generator load calculation

[dashco]

I have had 4 generators installed for our customers that used a kilowatt averaging on the high and low month for sizing. NEC does not have an article to support this.
Is there a product (such as an undervoltage breaker) that would require a reset when the voltage is lost?
Is load shedding appropriate? What is the easiest way to reduce the
calculated load for emergency generator backup?
I purchased a Fluke 1735 Power Logger and am going to try and submit a
30 day reading under provision 220.87, Exception.
Any suggestions are welcome

 

[coulter]

I have had 4 generators installed for our customers that used a kilowatt averaging on the high and low month for sizing. NEC does not have an article to support this. ...

An article to support what? - sizing a generator by this method? I wouldn't think the NEC would. It's a design issue.

...Is there a product (such as an undervoltage breaker) that would require a reset when the voltage is lost?...

Yes, as you suggested, a UV relay on or in the CB

..Is load shedding appropriate? ...

Sure. These are design issues between you and the customer.

... What is the easiest way to reduce the
calculated load for emergency generator backup?...

A question:
When you say "emergency", do you mean:
1. Art 700 Emergency Systems?
2. Art 701 Legally Required Standby?
3. Art 702 Optional Standby System?

The answer to this really matters. There are different legal requirements.

...I purchased a Fluke 1735 Power Logger and am going to try and submit a 30 day reading under provision 220.87, Exception. ...

Okay, I'm lost. Submit this to who? 220.87 is generally used in lieu of doing a load calc to see if there is sufficient feeder/service capacity to install additional equipment.

Items 1 or 2 above have legal requirements to meet. Calculate them, meet them.

If you are installing under Art 702, you and the customer decide what to power up. Calculate it, meet it - don't forget to watch for:
1. leading pf on such things as VFD's, UPS's
2. Motor starting loads

If you are trying to power the whole plant, maybe the recording power meter data will help.

Perhaps a more detailed description of what you are trying to do will help.

carl

 

[coulter]

one additional thought:

You may have issues requiring a PE. Paraphrasing:

In some states, buildings for public occupancy, require a PE stamp on product of engineering (drawings, specs, installation details).

If not a public occupancy, the customer's engineer (customer's employee) can do the work, but not you. And the customer can just about call anyone they want an "engineer".

carl

 

[Cavie]

I can only speak for Florida. The Generator and ATS must be sized to the connected load. Not a monthy reading from the power company. Yes you can install a Load shedding system. They work very well and solve the problem of having to buy a Large Generator.

 

[steve66]

But of course you can't shed Article 700 or 701 loads. What else is the generator feeding?

Steve