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Topic Title: Switchgear for large loads
Topic Summary: Do you have a preference
Created On: 23 April 2015 11:04 AM
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 23 April 2015 11:04 AM
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Zs

Posts: 3830
Joined: 20 July 2006

Hello Muckers, from the desk today.

Do you have a preference for switchgear for large loads?

I'm in the realms of 75kW, 250kW and so on. What we'd call the breakers in effect...first step upstream from the load.

The reason I ask is that I can see myself simply slipping into the habit of specifiying that which I've either seen in service or that which my peers use. I think that now is a good time for some original thought before I get too comfortable.

It's the old MK logic plus story again, only on a slightly more important scale...I specify those because that's what everybody specifies and I barely give it a thought. But I know they're not really all that great. At the sharp end, last week two socket outlet neutral terminals failed on me from brand new, you know how it goes, we get a bit routine.

So, on the bigger stuff, ....what's your choice? Time I made a real decision.

thank you,

Zs
 23 April 2015 11:30 AM
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OMS

Posts: 22436
Joined: 23 March 2004

Schneider NS Compact Range
ABB Promax
Seimens
Eaton MEM

or just plain old HBC fuses in MEM Glasgow pattern fuse switches

or even plain old bolted links in fuse switches



Presuming these aren't the only protective devices in the system, what does the rest of the switchgear comprise of - there is a lot of advantage in using equipment from the same manufacturers as you'll probably need relevant upstream data for coordination anyway

If it's first step upstream from the load, do you need protection at all - it's likley to be isolation (fault making, load breaking) - the protection being at the source end - and that triggers the question is the source new or existing - and if existing do you need to match existing patterns of switchgear.

Regards

OMS

-------------------------
Let the wind blow you, across a big floor.
 23 April 2015 11:43 AM
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John Peckham

Posts: 8793
Joined: 23 April 2005

I agree with OMS BS88 are a good choice because they are simple, relatively cheap and will sit there for years waiting to do their job without to much maintenance if any. Nice high breaking capacity in a small package.

Next choice consider NSX MCCBs as they are good quality gear with a range of add on trip units and adjustable for a range of situations. Schneider technical first class for help and promptness of response to technical enquiries.

Gone off Eaton. Loved Memshield 2 don't like Memshield 3 me thinks the 2 was designed by an engineer and the 3 by an accountant, but that is just me so probably wrong.

ABB battleship quality but put off by the fact that you can't get breakers for the older boards. I know a place that has 1000 ( yes not a typing error) DBs made by ABB, and not that old, but can't get replacement MCBs as they are no longer made.

Siemens look good and I have one of their MCCBs for demo purposes but have not specified them.

Harvalls look good on their display stand but have not seen them out on site as yet.

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/
 23 April 2015 12:09 PM
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mawry

Posts: 324
Joined: 26 April 2004

Schneider
ABB
Eaton
Dorman Smith were ok.

Was a big fan of the GE Miniform board if we're talking BS88. Not sure you can get it now tho.
 23 April 2015 12:35 PM
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timothyarnold

Posts: 215
Joined: 12 January 2012

In terms of switchgear manufacturers I prefer to use Mardix with either Schneider or ABB equipment (I prefer the latter but I hear good things with Schneider)

Let me know if you need a contact - but I am sure OMS has one too :-)
 23 April 2015 05:50 PM
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paulskyrme

Posts: 1292
Joined: 12 February 2003

Schneider because I have a local stockist who are really good & technical are really good.
Siemens, because I have a direct account, with technical as good as Schneider.
ABB because I have a direct account & they have always been helpful.
Dorman Smith, because it was the standard on a site I worked on and got to like using it, the rep was great (left for Havells, now elsewhere, but that's not the point), UK kit and seems good.
Havells, because I think it is built like an old battleship, but not had the opportunity, however, we do have a local stockist, & I have spoken to the MD & TD and they have a good attitude to quality.
BS88's given a chance, IF, I can be sure in my mind that they will be correctly replaced, if they go, in the future, else MCB's/MCCB's.
However, most of my design & specification hinges around what I can get that fits the bill, rather than a totally abstract desk exercise then giving the sourcing problem to AN Other!
Nothing wrong with that, but, I tend to have to implement my designs, so I go for the easy life, sorry.
 23 April 2015 06:20 PM
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calumbtw

Posts: 90
Joined: 22 October 2012

Stupid question - What does everyone look for in a good board?
I mean what is the difference between an outstanding board say the memshield 2 & one not so good (Memshield 3)? Build quality?

