I've never been impressed with most NEMA 3R enclosures. They always look like NEMA 1 with a different label. I was out today looking at a 3 year old installation that was well done. There are 3 brand name outdoor enclosures and they all look like the dickens. Door and cabinet enclosures are rusty, door hardware is corroded and barely workable or have corroded and fallen out. I'm sure they will "work" for several years. I know stainless steel enclosures would be better, but the cost is pretty extreme. Anybody have better experience?
NEMA 3R, REALLY?
- Thread starter sgunsel
- Start date
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ptonsparky
Tom
- Occupation
- EC - retired
What is location for these? Typical residential use or is there some other contributing factor like, livestock, saltwater, or chemical?
Cow
Senior Member
- Location
- Eastern Oregon
- Occupation
- Electrician
Like Tom said, it's all in where you put them. 3R enclosures last forever out here, the only problem is they fill with dust.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
3R works pretty well for the environments where it is appropriate.
Rust is not an issue in my mind. Steel eventually rusts. As long as it holds together it is fine.
Steel enclosures are a poor choice if there is any kind of corrosive agent involved. And there are a lot of non-obvious corrosive agents out there.
3R is not a good choice if you need protection from dust either. It just is not designed for that.
Enclosures rated 3R and 1 are usually on the low end. they are stamped out to be as cheap as possible, out of the lightest weight metal possible. They don't need to be dust tight so the doors don't have to be as stiff so they are not as substantial in appearance or use. But they meet the needs they meet very cost effectively.
Rust is not an issue in my mind. Steel eventually rusts. As long as it holds together it is fine.
Steel enclosures are a poor choice if there is any kind of corrosive agent involved. And there are a lot of non-obvious corrosive agents out there.
3R is not a good choice if you need protection from dust either. It just is not designed for that.
Enclosures rated 3R and 1 are usually on the low end. they are stamped out to be as cheap as possible, out of the lightest weight metal possible. They don't need to be dust tight so the doors don't have to be as stiff so they are not as substantial in appearance or use. But they meet the needs they meet very cost effectively.
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- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
A common misconception is that NEMA 3R is "water tight", it is not. It is not "tight" against anything but falling or wind blown rain under certain conditions. The spec for NEMA 3 is not that water will not enter the enclosure, but rather that the LIVE internal components will be protected from DIRECT contact with water. In other words, water (and thereby dust, bugs etc.) can enter, but will not build up inside to the point of shorting anything out. So if you look, you will always find a "weep hole" in a NEMA 3 enclosure (sometimes it's JUST a bottom corner folded to leave a small gap). NEMA 3R is the same, but adds the "Raintight" aspect, meaning driven rain will not get in and if the door is opened in falling rain, there is a drip hood to prevent rain from contacting the guts (but not wind blown rain by the way).
NEMA 3R also includes a salt spray test above and beyond NEMA 1, intended to simulate (IIRC) 10 years of normal exposure. So in most cases a painted enclosure will be over phosphatized or electro-galvanized steel. That just means if and when the paint eventually leaks, the steel won't rust through for a reasonable amount of time (but not forever). Hinges and latches (if any) must also survive so are usually SS or galvanized, whereas NEMA 1 would be cheapest available.
If you want something that won't rust, buy SS, plastic or fiberglass. If you want something where water, dust, bugs etc. will not enter, buy NEMA 4. If you want both, buy NEMA 4X.
NEMA 3R also includes a salt spray test above and beyond NEMA 1, intended to simulate (IIRC) 10 years of normal exposure. So in most cases a painted enclosure will be over phosphatized or electro-galvanized steel. That just means if and when the paint eventually leaks, the steel won't rust through for a reasonable amount of time (but not forever). Hinges and latches (if any) must also survive so are usually SS or galvanized, whereas NEMA 1 would be cheapest available.
If you want something that won't rust, buy SS, plastic or fiberglass. If you want something where water, dust, bugs etc. will not enter, buy NEMA 4. If you want both, buy NEMA 4X.
weressl
Esteemed Member
I hate to say this, but admittedly the IP system is a much clearer guideline with precise parameters as to what kind of environmental exposure the equipment is expected to withstand. On the other hand the combinations are much greater therefore more expensive as 10 types are less expensive to mass produce than 50+.
These enclosures are located outdoors in Ohio, in a rural setting. No corrosives present. Not on a farm. Dust is not an issue. Admittedly, they still do what they need to do, but rust is starting and at this rate it won't be too many years before replacement may be required. I have seen quite a few older units (age unknown) that were so rusty the doors barely hold on and corners are perforated by rust. I see that most of the new traffic dept. enclosures look like they are stainless.
tish53
Member
- Location
- richmond, VA
We deal with a quarry environment, lots of dust, rain, wind etc. We typically use Nema 12 gasketed enclosures to ensure dust and water is kept out and then we add a drip shield to keep the dust from accumulating on the top door joint.
At any severe locations, wash screens etc. we use Nema 4 and use Stainless steel at our locations near the ocean.
It just depends on how much you want to spend and how long you want them to last.
At any severe locations, wash screens etc. we use Nema 4 and use Stainless steel at our locations near the ocean.
It just depends on how much you want to spend and how long you want them to last.
- Location
- Massachusetts
You know a coat of quality outdoor paint can greatly extend the life of typical 3R enclosures.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Just a note on NEMA 12 enclosures used outdoors.
TECHNICALLY, it's not rated for that. NEMA 12 makes no provisions for "outdoor use" unless, by chance, the box design says "Type 12/4, suitable for outdoor use" on the label inside. Some of the newer styles are like that now, but the old Hoffman "LP" style boxes and their clones are NOT rated for outdoor use, even though Hoffman sells a drip shield for them (if pressed as to why, they'll say it's for INDOOR dripping). No pre-treatment of the steel, the paint is not rated for sun exposure etc. I've been red-tagged on that specific issue.
As to NEMA 3R boxes rusting, there's no accounting for quality in NEMA and UL standards, just passing the tests. The tests are designed to establish a minimum standard, and everyone that makes the claim ostensibly met that. But beyond that, you get what you pay for.
TECHNICALLY, it's not rated for that. NEMA 12 makes no provisions for "outdoor use" unless, by chance, the box design says "Type 12/4, suitable for outdoor use" on the label inside. Some of the newer styles are like that now, but the old Hoffman "LP" style boxes and their clones are NOT rated for outdoor use, even though Hoffman sells a drip shield for them (if pressed as to why, they'll say it's for INDOOR dripping). No pre-treatment of the steel, the paint is not rated for sun exposure etc. I've been red-tagged on that specific issue.
As to NEMA 3R boxes rusting, there's no accounting for quality in NEMA and UL standards, just passing the tests. The tests are designed to establish a minimum standard, and everyone that makes the claim ostensibly met that. But beyond that, you get what you pay for.
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