**A. ****Total connected load on feeder**

- Calculate load for Convenience power, Mechanical system, Elevators, Escalators, Lab equipment, Kitchen equipment, Appliances and lighting.

**B. ****Demand loads**

- General floor power: per local code.
- Computer equipment :100%
- Motors: 100% + 25% of largest motor.
- Elevators: per local code
- Laboratories: 75% of connected loads or 20 watts/square ft (if allowed by local code).
- X-Ray equipment: per local code.
- Appliances: Per local code.
- Lighting : 100%

**C. ****Spare Percent loads**

- General: 25% spare for future loads.

**D. ****Cable size selection**

- Cable size to be based on the following:

- Maximum Voltage Drop of 2.5% from service to last distribution point. Maximum of 5% from service to load device.
- Feeder serving continuous loads must have a cable ampacity equal to or greater than the feeder overcurrent protective device.
- The ampacity of the feeder must equal or exceed the continuos load times 1.25 plus the non- continuous load. For feeders serving multiple motors size feeder on demands amps + 25% of largest motor.
- Feeder serving elevator load to be sized on the connected load times the diversity factor per local code plus 40% of the largest elevator.

**E. ****Conduit size**

- Conduit size shall be based on cable size and insulation type. Maximum 40% of conduit cross section fills. Refer to local Codes.

**F. ****Calculations and formulas**

- Feeder Demand Amps= Connected Amps x Demand + Spare
- Voltage Drop= Impedence x Feeder demand Amps x Length
- V = 2 x R x L x I /CIRC.MILLS x 2

**G. ****Lighting Branch Circuiting**

a. 15A,120V circuits

1) General: 1100 watts

2) Maximum: 1300 watts

b. 20A,120V circuits

1) General: 1500 watts

2) Maximum: 1800 watts

c. 20A, 277V circuits

1) General: 3500 watts

2) Maximum: 4500 watts

Spare circuits: Approximately 25%

**H. ****Receptacles Branch Circuiting**

1. Convenience Receptacle- 180 watts per receptacle per NEC:

a. 20A,120V circuits per NEC

b. General: 6 outlets

c. Maximum: 10 outlet

2. Appliance Receptacles - check local electrical load for circuit limitations.

Spare circuits: Approximately 25%