Two Sectioned Electrical Panel

[zam]

I have a two sectioned 480/277V electrical panel. Section one has a 600A main circuit breaker. None of the electrical panels have been installed yet as the Architect is still coordinating the final locations with the client. The Architect's question is as follows: Does Section-1 and Section-2 have to be located right next to each other, or can they be installed at different locations (different rooms also, because of space constraints)? Thank you.

 

[charlie b]

I assume by saying "2 section" you are referring to two separate enclosures that are independent (i.e., not attached to each other). If that is right, then my answer is that the second section can be anywhere, as long as there is overcurrent protection for the conductors that run between the sections. That overcurrent protection device can also serve to protect the second section, if the rating is right. Or you can have a main breaker on section 2 to protect that section.

 

[augie47]

If I may add a bit to Charlie b's post,., if you Protect Section 2 by a breaker IN section 2 then the feeders between the two would need to meet the 240.21 tap rules. A breaker in Section 1 could be used to protect the feeders to Section 2 and they could be any length or they could be full size (600 amp) and be any length

 

[ggunn]

I have a two sectioned 480/277V electrical panel. Section one has a 600A main circuit breaker. None of the electrical panels have been installed yet as the Architect is still coordinating the final locations with the client. The Architect's question is as follows: Does Section-1 and Section-2 have to be located right next to each other, or can they be installed at different locations (different rooms also, because of space constraints)? Thank you.

Is section 2 a subpanel of section 1? If so it can be anywhere as long as the feeder to it and its busbars are protected. If it has a parallel connection to the service conductors with section 1, though, I believe they have to be grouped.

 

[zam]

I have a two sectioned 480/277V electrical panel. Section one has a 600A main circuit breaker. None of the electrical panels have been installed yet as the Architect is still coordinating the final locations with the client. The Architect's question is as follows: Does Section-1 and Section-2 have to be located right next to each other, or can they be installed at different locations (different rooms also, because of space constraints)? Thank you.

Charlie B: Yes, by two sections I mean two independent separate panelboard enclosures.

Augie47 & Ggunn: In this case section-2 is not a sub-panel of section-1. Section-2 is not being fed off a circuit breaker in section-1.

Section-1 has a 600A main circuit breaker, and section-2 will be 600A main lugs only connected via feed-thru lugs. These two panels will be located in different rooms.

Thank you.

 

[lordofthisworld]

Charlie B: Yes, by two sections I mean two independent separate panelboard enclosures.

Augie47 & Ggunn: In this case section-2 is not a sub-panel of section-1. Section-2 is not being fed off a circuit breaker in section-1.

Section-1 has a 600A main circuit breaker, and section-2 will be 600A main lugs only connected via feed-thru lugs. These two panels will be located in different rooms.

Thank you.

So are u stating the 600A main breaker in Cabinet 1 is the breaker for Cabinet #2 too? If so, I would think the Tap rules come into effect. Is there a breaker space in Cabinet 1 to protect Cabinet 2 down line?

 

[augie47]

I see no problem as long as the interconnecting cable is rated 600a.

 

[infinity]

So are u stating the 600A main breaker in Cabinet 1 is the breaker for Cabinet #2 too? If so, I would think the Tap rules come into effect. Is there a breaker space in Cabinet 1 to protect Cabinet 2 down line?

Cabinet #1 has a 600 amp OCPD and it has some sort of feed through bus to cabinet #2. As long as cabinet #2 is rated for 600 amps or more and the conductor between cabinets #1 & #2 are rated for 600 amps or more no tap rules apply. Then there is no limit as to how far apart these panels can be installed.

 

[Kansas Mountain]

Have submittals been approved and gear ordered? If not, are you able to just issue a revision to have (2) separate panels so that section 2 and its feeder don't need to be rated for the full 600A?

 

[charlie b]

Have submittals been approved and gear ordered? If not, are you able to just issue a revision to have (2) separate panels so that section 2 and its feeder don't need to be rated for the full 600A?

That's a good suggestion. If section 2 is drawing close to its rated 600 amps, and if section 1 has load of its own, then section 1 is likely underrated. It is more likely, however, that the total load is 600 or below. Thus, section 1 will carry all of its own load plus the total load on section 2. So it needs to be rated 600 amps. But section 2 will be carrying well under 600 amps, and therefore doesn't need to be rated 600 amps. A load calculation is in order.

 

[ggunn]

That's a good suggestion. If section 2 is drawing close to its rated 600 amps, and if section 1 has load of its own, then section 1 is likely underrated. It is more likely, however, that the total load is 600 or below. Thus, section 1 will carry all of its own load plus the total load on section 2. So it needs to be rated 600 amps. But section 2 will be carrying well under 600 amps, and therefore doesn't need to be rated 600 amps. A load calculation is in order.

Wouldn't its feeder still have to be rated at 600A? The only protection it has from the service available fault current is the 600A main breaker in the first panel.

