Large equipment and enclosed circuit breaker behind it

[hhsting]

I have 3000A over 6 feet wide switchboard. See below. The breakers are on the side of switchboard as shown below. Behind the breakers and the switchboard, engineer wants to place enclosed circuit breaker 1200A circuit breaker. All at 208/120V. I don't feel good about placing equipment behind large 3000A switchboard but I don't see anything in NEC 2017 prohibiting it. Does anyone know if this can be done according to NEC 2017 or not?

 

[Johnhall30]

110.33

As long as the entrance to the equipment is 24 inches wide and 6-1/2 feet high, it is ok

 

[PD1972]

110.33

As long as the entrance to the equipment is 24 inches wide and 6-1/2 feet high, it is ok

Your quoted section is for over 1000V, nominal, which wouldn't be applicable to this low voltage switchboard and enclosed circuit breaker. However, the idea is the same. The analog to 110.33 for <1000V is 110.26.

... but I don't see anything in NEC 2017 prohibiting it ...

You essentially answered your own question. There's nothing wrong with putting equipment behind the switchboard if there's an entrance of "sufficient area" to get to the back of the switchboard. The enclosed circuit breaker is not going to be large equipment over 6 feet wide so a single entrance to the working space is fine. I am going to assume that the entrance to that room is above the cropped snapshot and the distance between edge of switchboard to the wall is greater than 24".

I don't think that plan reviewers have to "what-if" themselves to death. You don't have to worry about "what if" the switchboard explodes and someone is working on the enclosed circuit breaker. If this scenario happens enough, I'm sure the CMP would have already made changes to the NEC to reflect this risk.

 

[stretch12]

To follow previous post and you have your working clearance you should be fine

 

[ron]

Where are the doors for Large Equipment?
Large Equipment. For equipment rated 1200 amperes or more and over 1.8 m (6 ft) wide that contains overcurrent devices, switching devices, or control devices, there shall be one entrance to and egress from the required working space not less than 610 mm (24 in.) wide and 2.0 m (61⁄2 ft) high at each end of the working space.

Even if the room legit with the existing equipment because it wasn't caught, if you add more equipment behind it, they might want compliance with the existing.

 

[infinity]

I don't feel good about placing equipment behind large 3000A switchboard but I don't see anything in NEC 2017 prohibiting it.

Why is that? If it has the required working space what's the problem?

 

[don_resqcapt19]

Where are the doors for Large Equipment?
Large Equipment. For equipment rated 1200 amperes or more and over 1.8 m (6 ft) wide that contains overcurrent devices, switching devices, or control devices, there shall be one entrance to and egress from the required working space not less than 610 mm (24 in.) wide and 2.0 m (61⁄2 ft) high at each end of the working space.

Even if the room legit with the existing equipment because it wasn't caught, if you add more equipment behind it, they might want compliance with the existing.

It might comply with 110.26(C)(2)(a) or (b) and only require a single egress.

 

[infinity]

The large equipment rule doesn't apply to the new installation so I wouldn't be concerned with it. If this is plan review check for compliance to the code sections that are applicable only to what's new.