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#20393 - 01/13/03 10:45 PM Sizing Generators - 12KVA enough?  
sparky66wv  Offline
Joined: Nov 2000
Posts: 2,236
West Virginia
Relatives of mine are trying to choose, with my help, a properly sized genset or genny and transfer switch(s) for back-up since the aged grandparents are living there complete with life-support and powered chairs.

Minimum, they want on the "EM" circuits:

2 Lift chairs @ 130W each

1 Breathing Machine with a nameplate rating of 4A 120V (480W)

1 Refrigerator, 600W

1 Freezer 600W

1 Water Pump 5A min, 240V

The clincher:

1 furnace 240V 35A min, 46A max. (unsure due to lack of model number versus a generic nameplate)

If possible add:

2 lighting circuits to include Living Room and Bedroom of elders (might get lucky and they're on the same circuit, but unlikely)

1 Water Heater (4800W) (Hah!)

My figures, 12KVA to 18+KVA, but this is a guesstimation big time.

How much diversity can I count on?

How small can we go and not have the genny stall when the furnace kicks on?

They originally had hoped to only spend $2K, but I dashed those hopes as soon as they said they wanted the electric furnace on the genset as well.

Hoo boy!

Would they be better off with a 200A transfer switch, and transfer everything, or isolated circuits? Or, a genset with auto-transfer (they kinda like that idea...)

They are looking at what Northern has to offer, and I told them I would investigate the possibilities (read: post on ECN and yell "help!")


[Linked Image]

Residential/Commercial Inspector
5 Star Inspections
Member IAEI

Work Gear for Electricians and the Trades

#20394 - 01/13/03 10:59 PM Re: Sizing Generators - 12KVA enough?  
ga.sparky56  Offline
Joined: Nov 2002
Posts: 558
young harris georgia usa
Virgil,I once helped my nephew (heat and ac contractor) install a 4 ton heat pump,don't remember amperage draw, But generator company brought 3 gen. before they got it right. It would kill a 15kw when it tried to start, It killed a 20kw when the heat strips came on. A30 kw allowed it to start and run ok. The heat pump was the only thing on it.

#20395 - 01/13/03 11:04 PM Re: Sizing Generators - 12KVA enough?  
HotLine1  Offline

Joined: Apr 2002
Posts: 6,853
Brick, NJ USA
18 KW, with mental math real quick.
20 KW is probably the "standard" available, either thru supplier, or the big box store.

Start-up of the furnace blower, and water pump, with frig & freezer, and the items you listed make me lean to 20KW.

If you have an Orange Apron store by you, they have gensets (propane or natural gas)
(Complete with transfer switch)
The "Electrical Advertiser" also has gensets available.

For what it's worth, I think your 2K figure was blown out the window.


#20396 - 01/13/03 11:50 PM Re: Sizing Generators - 12KVA enough?  
txsparky  Offline
Joined: May 2001
Posts: 552
Magnolia,.Texas U.S.A.
[Linked Image] A quick price check on a 20kw turned up this:

Onan standby generator
LP Propane System
MSRP: $17,884.00

Onan standby generator
Natural Gas System
MSRP: $17,884.00

at least the shipping is free [Linked Image]


#20397 - 01/13/03 11:55 PM Re: Sizing Generators - 12KVA enough?  
Bjarney  Offline
Joined: Apr 2002
Posts: 2,527
West-Southern Inner-Northeast ...
Find web sites for outfits like Kohler and Onan for local-rep contacts. They do load calcs all the time. The size of genset for 1ø might be somewhat more expensive than a 3ø version. The hitch is motor starting capability. 1ø motors are a little more difficult, too. Modern permanent-magnet excitation helps out some.

Put together as complete a load list as you can—reps will probably have some questions about anticipated duty and load diversity. And things like “just how automatic does it all need to be?” It doesn’t sound like a legally required system so that may simplify things a bit.

It’s a long shot—reps may know of some surplus equipment, but 3ø sets may be more common in that rating.

