Distribution systems

Question 1

What is a distribution system?

Answer 1

equipmen and feeder asociated with distributin power throughout the building

Question 2

Types of Distribution systems

Answer 2

Primary and utility service
main switchboard
panels
busways and feeders
equipment disconnects

Question 3

What are primary and utility services?

Answer 3

Any service electrical pathway, conductors or equipment that is either utility owned or high-voltage ( >600V).

Question 4

What is a main switchboard?

Answer 4

Electrical piece of equipment that is heart of the building’s electrical system. All electrical power runs through this piece of equipment

Question 5

How many disconnects may a switchboard contain before requiring a main breaker?

Answer 5

switchboards require a main breaker if they exceed 6-disconnects.

Question 6

What are panel boards?

Answer 6

They house over-current protection (circuit breakers/fuses) tat feed branch circuit (receptacles, lighting etc.)

Question 7

Feed-thru lugs

Answer 7

allows second panel to be installed downstream without cost of adding….

Question 8

What are transformers?

Answer 8

Convert power to usable voltage. step up, step down.

Question 9

difference between feeder and branch circuit?

Answer 9

feeders are generally larger than 2” and branch circuits are generally less than 2”

Question 10

difference between feeder and branch circuit?

Answer 10

feeders are generally larger than 2” and branch circuits are generally less than 2”

Question 11

When to use a busway or feeder?

Answer 11

Busway - high current and long runs, especially vertical .

Feeder - small current and short runs; most common

Question 12

What are equipment disconnects ?

Answer 12

Used as local disconnecting means for safety purposes. they can contain over-current protection

Question 13

What is a VFD?

Answer 13

Used on loads that have high starting current demand (motors - pumps/fans). they ramp the current up over a period of time making the motor last longer and inrush current more level reducing the risk of a tripped breaker/blown fuse, easier on the equipment and less risk of fire.

Question 14

What is a fuse?

Answer 14

Over-current protection devices that work until their rated current is exceeded; then they need to be replaced. the “blow”.

Question 15

What is a circuit breaker?

Answer 15

perform the same job but allow the ability to be reset making them more common for panel board applications. they “trips”. Detected by heat

Question 16

Fuses and circuit breakers.

Answer 16

Fuses and circuit breakers are designed to interrupt the power to a circuit when current exceeds safe levels.