existing loads

[Bryank]

when determining existing load in a building, the building being a medical office building or clinic, what are the requirements of taking the readings? Duration of test 3 day or 30 day? when would each be allowable?

 

[jumper]

See 220.87

 

[Johnbrett]

yes its very important to determine the existing load of the building.

John brett

 

[mike1061]

One time I asked an electrical engineer to help. He had me get the electric bill for 12 months.
Thanks
Mike

 

[vango]

Yes 220.87
I contact the utility company and request a "peak demand load" for a 12 to 24 month period (prefer 24 month).
The peak demand loads around here are of course mid to late summer for the AC and "dead of winter" months for electric heat
users. I wouldnt suggest a 12 month average (not saying the engineer did either) cause one can easily drown in a river that is only a few inches deep "on average".

 

[kwired]

One time I asked an electrical engineer to help. He had me get the electric bill for 12 months.
Thanks
Mike

If the meter records peak demands and that information is on the bill - you have something useful.

If the meter only records kWhrs used - the only thing you really know is how much was used in a one month period. You don't know if it was averaged out during the entire time period, or if it was heavier during certain periods, or maybe it was almost entirely in the first day and was idle the rest of the month.

Good example is a church that only has activity on Sunday morning and maybe Wednesday nights (somewhat common around here anyway) There is minimal load the rest of the month but most of what is on the bill happens during those periods and things can be loaded hard but only for a few hours one or two days a week.

 

[iwire]

I know most of us are guys here and reading directions is akin to going nick knack shopping but I am going to post the code section anyway.

The exception is often used.

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 (measure of average
power demand over a 15-minute period) 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 may be periodic
in nature due to seasonal or similar conditions.

(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.