UL label on Enclosure Question

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bob_g

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I have a panel rated NEMA 3R and want to UL label it. There is a heater attached to the back of the panel and it has the correct conduit fittings. The heater however is not rated NEMA 3R. Can the panel still be UL labeled for NEMA 3R or does it have to be derated. Is the heater considered part of the panel because it is attached externally to it, if so does the heater have to be rated NEMA 3R?

note: the heater is UL listed
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
bob_g said:
I have a panel rated NEMA 3R and want to UL label it. There is a heater attached to the back of the panel and it has the correct conduit fittings. The heater however is not rated NEMA 3R. Can the panel still be UL labeled for NEMA 3R or does it have to be derated. Is the heater considered part of the panel because it is attached externally to it, if so does the heater have to be rated NEMA 3R?

note: the heater is UL listed

Hmmm.

Table 19.1 covers conduit fittings for field connections. Since you are doing the connection it is not a field connection.

Para 19.2 does not seem to be at issue.

Para 19.3 covers openings for mounting components. Your opening is for a conduit fitting.

Para 19.4 does not seem to apply to your situation.

I am forced to conclude that perhaps you are OK labeling the panel as type 3R. You might want to just run this by your UL guy first though. The worst they would do is force you to label the thing as a type 1 enclosure.
 
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bob_g

Member
Now that I look at 19.3, I'm curious. I know I have a conduit fitting opening in the panel for the heater, but the heater itself is attached to the panel. So wouldn't 19.3 apply here? Are the screw holes attaching the heater to the panel considered openings? I assume so. If I use the correct washers and fittings for these screw holes does 19.3 still apply to the heater also?
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
bob_g said:
Now that I look at 19.3, I'm curious. I know I have a conduit fitting opening in the panel for the heater, but the heater itself is attached to the panel. So wouldn't 19.3 apply here? Are the screw holes attaching the heater to the panel considered openings? I assume so. If I use the correct washers and fittings for these screw holes does 19.3 still apply to the heater also?

All openings have to be closed in a way consistent with the rating of the enclosure. Presumably that includes screw holes.

The only other opening you made is for the conduit, and as long as you use an appropriate style conduit fitting, that opening is taken care of.

I suspect that what the UL inspector might say is that you should install the conduit fitting below where any live parts are and add a drain to the cabinet to maintain your 3R rating.
 
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