NEMA 4X enclosure

[a10jp]

Can you have ventilation openings for a NEMA 4X rated enclosure? Would that contratdict the definition of NEMA 4X, menaing splash-proof and protection against hose-down situation?

 

[itsmoked]

You can have anything that is tested and rated to be 4x. In this day and age you can probably find something to vent one that is 4x.

If you are trying to vent it because of the heat loading then you should hunt down my dissertation on the subject. It's in here somewhere. I had to do several NEMA 4x systems for oil fields and pipelines that had cooling demands.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[jeezlouise]

I've never seen a new 4X enclosure (offered for sale by and enclosure manufacturer) that had vents in it. Having said that, I have seen many NEMA 4X or 4 enclosures that have been modified with vents after purchasing. Can it still be considered a NEMA 4X enclosure once it's ventilated? Probably not. Does it matter? Maybe, maybe not. Here's the NEMA blurb on 4X: 'Enclosures are intended for indoor or outdoor use primarily to provide a degree of protection against corrosion, windblown dust and rain, splashing water, and hose-directed water; undamaged by the formation of ice on the enclosure'. I suppose it's your or your customer's intrepretation of the meaning of "a degree of protection".

 

[LionelHutz]

If you can find a Type 4X or NEMA 4X vent kit then it would be suitable to be installed in the enclosure. I highly doubt you will find such a kit and if you do then I'd have to question it's rating.

The main NEMA 4 test basically involves using a fire hose and spraying the crap out of the enclosure at almost every angle directing the stream at the seams and any possible place where water could enter. If there is any water found inside the enclosure then the test is a failure. I highly doubt you can come up with some type of vent which would block a fire hose stream and still be open enough to allow air to flow.

I suggest you use a 3R type of listing. This is still suitable for outdoor use and can be vented with suitable fans and hoods.

 

[jraef]

As Lionel said, it's highly doubtful that you can find any "vent" that would withstand a fire hose beng directed at it. The specs are 100GPM from a 1" nozzle, that's a lot of water to withstand. UL has taken over the testing and approval of enclosures and components to the NEMA standards, and per their rules if you have a penetrating device in the enclosure that is not SPECIFICALLY listed to the same level as the enclosure, you have violated the official integrety of the enclosure. There are NEMA 4X "breathers" that allow for air expansion in the boxes, but they have a little ball trapped in a tube that will stop any forced water entry. They cannot be counted on for "venting" of excess heat however.

So that said, it really depends on your application. A lot of people specify NEMA 4X enclosures simple because they are putting them outdoors in a corrosive environment, and there is no such thing as "NEMA 3X". So if that's your application, you would likely be fine with venting a N4X box as long as the vent is rated for outdoor (i.e. N3R) use, but if you need to ensure the UL listing of the box and the overall assembly, then it will not be possible as far as I know.

If you need heat rejection, there are N4X heat exchangers available, and I think there are now some Peltier Effect (TEC) air conditioners that are rated 4X as well. But traditional compressor type A/C units are not, to my knowledge, available with anything better than N3R, although you can get N3R with stainless steel components.


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[a10jp]

Thanks jraef, for your comments. I do have a specific application and an observation. In our spec for a 15KV MV substation equipment, it stated the the Substation shall be used for "outdoor service with ventilation openings and gasketing provided to ensure a weatherproof assembly under rain, snow, sleet, and hurricane conditions." Further, it stated, "Enclosure shall be NEMA ICS 6 Type 3R, fabricated entirely of ASTM A 167 type 304 stainless steel." The problem I see is, (1) I have trouble interpreting what hurricane condition is, it is not a term defined under NEMA definition; (2) Because it already stated to be NEMA 3R with gasketing and ventilations, that is the only possible product choice. In our application, the product was subjected to a type 1 hurricane last week, and as a result, water infiltrates the unit and caused a cascade tripping of several of the upstream vaccum breakers, a total of 14 breakers were tripped. Becasue this substation is installed along the coastline, I imagine a higer level of NEMA rating (4X) would be more suitable. But looking at the earlier product submittal from the manufacturer, they only list NEMA 1 and NEMA 3R as the only possible options. So I am very confused, is NEMA 3R truly the industry standard for this type of application, and is NEMA 4X unavilable becasue of the ventilation requirement to start with, but at the same time, what could possibly constitutes a protection against "hurricane conditions"? I feel like in a world contradiction.

 

[itsmoked]

A fairly common predicament.

You have to look at why it needs to be ventilated. If it is because someone thinks that would be 'nice' or the last box they saw was ventilated you may not need it. If on the other hand, it has to be cooled then you must do a thermal/dissipation assessment and work with that.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[jraef]

To my mind, they specifically called out "NEMA 3R" so that is what you build to. The "hurricane conditions" spec is a vague reference that could, for the most part, be met with regards to wind loading,. i.e. 70MPH wind speeds minimum. This would not conflict with nor be subject to the NEMA 3R spec. NEMA 3R does NOT dictate that water will not enter the enclosure, it only dictates that water will not build up to any live electrical parts.

