NEC 240.21.(C) Question

[liverpool]

I have a 2P-200A, 240V, 1 phase, circuit breaker type Automatic Transfer Switch fed from two sources: Source one is a 100KVA 480V-120/240V 1 phase transformer fed from utility. Source two fed from an 80KW 120/240V 1 phase diesel generator. The ATS feeds a 400A, 120/240V, 1 phase, Main Lugs Only panel board at downstream. The feeders running from the transformer through the ATS to the panel board are over 10 feet long.

Would the ATS circuit breakers meet the requirements for the over current protection device at the secondary side of the transformer per NEC 240.21.(C)?

Thanks,

 

[liverpool]

I have a 2P-200A, 240V, 1 phase, circuit breaker type Automatic Transfer Switch fed from two sources: Source one is a 100KVA 480V-120/240V 1 phase transformer fed from utility. Source two fed from an 80KW 120/240V 1 phase diesel generator. The ATS feeds a 400A, 120/240V, 1 phase, Main Lugs Only panel board at downstream. The feeders running from the transformer through the ATS to the panel board are over 10 feet long.

Would the ATS circuit breakers meet the requirements for the over current protection device at the secondary side of the transformer per NEC 240.21.(C)?

Thanks,

Sorry, I had an error above. It's a 2P-400A ATS and not a 2P-200A ATS.

 

[Pierre C Belarge]

As per your description, the Transfer switch seems to be your service disconnect.

Is your transfer switch listed as suitable as service equipment?
(if so, it should have a fused disconnecting means, if it is of the automatic type)

 

[liverpool]

As per your description, the Transfer switch seems to be your service disconnect.

Is your transfer switch listed as suitable as service equipment?
(if so, it should have a fused disconnecting means, if it is of the automatic type)

I have a fused disconnect ahead of the transformer's primary (service disconnect). My question relates more to the 10 ft rule at the transformer's secondary side [240.21.(c)]. Just for clarification above, the referenced transformer is not a utility transformer but rather a customer supplied one.

Thanks,

 

[Smart $]

I have a fused disconnect ahead of the transformer's primary (service disconnect). My question relates more to the 10 ft rule at the transformer's secondary side [240.21.(c)]. Just for clarification above, the referenced transformer is not a utility transformer but rather a customer supplied one.

Thanks,

Need more info...

Regarding secondary conductors: inside, outside, combination (provide details on latter)? ...under 10 ft, 25 ft. or longer? ...industrial or not?

Note: secondary conductors are from xfmr to breaker in ATS. ATS to panelboard are feeder conductors.

 

[pfalcon]

need more info...

Regarding secondary conductors: Inside, outside, combination (provide details on latter)? ...under 10 ft, 25 ft. Or longer? ...industrial or not?

Note: Secondary conductors are from xfmr to breaker in ats. Ats to panelboard are feeder conductors.

240.21(b)(2)?

 

[Smart $]

240.21(b)(2)?

 

[liverpool]

Note: secondary conductors are from xfmr to breaker in ATS. ATS to panelboard are feeder conductors.

Hmmm, I thought the secondary conductors are from the xfmr to breaker at ATS through to the panelboard. I guess your comment makes sense, but where is this talked about in the NEC?

Thanks,

 

[liverpool]

Article 450 Question

Article 450 Question

Hmmm, I thought the secondary conductors are from the xfmr to breaker at ATS through to the panelboard. I guess your comment makes sense, but where is this talked about in the NEC?

Thanks,

 

[jim dungar]

If your ATS is not "service entrance"rated, are the devices in the ATS actual breakers or are they molded case switches?
If they are 'breakers' are they listed (i.e. UL489) and intended to provide feeder/branch circuit protection?

Is this ATS application subject to the selective coordination requirements of article 700 or 701?