Working Space per 110.26 (A)(1)

[Transportation Guy]

We are retrofitting an existing office building into a multi family dwelling unit. To accomplish the power, we are installing 4000 amp switchgear, and 2 runs of 1600 amp bus duct running verticle up the 7 floors. Where the bus duct comes through the floors, the GC is building per the architects drawings, a "closet" to house the bus duct, bus plug, and panel that supplies all the feeders to the individual unit panels in each apartment. The "closets" are tiny and only provide 30" of clearance between the front of the panel and the door of this closet. The engineers intent is to leave the door open so you are standing in the doorway while servicing this panel and still meet the requirement of the code. Thoughts?

 

[charlie b]

I don't have a problem with taking credit for an open door as the means of establishing the required working clearance. You need to make sure you have the entire "box" available in front of the panel. By that I mean the clearance, with the door open, has to be 30" wide, 36" deep, and 78" high. If the opening of the doorway is less than 30" wide or 78" high, then you have a violation.

 

[cmaki]

Which way does the door open? in or out? If it opens into the space then I would have an issue with it just because it would then be in your way. The electricatians are going to be more likely to close the door to gain a few extra inches of working space. If it opens out of the space then I have no issues.

 

[Transportation Guy]

Thanks for the replies. The door will open out into the hall and we will have a minimum of 36" door and the panel will be directly in front of you. The inspector said he is going to get back with us with his interpretation.

Thanks

 

[kwired]

Unless I misunderstood - this equipment is supplied from the 1600 amp bus duct. Which makes me have to ask if this equipment is something that would apply to 110.26(C)(2) or (C)(3)? There may be more complexities to this install if it is large gear that is involved.

 

[charlie b]

Which makes me have to ask if this equipment is something that would apply to 110.26(C)(2) or (C)(3)?

That is an interesting question. My take would be that the bus duct is not more than 6 feet wide, so these rules do not apply. You may counter that the bus duct, as it appears within the room in question, is more than six feet high. My response would be that the code says "wide," not "in any dimension." For example, a switchboard that is 90" high (a common size) but only 4 feet wide would not invoke the "large equipment" rules.

 

[kwired]

That is an interesting question. My take would be that the bus duct is not more than 6 feet wide, so these rules do not apply. You may counter that the bus duct, as it appears within the room in question, is more than six feet high. My response would be that the code says "wide," not "in any dimension." For example, a switchboard that is 90" high (a common size) but only 4 feet wide would not invoke the "large equipment" rules.

I wasn't questioning the bus duct itself, but rather the fact we have a 1600 amp feeder, which kind of makes one have to question just exactly what kind of gear is it supplying. It potentially could be something that needs to comply with 110.26 (C)(2) or (3).

Or there may just be a tap to something that isn't in the scope of (C)(2) or (3).

 

[Transportation Guy]

I wasn't questioning the bus duct itself, but rather the fact we have a 1600 amp feeder, which kind of makes one have to question just exactly what kind of gear is it supplying. It potentially could be something that needs to comply with 110.26 (C)(2) or (3).

Or there may just be a tap to something that isn't in the scope of (C)(2) or (3).

The bus duct is a 1600 amp that leaves the gear, then runs vertical through 7 floors. We tap off the duct on every floor in said "closet" to feed the panel in question. We leave that panel and feed numerous individual 125 amp panels in the apartments. It is 1600 amps because it is serving approximately 10 apartments on each floor.

 

[kwired]

The bus duct is a 1600 amp that leaves the gear, then runs vertical through 7 floors. We tap off the duct on every floor in said "closet" to feed the panel in question. We leave that panel and feed numerous individual 125 amp panels in the apartments. It is 1600 amps because it is serving approximately 10 apartments on each floor.

Looks to me like 110.26(B)(2) doesn't apply unless the bus tap device/enclosure is really large.

That leaves us still possibly needing to comply with (B)(3). Depends on if the bus tap devices is considered 400 amps or if we need to look at the fact there is 1600 amps protection ahead of the bus. I'm really not all that sure which way one should look at it. I do say any arc flash potential will be based on what can be delivered by the 1600 amp bus and I would be more inclined to still call this 1600 amp equipment for the application of 110.26(B)(3).

thoughts of others?

 

[Transportation Guy]

The sketch below shows an overhead view of the room. Albeit not to scale, it gives you an idea of what we are doing.

 

[kwired]

The sketch below shows an overhead view of the room. Albeit not to scale, it gives you an idea of what we are doing.

I still think because the bus plug is connected to a 1600 amp feeder - you will need panic hardware on that door.

Whether or not that door is permitted to be opened to allow proper 110.26(A)(1) clearance may be interpreted differently by different AHJ's.

If it is permitted - the door will have to be at least be 30" wide or as wide as the equipment, and of course in front of the equipment that space is needed for. It will also need to be minimum 6.5 feet high (not normally a problem), but if the equipment should be higher then that the door must be at least as high as the equipment. Example: if you had an 84 inch top of panelboard, you can't have a door that is only 81 inches tall.