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Topic Title: DIversity
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Created On: 23 February 2013 06:42 AM
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 23 February 2013 06:42 AM
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paulskyrme

Posts: 778
Joined: 12 February 2003

I've recently been asked if it is OK to apply diversity to the supplies for washing machines & tumble dryers going into an industrial/commercial premises for their in house laundry.

The washing machine s are 21kW, & the dryers 30.8kW.

Any thoughts, bearing in mind that I believe they could be used at the same time, but we are only talking 2 of each.

I could not give a straight answer immediately to be honest, & still can't decide.

Anyone have any suggestions please?
 23 February 2013 07:37 AM
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broadgage

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With only two washers and two dryers I dont believe that any diversity can be sensibly applied.
It would seem sensible to assume that at the begining of the work day that both washers will be used and draw full load at the same time, when the first batch of laundry is done, it would be reasonable to assume that it will be transfered to the dryers which will both draw full load, probably whilst a second load is being washed.

The dryers probably draw full load for most of the cycle, probably reducing to half or less when nearly dry.
The washers probably only draw full load when heating the water, and much less for the rest of the cycle.

Still a significant risk of all 4 appliances using full load at the same time though.
 23 February 2013 02:11 PM
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Alexg

Posts: 406
Joined: 03 February 2004

I agree with Broadgage, for those appliances I would not apply diversity. Even if the customer says they won't all be used at the same time you can bet at some point they will.

 23 February 2013 03:33 PM
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slittle

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I think I've got to agree with them too Paul.

I'm thinking that if you are tight for supply there's always the option of some "control" to allow either washing or drying.


Stu
 23 February 2013 03:48 PM
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paulskyrme

Posts: 778
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Thanks guys, I have not really looked at it yet it was a request upon from a client spark, that I am called in to help on times, my gut feeling was no diversity really, or at least not much.
They have sufficient incoming supply capacity, they'll just need some mods to the distribution in the premises & a new board in the area.
I asked because he told me that he had been told elsewhere that he would only need a 63A supply for ALL the machines & ancillary supplies in the area!

Thank you all so far, further comments welcome.
 25 February 2013 10:41 AM
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OMS

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You are making big assumptions about how the washers and dryers are used.

It may well be the case (and often is) that in house laundry is designed for N+1 if the need is deemed important enough - nursing care for example, or industrial process where clean kit is a pre requisite for the next shift.

So, whilst there may be two washers and two dryers, the volume of laundry generated per wash cycle is such that only one machine and dryer are required as part of a consecutive process - so your best case is just a single washing machine followed by a single dryer - the worst is both washing machines going a second time, concurrent with both dryers operating - and washing/drying may well be an out of hours process as well

Remember diversity is both the varying nature of a load, the non concurrent operation of several loads coupled with not every load being used - as the designer you need to know how it is intended to operate.

That said, if you have capacity then a simple 160A TP&N system to the laundry covers every base.

Regards

OMS

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Failure is always an option
 25 February 2013 08:44 PM
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paulskyrme

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Since my last post I have had it confirmed that the washers & dryers will be in use 5-6 hours per day 5 days per week!

Cyclic loading will reduce the overall load profile I realise.

The proposed laundry is to be located in the next room to the DNO transformer on the site anyway.
Not got access to the transformer room, but the "head" is a 1600A/ph ACB!
We could easily stick in a 160 or 250A TPN sub to the area, as future proofing.
Mind either will require a major mod to the main switch gear!!!

Thanks OMS, got another Q for you when you have a chance, about something else but I can't PM you for some reason!
 26 February 2013 08:45 AM
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OMS

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Stay away from the main switchgear - you need to be connecting at the next tier of distribution downstream - unless you want high fault level ratings on your 160A or 250A supply switchgear.

Don't know why you cant PM - it seems to be enabled this end. I'll give you a call later if that helps

regards

OMS

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Failure is always an option
 26 February 2013 07:20 PM
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paulskyrme

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Hi OMS,
It's gonna have to be a mod to the main panel board.
'85 design, 15th install.
No spare fuse switches in the main panel board.
Looking to add a modular panel board off the side of the existing fed from the main bus bars in the existing panel.
Will have a 400A 25kA MCCB as an incomer & a 250A MCCB as the outgoer to the DB in the "laundry".
The PEFC @ the origin has been confirmed by the DNO to be limited to 25kA.
The impedance of the sub-main should attenuate this suitably, though perhaps an MCCB on the incomer to the board as a main switch, not decided yet, only priced a main switch so far, it only just dawned on me about the MMCB as an incomer, but, not sure if there would be anything to be gained.
Though we could cut down to 160A, but that would limit their use of the full capacity of the supply, which they will!!!
The panel board we have enquired about can take 35kA MCCB's, just in case!
 27 February 2013 09:30 AM
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OMS

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Originally posted by: paulskyrme

Hi OMS,

It's gonna have to be a mod to the main panel board.

