RESOURCE LIBRARY

1. Convert Watts to AMPS:

· Watts divided by Voltage

Example:

2,300 WATTS = 2300w divided by 120v = 19.1 AMPS

(for 3 Phase divide by 1.73)

2. Convert AMPS to Watts:

· AMPS multiplied by Voltage

Example:

19.1 AMPS multiplied by 120v = 2300 Watts

(for 3 phase multiply by 1.73)

3. Convert Horse Power to AMPS:

· Multiply Horse Power by 746w (1 HP = 746 Watts)

Find Circuit Voltage and Phase

Example:

30 HP at 480 (3 Phase) - 746 multiplied by 30 = 22380

22380 divided by 480 (3 Phase) = 46.5

46.5 divided by 1.73 = 29.5AMPS

Multiply all the motor loads by 1.50% and go to the next circuit size.

4. Convert KVA to AMPS:

· Multiply KVA by 1000/voltage

Example:

30 KVA multiplied by 1000v = 30,000 Watts

30,000 Watts divided by 480 = 62.5 AMPS

(for 3 phase divide by 1.73)

5. Convert KW to AMPS:

· Multiply KW by 1000/voltage and then by power factor

Example:

30KW multiplied by 1000v = 30,000

30,000 divided by 480 = 62.5 x .90 = 56.25amps

(for 3 phase divide by 1.73)

6. Building Supply Power:

· Large buildings generally have 277/480v.3ph.4w incoming power to a main disconnect. This is fed by the power company. Most lighting, air conditioning and equipment are fed by this voltage. To feed general receptacles a step-down transformer is installed (480v 3PH. Input and 120/208V/.3PH Output).

7. Panelboard Capacity

· 100A panelboard will handle 100A per phase

· Find the existing loads from each circuit

· Add them and multiply by the Circuit Voltage

· Divide by panel voltage and (1.73 for 3 Phase)

· The total should not exceed 80% of the 100A

· Remember Circuit Voltage is not the same as Panelboard Voltage.

· Panelboard Voltage 208v or 480v

· Circuit Voltage might be 120v or 277v

8. Portable Equipment:

· Portable equipment cannot be hardwired (this includes benches that are not fastened to the floor)

· Typical solution is to install a cord drop or a cord with a plug

9. Safety Disconnect:

· A circuit disconnect must be installed within sight or not more than 50ft. from the piece of equipment

10. Breaker Style and Brand:

· When a new breaker is installed in an existing panelboard, verify that the proposed breaker style is listed on the panelboard manufacturer’s name card (information posted on the panelboard cover)

· The AIC Rating of the breaker must be equal or greater than the panelboard’s AIC rating (located on the information card)

11. Clearances:

· All electrical panelboards, transformers, switchboards, disconnects, etc., must have the following working clearances:

· 42” for 480v equipment

· 36” for 240v equipment

12. Circuit Identification:

Even though it is not a code issue, it still is a good practice to –

· Require that all receptacles, light switches, and electrical equipment be labeled with the circuit information, including the panelboard designation and circuit number

13. Amount of Devices Per Circuit:

· Receptacles (Rule of Thumb):

Not more than (6) per circuit

· Copiers and appliances (coffee pots, microwaves. refrigerators, water coolers, etc.) should be on a dedicated circuit

· Dedicated means no other load or device should be connected to this circuit

14. Light Fixtures Per Circuit:

· Multiply ballast AMPS by the amount of ballast or lamp watts

· The total should not exceed 80% of the Circuit AMPS

Example

A 20AMP 120v circuit could only be loaded to 16 AMPS which equals 57 fluorescent lamps-34 Watt or 19 2 x 4 Fluorescent Fixtures-3lamp.

15. Device Mounting Heights:

· Receptacles 15”

· Receptacle in bathroom 44”

· Receptacle above counter 4” above back splash

· All heights are the center line of the device and above finished floor or surface.

· Light switches 46”

· Restroom light switches 42”

· Disconnects and panelboards should not be more than 6’ from the finished floor to the top of it

16. Required GFI Protection:

· All receptacles within 6’ of any water source

· Receptacles on the roof

· Receptacles exposed to the outside weather and in wet locations must be GFCI protected. This can be accomplished by installing an approved GFI breaker or a receptacle with built-in GFI protection.

17. New Building Electrical Services Protected by Main GFI Breaker:

· All electrical services 1000AMPS at 480v or greater must be protected by a GFI (Ground Fault Interrupter) main breaker

· Ground fault testing must be performed by an approved testing agent. A ground neutral could cause the main GFI breaker to trip

· A short circuit on a lighting circuit could cause the main circuit breaker to trip which would result in the entire building being shutdown until the beaker is restored to the ON position

18. Isolated Ground Receptacle:

· All critical computer equipment and some copiers should be connected to an isolated ground receptacle(commonly orange color)

19. Server, Telephone and Data Rooms:

· All circuits feeding these rooms should not be shared with other devices that are not part of these rooms

· An overload on a circuit caused by someone plugging in a piece of equipment into a receptacle that is connected to the same circuit as these rooms will trip the breaker and data loss or hardware damage could occur

20. Energy management Systems:

· Typical Energy Management System controls the light fixtures per title 24, automatic lighting control should be in 5,000sf increments (maximum) in a building on the following schedules:

· Lights on at 6:00 a.m.

· Lights off at 6:00 p.m.

· Off every 2 hours thereafter during week days if overridden

Saturday, Sunday and Holidays - off all day

Saturday, Sunday and Holidays - off every 2 hours thereafter if overridden

21. Outside Lighting Controls:

· Outside lighting is normally controlled by a timer and a photo cell

· The timer is typically located in the main electrical room or electrical closet

· The photo cell is typically located on the roof

· Some building outside lights are controlled by a photo cell. If lights remain on during the day, the photo cell is not functioning and requires replacement.

The foregoing guidelines are given for guidance purposes only. Please consult your electrical contractor.

UPDATE 6/99