Generator Sizing!

Take a class in grade-school arithmetic.

Dear Tornado,

That's what I want to know. Is it the only criteria for selecting the gen. set?

250 x 1.2 = 300. No large motors have been mentioned, nor other special needs to start large loads. 300kVA should do, or maybe the next size up for a bit of reserve.

Thanks!

Just to clarify, we have :

40 no.s of 18000 btu air conditioners.

60 no.s of Personal computers

and lighting requirement for 24 x 24 sq. m area.

I am planning to request a gen of 300 KVA.

That sounds about right, especially if you don't start all the air conditioners at once.

Dear Mr. Magnetic_flux,

You have referred 40 Nos. of 18000 Btu Air Conditioners. 18000 Btu means it is 1.5 Tonner Air Conditioner, which will will take about 7.2 Amps - if it is single phase machine, and for 380 Volts, the single phase voltage will be 219.39 Volts, say 220 Volts.

If the AC machines are of single phase, the choice before you is to connect 13 AC Machines in each phase and one additional AC in any one phase, and distribute the lighting load in such a way the load is equally (as for as possible) distributed. Since the Personal computers to be connected 20 nos. in each phase. I am considering the lighting load will be 12 to 15 KW. Only thing is 13 AC machines in particular phase should not be switched on. When AC machine is started, it should be from different phase.

If this aspect is taken in to account the AC load will be about 85 KW, Lighting will be 15 KW, and personal computers about 7 KW, totaling to 107 KW say 110 KW. Take 20% on 110 KW which will be 132 KW.

Since you are not having any motor, 200 KVA Generator should be sufficient. If you can get 3 phase motor for AC machines, nothing like it and the load will be balanced irrespective of no. of AC machines switched on, and 200 KVA Generator will be sufficient.

Let us see what other Members suggest.

DHAYANANDHAN.S

Thanks for your detailed response. There will be power sockets as well. The site office will be there for 4 years and I am not sure what loads we will have in future. So even in the worst case, 300 KVA would be sufficient.

Thanks again for your suggestion!

Looking at the type of loads, the overall power factor is likely to be much lower that 0.8. This means, your kW loading may be low but the kVA requirement of the generator will be high.

Other point is step loading requirement of DG set to be spelt out. It would be good idea to ensure that all the A/Cs switch-off automatically when the power fails and are switched-on one-by-one after restoration of power.

Just a caution.

Thanks for such a good suggestion!

If your office is going to be there for 4 years, may I also suggest you select a unit from someone (company) that offers service on site. Even if you have your own maintenance staff for the everyday stuff, be prepared for some kind of failure that they may not be able to handle.

Will you now order a generator, on-line, from a company you've never heard of and about which you know nothing?

Write down ALL the potential devices that will, or may, consume power, and the amount of power they will consume.

Then get in touch with three generator suppliers, with your COMPLETE list and get bids from them, after they have determined your power needs.

Dear Lyn,

Thanks for your counsel.

This appears to be in either Korea or Brazil, by the power used.

My advice is still to consult with professionals who sell and service this equipment.

I already have sought a professional advice. There recommendation is 300 KVA.

Really appreciate all those who helped!