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Topic Title: Home made DBs
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Created On: 15 January 2013 06:14 PM
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 20 January 2013 11:58 AM
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Zs

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Thank you OMS. Are you at work on a Sunday? Pot/Kettle.

Great feedback on the paragraph, thank you. I don't need it for this job since talking with them last week, but I will be needing it so I'll do that at some point.

I've got 45 outgoing ways to accommodate at the moment. Yes, I might be able to drop a few if I move the contactors and timers and I'm thinking along the lines of an added chamber right this minute, such as Merlin G do. I'm still trying to stay with the MCG kit if poss. I'm not sure where the supply power (and neutrals) to them will come from. Desparately trying to avoid splitting armoured cables which have already been cut to length for the existing home made DB,outside of the boxes.

I am not keen to double up any circuits into shared breakers, even though some of them only have one or two light fittings on them. My original report suggested DB changes and the introduction of RCBOs in order to provide a messenger of individual circuit failure and in order to provide a higher Zs requirement than their previous type D breakers.

At the moment it is really beginning to look as though I'm going to have to specify something like an MG cabinet wich can accommodate all of the breakers and get them to sell the MCG ones on ebay. At a push they could keep the MCG breakers and buy small DBs for them to use as they change boards around the place. There are still a few of the old boards dotted around so that could be an option.

MCG = City? Hmmm, that throws a cat amongst my personal pigeons. Aren't proteus also a City brand?

Thanks OMS, you not snowed in like us then?

Zs
 20 January 2013 12:15 PM
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OMS

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Originally posted by: Zs

Thank you OMS. Are you at work on a Sunday? Pot/Kettle.

Yes, I know - a few bids to resolve, I'm afraid - looking to keep the team gainfully employed this year -


Great feedback on the paragraph, thank you. I don't need it for this job since talking with them last week, but I will be needing it so I'll do that at some point.

OK - no drama - you'll know where to find me most days


I've got 45 outgoing ways to accommodate at the moment. Yes, I might be able to drop a few if I move the contactors and timers and I'm thinking along the lines of an added chamber right this minute, such as Merlin G do. I'm still trying to stay with the MCG kit if poss. I'm not sure where the supply power (and neutrals) to them will come from. Desparately trying to avoid splitting armoured cables which have already been cut to length for the existing home made DB,outside of the boxes.

OK - all the big players will have 16way + boards, but i guess that means dumping everything and starting new - ouch. Can you get 2 x 12ways to fit and see if MCG do a linking kit - or do you have room for a 900mm bus bar chamber and go from there.


I am not keen to double up any circuits into shared breakers, even though some of them only have one or two light fittings on them.

Nope - you are delving into design territory there that may take a fair bit of effort to validate by calculation (as in collecting the relevant info)

My original report suggested DB changes and the introduction of RCBOs in order to provide a messenger of individual circuit failure and in order to provide a higher Zs requirement than their previous type D breakers.

yep - I wouldn't have any doubt the design intent and the design criteria you stipulated in the basis of design are all fine - just that the installer appears to have taken leave of his senses somewhat.


At the moment it is really beginning to look as though I'm going to have to specify something like an MG cabinet wich can accommodate all of the breakers and get them to sell the MCG ones on ebay. At a push they could keep the MCG breakers and buy small DBs for them to use as they change boards around the place. There are still a few of the old boards dotted around so that could be an option.

OK - don't give up yet - look hard at the two x 12 way options (or two x 8 way if that helps the space allocation


MCG = City? Hmmm, that throws a cat amongst my personal pigeons. Aren't proteus also a City brand?

They are - worth asking MCG what thier approach is to interchangeability - ie will the MCG breakers fit a proteus pan assembly (and will they warrant that)


Thanks OMS, you not snowed in like us then?

Not quite - it was more than a bit touch and go Thursday/Friday for sure, particularly with travelling west - yesterday the roads opened up quite a bit and this morning dawned fine and bright, if a tad icy - it's the south east that's getting a pasting today I believe.

