Individual vs. group mounted circuit breakers? 1

[anbm]

What's the difference between individual vs. group mounted circuit breakers in term of switchborad? It it depending on breakers and bus size? Are there any advantages to use group mounted CBs? Thanks!

 

[alehman]

Group mounted would be basically a panelboard arrangement. The breakers are stacked against one another and plug on or bot on to vertical bus. The load terminals are accessible from the front. Group mounting applies to molded case breakers only.

Individual mounting provides separate compartments for each breaker. Commonly the load terminals are accessible only from the rear of the switchboard.

Group mounting is less expensive and arguable more convenient to service - by far the most common. Individual mounting provides isolation that provides safer maintenance and less probability of an arcing fault spreading throughout the switchboard. Generally a safer arrangement.

 

[anbm]

Thanks alehman, so you don't think there are group mounted breakers in low voltage switchboard?

 

[rovineye]

Sure there are group mounted CBs in LV switchgear. Molded case as aleman said. All I have dealt with were accessed in the rear, but I guess a different mounting block would provide load access in front.

I will dig up some pics and post.

 

[rbulsara]

Besides the difference in costs, group mounted breakers have no separation between adjacent breakers and therefore more prone to damange or disturb the adjacent breakers should there be a fault on one.

Individually mounted breakers have some physical separation from other breakers and can also have compartments/barriers.

Also individually mounted breakers would typical afford more cable space, servicable withput disturbing adjacent breakers, etc.

In short, for run of the mill applications group mounted breakers are fine. If the application involves serving critical loads, you may want to consider individually mounted breakers or even a switchgear vs a switchboard but that is different disussion.

 

[rovineye]

I have a good view of the back showing the bussing and load terminations. The front just shows how close the molded case CBs are together with the door open.

 

[rovineye]

Rear

 

[alehman]

Rovineye, I don't think I've seen a board quite like that before. That's not what I would call group mounted as it appears there is a gap between each breaker, and the breakers apparently are bolted to the back panel.

Two photos of what I think of as group-mounting...

 

[alehman]

close-up

 

[rovineye]

alehman,
In my world, I guess what you show would be a power panel, altho a big one.

My switchboards have what may be unique requirements. I must be able to remove breakers from the front without disassembling the switchgear so we can change them out without shutting down if need be (shipboard). The breakers are screwed into mounting blocks (load and line side) which are bolted to the back panel. It is the dimension of the mounting blocks that result in a small gap between breakers.

Some of the disadvantages would be the same. A fault on the bus or load connections can disable the entire section, same on the breaker side where a breaker fault can damage other breakers adjacent.
The advantage in a fault would be that a bus fault or load connection fault might not destroy breakers (and vice-versa), but it usually takes out at least the one associated breaker.

 

[alehman]

Yes, basically a big power panel.

Yours is interesting. It looks more like individual mounting, but without the barriers. I might have a use for something like that. Is it something that's available from one of the major manufacturers?

 

[rovineye]

Many manufacturers make them, but we get them exclusively from Point Eight Power now, just outside of New Orleans. Great support and quality work.

SPD has good quality as well, but too rich for my blood.