VFD in Class II Div 1 Area

[eeprom]

Hello,
I have a design for which it has been requested that the VFD be placed near the equipment. The equipment area is class II, division 1, grain dust. NEC only says that the enclosures have to be dust tight, which I can achieve with a Nema 12 panel and filtering fans (also rated for 12). Is there are reason not to place the VFD in this area?

EE

 

[itsmoked]

The biggest would be the gross dependence on motor driven fans and filters in a big dust location. I have never seen a single facility that was capable of dependably maintaining that kind of setup.

I would go with a single bottom vent and thermostatically controlled filtered air providing positive pressure to the enclosure. I'd include a temp switch to shutdown the drive if the enclosure temperature exceeded a normally expected temperature.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[eeprom]

Thanks. I think the temperature switch is a good idea, as is the pressurized air. I cannot control the temperature of the plant air though.

 

[davidbeach]

If you've got lots of compressed air you can use a vortex cooler to both pressurize and cool. Not highly efficient, but very effective.

 

[jraef]

Just be aware that you MUST install a good moisture and oil separator on the feed for that vortex cooler.

What size VFD are we discussing here? Smaller HP VFDs can be fully enclosed and in some cases, different mfrs offer a "fins out" or "flange mount" option wherein the VFD has the heat sinks designed to be shoved out of the back of the enclosure, no air exchange needed.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[ScottyUK]

Just a word of caution on the fins-out type of drive: if the heatsink is force-cooled by fans then make sure the fans are easily replaced. At a former employer we had a lot of troubles with an A-B Powerflex 70 of this type, with numerous fan failures. Fan replacement was an absolute pig of a job. In the end we made our own modifications and adapted a venturi airmover to fit on the heatsink which solved the problem completely. I think I've discussed these troubles in the past, perhaps with jraef?

 

[GroovyGuy]

hi eeprom,
Sorry about responding so late to your inquiry above, but I was away.
What is the size of this VFD? Is the VFD and motor supplied by the same Vendor?
I'm curious as to why anyone would 'requested that the VFD be placed near the equipment', especially if the location is classified. To me this sounds like this request originated from a Vendor who does not fully appreciate what he is requesting.
Is the requestor concerned about the cable length from the drive O/P to the motor? If so there are solutions for that (ie a dv/dt filter on the drive O/P).
Is there no space in the local electrical room to place this VFD?
I always try to avoid installing non-rated electrical in a classified area if at all possible.

It's been a few years (ie decades) since I have done any work in a Class 2 area, but in a Class 1 area, where I routinely work know, there is a requirement that the motor OEM state that the T-code for the motor will not exceed the AIT of the gas involved. A special CSA NP is required as well, on any VFD-driven motor installed in Class 1 area. I do not know if this is a requirement with your AHJ, but I would suggest that motor OEM be made aware of the fact that his motor will be located in a Class 2 area and be VFD driven. Even more so if the load is constant-torque.
Good luck, but I would push back on the requirement that the VFD be located in a classified area.

 

[dogzzz]

Sir
When you say " class II, division 1, grain dust" .
Then I assumed that it is a hazardous location ( Class II locations are those that are hazardous because of the presence of combustible dust. Note that the dust must be present in sufficient quantities for a fire or explosion hazard to exist. The fact that there is some combustible dust present does not mean a Class II hazardous location exists. To be considered a “dust”, the combustible material must exist as a finely divided solid of 420 microns (0.420 mm) or less. )

So if it is a hazardous location , then you fit in as shown below , in red color.

Had it been a Non Hazardous area then you fit in as shown below , in red color .

Since , we use IEC , thus I am more accustomed to "Zone System" instead of Class / division .
So if you think I am not correct , then please correct me , and help me to increase my knowledge.
Thanks

 

[jraef]

Typically over here, when someone tells you an area has a hazardous classification, it's not an introduction to begin a debate. The hazard classifications are usually determined by fire safety authorities and given TO the engineering team so that they know what they must deal with.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[dogzzz]

Did I asked you for your advice ?

 

[FreddyNurk]

dogzzz, your adversarial attitude to other posters here is becoming tiring.

 

[John2025]

It's a discussion forum. People are going to comment and give advice. That's the point. Lots of us search out names like jraef because we've come to trust their expertise.

 

[dogzzz]

whatever .......all I can say if anybody dont like anybodys post or replies or comments then simply ignore or make it correct .
There is no need to play each others advocate.

 

[resqcapt19]

Very few places that handle combustible dust can maintain the required house keeping to prevent the area from being a classified area.

 

[jraef]

Did I asked you for your advice ?

No. And my response was directed not at you, but to the OP in counterpoint to your suggestion that the solution was to challenge the inspector'so request. In a general that is a task for those with the authority to carry it out and it is a reasonable assumption that had the OP possessed that kind of authority, he/she would not have asked for assistance in implementation. In other words he question was not if, but how. Your response was shifting it toward if and I was attempting to get the OP back on course. If that offended you, it was unintentional in my part and for that I apologize.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[dogzzz]

Applogies from my side too...if something offended you from my side.