I need to install a 50HP VFD and some additional controls in an explosion proof enclosure. however I'm unable to find an enclosure that is large enough. Any recommendations? The largest I found was 36"x30"x12". I need double that size.

Also, this VFD will need a braking resistor which will have to be mounted inside the enclosure. How do I cool this enclosure? Explosion proof A/C unit? No compressed air available, so I can't use a vortex cooler. Won't an A/C or heat exchanger derate the enclosure once I start making holes on it for the A/C vents?

Any comments are greatly appreciated, thanks in advance to everyone who answers.

 

Seriously consider installing the VFD in the safe area and running EXP conduit to the motor.

NEC has provision for purging an EXP enclosure with requirements for dropping out power if positive pressure inside the enclosure is not maintained.

I've had purged enclosures done for instruments, but not for a heat generator like a VFD.

 

A 50 HP drive is not very big. Must be a bunch of other stuff.

A few thoughts I had.

Is it possible to move the stuff to an area that is not classified?

Multiple enclosures.

Why do you "need" a brake resistor? There are other ways of dealing with energy stored in the system, both electric and mechanical.

Since compressed air is not available maybe you can use bottled air or nitrogen and put it in a pressurized/purged enclosure. if you seal it up tight enough a bottle will last a long time.

Considering the expensive involved already, running a compressed air line out to the area may not add all that much cost, especially if it allows you to get rid of explosion proof enclosures.

The other thing I would consider is whether the area is actually properly classified in the first place and how high it extends. Often the classified area is only from the floor up a relatively short distance and you may be able to install the VFD cabinet above where the classified area ends.

I don't think you can add holes in an XP big enough for A/C. Not sure you can even use a vortex cooler on an XP enclosure. Generally you can only use stuff that threads into the enclosure wall and is identified for use in the specific classified area.