#20398 - 01/13/03 11:56 PM Re: Sizing Generators - 12KVA enough?  
sparky66wv  Offline
Joined: Nov 2000
Posts: 2,236
West Virginia
Ahhh... Don't worry.

The $2K was the price THEY said. Not me.

I have given them nothing but an hourly rate quote so far.

The materials are their problem.

They were just "hoping" it would be in the $2K range. That was even after my wife warned them that a 200A transfer switch would cost $750, they had initially wanted a 200A genset (for $2K!!!).

[Linked Image]

I just want to insure that they have enough Umph without spending too much and crying "overkill".

[This message has been edited by sparky66wv (edited 01-13-2003).]

Residential/Commercial Inspector
5 Star Inspections
Member IAEI

#20399 - 01/14/03 02:06 AM Re: Sizing Generators - 12KVA enough?  
nesparky  Offline
Joined: Jun 2001
Posts: 642
try this link
Also take a look at thier home page about fuel cells.
may be this would be something interesting inthe future?


#20400 - 01/14/03 02:17 AM Re: Sizing Generators - 12KVA enough?  
Scott35  Offline

Broom Pusher and
Joined: Oct 2000
Posts: 2,707
Anaheim, CA. USA
I was thinking of a 20 KW size also - having seen the projected / possible loads; however, just what will be running at the same time?

Also, the thought of a 20 KW Genny coupled to a 30 HP Prime Mover is - in simple terms "Tim Taylor Overkill" for a small Residential setup! [Linked Image]

Not that it wouldn't be cool! I would do it, but I also have a "touch of the 'ol Tim Taylor" in me!
The Neighbors would just love hearing that 30 HP Diesel Prime Mover chuggin' all night long!
(I would most likely use a Diesel Prime Mover - once again, the "Tim Taylor" Syndrome [Linked Image]... although, a Gasoline Prime Mover would be fun too!).

Hefner (as in Hugh Hefner - Playboy Magazine) has two standby gensets at the "Playboy Mansion West" (Belair, CA).
The original first one is a 750 KW Diesel Genny.
The newest is a 1 MW or 1.5 MW Genny.
These get plenty of use during the Raging Parties thrown at the place!
The PoCo cannot upgrade the original 4160 VAC Primary Feeders (something like a 100 amp circuit???), so when the KW load in this area gets high (and corresponding Party-Personnel get high [Linked Image]... ), the Breaker trips at the yard, leaving the customers Sans Ready Killowatt!
(Credits to Virgil, for the "Sans" term!)

Now when the breaker trips, everyone else loses power, but Party keeps on Raging!
All thanks to Standby Gensets!

This story, along with others, are more indepth and kind of interresting!
Maybe sometime when I have an urge, I'll post more about the Mansion.
Sorry, no naked women stories!

Scott s.e.t.

Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

#20401 - 01/14/03 02:23 AM Re: Sizing Generators - 12KVA enough?  
txsparky  Offline
Joined: May 2001
Posts: 552
Magnolia,.Texas U.S.A.
Scott,are you pleading the 5th? [Linked Image]

Theres alot to be said for having appliances that is.I can get by on a 5000watt and the only thing I won't have is a/c.

[This message has been edited by txsparky (edited 01-14-2003).]


#20402 - 01/14/03 07:38 AM Re: Sizing Generators - 12KVA enough?  
Trainwire  Offline
Joined: Mar 2002
Posts: 360
Funny how all of a sudden generators are all the rage.

I am currently installing two brand new 25KW 240volt 3 phase desiel generators in our train. We use them to power the kitchen in the dining car,and the parlor car.

They were $15000 each, in a railroad grade box (read whacking heavy)with remote starts.

I really think you would be money ahead to find some sort of standby heat source, A ventless propane fire place for instance, as well as abandon the hot water heater. It might be that if you contact the power company, they might work with you if they realize there are "life issues" on that particular curcuit, and make restoration of power a priority. Which would make what you have to tie to the generator much less, just the breathing machine, chairs and some lights.

Good luck, and let us know how it turns out.


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