NEC 220.87 (1) Exception

[hbendillo]

I have measurements for a project that were taken over a 30 day period using a recording ammeter. The measurements are going to be used to determine if additional loads can be added to a generator. The relevant portion of the exception that I want to confirm is as follows:

"..........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......."

My interpretation is that the maximum demand value to be used is the highest of 15 minute average power demand readings recorded over the 30 day period. I also understand this value must be multiplied by 1.25. Yes, I am kind of repeating what it says but for some reason I am doubting my reasoning.

Is this correct?

Thanks.

 

[charlie b]

You have the right concept. But I hope your recording device was not just an ammeter. You need to have measured average values of power demand, and that would require a voltage measurement at the same time as the current measurement.

 

[hbendillo]

You have the right concept. But I hope your recording device was not just an ammeter. You need to have measured average values of power demand, and that would require a voltage measurement at the same time as the current measurement.

Yes, they did voltage measurements at the same time. However all I have from them right now are peak and average voltage measurements and peak and average current readings along with their graphs. I hope they can extract the information for me from the data they gathered. I was not involved in the project when the measurements were done.