Diversity factor to total connected load!

[helzaiat]

Q. We have a 480-277V, 3 phase, 4 wire, 2000A Service entrance main switchgear that feeds 1243 KVA mechanical loads in addition to 400 KVA
of lighting and recepticales (utlization volt for them is 120V)
The 400 KVA load has been calculated as 100% lighting load 100% equipment loads and first 10KVA of receptical loads + 50% of the remaning receptacles. To size the transformer for the above described
400 KVA load ? could we apply a 75% diversity factor to total connected loads and choose 300KVA transformer??

 

[bennie]

Re: Diversity factor to total connected load!

Diversity factor will affect the demand factor. The transformer will see the peak demand and must be sized accordingly.

Calculating the peak demand is a crap shoot. Apply data from existing installations that are like the design of this project.

 

[charlie b]

Re: Diversity factor to total connected load!

Originally posted by helzaiat:The 400 KVA load has been calculated as 100% lighting load 100% equipment loads and first 10KVA of receptacle loads + 50% of the remaining receptacles. Could we apply a 75% diversity factor to total connected loads and choose 300KVA transformer?

The NEC does not use the concept of a ?Diversity Factor,? in the standard engineering context of that phrase. The key NEC statement of interest here comes from 220.10, ?The computed load of a feeder or service shall not be less than the sum of the loads on the branch circuits supplied, as determined by Part I of this article, after any applicable demand factors permitted by Parts II, III, or IV have been applied.? You are describing a feeder (i.e., to your transformer), as well as the size of the transformer itself.

You have already applied the correct demand factor for receptacles in a non-dwelling unit (per Table 220.13). There are no other demand factors available to a non-dwelling unit, unless it is a school, a restaurant, or a farm.