Originally posted by: John Peckham
Gone off Eaton. Loved Memshield 2 don't like Memshield 3 me thinks the 2 was designed by an engineer and the 3 by an accountant, but that is just me so probably wrong.


John,

Forgive my ignorance - Why don't you like Memshield 3 boards?

P.s Zs sorry for hijacking your thread
 23 April 2015 06:36 PM
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OMS

Posts: 22436
Joined: 23 March 2004

Stupid question - What does everyone look for in a good board?


I wouldn't say a stupid question by any means

Basically, it's quality, quality and quality followed by back up technical and a proven record of doing the job. Ohhh - and will it fit in the gap

If I want a new switchboard for say a hospital, then I'm likley to go with a supplier that:

a - uses equipment such as breakers that have known provenance and plenty of tech support available
b - can demonstrate that they have supplied similar items in similar situations and that it's doing the job
c - has a gold company credit card to buy me lunch

maybe not c - that should read "what other switchgear do I need to be compatible/discriminate with"

If it's just run of the mill type A and B dist boards, then basically the current ranges are all crap - you pays the money and takes the risk - and because of that, I leave it up to contractor choice - and blame him when it goes Pete Tong

regards

OMS

-------------------------
Let the wind blow you, across a big floor.
 23 April 2015 10:20 PM
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Zs

Posts: 3830
Joined: 20 July 2006

No problem at all Calum, another good question.I have a notion that your question and mine will go hand in hand.

Going back to the big load switchgear for a mo though, the reason I ask is more than one-fold.

At the small level I'd be hard-pushed to draw you a diagram of what a simple MCB does to break a circuit although I reckon I could hazard a half-decent mark out of it.

But I've used them for years and I know what they feel like, what they sound like, what goes wrong with them. I expect most of us are good for that.

Go a bit bigger, with maybe a slightly different fault level and I'd probably still be able to hack my way to sounding like I know stuff.

Offer me an ACB on something even bigger still and I'll tell you that it uses air and stuff to make separations but then I'd shut up.

But tell me that it is an xyz with magnetic coils and is a type Q set to level 0.01on Thursday morning and I'll only nod sagely.

So, first I need to know what is popular - hence the question- and then next I'll set about finding out how they work and why they are chosen.

Like most of us, I can use a drop-down list on Amtech to extremely good effect. I'm supposed to be embarking on a course in HV distribution right now but TBH, between you and me of course, I'd rather have a better understanding of some of the stuff I'm already supposed to know and which I specify by instruction from a drop-down list. There might be a hint of rebellion there but I don't think so.

So, I expose my lack of knowledge in search of where to search. I'd like to be able to understand higher load switchgear. The day I comment with confidence on a poor choice on something huge will be the day I sign up for the HV course ( provided I'm not too busy and short of money of course).

Eric Jacks' book is on the list ( didn't you read it recently Zoomup?) but prior to that just a bit of scribbling and checking of understanding.

I'm going to have a chat with the companies you recommend and get them over for tea and brain-picking. it's a good job my Mum can bake lemon drizzle cake and doesn't mind me pretending that I made it.

Thank you,

Zs
 24 April 2015 09:59 AM
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OMS

Posts: 22436
Joined: 23 March 2004

Do a few things over the weekend

1 - work out how long one half cycle of a sine wave is at 50Hz

2 - Do a google for "Form of Seperation" in relation to switchgear BEAMA do a good guide

3 - Assuming an infinite HV busbar (ie ignore any impedance on the primary side) calculate the prospective short circuit current for a typical 1.5MVA transformer of 5% impedance - and then for a pair of those transformers connected "A" and "B" side run with the switchboard bus coupler closed - ie two in parallel.

4 - Keep repeating I2t under your breath and then from 3 (above) plug the short circuit current into I2t and assume 3 seconds - derive an answer in joules

5 - Estimate, ignoring losses, how may joules go into making your morning cuppa - (Q(kw x 1000 and hence joules) = (mass(kg) x shc(kj/kg) x temperature rise(Degree C))/1second)

Compare 5 with 4 - estimate how many wets 4 equates to

Regards

OMS

-------------------------
Let the wind blow you, across a big floor.
 24 April 2015 04:37 PM
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calumbtw

Posts: 90
Joined: 22 October 2012

Originally posted by: OMS

Stupid question - What does everyone look for in a good board?




