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#175259 - 02/25/08 06:40 PM load diversity factor for car parking lift
theseus Offline
Member

Registered: 02/23/08
Posts: 11
Loc: china
I have 50 car parking lifts,each is 2.2kW.I want to know how to calculate the feeder size and the breaker size.

Thank you.

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#175262 - 02/25/08 08:10 PM Re: load diversity factor for car parking lift [Re: theseus]
NORCAL Offline
Member

Registered: 09/25/02
Posts: 807
You don't provide much info, like voltage, # of phases....

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#175266 - 02/25/08 08:32 PM Re: load diversity factor for car parking lift [Re: NORCAL]
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
Since lifts are little more than a motor, I would apply the usual motor rules. I believe that your situation is covered in 430.24, exception 1.

Still, I would not carry that exception to an extreme. One does need to make a judgment call as to how often the lifts will operate, and how many will operate at once. For example, the pattern of use will differ between a transmission shop, a tire shop, and a school shop.

Indeed, this might be a good time to review the 'tap rules,' and plan your distribution accordingly. Here is where the importance of a fusible disconnect becomes clear.

One wild guess might be to have a 30 amp circuit feeding a cluster of 5 lifts, with each lift fused (time delay) at 10 amps.
As for the size of the service feeding the shop, I'd be happy with the usual load calculation method, relying on the square footage allownace for 'general lighting.'

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#175270 - 02/25/08 10:54 PM Re: load diversity factor for car parking lift [Re: renosteinke]
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
Hi there Theseus,
OK, you have 50 of these lifts, now, you have to figure in the fact that they will not all be running at the same time,or will they?, this is called a diversity factor.
For the purposes of supply, what voltage are you working with?
Unless you give more information on how your area of the world sizes electrical supply to buildings such as this, I'm sorry we can't help you.

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#175287 - 02/26/08 05:38 AM Re: load diversity factor for car parking lift [Re: Trumpy]
theseus Offline
Member

Registered: 02/23/08
Posts: 11
Loc: china
Electrical data is as follows:
Main electrical supply 230/400V,50 Hz, 3 phase. Power consumption 3.0 kW. Fuse or automatic circuitbreaker 3 x16A slow blow.

Somebody suggested that the demand factor is 0.3,but I don't know why.Can I consider car parking lifts as elevators and use the 0.72 demand factor?

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#175288 - 02/26/08 05:46 AM Re: load diversity factor for car parking lift [Re: theseus]
theseus Offline
Member

Registered: 02/23/08
Posts: 11
Loc: china
Thanks all.
These car parking lifts will be used in a parking lot.

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#175296 - 02/26/08 09:23 AM Re: load diversity factor for car parking lift [Re: theseus]
Wolfgang Offline
Member

Registered: 09/25/05
Posts: 154
Loc: the very West of Germany
I suppose that those motors won't be charged completely but being overdimensioned will draw rather 4 or 5 than theoretical 6 Amps per phase.
Furthermore "downlifting" will draw less power than "uplifting".

Sounds like some 7 amps for both at a time?

So how many of those motors will run simultaneously? I'd take
50 - 100% security and check in a next step whether this power is easily available at your place. If not you rather should install a sort of "exclusion logic" than to invest in excessive copper graves.

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#175348 - 02/27/08 07:54 AM Re: load diversity factor for car parking lift [Re: Wolfgang]
theseus Offline
Member

Registered: 02/23/08
Posts: 11
Loc: china
renosteinke Said:
One wild guess might be to have a 30 amp circuit feeding a cluster of 5 lifts, with each lift fused (time delay) at 10 amps.
As for the size of the service feeding the shop, I'd be happy with the usual load calculation method, relying on the square footage allownace for 'general lighting.'

Is that OK?
1) a 30 amp circuit feeding a cluster of 5 lifts, with each lift fused (time delay) at 10 amps.
2) the usual load calculation method, relying on the square footage allownace for 'general lighting.'

and what's the feeder breaker size?

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#175359 - 02/27/08 06:34 PM Re: load diversity factor for car parking lift [Re: theseus]
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
I did say "wild guess." \:D At the time, there was NO voltage info available ... any every area has its' own rules and practices.

When I said "30 amp circuit," I was thinking in terms of #10 wire and a 30 amp inverse time breaker. Our tap would allow you to feed the fused disconnects, because a) there are fuses in them and b) our smallest disconnects are rated for 30 amps (maximum load).
I took the liberty of assuming 208-230v single phase motors.

As far as the feeder breaker ... again, here we start off our load calculations with the square footage - not the appliances used. Since the loads are sporadic, I did not consider it necessary to place much weight on the appliance contribution to the lighting load.
A rough estimate of the space occupied, again a wild guess, my numbers suggest a 60 amp feed is plenty for the lifts, the lights, and the convenience outlets.

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#175364 - 02/28/08 05:33 AM Re: load diversity factor for car parking lift [Re: renosteinke]
theseus Offline
Member

Registered: 02/23/08
Posts: 11
Loc: china
Hi,renosteinke.Thank you very much.
By the way,is there any reference books showing the load calculation of parking lot containing these parking lifts?

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