600V or less transformer primary and secondary protection

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Dee95

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New Jersey
hi
I am checking an existing installation done by others.
I have a 30kVA 480-480/277V, Delta/WYE grounded transformer. This transformer is fed from a panel where circuit breaker is rated 60A, four #4 and it is 9 feet from this panel.
Secondary of the transformer has five #4 AWG conductor inside the conduit to a panel 8 feet away.
The panel that is connected to the secondary has a 100A main circuit breaker.

When I look at 450.3(B), main circuit breaker in the panel violates the code. Am I right, because it is less than 10 feet?
Thank you all...
transformer OCPD.jpg
 

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david luchini

david luchini

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Dee95 said:
When I look at 450.3(B), main circuit breaker in the panel violates the code. Am I right, because it is less than 10 feet?
Thank you all...
Click to expand...

Yes, you have a violation of 450.3(B). The secondary length is not relevant to 450.3(B).

You also have a violation of 240.21(C).

Changing the panel main breaker to 50A would remedy both violations.
 
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texie

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Fort Collins, Colorado
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Electrician, Contractor, Inspector
david luchini said:
Yes, you have a violation of 450.3(B). The secondary length is not relevant to 450.3(B).

You also have a violation of 240.21(C).

Changing the panel main breaker to 50A would remedy both violations.
Click to expand...

I agree except that I think that a 45 amp would be max on the secondary. I don't know-does 45.11 amps qualify for the next size up? I'm inclined to say no.
 
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texie

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david luchini said:
Why? 45.11 amps is not a "standard rating" of an OCPD. 50A is the next higher standard rating.
Click to expand...

I see where you are coming from and I don't think it is a big deal either way. Sort of an odd ball value. I was thinking of 220.5(B), but I think you are right, you would not be required to drop the fraction of an amp, rather permitted. Would make a tricky exam question.
 
david luchini

david luchini

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texie said:
I see where you are coming from and I don't think it is a big deal either way. Sort of an odd ball value. I was thinking of 220.5(B), but I think you are right, you would not be required to drop the fraction of an amp, rather permitted. Would make a tricky exam question.
Click to expand...

Yes, 220.5(B) permits (but does not require you) to drop the fraction of an amp.

But 220.5(B) relates to load calculations and wouldn't be relevant to the transformer overcurrent protection calculation of 450.3, even if it did require you to drop the fraction of an amp.
 
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texie

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Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
david luchini said:
Yes, 220.5(B) permits (but does not require you) to drop the fraction of an amp.

But 220.5(B) relates to load calculations and wouldn't be relevant to the transformer overcurrent protection calculation of 450.3, even if it did require you to drop the fraction of an amp.
Click to expand...

Oh, I know 220.5(B) relates to load calcs but don't you remember the big dust up here about that? I seem to recall when Mike Holt invoked this on a similar calculation and the debate was whether 220.5(B) applied globally to the code or just to 220 calcs.
 
david luchini

david luchini

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texie said:
Oh, I know 220.5(B) relates to load calcs but don't you remember the big dust up here about that? I seem to recall when Mike Holt invoked this on a similar calculation and the debate was whether 220.5(B) applied globally to the code or just to 220 calcs.
Click to expand...

I don't recall that dust-up. But it's clear to me reading 220.1 that Article 220 provides requirements for "calculating branch-circuit, feeder and service loads." I don't see anything about transformer overcurrent protection in those requirements. Nor do I see anything in Article 450 that directs me back to Art. 220.
 
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