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Topic Title: Home made DBs Topic Summary: Created On: 15 January 2013 06:14 PM Status: Post and Reply |
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 15 January 2013 06:14 PM
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Do you have any views on the subject of Distribution Boards which are made up of component parts assembled as a distribution board?
I have some reservations because they will not have been type tested or approved. I am also not dead keen on mixing brands in a board and most of these have MK main switches and some other brand of breaker. Some have contactors and timers built in. I have been to four commercial installations in the past 18 months with these. I expect it is normal practice in other parts of Europe and the practice is migrating to here. I have had one covered in because of exposed conductive parts but most of them do have some kind of cover made up for them. I can do you an avatar change to show you one if need be, but it'd take a bit of doing as I'd have to crop out the installer's name which is in shot on a sticker. I think you probably know what I mean anyway. What's the risk? Zs ------------------------- 'The desk is a dangerous place from which to view the world.' John Le Carre |
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15 January 2013 06:24 PM
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They may well not be capable of accepting without damage any earth fault they are exposed to
Ditto for short circuit conditions IP ratings will be suspect - access to live parts may be readily achieved They are probably not in accordance with any manufacturing standard - so thier selection and erection will be suspect in terms of BS 7671 and specifically 134.1 They may well provide case temperatures that are excessive resulting in a fire or burns risk They may well not contain products of combustion resulting from overheating or fault conditions They probably won't meet any design specification There will be no type testing or partial type testing of the assembly They will probably have insufficient markings including a CE mark The colour will probably be horrible - 
I think I can picture what you mean but any chance of a bit more description - does the installer start with a metal box that is in fact a DB and then assemble his own busbars, din rails, mcb's , switches etc as an ad hoc collection of parts ? Regards OMS ------------------------- Failure is always an option |
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15 January 2013 06:38 PM
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What about a bespoke control panel? A box full of MCBs or fuses with some contactors. This is an example of a home made DB.
------------------------- Regards Dave(not Cockburn) |
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15 January 2013 06:44 PM
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@OMS,
Lol, as someone who disdains the regimentally insane your last post now appears to be supporting them. I have seen several 'home made' assemblies made for specific industries. In each case, i doubt that they would have CE markings on them. But that doesn't mean they haven't been built to a professional standard and most likely over engineered Legh ------------------------- Why do we need Vernier Calipers when we have container ships? http://www.leghrichardson.co.uk "Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections." |
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15 January 2013 06:50 PM
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What about a bespoke control panel? A box full of MCBs or fuses with some contactors. This is an example of a home made DB. Isn't that a manufactured assembly built to a product standard ? - will it usually contain equipment that is type tested and have an enclosure that is type tested along with internal distribution that is type tested, to form as a minimum a partially type tested panel ? Regards OMS ------------------------- Failure is always an option |
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15 January 2013 06:55 PM
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@OMS, Lol, as someone who disdains the regimentally insane your last post now appears to be supporting them. I have seen several 'home made' assemblies made for specific industries. In each case, i doubt that they would have CE markings on them. But that doesn't mean they haven't been built to a professional standard and most likely over engineered Legh Really Legh - I suspect we are talking about radically different approaches in the design and manufacture of bespoke switchgear to that described by Zs - which is why I guess concerns have been raised Home made and bespoke suggest different things to me I guess. I've designed plenty of bespoke switchgear, MCC's and control panels in a previous life - the ones I've seen that weren't put together by competent manufacturers working to a variety of directives and standards are pretty shocking to say the least. Regards OMS ------------------------- Failure is always an option |
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15 January 2013 06:58 PM
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They may well not be capable of accepting without damage any earth fault they are exposed to Any sensible way I can prove that? Ditto for short circuit conditions and Ditto can I prove that? IP ratings will be suspect - access to live parts may be readily achieved I agree hugely. Hence demanding action on one of them. However, they are usually very well enclosed They are probably not in accordance with any manufacturing standard - so thier selection and erection will be suspect in terms of BS 7671 and specifically 134.1 That may be the nub of it OMS, the component parts are in accordance with manufacturing standards though. They may well provide case temperatures that are excessive resulting in a fire or burns risk Ok, they are not running hot. Where do I go to begin proving case temperatures. I can prove actual cable operating temperatures but presumably you are taling about an aggregate and the introduction of other factors? They may well not contain products of combustion resulting from overheating or fault conditions Likewise, all the component parts are respectable, so does the whole have to be considered separately? They probably won't meet any design specification What is a design specification?
