Space requirements

[marktsv]

We are installing two 1000A services to feed several 480V loads. We are providing two 750kw standby generators, as well as two 1000A outdoor circuit breakers to break the utility supply. My question regards two 1600A(oversized) automatic transfer switches that are 38" wide, 60" deep, and 84" tall each. The ATA's require front and rear access, the space I have been given is 10' by 10'. By placing the ATA's on opposite walls, we only have a 36" aisle between them, no live exposed parts are on the sides, are we required to have two entrances or is the aisle enough for the 24" W clearance? All piping except from MOCPD to ATA's is underfloor.

 

[jwelectric]

Re: Space requirements

110.26(C) (2) Large Equipment. For equipment rated 1200 amperes or more that contains overcurrent devices, switching devices, or control devices, there shall be one entrance to the required working space not less than 610 mm (24 in.) wide and 2.0 m (6? ft) high at each end of the working space. Where the entrance has a personnel door(s), the door(s) shall open in the direction of egress and be equipped with panic bars, pressure plates, or other devices that are normally latched but open under simple pressure.
A single entrance to the required working space shall be permitted where either of the conditions in 110.26(C)(2)(a) or (C)(2)(b) is met.
(a) Unobstructed Exit. Where the location permits a continuous and unobstructed way of exit travel, a single entrance to the working space shall be permitted.
(b) Extra Working Space. Where the depth of the working space is twice that required by 110.26(A)(1), a single entrance shall be permitted. It shall be located so that the distance from the equipment to the nearest edge of the entrance is not less than the minimum clear distance specified in Table 110.26(A)(1) for equipment operating at that voltage and in that condition.

Table 110.26(A)(1) Working Spaces
151?600 condition three 1.2 m (4 ft) Condition 3 ? Exposed live parts on both sides of the working space.

Sounds like you have problems

 

[charlie b]

Re: Space requirements

I am missing part of this story. But I think you do not need two entrances. An ATS does not contain overcurrent devices, and the circuit breakers are rated below 1200 amps. So 110.26(C)(2) would not apply.

But if the ATS's are each 5 feet deep, and you need to access the front and back of each ATS, then you do have a problem, and would have, even if there were only one ATS. Under "Condition 2," live parts on one side and grounded parts on the other, you need 3.5 feet of clearance. You need that on the front and back of the 5 foot deep ATS. So you need 12 feet of total room, just for one ATS. If you had two ATS's that were not right across from each other, you would still need 12 feet in that direction. If the two ATS's did face each other, it would be Condition 1, as Mike said. That would mean that you need 13 feet of total room, in that direction.

 

[marktsv]

Re: Space requirements

We do have 14' of clearance, the 10' x 10' is an addition to an existing panel room, where the closest panel is 3.5' from the ATS front panel. Is 36" enough (code requires 24") between the two ATS for aisle space? The 5' wide ATS would have 6' behind (rear access) and over 3.5' in front. Would a plaque reading "do not service equipment opposite each other at the same time" suffice?

 

[charlie b]

Re: Space requirements

A plaque is not an adequate safety measure. But if you move things 6 inches, you won't have to worry about it. Make it 5.5 feet behind (instead of 6) and 4.0 feet in front (instead of 3.5 feet). That way it has enough room (minimum 4 feet) for there to be exposed live parts in both ATS's at the same time (i.e., for Condition 1).

 

[ryan_618]

Re: Space requirements

Originally posted by marktsv:
Would a plaque reading "do not service equipment opposite each other at the same time" suffice?

Not a chance if I am the AHJ

 

[pierre]

Re: Space requirements

110.26(C)(2)
...or control devices...

ATS equipment contain control devices, yes?

This installation needs some review.

Remember this is a safety requirement that protects electricians. Where most requirements in the NEC protect the consumer.

I also agree with Ryan that the plaque is not enough.

 

[charlie b]

Re: Space requirements

Originally posted by pierre: 110.26(C)(2) - or control devices. . .

ATS equipment contain control devices, yes?

I guess I missed that. I see that it also includes switching devices. So I have to change my statement to read, "Yes, you do need two exits."

See, that is what I get for thinking that it says only what I remember it to have said. Mea culpa.

 

[marktsv]

Re: Space requirements

That's what we thought, two entrances, 4' in front and behind, thanks for the info.