NEC 110.26 / Equipment in Outdoor Enclosures

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Darold66

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We've seen twice lately that inspectors have insisted on Working Space per 110.26 for enclosed (at least NEMA 1) equipment mounted inside a large outdoor enclosure.

The first question was regarding 110.26 A 1 where a transformer secondary circuit breaker was mounted on a backpan above a dry transformer. Definitely not allowed indoors near a wall, but I was surprised that there was a problem with this arrangement in a panel.

The other is a panel shop concerned about depth between the face of equipment and the closed door when mounting a transfer switch or generator plug within a large enclosure. As this isn't an indoor location, I'm not following how 110.26 A 1 would apply.

Anybody care to shed any light on this or share your experiences?

Thanks,

Darold
 
Re: NEC 110.26 / Equipment in Outdoor Enclosures

The working space is to both to allow energized trouble shooting and to allow enough space for people to work deenergized.

What Alcoa's crane repair contractor told me is that I am not fat enough to work for his customers. Evidentally, the daffynition of heavy industrial is that a man has to weigh at least 250 pounds to work there. In other words, the higher the voltage or amperes, the more space that is needed for Big Guys.

A secondary or primary circuit breaker can be mounted above a dry transformer just as long as the box does not encroach on the ventilating space around the transformer. However, doing that can cause nuisance tripping of thermal-magnetic circuit breakers and nuisance blowing of fuses because of the heat from the transformer.

In the case of a panelboard the working space underneath is the width and depth of the box and cannot overlap with the ventilation space of a transformer. I have seen panelboards installed over transformers in small electrical closets.

Actually, architects try to use the smallest electrical closet that they think that they can get away with. Owners and tenants somehow think that adequate space for electrical, water and so forth is wasted space.

We had an instance where we installed the panelboards in a Walgreens Pharmacy right where the print said that they were supposed to go. Then, somebody else said that a panelboard was too close to the door for a wheelchair bound person to open the door. There was not a way to comply because a lot of the branch circuits came up through the floor and the junction boxes would have presented the same problem. There was no alternate mounting location for the panelboard except all the way across the long ways of the room!
 
Re: NEC 110.26 / Equipment in Outdoor Enclosures

In my opinion per 110.26(A)(1) - depth of working space is from the exterior of the enclosure if the equipment is an industrial control panel per 409.2 or a motor control center.
 
Re: NEC 110.26 / Equipment in Outdoor Enclosures

Interesting info, but don't forget that the xfmr and other equipment are all inside a big NEMA 3R enclosure and the issue is about space from the front of the enclosure to the equipment and the 6" allowance for the depth requirement within the enclosure.

The outdoor enclosure is not large enough or intended for someone to enter. There is no door for entrance to the enclosure, just a door on the front that swings open to provide access to the equipment.

Thanks,

Darold
 
Re: NEC 110.26 / Equipment in Outdoor Enclosures

If this is an industrial control panel or motor control center (panel) then the work spacing is from the outside only, internal spacing is governed by the standards used to construct the panel. If this is a structure built to protect equipment then the clearances must be maintained inside of the structure.

What do you have a structure or a piece of equipment? 90.2, 100, 110.1,
 
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