Zs


Best regards

OMS

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Failure is always an option
 20 January 2013 03:19 PM
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Martynduerden

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Mcg are via city and are akin to proteus - might be worth checking a couple of things on the existing rcbo's,

Are the terminals in good shape proteus don't like to be installed twice.

Have the flying leads been shortened? MK condemned a whole hotel worth of rcbo's that had shortened flying leads, they were not meeting the required times and decided that because the neutral lead had been "modified" that was the cause and they must be changed.

I'm not sure how a shortened neutral lead could cause that effect but it released MK from their obligation.

What is the kA rating of the existing breakers?

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Martyn.

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 20 January 2013 03:31 PM
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Zs

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Originally posted by: Martynduerden

Mcg are via city and are akin to proteus - might be worth checking a couple of things on the existing rcbo's,

I'm not a fan of Proteus, hence my earlier Hmmm. But didn't you once tell me MCG are highly respected?

Are the terminals in good shape proteus don't like to be installed twice.

Brand new last october.

Have the flying leads been shortened? MK condemned a whole hotel worth of rcbo's that had shortened flying leads, they were not meeting the required times and decided that because the neutral lead had been "modified" that was the cause and they must be changed.

I've not seen inside so I don't know, but very good point.

I'm not sure how a shortened neutral lead could cause that effect but it released MK from their obligation.



What is the kA rating of the existing breakers?
10, and they are type B

 20 January 2013 03:39 PM
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paulskyrme

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Zs,
Please remember that there are others who will help, just because they don't post often does not mean they are not around, and will not help, if they can!
 20 January 2013 03:39 PM
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Martynduerden

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Did I, I'm not sore I've used mcg, though I do recall a conversation about another three letter brand racking my brains...

I was mainly referring to proteus once tightened never retightened

Don't take my word for it on the shortened neutrals, just a thought.

Why am I thinking they should have been type C?

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Martyn.

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 20 January 2013 03:48 PM
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OMS

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Why am I thinking they should have been type C?


On what grounds Martyn - I think Zs said they are general lighting and power loads with very few outlets on very many circuits - Type B is probably fine, as is the 10kA against a probable 3 - 4 kA fault level.

Starting afresh, I might go for type C for avoidance of design risk due to some numpty pressing a twelve gang switch with the palms of both hands, zs notwithstanding - but apart from that it serves no real purpose and in many cases can take circuits closer to potential failure points in terms of disconnection.

Using RCBO's you may also have much more limited options though

regards

OMS

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Failure is always an option
 20 January 2013 03:55 PM
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Martynduerden

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Originally posted by: OMS

Why am I thinking they should have been type C?


On what grounds Martyn - I think Zs said they are general lighting and power loads with very few outlets on very many circuits - Type B is probably fine, as is the 10kA against a probable 3 - 4 kA fault level.

Starting afresh, I might go for type C for avoidance of design risk due to some numpty pressing a twelve gang switch with the palms of both hands, zs notwithstanding - but apart from that it serves no real purpose and in many cases can take circuits closer to potential failure points in terms of disconnection.

Using RCBO's you may also have much more limited options though

regards

OMS


I was asking the question .... I didn't know why I instinctively thought C,

I have no idea what the fault levels are, I asked mainly to confirm they were not 3kA.

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Martyn.

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 20 January 2013 04:03 PM
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OMS

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I have no idea what the fault levels are, I asked mainly to confirm they were not 3kA.


I suspect there'll be back up protection on the source end of the sub mains

from an earlier post:

From 1 year ago before the board was changed ( it used to be two boards of the Dorman Smith D type):

Ze(db) 0.24 ohms
three phase so about 2K.

Those measurements were taken by Pete TLM so I reckon we can trust them.


regards

OMS

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 20 January 2013 04:42 PM
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sparkingchip

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Martyn- is the other three initial brand CGD by any chance?

