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Estimating available capacity based on peak demand

K

katwalatapan

Member
Joined
Mar 14, 2014
Messages
11
Location
halifax
Hello,

I wanted to inquire if it is possible to estimate available electrical capacity in an electrical distribution system based on only peak demand information available. For e.g. if an 800A, 347/600V, 3-phase electrical service has a peak demand of 175kW, would it be safe to assume the following calculation to estimate available electrical capacity at unity power factor:

800A x 0.8 = 640A (max. loading)
175kW = 600V x A x 1.732 i.e. A = 168A
Available capacity would be 640A - 168A = 472A.

Would the estimation of available capacity change if there are 600V - 208V step-down transformers downstream of the electrical distribution system?

Thank you.
 
I don't know about Canada, but the National Electrical Code 220.87 allows you to use the maximum demand for a one year period as the existing load. New loads would be calculated in accordance with NEC 220.40.
 
Thank you. I believe there are demand factors as well which could be applied for existing load and new loads to be calculated based on applicable code section.
 
The demand factors in the NEC only apply to new loads. I have found that actual demand is often less than half the calculated load, so you can look at the actual demand as a real-life demand factor.
 
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