What I have seen on similar installations is a "doghouse" style setup, with NEMA 3R gear mounted inside of another overall 3R structure around it. Both have ventilation, but water would need to be blown through the vents of the first enclosure and then again through the second one and then build up in the 2nd one to get to live components. the velocity of the wind blown water inside of the first box is significantly lower than what it would take to get it into the inner box. Not technically impossible, but a level of improbability that satisfies most people.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
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[dbaird]

Check:

http://www.waukeshaelectric.com/pdf/Transformers/Worldbox_Control_Brochure.pdf

David Baird

Sr Controls Designer
EET degree.
Journeyman Electrician.

 

[itsmoked]

dbaird; Nice design but I'm not sure why you are referencing this?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[racobb]

If it is that bad, you could consider putting a NEMA 1 inside a 3R and maybe even still vent it to the outside box with hose that would limit moisture intrusion. Sort of like putting an outdoor enclosure under an additional roof. Just a thought if it is that bad.

"Rube Goldburg" approach, but if it works, why not. We do need to think outside the "box" sometimes.

Alan

 

[jraef]

This is a bit closer to what I had in mind. These people show galvanized, but I'm sure that for a price, they would do Stainless Steel.

Link


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[LionelHutz]

Have you talked to the different suppliers to seee what they offer or if they have any extra insight?

Would the equipment fit inside a shipping container?

 

[ozmosis]

I once advised our US team (this was relating to a VFD project) to fit a NEMA12 unit inside a NEMA3R enclosure for an application that was marine based and subject to some extremes in weather conditions. As I understand it, it's still operating and 'weathered' a number of tropical storms.

I wish that the IP world had the same sort of classifications as NEMA have for enclosures. At least they determine "indoor" and "outdoor" use in the recommended designs.

 

[a10jp]

Hi LionelHutz, we tried to talk to the mfr (C-H) but they would not respond. Moreover, there were some defects in some of the gasketing around the enclosure and joints along the bus ducts, which exacerbate the problem. As afew others have mentioned in this forum, the best, long-term solution is to build another enclosure on top of all the line-up switchgear. I see not other way.

 

[bisonprofab]

The simple answer is "no" - you can't have basic open vents with passive airflow and still maintain a NEMA 4 or NEMA 4X rating. However, it is possible to have active ventilation, but there must be added protection to prevent moisture from entering the enclosure while still maintaining ventilation.

 

[7anoter4]

For NEMA 4X enclosure drain and breather see[for instance]:

http://redapt2.axcess10.com/assets/182/001dpe.pdf

 

[stevenal]

The water will always get in. NEMA 4 (no substitute for 3R) is worthless since temperature cycling will suck the water in leaving no way for it to get out. Drain holes, vents, and heaters is the way to deal with the moisture that will invariably make it inside. Keep any exposed terminals above the floor of the cabinet to avoid the tripping mentioned above.
I'm on the Oregon coast where we don't have hurricanes, just hurricane force winds. And it rains a bit here. Our crews keep their drill bits sharp for putting drain holes in equipment where the manufacturers thought "sealed" must be better.

 

[a10jp]

Actually, the problem happened at the bus ducts between the transformer and the switchgear. The bus ducts were fabrciated and certain locations you can see gaps between the metal. It is questionable it is rated for NEMA 3R. The bus inside the ducts had low points that is close to the bottom of the duct. It was obvious that was the cause of the problems.

The discussion rasied an interesting point. If moisture is a main problem for NEMA 4X enclosure, how was it circumvented in the past? Other than an ingenius device like 7anoter4 has pointed out, is the only way to just drilled a drain hole like stevenal has stated? In areas where salt content is high, or it is known to be corrosive, is the drain hole still the better choice among all?

 

[jraef]

If you drill any hole in a NEMA 4X enclosure, it becomes NEMA 1 (assuming the hole is too small to pass a 1/8" rod), maybe NEMA 3R at best. The only exception is when you make a hole that is then used to hold a device that itself has been rated NEMA 4X. There are no exceptions to this.

And by NEMA, I mean UL now, because NEMA was not really a testing authority, so each manufacturer could make any claim they thought they could get away with. For that reason, UL adopted the NEMA Type Tests into their UL-50 (I believe) electrical enclosure standards. The device linked to above does not say it has UL Type 4X, although it does have CSA Type 4X so you could use it in Canada and in the US if you find an AHJ savvy enough to allow it.

But a weep hole? Not in 4X.



"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
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