Determining and Adding KVA for a Building

[BigBreakfastJohn]

Three questions about KVA requirements

Background:
We have a building with a mix of 480V, 208V, and 240V panels. No drawings to speak of, almost all panel schedules are out of date. I'm trying to determine load requirements so we can reroute power to it. It's a lab building with a variety of equipment that runs at random hours for random times, so figuring out power draw from their loads is difficult. I talked to their process engineer, the run-time numbers he gave me seemed way too long.
I also plan to go in the morning before their work day, check the power meter (old style analog, with no ammeter or remote monitoring), and go at the end to see their power draw for a single 8 hour shift.
Daily average KWh for the building is about 1400, but without knowing when they're using the different load, I don't know their peak loads.

Question 1: Is there anything else I do/look at to determine loading?

All of the building's power is supplied from one 480V 100A breaker and one 480V 400A breaker.

Question 2: Is it reasonable to say I need 240KVA of transformer from the utility using this method?

2nd question:

On a walkthrough for re-powering the same building with the utility, the utility engineer said that 3 100 KVA transformers are sufficient for a 300 KVA service.

Question 3: If it's 3 phases, doesn't that just mean that it's 3 phases of 100KVA capacity?

 

[Dennis Alwon]

This is all I can add to it

220.87 Determining Existing Loads.

The calculation of a feeder or service load for existing installations shall be permitted to use actual maximum demand to determine the existing load under all of the following conditions:

• (1)
  The maximum demand data is available for a 1-year period.
  Exception:
  If the maximum demand data for a 1-year period is not available, the calculated load shall be permitted to be based on the maximum demand (the highest average kilowatts reached and maintained for a 15-minute interval) continuously recorded over a minimum 30-day period using a recording ammeter or power meter connected to the highest loaded phase of the feeder or service, based on the initial loading at the start of the recording. The recording shall reflect the maximum demand of the feeder or service by being taken when the building or space is occupied and shall include by measurement or calculation the larger of the heating or cooling equipment load, and other loads that might be periodic in nature due to seasonal or similar conditions. This exception shall not be permitted if the feeder or service has a renewable energy system (i.e., solar photovoltaic or wind electric) or employs any form of peak load shaving.
  
  
• (2)
  The maximum demand at 125 percent plus the new load does not exceed the ampacity of the feeder or rating of the service.
• (3)
  The feeder has overcurrent protection in accordance with 240.4, and the service has overload protection in accordance with 230.90.

 

[Elect117]

Question 1: Is there anything else I do/look at to determine loading?

Reading nameplates of the loads. Adding the receptacles at their load. etc.

Ask for utility metering data and hopefully the record max demand. They might not.

You can get a 3rd part device and run it for a year.

Question 2: Is it reasonable to say I need 240KVA of transformer from the utility using this method?

That is not really a method. If you are trying to see what the max kVA you could put on those services continuously then that would be 333kVA. (80% of 100A + 80% of 400A = 400A => 480V*SQRT(3)*400A = 333kva

Question 3: If it's 3 phases, doesn't that just mean that it's 3 phases of 100KVA capacity?

Yes. They will hang a 3x100kva transformers. That is a 300 KVA capacity (and arguably quiet a bit more depending on overloading factors and utility specs).

 

[Knightryder12]

You cannot determine the load from KWh. Even if the meter is not a kw meter, if you get the electric bills it will have peak demand KW on the bill. That is what I have found from the POCOS here in Florida.

 

[MI_Engineer]

I have also had luck reaching out to the POCO with a phone call if it's not printed. You may have to give them the background and a sob story for them to help.

They usually don't give out any more information than that without an Owner's "representative" giving the okay to share it.