Junction Box mounting on duct

[john2016]

With the exception of not properly securing the conduits within 12" of the junction box, is installing the junction box on the duct like this acceptable?

 

[infinity]

The way I see it it's done all of the time. Some duct equipment even comes with JB's mounted to it.

 

[LarryFine]

I effectively do the same thing when I use a handy box, either a standard or extension, to house the connections to a temperature probe in a commercial kitchen hood fire-suppression system.

 

[john2016]

The conduit would still need to be strapped within 12" of the junction box even though it's low voltage control wiring in the conduits/junction box correct?

 

[MAC702]

Yes, the raceway needs proper support regardless of which class of conductors are inside.

While I don't have a problem with it, would Code or inspector care about the insulation between the box and the substrate duct? Would you mash the insulation to secure the box better?