Single Line Diagram and Grounding

[iwire]

I've never known about this. Thank you for letting me know.

Always check the local power company requirements but I know some here in MA have that limitation.

Any of the 4,000 amp services I have worked on where supplied with tens sets of 600 copper.

I find 600 is no worse to work with than 500, might even be a bit easier as the standing if finer. (500=37 strands of 2.95mm, 600=61 strands of 2.52mm) Neither is easy to work with so either way it's going to be a tough day.

The companies I have worked for since the 1990s have used a lot of 600, it is convenient as it provides a true 400 amps per set while 500s do not. Typically people use 500s and count on 240.4(B)s allowance to use a larger breaker ........ even when it does not apply. It is not unusual for me to find a 1,200 or 1,600 amp service with parallel sets of 500 and that is a violation.


I have never done a busway service but it looks to me like the OPs service would be a good candidate for a busway.

 

[sandsnow]

Always check the local power company requirements but I know some here in MA have that limitation.

Any of the 4,000 amp services I have worked on where supplied with tens sets of 600 copper.

I find 600 is no worse to work with than 500, might even be a bit easier as the standing if finer. (500=37 strands of 2.95mm, 600=61 strands of 2.52mm) Neither is easy to work with so either way it's going to be a tough day.

The companies I have worked for since the 1990s have used a lot of 600, it is convenient as it provides a true 400 amps per set while 500s do not. Typically people use 500s and count on 240.4(B)s allowance to use a larger breaker ........ even when it does not apply. It is not unusual for me to find a 1,200 or 1,600 amp service with parallel sets of 500 and that is a violation.


I have never done a busway service but it looks to me like the OPs service would be a good candidate for a busway.

Your POCO is different than ours. Out here in SoCal, the POCO pulls cable all the way to customer terminals for UG services. Very rarely will the customer install cable. Usually it's for long runs to paramount. On overhead customer still installs cable in the riser.

I get the 500kcmil equals 400 amps from engineers and electricians.

 

[steve66]

Utilities often limit us to ten sets from a transformer.

The last large service I did had a limit of 8 sets per xformer. And I believe the lug size was limited to 600KCM wire.

 

[Haji]

if main breaker were 4000AF/3800AT, it would not be a problem... as long as the calculated load, with continuous factored 125%, does not exceed 3800A.

If 3800A exceeds the 75C current rating of the 90C cable conductor, it would be a problem for the terminations of the breaker.

 

[Smart $]

If 3800A exceeds the 75C current rating of the 90C cable conductor, it would be a problem for the terminations of the breaker.

Yes, that is the significance of what I stated.

3800A does not exceed 10 times the 75?C Column value of the 90?C-rated 500kcmil copper conductor (380A).

 

[iwire]

Yes, that is the significance of what I stated.

Yes when you state something it is significant.

The selected cables installed that way are only rated 3,800 amps. You need to change the cables or lower the trip setting.

With the drawing as annotated, correct.

However, if main breaker were 4000AF/3800AT, it would not be a problem... as long as the calculated load, with continuous factored 125%, does not exceed 3800A.