There will be no type testing or partial type testing of the assembly That'll be an insurance related issue then? They will probably have insufficient markings including a CE mark But all the parts are respectable and approved The colour will probably be horrible -
Not too bad when closed, just white boxes. I think I can picture what you mean but any chance of a bit more description - does the installer start with a metal box that is in fact a DB and then assemble his own busbars, din rails, mcb's , switches etc as an ad hoc collection of parts ? They seem to buy an empty steel locking case from schneider and a slection of Din rails and Bus bars. RSA components and Maplin I imagine. Then they buy the main switch and all the breakers. I have not taken one apart but intend to do so when I can. As extra information, I'm alarmed by the amount of flexible 'tails' involved but am reserved about commenting on that, it's personal more than regulatory I think. After all, even a simple domestic Wylex distribution board is awash with a daisy chain of flexible tails and makes use of incoming terminals as junctions. I will show you one, as a temporary avatar for ease and I'll do a job on cropping it later on I hope. So if my avatar currently bears a picture of, in this case, a small control panel with a brown front, then you are looking at one of these boards with the locking door of the steel cupboard open and the brown surround is a piece of cut-out fire proof stuff which cost £160. The step at the top left is where the entire neutral bar was exposed as soon as the box was open. You will like the switch attached to the side of the casing. Bit of a long story about it still being there. I gave it a code 1 for some of your reasons, mostly the exposed parts and fire risk. They took the reasons on board and dealt with them. I have taken a blow torch to the brown stuff (cannot remember what it is called) and have put a piece on the fire. It does not catch light under a blow torch and took about an hour to even change colour on the fire so I expect it is pretty good stuff. Regards and back at you Zs OMS Edit: I'm having a go at it now. This one is at the theatre I tell you about. My meeting with the owner has been postponed until next Tuesday. If you've ever seen a bunch of body guards with dark suits and ties, who look like gangsters surrounding their 'man', you'll know what it is like, except the three men in black are his facilities managers. He walks with a cane with a silver top, very Bond. He's ok. They genuinely do sit at one end of a long glass table and I sit at the other. Yet we all have the same goal for his building. It is funny but I do behave. Pass the milk will you? ------------------------- 'The desk is a dangerous place from which to view the world.' John Le Carre Edited: 15 January 2013 at 07:22 PM by Zs |
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15 January 2013 07:06 PM
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@OMS,
Ok, I can see your point but 'home made'/bespoke can be a collection of manufactured items such as timers, contactors, RCD/RCBOs Isolators at el, as suggested by dg66, assembled into a third party container with the use of din rails, designed to house electrical switchgear and assemblies. I cannot see this contravening much unless someone from competing manufacturers wants to get stroppy about their products being used in conjunction with their rival's ... Legh ------------------------- Why do we need Vernier Calipers when we have container ships? http://www.leghrichardson.co.uk "Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections." |
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15 January 2013 07:14 PM
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The brown board is probably Paxolin or Tufnol which are trade names for phenolific board.
You ask what are the risks for your home made boards. The answer is you cannot quantify them because they have nor been tested to extremes of voltage and fault current for extended periods which the manufacturers do for type testing. OMS lists some of the possible consequences of substandard equipment. You ask if you could apply some tests to the equipment? Some of these tests applied by in type testing require testing to destruction. I have applied high current Ductor tests to bus bar joints after a panel was dismantled and moved to another location and also a high voltage test of the insulation. The panel failed both tests 1st time round. ------------------------- John Peckham http://www.astutetechnicalservices.co.uk/ |
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15 January 2013 07:14 PM
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Provided it's all being assembled in a suitable enclosure and not an old biscuit tin I can't see any real problems.
I also don't really see any problem mixing mcb's etc, as they are all type tested to the same standard by their manufacturer, Dave, |
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 15 January 2013 07:17 PM
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To be honest to get into the issue of type testing etc; and the legal minefield that exposes is grossly OTT and way beyond your remit for something which is a basic risk assessment, the questions are is the enclosure in safe condition and does it achieve what it is required, for example, limits a persons contact with items that can cause danger such as live parts etc;.