Am I right in thinking that the enclosure shown by Zs at the time of the OP is actually a Telecoms cabinet and never intended for use as a distribution board or consumer unit?

Regards the shortening of flying leads on RCBO's are MK suggesting it is safer to have a enclosure stuffed full of coiled cables that it is to shorten a lead to the required length?

Andy
 20 January 2013 04:55 PM
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perspicacious

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"flying leads on RCBO's"

I recall a report where I questioned the use of a brand of RCBOs whose tail were 2 mm2 and thus the 32 A ones ran at a temperature exceeding the rating of the adjacent PVC TW/E

Probably quite a few still not being picked up on EICRs

Regards

BOD
 20 January 2013 05:39 PM
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sparkingchip

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Still tied up with a cable tie in a nice tight coil, as supplied by the manufacturer?

Andy
 20 January 2013 10:07 PM
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Shetland

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Hello All. This is an interesting thread. A few thoughts regarding the application of BS EN 61439 -

Where do the requirements regarding "design verification" and "routine verification" begin and end? And what is defined as a control panel as covered by the standard?

If Zs removes the relays and timers said to be lurking in the aforementioned home made distribution board and relocates them to another enclosure, does this now become classed as a control panel and be subject to verification of compliance with BS EN 61439?

Referring to Schneider Electrics website, the original manufacturer of an assembly system is deemed responsible for "design verification" of that system. The assembly manufacturer using a compliant assembly system has responsibility for the completed assembly and, assuming the original manufacturers instructions have not been deviated from, must complete only the "routine verification".

What constitutes an assembly system? If one were to build for example a star delta motor starter incorporating a 24V AC control transformer inside an enclosure which conformed to BS EN 62208, using components from a single manufacturers range which complied with all relevant component standards, would this be subject to full design verification or would compliance be presumed and only routine verification be required in order to state compliance with BS EN 61439?
 21 January 2013 12:44 AM
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Zs

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Originally posted by: Shetland

If Zs removes the relays and timers said to be lurking in the aforementioned home made distribution board and relocates them to another enclosure, does this now become classed as a control panel and be subject to verification of compliance with BS EN 61439?


Welcome back Shetland.

Given that I have now persuaded the man with the cane that the board must be replaced, and given that whatever replaces the current board has to be absolutely perfect. That is an important point.

I would really describe the existing as a small control panel because of everything it has in it at the moment. However, semantics in the face of the safety of the visitors and staff of the building. I'm pretty sure that a few timers and a contactor positioned in a board, such as MK and hager sell for attaching as accessories in their boards, would not have made me think so hard about this and I'd probably have walked on by ticking little boxes on my way.

Mart, remember that type B or C was not a design decision and was probably the result of a quick on-line order or similar. Knowing the cabling in this place though, and how very high the Zs readings were via the old boards, I might have gone for a type B set-up myself, on account of required Zs. That to give me some leeway and I might yet do that with the new board. I've been on it all day unlike the original 'designer'.

All these issues are an indication of the sea-change which is going on in the world of electrical installation right now. Be it the Recession, be it a more competitive attitude, be it cosmopolitan. I suspect that being able to pass on a package of responsibilities to an installer, including liability is very attractive to corporates.

E&OE of course,
Zs
 21 January 2013 10:13 AM
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BigRed

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mornin'
so what are you thinking? schnider Pragma times two with the associated bits and bobs from the range to keep it all compliant? As for the MCG stuff, its cheap and chereful, just badged stuff for CEF, quality jobs demand quality goods. At least the schnider/MG stuff should last the test of time. Having seen a pragma set up, looks pretty good.
 21 January 2013 02:03 PM
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OMS

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Originally posted by: Zs

Originally posted by: Shetland

If Zs removes the relays and timers said to be lurking in the aforementioned home made distribution board and relocates them to another enclosure, does this now become classed as a control panel and be subject to verification of compliance with BS EN 61439?



Welcome back Shetland.

