Class 1 div 1 requirements for a j-box containing non-arcing and sparking devices

[Dsg319]

What is the reasoning behind having to have a seal in raceways 2” or larger (but not smaller raceways) entering an explosion proof junction box containing no arcing/sparking devices.

 

[petersonra]

I think someone decided long ago that the risk of an explosion inside conduit smaller than 2" is very low.