Lighting Fixture Seal-Off

[augie47]

Sorry,,. Art 501 remains a "weak point"
I was asked today about the need for a seal-off in conduit runs to a expl. proof lighting fixture in a Class 1 Div II area.
At this time I have no input on the type fixture so my question is generic.
If I read correctly, a seal-off would be needed since the lighting fixture is an explosion proof enclosure IF there are arcing devices or high temperature present.
In general terms do explosion proof fixtures (Incadescent, fluorescent or HID) require seal-offs in a Class 1 Div II area ?

 

[weressl]

Sorry,,. Art 501 remains a "weak point"
I was asked today about the need for a seal-off in conduit runs to a expl. proof lighting fixture in a Class 1 Div II area.
At this time I have no input on the type fixture so my question is generic.
If I read correctly, a seal-off would be needed since the lighting fixture is an explosion proof enclosure IF there are arcing devices or high temperature present.
In general terms do explosion proof fixtures (Incadescent, fluorescent or HID) require seal-offs in a Class 1 Div II area ?

Cl I, Div. 2 fixtures do not require seal-off as they are not explosionproof. By design they are temperature limited to the T-rating stamped on them. That means that the temperature on any external OR internal components can not exceed the T-rating. (There are certain fixtures with 'restricted breathing' provision that require special installation of a 'seal' that is not an XP rated seal, but integral to the fixture.)
Cl. I Div. 1 fixtures are 'factory sealed' so the do not require seals either. There are internal temperatures - but not external - on these fixtures that are allowed to be higher than the T-rating, eg. they are designed to withstand an internal explosion.