Walked away from the middle of a project

Merry Christmas
R

Rajun Cajun

Member
Location
upstate SC
Existing client for a 100' x 250' building where I previously issued drawings for a 120/208V service. Client changed it to 460V service and hired an "electrician" to make the changes. Need me to revise my drawings.

My first clue there was a problem was when the electrician said "I've done thousands of jobs like this". To which I replied you have violated the code thousands of times!

75 KVA 480-120/208V dry type transformer. 90A primary breaker. 200A 120/208V panel board with 200A breaker. Transformer was also <6" from wall. Electrician said he could have his engineer provide stamped drawings.

There were other "issues". No way was I going to re-stamp my drawings for this situation. Client, who is a friend, understood my walking away.

RC
 
Rajun Cajun said:
75 KVA 480-120/208V dry type transformer. 90A primary breaker. 200A 120/208V panel board with 200A breaker.
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Absent any additional information about distance from the transformer to the panel or load calculation of the panel, what is the code violation you see with this arrangement?
 
Rajun Cajun said:
75 KVA full load is 90A @ 480V, a 90A CB is way too small. Code allows 250% to avoid tripping on inrush, or 225A..
200A panel is undersized.
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We would typically use a 125 amp on the primary and a 225 amp on the secondary. What code section would prohibit the 90 and 200 amp OCPD's? Distance from the wall is determined by the transformer manufacturer did they specify a distance?
 
Technically, I guess what they have MAY not be a violation, but the 90A primary breaker is subject to tripping under inrush. It does happen!
Also, the owner is paying the price for a 75 KVA transformer but not getting use of what he paid for. The electrician still didn't see why the 90A breaker wasn't good for 75 KVA! Maybe I am being picky, but that's not what I will put on my drawings. The electrician was making changes to my drawings without consulting me as to their being suitable. I have a "null void" note on my drawings which says you make unauthorized changes, the drawings are null and void. I don't want the liability for someone else's changes.!
 
Rajun Cajun said:
Technically, I guess what they have MAY not be a violation, but the 90A primary breaker is subject to tripping under inrush. It does happen!
Also, the owner is paying the price for a 75 KVA transformer but not getting use of what he paid for. The electrician still didn't see why the 90A breaker wasn't good for 75 KVA! Maybe I am being picky, but that's not what I will put on my drawings. The electrician was making changes to my drawings without consulting me as to their being suitable. I have a "null void" note on my drawings which says you make unauthorized changes, the drawings are null and void. I don't want the liability for someone else's changes.!
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If the electrician is being paid to follow the drawing then that's what he owes the client.
 
They are probably value engineering it, don’t know why they didn’t go ahead and use 100 amp instead of 90, unless they are using aluminum wire. 125 amp breaker would most likely jump to a 200 amp frame on a lot of manufacturers. I just installed a 45 kva transformer that could be wall or floor mount, the back flange is probably 4”.
 
infinity said:
We would typically use a 125 amp on the primary and a 225 amp on the secondary. What code section would prohibit the 90 and 200 amp OCPD's? Distance from the wall is determined by the transformer manufacturer did they specify a distance?
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4/0 CU and a 250A work out nice on the secondary if I remember right.
If a panelboard does not take a 125 I could see using a 100, not sure why a 90 would make sense unless the pipe and or wire were too small.
Someone posted about how some big utility in the US still employs the service voltage of '460' if '460' is common in SC and they need the full 75 that might be an issue.
 
hillbilly1 said:
They are probably value engineering it, don’t know why they didn’t go ahead and use 100 amp instead of 90, unless they are using aluminum wire. 125 amp breaker would most likely jump to a 200 amp frame on a lot of manufacturers. I just installed a 45 kva transformer that could be wall or floor mount, the back flange is probably 4”.
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I probably would use 100 A RK5's, save the cost of going up to 200 amp equipment and never in a million years going to have a problem starting a 75 KVA transformer.
 
electrofelon said:
I probably would use 100 A RK5's, save the cost of going up to 200 amp equipment and never in a million years going to have a problem starting a 75 KVA transformer.
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I’ve had issues with 100 amp breakers tripping, but it was due to the magnetic trip set on minimum, and the problem didn’t surface until the entire store was put on generator, and was exercising under load.
 
electrofelon said:
I probably would use 100 A RK5's, save the cost of going up to 200 amp equipment and never in a million years going to have a problem starting a 75 KVA transformer.
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And for the same reason use a 200A OCPD on the secondary. Although 225A panels seem to be priced more attractive than they were 40 years ago.

Many customers are probably requesting a 200A 208Y/120V panel. The fact it requires a 75kVA transformer is not really their concern.
 
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If they went with a 100A (or less) on the primary and the secondary was 10' or less and met 240.12(C)(2) would they even need secondary protection for the panelboard? :unsure:
 
I prefer the 480/277v service if it's available, and, depending on the application, once you feed everything you can at the higher voltage, you may even be able to reduce the size of the Transformer for the 120/208v loads.

Jap>
 
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