Non-class 480V LC and MCC (NG/NH)

Question 1

Describe the purpose of Non-Class 480v AC LOAD center system. (NG)

Answer 1

•Distributes power to:
-Non-class loads >50Hp
-Non-class 480vAC Motor Control Centers (MCC’s)

Question 2

Describe the purpose of Non-class 480vAC Motor Control Centers(NH).

Answer 2

•Distributes power to:
-Non-class loads less than <50HP
-Non-class 120vAC to power small loads(Via distribution panels)

Question 3

All Non-class MCC’s receive power from Non-class LC’s except which 4? And what are they called?

Answer 3

SIAS Load Shed MCC’s
•NHN-M19
•NHN-M20
•NHN-M71
•NHN-M72

Question 4

What supplies power to the Non-class 480v Load centers?

Answer 4

•The Non-class 13.8kv system(NA) supplies power to the non-class 480v load centers.

Question 5

Transformers step down the non-class 13.8kv to Non-class 480v LC’s, how are they cooled?

Answer 5

Inside XFMRS
•Cooled by the rooms AC and the air vents on the XFMR panel.

Outside XFMRS
•Cooled by natural circ of oil and air.

Question 6

What switch will kill power to a single load center?

Answer 6

•The interrupter switch (Disconnect switch)

•It will allow isolation to a single load center without killing power to the other 2 load centers the same (NA) breaker supplies.

Question 7

What does the Kirk Key interlock do on a Non-class 480v Load center do?

Answer 7

•It prevents and AO or Electrician from opening the Load Centers disconnect under load (with equipment running drawing current).

•The (B2) breaker must be locked tripped and the plunger under the key must be pressed, allowing you to get the key

•Then you can insert the key into the interrupter switch(Disconnect switch) and open the disconnect.

Question 8

The transformers on the 480v LC steps down voltage from _____ kvAC to ______vAC

Answer 8

1st space
•13.8kvAc

2nd space
•480vAc

Question 9

What will the over current on the XFMR’s neutral isolate and how?

Answer 9

It will isolate the transformer by:

• Tripping the 13.8kv feeder breaker by activating its 86LO.

•Tripping the Load Centers main feeder breaker (B2).

Question 10

Describe Non-class 480v load center circuit breakers

Answer 10

•480 vac Feeder breaker (B2 breaker)
•Motor supply breaker
•MCC supply breakers

Uses springs to open/close breaker and has a mechanical interlock to prevent unracking while breaker is closed

Question 11

Who normally operates the non-class 480v LC’s?

Answer 11

•The control room does

•Can be controlled locally in an emergency

Question 12

Describe the B2 breaker on non-class 480vac load center.

Answer 12

•Main feeder breaker
• Has over current relay that trips an 86LO which prevents closing until it’s reset.

Question 13

Describe Motor Feeder breakers on non-class 480vac load centers.

Answer 13

•Supply power directly to motors
(E.g-Oil pumps, IA Compressors, ZT HVAC fans)
•However, just cause the breaker is closed doesn’t mean it’s running, it can power a controller that starts and stops the equipment on set points.

Question 14

What push buttons does the Non-class 480vac load centers have on it?

Answer 14

Two for manual operation
•Close
•Trip

Two for Testing.
•Close and trip

Question 15

What does the bell alarm switch do?

Answer 15

It’s basically another 86Lockout
•It’s activated by an over current
•Or activation of the mechanical interlock from racking while it’s closed
•Has to be pushed back in manually