?.

Integrity!

Hah, the Law of Integrity!

 

[EFLImpudence]

I'm not sure whether it's deliberate or not, but you seem to be repeatedly missing/overlooking the point I have made several times

I don't agree with it.

... the devices are not tested 'in isolation', nor even in some sort of 'generic enclosure', but in the specific enclosure (accompanied by other specific devices) in which their use is to be approved.

...but if they are all tested to same criteria...
Is the enclosure not tested as well?

You, I and lots of other people may regard it as fairly 'far fetched' but there are clearly some people who believe that a device may behave differently (hence with different test results) in different enclosures and/or in the company of other devices.

Not if they are all tested to the same criteria.

For example are we thinking that Wylex MCB will melt when next to a Hager MCB at 60º (or whatever) but not when next to a Wylex MCB at the same temperature?

I've been trying to think of analogies to help you understand, but I have yet to think of any others which are anythiung like as apparently 'silly' than this one appears (to me) to be.

Likewise.

 

[JohnW2]

Yes I have never done it, I have never had the need to.

Fair enough - but, as I wrote, I certainly know some electricians who would answer differently (if they were being truthful )

 

[JohnW2]

...but if they are all tested to same criteria...

You keep saying that, but they are not - because ....

Is the enclosure not tested as well?

The device is tested when in a particular enclosure - i.e. the test is how device A is housed in enclosure B

Not if they are all tested to the same criteria.

See above - the devices are not being tested in isolation - what is being tested is "device+enclosure+other devices".

For example are we thinking that Wylex MCB will melt when next to a Hager MCB at 60º (or whatever) but not when next to a Wylex MCB at the same temperature?

Well, as I've said, I personally find the proposition far-fetched but, yes, my understanding is that some people believe that such 'is not impossible', hence the requirement to test the device in precisely the 'approved environment' (i.e. enclusre and other devices.

However,as I wrote yesterday, I personally feel not only is it all pretty 'far fetched', but I strongly suspect that it is also 'flawed', since I doubt that, even if all the devices are 'theirs' (i.e. the same as the enclosure) the will undertake a full set of tests for every possible ordering of the devices and, for each ordering, a wide range iof load condityions for each and every device.

However, a lot of official bodies and organisations seem to have 'bought into' this thinking - so who am I to criticise?