Large equipment

hhsting

Senior Member
Please see attached sketch. The large equipment switchboard 2000A 277/480V in the attached sketch is in main electrical room with 225kva transformer 480v to 208/120V, 150kva transformer 480v to 208/120v, and bunch of 277/480V and 120/208V three phase panelboards.

I an wondering would the egress from working space be in compliance with NEC 2017 section 110.26(C)(2) or not? I am thinking 110.26(C)(b) is met but then not sure since on the other side of switchboard where transformer T4 is the door is way at the end


bb50415720a809f137c6a45ecd99ce6f.jpg
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
Please see attached sketch.
Thank you I love it when we have a sketch.
The large equipment switchboard 2000A 277/480V in the attached sketch is in main electrical room with 225kva transformer 480v to 208/120V, 150kva transformer 480v to 208/120v, and bunch of 277/480V and 120/208V three phase panelboards.

I an wondering would the egress from working space be in compliance with NEC 2017 section 110.26(C)(2) or not?
I'd say its met if the door at the bottom of the sketch is 24In or wider and those dashed lines are just describing working space.
I am thinking 110.26(C)(b) is met but then not sure since on the other side of switchboard where transformer T4 is
We'd only need to look into (b) if the second door does not count or if say they want to eliminate that door.
Then in that case we'd have to take a closer look at T110.26(A)(1) and transformer T3 to see if its 'exposed live parts' or grounded parts.
the door is way at the end
I think thats OK as long as its unobstructed and 24 in or greater wide.
 

hhsting

Senior Member
Thank you I love it when we have a sketch.

I'd say its met if the door at the bottom of the sketch is 24In or wider and those dashed lines are just describing working space.

We'd only need to look into (b) if the second door does not count or if say they want to eliminate that door.
Then in that case we'd have to take a closer look at T110.26(A)(1) and transformer T3 to see if its 'exposed live parts' or grounded parts.

I think thats OK as long as its unobstructed and 24 in or greater wide.

Yea those dashed line are working space.

There are two doors main electric room one at the bottom and one double door 18 inch from MSB large equipment 2000A 489/277V switchboard at top near T3 and the distance between is 7.7 ft marked on sketch post #1

I am wonder if the top double door alone and not counting the bottom would the install comply per NEC 2017 section 110.26(c)(2)(b)?
 

hhsting

Senior Member
Thank you I love it when we have a sketch.

I'd say its met if the door at the bottom of the sketch is 24In or wider and those dashed lines are just describing working space.

We'd only need to look into (b) if the second door does not count or if say they want to eliminate that door.
Then in that case we'd have to take a closer look at T110.26(A)(1) and transformer T3 to see if its 'exposed live parts' or grounded parts.

I think thats OK as long as its unobstructed and 24 in or greater wide.

Where is the 24 inch bottom door and unobstructed coming from? There are 2 doors one at top and one at bottom
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
I am wonder if the top double door alone and not counting the bottom would the install comply per NEC 2017 section 110.26(c)(2)(b)?
Assuming this is a new building and transformer T3 is not considered 'exposed live parts', then you can use 3'6" condition 2 as the basis for the working space, so 7 foot.
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
Recent 480/208 ones I'd doubt its 'likely' it will need to be worked on energized.
As long as there are no overcurrent devices in it i'd say no its not.
But your the AHJ, its a judgement call.
 

hhsting

Senior Member
Recent 480/208 ones I'd doubt its 'likely' it will need to be worked on energized.
As long as there are no overcurrent devices in it i'd say no its not.
But your the AHJ, its a judgement call.

Its new building new electrical room might as well have 8 feet

I am wondering there are two doors one at top and one at bottom would that not comply per NEC 2017 section 110.26(c) first paragraph? Door at each end of working space
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
Its new building new electrical room might as well have 8 feet

I am wondering there are two doors one at top and one at bottom would that not comply per NEC 2017 section 110.26(c) first paragraph? Door at each end of working space
Yeah thats what I was saying in my first reply, as long as that bottom door is not less than 24 in wide:
2017 NEC 110.26(C)(2)
Code:
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 (6 1⁄2 ft) high at each end of the
working space
 

hhsting

Senior Member
Yeah thats what I was saying in my first reply, as long as that bottom door is not less than 24 in wide:
2017 NEC 110.26(C)(2)
Code:
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 (6 1⁄2 ft) high at each end of the
working space

Ok but the second door is literally not at the end of working space of swbd MSB instead it is at very bottom. Would 110.26(c)(2) first paragraph apply? Also that double door at top would you say it is unobstructed?
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
Ok but the second door is literally not at the end of working space of swbd MSB instead it is at very bottom. Would 110.26(c)(2) first paragraph apply?
I'd say there is plenty of egress at the bottom, its not uncommon to have egress thru another working space, then to a door.
Both those doors would need panic hardware.

Also that double door at top would you say it is unobstructed?
I cant tell what that grey box is in front of the door, but it should be unobstructed.
 

hhsting

Senior Member
Thank you I love it when we have a sketch.

I'd say its met if the door at the bottom of the sketch is 24In or wider and those dashed lines are just describing working space.

We'd only need to look into (b) if the second door does not count or if say they want to eliminate that door.
Then in that case we'd have to take a closer look at T110.26(A)(1) and transformer T3 to see if its 'exposed live parts' or grounded parts.

I think thats OK as long as its unobstructed and 24 in or greater wide.

Is not the transformer considered grounded part? Secondary windings is grounded and so is the transformer enclosure. I don’t see how this can be considered exposed live parts?
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
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I say the transformer frame is a grounded part, not exposed live. But it depends on the transformer.
I'd go with probably go with condition 2 in the 151-600 row.
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
From the perspective of 110.26 a transformer will be either 'grounded parts' or 'exposed live parts', there are some older transformers that can be considered 'exposed live parts', most newer ones will be 'grounded parts'.
 

Carultch

Senior Member
Location
Massachusetts
Please see attached sketch.
"Thank you I love it when we have a sketch."

I couldn't agree more. Proactively providing a visual aid helps out tremendously.

It appears that you photographed your screen to get your image. I'd like to advise you of the "Print Screen" button on your keyboard, usually nearby the F12 key. This takes an image of your screen, and stores it on the virtual clipboard. You can then CTRL+V this image in to a graphics program and crop to the part you want to share. There is also the Sniping Tool that comes standard with Windows 7 and later.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Unless transformer primary windings are exposed they are not grounded?? Only secondary windings and transformer enclosure are grounded
For the purposes of defining the work space for other equipment, the transformer is condition 2 or 3 depending on what the AHJ says. It would be unusual to see the transformer as creating a condition 3 as they are unlikely to be worked on while energized. Of course this comment assumes a transformer within an enclosure.
 
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