I wouldn't say a stupid question by any means



Basically, it's quality, quality and quality followed by back up technical and a proven record of doing the job. Ohhh - and will it fit in the gap



If I want a new switchboard for say a hospital, then I'm likley to go with a supplier that:



a - uses equipment such as breakers that have known provenance and plenty of tech support available

b - can demonstrate that they have supplied similar items in similar situations and that it's doing the job

c - has a gold company credit card to buy me lunch



maybe not c - that should read "what other switchgear do I need to be compatible/discriminate with"



If it's just run of the mill type A and B dist boards, then basically the current ranges are all crap - you pays the money and takes the risk - and because of that, I leave it up to contractor choice - and blame him when it goes Pete Tong



regards



OMS


Well, I keep hearing that certain boards are very good & others not so good. Last night my girlfriends dad was saying how he really liked / liked Memshield 2 boards - the newer one wasn't great he said.

He mentioned this because I did a site survey and found about 40 Memshield 2 boards - which the client wants to strip out. They seem in better condition than the newer boards that were added in.

Originally posted by: Zs

No problem at all Calum, another good question.I have a notion that your question and mine will go hand in hand.



Going back to the big load switchgear for a mo though, the reason I ask is more than one-fold.



At the small level I'd be hard-pushed to draw you a diagram of what a simple MCB does to break a circuit although I reckon I could hazard a half-decent mark out of it.



But I've used them for years and I know what they feel like, what they sound like, what goes wrong with them. I expect most of us are good for that.



Go a bit bigger, with maybe a slightly different fault level and I'd probably still be able to hack my way to sounding like I know stuff.



Offer me an ACB on something even bigger still and I'll tell you that it uses air and stuff to make separations but then I'd shut up.



But tell me that it is an xyz with magnetic coils and is a type Q set to level 0.01on Thursday morning and I'll only nod sagely.



So, first I need to know what is popular - hence the question- and then next I'll set about finding out how they work and why they are chosen.



Like most of us, I can use a drop-down list on Amtech to extremely good effect. I'm supposed to be embarking on a course in HV distribution right now but TBH, between you and me of course, I'd rather have a better understanding of some of the stuff I'm already supposed to know and which I specify by instruction from a drop-down list. There might be a hint of rebellion there but I don't think so.



So, I expose my lack of knowledge in search of where to search. I'd like to be able to understand higher load switchgear. The day I comment with confidence on a poor choice on something huge will be the day I sign up for the HV course ( provided I'm not too busy and short of money of course).



Eric Jacks' book is on the list ( didn't you read it recently Zoomup?) but prior to that just a bit of scribbling and checking of understanding.



I'm going to have a chat with the companies you recommend and get them over for tea and brain-picking. it's a good job my Mum can bake lemon drizzle cake and doesn't mind me pretending that I made it.



Thank you,



Zs


Sounds interesting - Something I'll definitely have to look into after I get through about 50 standards I've promised to myself to re-read!! Somehow I only manage to get through 1-2 a week though and I add about 10 a week!!
 24 April 2015 05:35 PM
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OMS

Posts: 22436
Joined: 23 March 2004

He mentioned this because I did a site survey and found about 40 Memshield 2 boards - which the client wants to strip out. They seem in better condition than the newer boards that were added in.


Can they be repaired or modified - ie are there MEMshield 2 breakers available - I believe not, and MEMshield 3 isn't compatible with 2

It might be better, but no use at all if you can't maintain it - that's the real cost of our design descisions in terms of obsolescense - owning switchgear of any size is expensive over a lifetime of a building

Regards

OMS

-------------------------
Let the wind blow you, across a big floor.
 24 April 2015 08:03 PM
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Zs

Posts: 3830
Joined: 20 July 2006

Calum, second-hand Memshield 2 is fetching a very good price if you can be bothered to do it.

No question Memshield 2's days are over. Thanks to MEM3 not fitting the 2 boards. That's another reason for not wanting to go into the MEM camp...We were taken to the cleaners by them. Our loyalty has been rewarded with a smack round the head from those we have supported. Grrr.

I've been looking for a Mem2 4 pole RCD main switch but I specifically wanted a new one, or rather, one with a warranty. I just paid £162+ Vat for it. A second hand version on flea bay is about £45.

