Commercial Service Calculations

Ampacity Correction
Temperature Correction
Continuous Load Correction
Conduit Fill Correction
Minimum Number of Circuits
Bus Bar Ampacity
Conductor Resistance
Resistance Change
Motor Disconnect Sizing
Full Load Current Interpolation
Motor Conductor Sizing
Motor Overcurrent Protection
Motor Overload Sizing
Lighting Loads
Fixed Appliance Loads
Range Loads
Range Loads Note 1
Range Loads Note 2
Dryer Water Heater Loads
Heat AC
Standard Residential Service
Optional Residential Service
Standard Multi Family Service
Optional Multi Family Service
Commercial Services
Optional School Services
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The calculation for a commercial building service has to be the easiest one to make. Typically all the connected load is added together. Then this va number is divided by the service voltage and 1.732 if it is a three phase service.

There are always little glitches to be concerned about.

First, restaurants have a reduction factor for kitchen equipment. And there is even a separate calculation rule set for a remodel of a restaurant. Also keep in mind that for a restaurant, and only a restaurant, the heat and air conditioner load BOTH are included in the service calculation.

Also, in office buildings there is a reduction in va permitted for receptacle loads over 10kVA. See the table for that percentage.

Other rules for specific occupancies can be obtained from NEC220 as needed.

Here are some practice problems for various occupancies:

Recycling Center
Convenience Store
Gas Station
Sanitary Lift Station
Car Wash
Recreation Center
Department Store
Manufacturing Plant
Waste Water Treatment Plant



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