Commercial Office Building Service Load Calculation - 220 Estimates

[ron]

Does anyone keep records on how their service calculations have turned out based on occupancy and VA/square foot?

Article 220 is relatively conservative compared to utility demand, so estimating early in the design is a challenge.

I asked a similar question about a year ago (linked below), but wondered in anyone had more up to date info since LED lighting has become so accepted.

http://forums.mikeholt.com/showthread.php?t=180987

http://forums.mikeholt.com/showthread.php?t=186305

 

[JoeStillman]

That sounds like a good job for an intern - go back through the old jobs and analyze the load statistics for different types of buildings.

A common problem I've seen is for a senior engineer to take a well educated guess at the service size, just so he can get the paperwork started with the utility company. Then the job gets delegated to a junior designer who takes that estimate as gospel and never revisits it with connected load. Load calcs are iterative and have to be updated constantly throughout design.

But still, those earlier threads make a good case for non-NEC diversity factors on a really big building. The only place in the NEC where I could find a load-calc reference to "Engineering Supervision" is high-voltage feeder loads.