Looking for ideas on Electrical Enclosures 1

[Smoothcriminal]

Hello Everyone,

We have an Electrical enclosure that is located in a very silica dusty area. The enclosure is under positive pressure, but for some reason,we are still having dust accumulation. Any ideas on what might be going on?

Regards,
Mr T
Reliability Engineer

 

[danw2]

the supply air for the positive pressure isn't adequately filtered?

Dust intrusion while the door is open for servicing, but, of course, 'that never happens'.

 

[Smoothcriminal]

No Sir, the supply air is not even filtered at all. Also I did observed when I did the initial inspection, that the door was not completely closed.

 

[EdStainless]

Is it a box rated for full seal (NEMA 4)?
We used to filer and dry purge air (particle filter, charcoal filter, desiccant all in line).
And our sealed boxes used a filter on the outlet vent valve also.

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P.E. Metallurgy, consulting work welcomed

 

[Smoothcriminal]

Hi EdStainless,

The box is rated for NEMA 4x. The enclosure has two vents on the front. The duct that supplies air is located on the bottom of the enclosure.

Regards,
Mr T

 

[EdStainless]

So do the vents only release at a specific pressure or are they open?
Our boxes were interlocked, if they didn't pressurize (door ajar) an alarm went off.

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P.E. Metallurgy, consulting work welcomed

 

[Smoothcriminal]

The vents are always open. The air that is being fed into the enclosure goes out through the vent. I do like the idea of an interlocking system that will alert us if the door is open. Thank you Ed

 

[danw2]

A low pressure differential pressure switch will tell you when any part of the sealing system is not holding positive pressure, as opposed to a door switch that just informs that the door is open.

There's lots of relatively low cost HVAC low DP switches out there. You'd probably want a filter on the atmosphere low side port.

 

[EdStainless]

The vents need to have some restriction to them. We used ones with a lightly weighted flapper and then vented out though an exhaust filter. This provided some back pressure and kept debris out.
The HVAC DP switches work fine for this.

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P.E. Metallurgy, consulting work welcomed

 

[buzzp]

Conduits can also contribute to this...if not properly sealed. The dust could actually be pulled in from a conduit, depending on your intake/exhaust fan. I have seen this more than once.

 

[mparenteau]

I wonder if you would be better off w/ an environmental purge system, basically like purge systems used for electrically classified areas (think Z purge or X purge setup). Only in this case, you aren't alarming or interlocking a "power-off" setup. You would have a NEMA 4x enclosure, no vented openings, purge controller and a relief vent. Stuff your conduit openings to your box and you should be good.

Mike

 

[ASHISHRAMAN]

Enclosure alone won't work, check the selection of glands.

 

[Smoothcriminal]

Thank you for all of your replies. I really appreciate you taking the time to reply. I will take all your advice into consideration.

 

[Shanaya]

Electrical boxes (like light switches) can work. Radio Shack is offering project boxes. Small projects fit comfortably into the Altoids tin.

 

[cranky108]

What? You still have a radio shack? Most of us don't have any radio shacks any more.

 

[IRstuff]

Still lots of stores left, surprisingly

https://www.radioshack.com/pages/store-locator

Oh, they're not real Radio Shacks, just dealers kiosks, I guess

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[cranky108]

I don't see many electronics stores here. Have to order things, if I want them.

Then again, people don't repair stuff anymore.