Service Switchgear

[infinity]

OK I'll preface this by saying I know that you cannot simply add up the size of the OCPD but does something about this seem odd?
In reviewing the service switchgear drawings I found this. I have a 4000 amps service with no main and these switch/OCPD combinations.

Switch #:
1) 3000 AS/2500A Fuse
2) 3000 AS/2500A Fuse
3) 3000 AS/2500A Fuse
4) 4000 AS/3500A Fuse
5) 3000 AS/3000A Fuse

All of the feeders are full sized based on the OCPD in each service disconnect. Other services have similar setups. My gut tells me something isn't right. Opinions?

 

[Ingenieur]

What is bus/lug rating?

 

[infinity]

Bus is 4000 amps as well.

 

[chris kennedy]

What type of facility?

 

[jtinge]

Is this truly a service fed switchgear or possibly a customer owned switchgear supplied by a feeder, like might be the case on an industrial campus or plant?


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[infinity]

What type of facility?

High rise apartment complex.

 

[ptonsparky]

OK I'll preface this by saying I know that you cannot simply add up the size of the OCPD but does something about this seem odd?
In reviewing the service switchgear drawings I found this. I have a 4000 amps service with no main and these switch/OCPD combinations.

Switch #:
1) 3000 AS/2500A Fuse
2) 3000 AS/2500A Fuse
3) 3000 AS/2500A Fuse
4) 4000 AS/3500A Fuse
5) 3000 AS/3000A Fuse

All of the feeders are full sized based on the OCPD in each service disconnect. Other services have similar setups. My gut tells me something isn't right. Opinions?

Take a zero off the end and you would be working in my typical range. Would we be having the same discussion?

 

[infinity]

Take a zero off the end and you would be working in my typical range. Would we be having the same discussion?

Not sure what you mean?

 

[electrofelon]

OK I'll preface this by saying I know that you cannot simply add up the size of the OCPD but does something about this seem odd?
In reviewing the service switchgear drawings I found this. I have a 4000 amps service with no main and these switch/OCPD combinations.

Switch #:
1) 3000 AS/2500A Fuse
2) 3000 AS/2500A Fuse
3) 3000 AS/2500A Fuse
4) 4000 AS/3500A Fuse
5) 3000 AS/3000A Fuse

All of the feeders are full sized based on the OCPD in each service disconnect. Other services have similar setups. My gut tells me something isn't right. Opinions?

they do seem rather high. Do they provide a load calc for each feeder? Perhaps the conductors were increased for voltage drop and they increased the switch size commensurately for easy terminating?

 

[infinity]

they do seem rather high. Do they provide a load calc for each feeder? Perhaps the conductors were increased for voltage drop and they increased the switch size commensurately for easy terminating?

Not really sure I'm just reviewing the switchgear drawings and IMO the numbers seem high for a 4000 amp service especially given the fact that these feeders have a high cost associated with them. You're looking at 6, 8 and 10 sets of parallel conductors for each feeder and a service that can feed nowhere near even a small percentage of each individual feeder's ampacity.

 

[Cow]

Not sure what you mean?

He's saying if you knocked a zero off the end of all those breaker/feeder sizes that would be more commonplace. 250, 300 amp etc.

I agree that I'm also used to seeing something smaller like Tom mentioned.

Infinity, I think I'd like to look at the rest of the one line to see what they are trying to accomplish but it does seem very odd to have those feeder sizes in main lug gear that size.

 

[infinity]

He's saying if you knocked a zero off the end of all those breaker/feeder sizes that would be more commonplace. 250, 300 amp etc.

Ah, got it. I thought a 0 off the 4000 amp service too. I agree that would make more sense.

 

[Jraef]

That would need to be one heck of a diversity factor!

 

[charlie b]

It might be OK. If the calculated load does not exceed the 4000 amps, and if each 2500 amp fuse is protecting conductors that are themselves rated for at least 2500 amps, then I think it meets code. But I do agree that this is out of the ordinary.