Given that I have now persuaded the man with the cane that the board must be replaced, and given that whatever replaces the current board has to be absolutely perfect. That is an important point.

You'll effectively have a multi service unit that, provided the manufacturere of the enclosure and the components has initialy verified the worst case configuration of equipment, is essentialy a partially type tested assembly PTTA.


I would really describe the existing as a small control panel because of everything it has in it at the moment. However, semantics in the face of the safety of the visitors and staff of the building. I'm pretty sure that a few timers and a contactor positioned in a board, such as MK and hager sell for attaching as accessories in their boards, would not have made me think so hard about this and I'd probably have walked on by ticking little boxes on my way.

Indeed - provided you are happy with the partially type tested assembly - they are almost certainly not a problem, always wisest to check

Mart, remember that type B or C was not a design decision and was probably the result of a quick on-line order or similar. Knowing the cabling in this place though, and how very high the Zs readings were via the old boards, I might have gone for a type B set-up myself, on account of required Zs. That to give me some leeway and I might yet do that with the new board. I've been on it all day unlike the original 'designer'.

Yep - moving away from type b unless there is a good reason to do so is pointless - and when i see it with type C or D MCB's on lighting circuits with 3 fittings in seperate rooms and manual switching I raise an eyebrow - the designer often fudges the issue with "dealing with Inrush current mate" - "or it's safer, innit" - only to find the designer is so close to the envelope the limiting Zs can't be met.


All these issues are an indication of the sea-change which is going on in the world of electrical installation right now. Be it the Recession, be it a more competitive attitude, be it cosmopolitan. I suspect that being able to pass on a package of responsibilities to an installer, including liability is very attractive to corporates.

It was ever thus - the practices of the baazar just get worse the deeper the reccession. Remember what I said about contractors getting invited to the late night poker game - and never getting the chance to cut, shuffle or deal.

That's why D&B is so popular, particulary under NEC forms of contract - the client passes on everything including the design risk in return for issuing a simple performace based spec from his (now much cheaper) consultant engineer. If the contractor is not clued up on compensation events and early warning notices , he runs out of time on changes, variations etc and won't get paid - the works then being deemed to be included in th original bid.

E&OE of course,

Of course - would you like to stand by that cost or withdraw ? -

Zs


regards

OMS

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Failure is always an option
 21 January 2013 03:50 PM
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Martynduerden

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Originally posted by: Zs

Mart, remember that type B or C was not a design decision and was probably the result of a quick on-line order or similar. Knowing the cabling in this place though, and how very high the Zs readings were via the old boards, I might have gone for a type B set-up myself, on account of required Zs. That to give me some leeway and I might yet do that with the new board. I've been on it all day unlike the original 'designer'.

Zs


Yes I was aware that the element of design had been limited by ability yes bitching I know.

From my limited knowledge of the installation I had assumed that type B would have been tripping frequently, I have not been on the forum of late as many of you will have noticed...or not, and hence I have not read this topic from the beginnings, if as suggested the limiting Zs is a problem and there is no cause for concern on inrush then it seems the initial designer made the right choice.

I guess my initial response comes from experience in commercial building such as this, I fit and design for all types of cpd based on a circuit by circuit assessment, the majority of mcb's I fit in commercial/industrial premises are type C, with the very occasional type D.

As for the assembly of other devices in a DB such as timers and relays, some manufacturers, Hager, MG/Schneider provide enclosures for the purpose, this is indeed common practice for things like lighting control,
i guess one of the main stipulations would be that isolating the DB isolates everything within it, ie none of the relays/contactors or timers etc are supplied from elsewhere or indeed any of their coils.

Beyond the common sense of the above and confirming fault level capabilities, most if not all of these enclosures require isolation to access the component parts in extension chambers, Whilst some may see ths as a problem it makes for a safer overall installation.

Now where is that parapet?

-------------------------
Regards

Martyn.

Only a mediocre person is always at their best



www.electrical contractors uk.com
IET » Wiring and the regulations » Home made DBs

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