OMS, that looks suspiciously like homework to me. I'll give it a shot though (but not now and not in public, I'll email you what I come up with). It'll be like old times to have you marking my work, am a tad scared but I'm all over it. Welcome back pal get that red pen ready.

Zs
 24 April 2015 08:36 PM
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calumbtw

Posts: 90
Joined: 22 October 2012

Originally posted by: Zs

Calum, second-hand Memshield 2 is fetching a very good price if you can be bothered to do it.



No question Memshield 2's days are over. Thanks to MEM3 not fitting the 2 boards. That's another reason for not wanting to go into the MEM camp...We were taken to the cleaners by them. Our loyalty has been rewarded with a smack round the head from those we have supported. Grrr.



I've been looking for a Mem2 4 pole RCD main switch but I specifically wanted a new one, or rather, one with a warranty. I just paid £162+ Vat for it. A second hand version on flea bay is about £45.



OMS, that looks suspiciously like homework to me. I'll give it a shot though (but not now and not in public, I'll email you what I come up with). It'll be like old times to have you marking my work, am a tad scared but I'm all over it. Welcome back pal get that red pen ready.



Zs


Unfortunately, I won't be able to get the kit myself - Would have been a good side-earner though! Although, I'll probably try to take some of it to tinker with, if they'll let me.

I was aware of memshield 3 not being backwards compatible shame really - I've always stuck to Schneider personally - I had an invite to visit their production factory, not sure if that offers still open - but I've always stuck to Schneider generally! I should probably ring the rep, and see if the offer is open when I get time.
 27 April 2015 09:36 AM
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OMS

Posts: 22436
Joined: 23 March 2004

OMS, that looks suspiciously like homework to me. I'll give it a shot though (but not now and not in public, I'll email you what I come up with). It'll be like old times to have you marking my work, am a tad scared but I'm all over it. Welcome back pal get that red pen ready.


It is, It will be - not intended to be frightening, but it will form the basis of a chat next time I get to Sleeepy Hollow

Regards

OMS

-------------------------
Let the wind blow you, across a big floor.
 27 April 2015 05:54 PM
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mawry

Posts: 324
Joined: 26 April 2004

Zs,
Out of interest, what HV course are you thinking of doing?

Cheers,
 27 April 2015 07:04 PM
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Zs

Posts: 3830
Joined: 20 July 2006

I have sent you a pm mawry. I know others who are going through it too so I'll keep it quiet on here just in case the examiners mark them down because they know Zs . As far as I can see it is tough.

I am about to disconnect the computer for the big move of all the screens to the new office....I'll be letting you know if my cable pulling was gentle enough, and if gold plated RJ45 plugs make any difference in a day or so.... or from the desk job....

Zs
 30 April 2015 12:12 AM
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Zs

Posts: 3830
Joined: 20 July 2006

On my way to bed so a bit bleary-eyed but just one thing left to do and this is it..

I'd like to say thank you to OMS. O came down to brief me on a project today (lovely to see you), and I think he pretended that I needed to know some stuff about switches for big things as part of it. Seeing as it was the lighting for a bike-shed (I jest) I think I rumbled him, but who is complaining?

I had an hour of tuition on how breakers work, what they are capable of and when to change from one type to the next today. For which I am truly grateful. Drawings of extra windings and everything.

Unfortunately we wrote all our notes on the bottom of a drawing which I now realise I cannot bring out of the office because of the security marking on it so I will do some copying, cutting and sticking so as to be able to share it with some of you when you need it. I also have a reading list. I am now ready to tackle the nuances of the Amtech drop-down list of breakers and only have to find out what all the codings mean. That ought to be do-able with some catalogues and a few phone calls though. I feel more comfortable asking them now.

Thanks Mister, really appreciated.

Zs
 30 April 2015 01:07 AM
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mapj1

Posts: 9716
Joined: 22 July 2004

Well let us hope any extra copies of said drawing are accounted for in the big register or are seen to be destroyed ;-)
We really don't want you disappearing suddenly.

-------------------------
regards Mike
 01 May 2015 01:15 PM
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OMS

Posts: 22436
Joined: 23 March 2004

LoL - what we call "The interview without coffee", Mike

Not my finest hour, marking up operational characteristics of circuit breakers on the back of official-sensitive drawings for the bike shed

Regards

OMS

-------------------------
Let the wind blow you, across a big floor.
IET » Wiring and the regulations » Switchgear for large loads

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