# Service calculations help..

1873 Views 7 Replies 4 Participants Last post by  N PHILLY KID
Hello all, hoping to get some input.... Looking at a new office build out. Space in inside existing building. Never had to do Service calculations before, trying to work my way through it. It will have to be submitted for plan review. Square foot of office space=3495 sgft. Existing is a 42 ckt,225 amp 3 phase panel 120/208 fused by a disco at 100a. They came off a 75kvs trans, tapped to (2) 100a disco's. The panel Im looking at using has the following existing loads, (3) 20a recep circuits- number of recepts unknown, (1) 20a s.p. fuel pump-amps unknown, and (2) 20a s.p. over head doors.
1- 30a 2p electric water heater
63- 20a. receptacles (9 per circuit)
2- 20a. garbage disposals
4- 20a. kitchen circuits- each circuit will have (4) 20a recepts
4- 20a. bathroom exhaust fans

I know this.... 63x180=11340va..first 10000+(50% of 1340)=670
10670/208=52 amps

Can anyone point me in the right direction of where in ART 220 I can find how to calculate the remainder? My hopes are this 100a panel will support the load. Thanks in advance!
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#### michigan sparky

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Would 220.60- noncoincidental loads apply for the 2 garbage disposals and 2 overhead doors?

#### wildleg

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not likely. a noncoincident load would be something like a heating/cooling unit that could only heat or cool, but not both at the same time.

#### michigan sparky

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thinking back your 100% right..almost word for word from my teacher..thanks!

#### michigan sparky

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any advice on calculating the other loads?

#### MikePEC

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Around here you would need stamed engineered drawings for that

#### michigan sparky

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Around here you would need stamed engineered drawings for that
I submitted all my info, loads and existing service to an engineer, hoping to get the stamp. I guess I'm trying to do it on my own, just to see if it will be possible. Thanks!

#### N PHILLY KID

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service calculation help

the appliances dispossal fans ect are determined by the name plate ratingof the appliance not the breaker size . 20 amp recept. circuits would be 1500 va each water heater would be the wattage of the heater . Also keep in mind article 422appliances requires 125 % increase in branch circuit capacity, this would apply to all appliance loads but not the 20 recept. load .

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