 

[infinity]

Wouldn't its feeder still have to be rated at 600A? The only protection it has from the available fault current from the service is the 600A main breaker in the first panel.

Yes, if you go with Charlies idea then you would need an OCPD to protect the conductors and the section #2 panelboard if they're less than 600 amps.

 

[Kansas Mountain]

Yes, if you go with Charlies idea then you would need an OCPD to protect the conductors and the section #2 panelboard if they're less than 600 amps.

Well now I'm a bit confused. If the panel the OP mentioned is the main panel (which it sounds like it is to me, and I think that's what charles was getting at too, but he can correct me if I'm mistaken), then the second section could be revised to a separate panel being sub-fed from a breaker in the main panel. The second panel and its feeder now only need to be rated per the breaker feeding it + VD of the actual load, and not the full 600A. If the original "section-2" is supplying the majority of the load, then I agree that my original suggestion wouldn't work. Guess I'm not understanding why fault current is coming into the equation here?

 

[charlie b]

Section-1 has a 600A main circuit breaker, and section-2 will be 600A main lugs only connected via feed-thru lugs.

That tells me that every amp flowing from Section 2 to a load had to first flow through Section 1. Thus, Section 1 must be rated for the full load of the two sections. It also tells me that the conductors between the two sections need to have an ampacity of 600 amps or higher, as they will be protected by the Section 1 600 amp breaker. However, you still have an option (depending on the calculated load on Section 2) to have a lower-rated panel with a main breaker that protects that panel at its rated current.

 

[charlie b]

Guess I'm not understanding why fault current is coming into the equation here?

The statement was that the 600 amp breaker in Section 1 is the only protection for Section 1 and for the conductors between them. That includes protected against minor overload conditions and against fault conditions. The same 600 amp main breaker would have to handle either situation.

 

[infinity]

That tells me that every amp flowing from Section 2 to a load had to first flow through Section 1. Thus, Section 1 must be rated for the full load of the two sections. It also tells me that the conductors between the two sections need to have an ampacity of 600 amps or higher, as they will be protected by the Section 1 600 amp breaker. However, you still have an option (depending on the calculated load on Section 2) to have a lower-rated panel with a main breaker that protects that panel at its rated current.

I agree, might be a good idea if the load is small in section #2. If you did set it up with a main to protect the panelboard and fed through to it from section #1 the you would still need 600 amp conductors or the tap rues would apply.

 

[zam]

Thank you to everyone who replied to this thread. Section-2 of this 480/277V panel goes on to feed a 300KVA transformer followed by one 208/120V distribution panel which in turn serves four 208/120V electrical panels. Things were OK until the Client & Architect noticed the actual dimensions of the panelboards on the submittal and decided to spread out the electrical panels because of lack of space. One such decision they made was to locate the 480/277V Section 1 and Section 2 in two different rooms based on their respective dimensions and mounting type (recessed vs surface mounted). The approved submittals were revised, and this is the decision that our electrical engineer made: Section 1 of the 480/277V panel will have a 600A main circuit breaker. The incoming electrical service feeder connected to Section 1 has been sized for 600A. Section 2 is located in a different room. The feed-thru lugs/feeders serving Section 2 in the other room has also been sized for 600A, and Section 2 will also have a 600A main circuit breaker.

 

[infinity]

this is the decision that our electrical engineer made: Section 1 of the 480/277V panel will have a 600A main circuit breaker. The incoming electrical service feeder connected to Section 1 has been sized for 600A. Section 2 is located in a different room. The feed-thru lugs/feeders serving Section 2 in the other room has also been sized for 600A, and Section 2 will also have a 600A main circuit breaker.

Sounds good. You could save some money and eliminate the 600 main CB in section #2.

 

[ggunn]

Well now I'm a bit confused. If the panel the OP mentioned is the main panel (which it sounds like it is to me, and I think that's what charles was getting at too, but he can correct me if I'm mistaken), then the second section could be revised to a separate panel being sub-fed from a breaker in the main panel. The second panel and its feeder now only need to be rated per the breaker feeding it + VD of the actual load, and not the full 600A. If the original "section-2" is supplying the majority of the load, then I agree that my original suggestion wouldn't work. Guess I'm not understanding why fault current is coming into the equation here?

The first panel is a feed through, i.e., the second panel is fed from lugs on the opposite end of the first panel's busbars from its main breaker. If the second panel were fed from a breaker in the first, then that breaker would be the protection for the feeder and the conductors could be sized accordingly.

 

[Kansas Mountain]

The first panel is a feed through, i.e., the second panel is fed from lugs on the opposite end of the first panel's busbars from its main breaker. If the second panel were fed from a breaker in the first, then that breaker would be the protection for the feeder and the conductors could be sized accordingly.

Thanks for the feedback. That's what I was initially trying to suggest, revising from feed-thru to a sub-feed. After reading a bit more from the OP, sounds like that's not the best course of action at this point though.