regards ------------------------- "Take nothing but a picture, leave nothing but footprints!" ------------------------- "Oh! The drama of it all." ------------------------- "You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!" ------------------------- |
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15 January 2013 07:38 PM
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They may well not be capable of accepting without damage any earth fault they are exposed to Any sensible way I can prove that? Not really - not without dropping it off in Culham or similar and hitting it repeatedly with about 25kA Ditto for short circuit conditions and Ditto can I prove that? as above but with usually more current - these are 3 phase aren't they IP ratings will be suspect - access to live parts may be readily achieved I agree hugely. Hence demanding action on one of them. However, they are usually very well enclosed OK - they may look well closed up, but only an IP test could prove that They are probably not in accordance with any manufacturing standard - so thier selection and erection will be suspect in terms of BS 7671 and specifically 134.1 That may be the nub of it OMS, the component parts are in accordance with manufacturing standards though. OK - so it may be the assembly is partially type tested They may well provide case temperatures that are excessive resulting in a fire or burns risk Ok, they are not running hot. Where do I go to begin proving case temperatures. I can prove actual cable operating temperatures but presumably you are taling about an aggregate and the introduction of other factors? If they aren't hot in normal use then they probably won't get any hotter - I was thinking more of bits inside them evaporating and spraying hot bits everywher under fault. They may well not contain products of combustion resulting from overheating or fault conditions Likewise, all the component parts are respectable, so does the whole have to be considered separately? Ideally yes - we specify distribution boards, switchgear etc in accordance with a standard - that a manufacturere of DB's can supply becaue he's done all the tests (and we prohibit the practice of making them up on site from various parts) They probably won't meet any design specification What is a design specification?
Ahhh - that sort of job - not like your desk job then 
There will be no type testing or partial type testing of the assembly That'll be an insurance related issue then? or manslaughter if it really goes Pete Tong They will probably have insufficient markings including a CE mark But all the parts are respectable and approved For sure - I have a very respectable and approved MG, that doesn't make it a london Taxi though. The bits may be fine - it's the impact of collecting them together that's the issue The colour will probably be horrible -
Not too bad when closed, just white boxes. OK I think I can picture what you mean but any chance of a bit more description - does the installer start with a metal box that is in fact a DB and then assemble his own busbars, din rails, mcb's , switches etc as an ad hoc collection of parts ? They seem to buy an empty steel locking case from schneider and a slection of Din rails and Bus bars. RSA components and Maplin I imagine. Then they buy the main switch and all the breakers. I have not taken one apart but intend to do so when I can. As extra information, I'm alarmed by the amount of flexible 'tails' involved but am reserved about commenting on that, it's personal more than regulatory I think. After all, even a simple domestic Wylex distribution board is awash with a daisy chain of flexible tails and makes use of incoming terminals as junctions. I will show you one, as a temporary avatar for ease and I'll do a job on cropping it later on I hope. So if my avatar currently bears a picture of, in this case, a small control panel with a brown front, then you are looking at one of these boards with the locking door of the steel cupboard open and the brown surround is a piece of cut-out fire proof stuff which cost £160. The step at the top left is where the entire neutral bar was exposed as soon as the box was open. You will like the switch attached to the side of the casing. Bit of a long story about it still being there. I gave it a code 1 for some of your reasons, mostly the exposed parts and fire risk. They took the reasons on board and dealt with them. I have taken a blow torch to the brown stuff (cannot remember what it is called) and have put a piece on the fire. It does not catch light under a blow torch and took about an hour to even change colour on the fire so I expect it is pretty good stuff. Regards and back at you Zs OK - perhaps not as bad then. If they are buying DB enclosures and possibly pan assemblies and just stacking them out with 3rdparty MCB's etc then I suspect they'd perform about as well as one bought direct as a DB - the key issue is that you don't know that (and neither do they) so your report should say that. The risk is unquantifiable, but may well be one or more of those I mentioned initially. like all these things, it's not likley anyone will die, but both you and your client just need to be sure you are not accepting the risk back from the contractor, that someone neatly gave him at let of contract. OMS Edit: I'm having a go at it now. This one is at the theatre I tell you about. My meeting with the owner has been postponed until next Tuesday. If you've ever seen a bunch of body guards with dark suits and ties, who look like gangsters surrounding their 'man', you'll know what it is like, except the three men in black are his facilities managers. He walks with a cane with a silver top, very Bond. He's ok. They genuinely do sit at one end of a long glass table and I sit at the other. Yet we all have the same goal for his building. It is funny but I do behave. Pass the milk will you? LoL - all have the same goal ? - I find it best not to include the word team when dealing with FM guys and thier principal - but you'll know that Regards OMS ------------------------- Failure is always an option |
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15 January 2013 08:06 PM
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Thanks chaps, there's a picture up for a day or so.
Only because I am seeing these around, and saw another three on the double insulation job yesterday, do I ask your views. I don't think they're all that bad. I expect you are also encountering them. They look as though they cost a bit. Zs ------------------------- 'The desk is a dangerous place from which to view the world.' John Le Carre |
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15 January 2013 08:33 PM
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OK - I guess my mince pies and that photo are not a good combination, but it looks to me that may be an off the shelf pan assembly plonked in someone elses enclosure - if so, good.