'85 design, 15th install.

No spare fuse switches in the main panel board.

OK - Noted

Looking to add a modular panel board off the side of the existing fed from the main bus bars in the existing panel.

Will have a 400A 25kA MCCB as an incomer & a 250A MCCB as the outgoer to the DB in the "laundry".

The PEFC @ the origin has been confirmed by the DNO to be limited to 25kA.

Right - probably not the best time to mention type-tested equipment, partially type-tested equipment and BS EN standards for switchgear. Form of seperation is also worth a mention - modifying switchgear - particulary with bus bar tappings isn't the done thing anymore - so you are taking on a big risk. I wouldn't specify it that way for sure - at least not without going through the implications and consequences with the client in some detail.

The impedance of the sub-main should attenuate this suitably, though perhaps an MCCB on the incomer to the board as a main switch, not decided yet, only priced a main switch so far, it only just dawned on me about the MMCB as an incomer, but, not sure if there would be anything to be gained.

Well, lots of considerations really including potential back up protection to DB MCB's which will be at best 15kA and probably less, control of load current to the board etc etc.

If you have source end protection at 250A though, then just get a type b dist board with a 250A main switch (usually a non auto MCCB) - no point buying kit you don't need.

Though we could cut down to 160A, but that would limit their use of the full capacity of the supply, which they will!!!

You could adjust the source end MCCB if you buy electronic tripping modules - don't worry about that bit for a moment

The panel board we have enquired about can take 35kA MCCB's, just in case!


OK - it's not that bit that bothers me - it's how/where etc you are going to connect to the existing board - what make/type is it and was it provided originaly to be extensible. The installation design is a piece of p**s - it's the the switchboard mod that will be the risky affair.




Regards

OMS

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Failure is always an option
 27 February 2013 03:49 PM
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paulskyrme

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Thanks OMS,
Can't expand existing switchgear.
Maker no longer in existence, component fuse switches used, no longer available!
We have space to add 4, but can't get the bits.
Design early 80's, build std. unknown, not marked, will need to check.
Form, hmmm, no separation at all.
Got some pics & makers names outgoing cables are bolted to bus bars on the output of the FS, the input is bolted to the main bus bars!
 27 February 2013 04:03 PM
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OMS

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Originally posted by: paulskyrme

Thanks OMS,

Can't expand existing switchgear.

Maker no longer in existence, component fuse switches used, no longer available!

try JWE Morris up the road from you

We have space to add 4, but can't get the bits.

Again, try Morris or RF Winder

Design early 80's, build std. unknown, not marked, will need to check.

OK - possibly a partialy type tested system then - given it was modular design. I'd be very careful about modifying it personally

Form, hmmm, no separation at all.

Really ? - at 1600A I would have expected something in place

Got some pics & makers names outgoing cables are bolted to bus bars on the output of the FS, the input is bolted to the main bus bars!

OK - not clear from that, but it sounds as if you have functional assemblies seperated from cabling and bus bar - so at least form 2



Zs had a thread running on here about home brew dist boards used in a theatre - worth taking a read through - lots of background in there on assemblies and current standards.

If it really is an obsolete, 30 year old partially type tested assembly with a poor form of seperation it might be better to advise the client up front of the problems before attempting a modification and then raising the problem afterwards.

Regards

OMS

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Failure is always an option
 27 February 2013 04:55 PM
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paulskyrme

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Tried JWE through one of their other companies.
Pulled Dorman Smith area rep in too, he has been in contact with others he knows in the industry & failed to locate parts.
He has passed my details on to another integrator further West, which you may have heard of, HAC, nickname "Hacker"?
Not derogatory as far as I know, more to do with the work that they do hacking panels around to make / mod them etc AFAIK.

Needs to be completed by 31/3/13!

I'll check the descriptions of separation in the current standards & relate them back.
Certainly not enough separation/protection to do anything other than look at the thing without shutting the whole building down!
 27 February 2013 05:38 PM
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OMS

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Originally posted by: paulskyrme

Tried JWE through one of their other companies.

Pulled Dorman Smith area rep in too, he has been in contact with others he knows in the industry & failed to locate parts.

He has passed my details on to another integrator further West, which you may have heard of, HAC, nickname "Hacker"?

Not derogatory as far as I know, more to do with the work that they do hacking panels around to make / mod them etc AFAIK.


OK - well if that gang of suspects can't help, drop me what photo's you have and I'll take a look - maybe something that a few of my contacts might be able to resolve.


Needs to be completed by 31/3/13!

LoL - don't they all - offer to get the design done out of this years budget with a letter of intent to a switchboard supplier - they can do installation next financial year


I'll check the descriptions of separation in the current standards & relate them back.

Certainly not enough separation/protection to do anything other than look at the thing without shutting the whole building down!

OK - all the more reasoning to seriously consider a new switchboard - or think about a total redesign of the laundry supplies from one or more downstream boards



Regards

OMS

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Failure is always an option
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