Electrical Equipment in Plenum

[ron]

There are many times that a safety switch for a fan motor or light fixture is installed inside of a plenum.
Is there any reason that I couldn't have an 800A automatic transfer switch installed in a plenum?

 

[don_resqcapt19]

Ron,
Take a look at 300.22. Are you really asking about equipment in a plenum or in "other space used for envriomental air"?
Don

 

[ron]

I thinks it's a plenum. Big sheetmetal enclosure.

 

[adalewhite]

Ron,

Beside meeting the requirements in 110.26, 300.22 prevents equipment not directly related to the function of the duct/plenum from being mounted inside. I'd be surprised to find a disconnect in an HVAC plenum. A maintenance light is common.

Dale from GA

 

[don_resqcapt19]

Ron,
The installation of the ATS would be a violation of 300.22(B). Even the fan disconnect may be a violation.

300.22(B) ... Equipment and devices shall be permitted within such ducts or plenum chambers only if necessary for their direct action upon, or sensing of, the contained air. Where equipment or devices are installed and illumination is necessary to facilitate maintenance and repair, enclosed gasketed-type luminaires (fixtures) shall be permitted.

Don

 

[ron]

Don,
Unfortunately I agree.

 

[DHkorn]

Don is right

Don is right

In my jurisdiction, Chicago, we typically called the ceiling space used for environmental air a 'plenum'. I believe our code book still defines it as so.

The NEC considers this area an 'other space for environmental air'; an example of a plenum would be the exhaust ducts over cooking equipment, or the ducts of an exclosed air system.

Hope that helps. I overworked a few jobs when I was young before I figured it out. Thats why all our plenum boxes and gasketed blanks were only available thru local manufactures.