Equipment rated as an “assembly “

[bubbarhd]

When does an enclosure with, say, 4 modules or relays and an enclosure heater become an assembly and need to be rated as such? What is the tipping point in code? Is there an NEC reference?



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[infinity]

What is the assembly rating that you're referencing?

 

[bubbarhd]

I am not exactly sure. Listing agency issue such as UL. It was brought up by an inspector as a requirement. Essentially saying it was not ok to put together an assembly of various UL parts and assume that it is safe. The sum of the listed safe parts may be unsafe when combined. This makes sense to me if it involves a hazardous potential such as batteries but not so much sense if it is just an enclosure with modules and relays. I am trying to get more informed on the subject. Thanks for the interest.


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[infinity]

Take a look at Article 409, Industrial Control Panels and see if anything from there applies.

 

[tom baker]

Interesting question. I would look at UL 508A to see what the definition is of a control panel is. Art 409 may have a definition.
In Washington, we can build a control panel, but only from all UL Listed Parts. Control panels often used UR (component recognized) parts.
If a control panel is not 508A listed, the job starts and a third party inspection is required

 

[Jraef]

It's in Article 100 definitions, under "Industrial Control Panel":

Industrial Control Panel. An assembly of two or more
components consisting of one of the following: (1) power
circuit components only, such as motor controllers, overload
relays, fused disconnect switches, and circuit breakers;
(2) control circuit components only, such as push buttons,
pilot lights, selector switches, timers, switches, and control
relays~ (3) a combination of power and control circuit components.
These components, with associated wiring and terminals,
are mounted on, or contained within, an enclosure
or mounted on a subpanel.

The argument I've been pulled into is whether or not the enclosure itself counts as one of the "components", i.e. push button station with one button like an E-Stop. I've argued that it is not, I've lost that argument.

 

[bubbarhd]

Thanks Jraef. That is super helpful.


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[don_resqcapt19]

While not typically enforced, the OSHA rules require all electrical "assemblies" installed or used in a workplace to be listed assemblies.