Feeder Tap Rule

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philly

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I wanted to confirm my understanding of the feeder tap rule. This question kind of goes along with my other Chiller post but thought I'd post it separately to not confuse topics.

There is currently a 1600A Service entrance switchboard with only a 1600A main breaker which feeds another downstream 1600A MLO switchboard. This existing service entrance switchboard is being upgraded to a 2000A switchboard in order to re-feed the downstream switchboard as well as feed a new 1200A Chiller Switchboard.

Because of space constraints it was proposed that the new service entrance switchboard only have a single 2000A Main breaker and then off of that main breaker there will be two taps to feed the existing downstream switchboard as well as the new 1200A switchboard.

The new 1200A switchboard will have a 1200A main so as long as the feeder cables from the tap are (3) sets of 600MCM (1260A ampacity) then this feeder tap is o.k.

The issue I see is with the feeder to the existing downstream 1600A Switchboard. Because this existing switchboard is a 1600A MLO switchboard the switchboard itself and the existing (5) sets of 500MCM would not be adequately protected by the new 2000A main breaker in the service entrance switchboard. In order to be adequately protected under this arrangement a 1600A main breaker would need to be added to the existing switchboard. Is this correct?

Of course the best solution would be to add two feeder breakers to the new service entrance switchboard but this may not be possible due to switchboard footprint available. All of these switchobards and feeders are located outdoors so they fall under 240.21(B)(5).
 
infinity

infinity

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Changing the MLO to a 1600 amp main OCPD would solve the problem with the 5 sets of 500's only having an ampacity of 1900 amps.
 
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philly

Senior Member
jumper said:
Looks right to me. Adding a main to the 1600A panel will satisfy the rule of protection for the tap conductors and protect the panel with OCP not exceeding its rating.
Click to expand...

Are there any requirements for where the tap must be made? Is there any reason why the load side of the service entrance breaker cant be used as the tap point if it is able to accommodate the new tapped feeders, or if it can be modified to accept the new feeders?

I don't think you would want to make the tap on the line side of the service entrance breaker correct? I believe in this case that would then require my new downstream equipment to be service entrance rated?
 
kwired

kwired

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Location
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philly said:
Are there any requirements for where the tap must be made? Is there any reason why the load side of the service entrance breaker cant be used as the tap point if it is able to accommodate the new tapped feeders, or if it can be modified to accept the new feeders?

I don't think you would want to make the tap on the line side of the service entrance breaker correct? I believe in this case that would then require my new downstream equipment to be service entrance rated?
Click to expand...
Correct, anywhere on load side makes it a "feeder tap", unless the conductors are protected by the upstream device, then they are just an extension of the feeder.

Anything on supply side of service disconnect is not a feeder or feeder tap - it is service conductors.
 
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