Size of Service Disconnect

[5Spot]

I've got a new office building going up with 8 office spaces for tenant improvement. Each office space has a calculated load of 87 amps. I'll be providing 100 amp sub panels at 120/208, 3 phase for each office. For my switch gear, how do I calculate the size of the main service disconnect feeding all 8 panels? The power company is providing 120/208, 3 phase to the building?

 

[dicklaxt]

Do you have an operating load????????If not I think this is a spot for a SWAG of .5 diversity,in the absense of no direction from client,that would give you roughly a 400 amp disconnect. It will be interesting to see others approach.I would size the wire for nearly max connected in case you start getting nuisance trips and then you could simply upgrade your trip or fusing protection as needed.

dick

 

[JohnJ0906]

Don't forget the house loads and house meter.

 

[bob]

A/C and lighting are figured at 100%. Article 220 gives you a reduced demand factor for receptacles and kitchen equipment if you have any. SWAG factors are not listed.