If not - again perhaps not a critical issue but the mechanical restraint of the din rails, clearance and creepage distaces between phases etc are all potentially suspect. excuse if this sounds a bit thick but are we loking at L1 at the top, then L2 and L3 below - in the style of 3 single phase DB's in the same box mounted one above the other ? regards OMS ------------------------- Failure is always an option |
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15 January 2013 08:49 PM
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Depends, the home made db, could have been made by a panel manufacturer?
After all you can buy bare boards, interconnecting cables, main switches all from a manufacturer, they are all individually tested. Assemble and certify, Buy some ce stickers and a flash tester!! |
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15 January 2013 09:20 PM
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OMS, you can do a screen zoom for a bigger look, it's in 'view' at the top of the page.
There are three vertical columns and each starts at the top with L1 and then goes down through 2,3,1,2,3 etc. so each column of breakers is not dedicated to a single phase. The picture is the right way up in case you are wondering. Zs ------------------------- 'The desk is a dangerous place from which to view the world.' John Le Carre |
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15 January 2013 10:34 PM
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My suspicion in all this is that the Europeans tend to use components within their stated capability - most significantly breaking capacity - 6kA MCBs installed only where Ipfc < 6kA etc. Whereas the good old British tradition is to stick a bunch of 6kA MCBs (or even 3kA fuses) in a box and sell it as suitable for 16kA duty - hence the worries about MCBs not being able to contain arcs etc and needing to be co-ordinated with the enclosure and so on. Conceivably one brand of MCBs might contain the arc from a 16kA fault and so the manufacturer might content matching it with a low strength enclosure, whereas another manufacturer might have MCBs that emit a certain amount of arc/molten metal etc when breaking a current over their rating, but compensate for that with a tougher enclosure. Mix brands one way and you've over-engineered, but the other way and you could have a problem. I think that's what reg 530.3.4 is getting at. So I'd suggest that as long as all the individual components are used within their stated capabilities (and in accordance with their manufacturer's instructions - (I've yet to see an MCB that says only to be installed in a particular brand of enclosure)) - then there should be little to object to on the mixed manufacturer's score. - Andy. |
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15 January 2013 10:37 PM
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Just like a B-type UK-style DB then? (except that there are three columns rather than two?) - Andy. |
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15 January 2013 11:20 PM
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OK - See it now.
Well, in addition to Andy's comments about being within capacity (what is the fault level at these DB's incidentally) I suspect the clearance distances between stacks are not spcific to a manufacturing standard. I don't think its multiple "B" type stacks Andy as the breakers appear to use a single sided busbar comb assembly. I think my observations in the report would be a lack of 3rd party testing (ASTA or KEMA for example), no evidence of compliance with relevant standards (BS EN 60439-3), potential inadequate shrouding of live parts and no evidence of withstand capability at the system fault level. If the fault level is quite low at that point, then perhaps less of an issue - if we are above say 6 - 10kA, then I would worry a lot more and highlight that aspect in the report. I guess we've gone from true "home made" to "site assemblies" which is perhaps less of a problem - I guess the key issue is the installer trading cost for a lack of certification - with all the attendant problems that brings. Basically, no one actually knows how that assembly is going to perform under fault conditions - it's that certainty that's been traded for a cost. not a risk I'd be willing to sign off on if faced with authoring a report on the issue. perhaps the final aspect is resilience and life expectancy - does the design leave loads at risk - and are they "high value" loads. - and will anyone be able to add extra MCB's or swap existing MCB's in the future if required. You could also look at it from a maintainability and testability perspective as well - is it safe to maintain and test - will any subsequent testing just raise all the same issues and the process of validating needs to be repeated again and again. Regards OMS ------------------------- Failure is always an option |
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15 January 2013 11:55 PM
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It is difficult to tell from the photo, but my take on it would be to examine the breaking capacity of all the mcbs & switches in the panel, and compare this with the measured PSCC at the incoming terminals. If the mcbs etc are rated higher, then it is a judgement call on the quality of the assembly. If they are rated lower, then I would code it as a "1", on the basis that I would be unable to determine the effects of a high current short on an assembly. Even with a suitable upstream fuse, you cannot claim the "ZA" derrogation, as the assembly has not been type-tested. This would be the same with a standard CU with other manufacturers mcbs fitted in my opinion.
Regards, Alan. |
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