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UL508a Enclosure type 12 derated to type 4??

UL508a Enclosure type 12 derated to type 4??

UL508a Enclosure type 12 derated to type 4??

(OP)
OK guys. Need some help here as this has been a thorn in my side for quite a while. We are an industrial machinery builder that is UL508A certified for building our electrical control panels. Our UL inspector has come in and flagged our Type 12 enclosures and said we need to "de-rate them" to Type 4 because we are using type 4 components (i.e. panel switches). Of course, this is completely asinine as type 4 is wash down and type 12 is oil/dust tight. Then he came back in and said we need to de-rate to UL type 5. Type 5?? I asked him what that was and he pulled out an obscure table in the 508A code book. Table 19.3 says if you plug a type 12 enclosure with a type 4 device, it makes your panel type 5. Not even the rep from Hoffman knew what type 5 was.

So to summarize, our inspector thinks that since the buttons and HMIs we use are ONLY marked type 4, 4x that our type 12 enclosures should be de-rated. Isn't a type 4 better than a type 12? If it's type 4, wouldn't it automatically be dust tight as well? I'm not sure if I should just roll over, or find this guy's supervisor. He even admitted to not knowing anything about enclosure environmental ratings.

RE: UL508a Enclosure type 12 derated to type 4??

From 15 years engineering panels for a 508a shop:

Sorry, my answer is no good for ya. Your argument is good, but it doesn't fit with the 508a standard.

You can argue your point, appeal, submit an engineering report from a respected third party, pay for an engineering evaluation by UL engineering, or whatever you can think of. None of them will work. Derating to Type 5 is specified very clearly in the standard for your situation. They won't vary from what's written.

Read the Type 5 definition closely, see if it will still be acceptable for your application.

For everyone's reference, from UL 50:

Type 4:

Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt, rain, sleet, snow, windblown dust, splashing water, and hose-directed water; and that will be undamaged by the external formation of ice on the enclosure.


Type 5:

Enclosures constructed for indoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt; against settling airborne dust, lint, fibers, and flyings; and to provide a degree of protection against dripping and light splashing of non-corrosive liquids.

Type 12:

Enclosures constructed (without knockouts) for indoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt; against circulating dust, lint, fibers, and flyings; against dripping and light splashing of non-corrosive liquids; and against light splashing and consequent seepage of oil and non-corrosive coolants.

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

RE: UL508a Enclosure type 12 derated to type 4??

(OP)
Bugger! That's what I was afraid of. I'm not sure why manufacturers stopped putting all of the type ratings on, but it's probably that they don't want to pay for type 12 testing when they already are paying for type 4/4x. Thanks for the help!

RE: UL508a Enclosure type 12 derated to type 4??

No kidding.

I remember buying Type 3R / 4 / 12 long ago. Square-D used to sell a Type 12 with instructions labeled on the inner panel door to drill a couple 1/4" holes in the bottom to convert to approved 3R.

I don't remember seeing anything nice like that lately.

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

RE: UL508a Enclosure type 12 derated to type 4??

I know this is late, but I just saw this forum for the first time.

The key component you are missing is "oil". UL type 12 requires that any gasket material be resistant to oil degradation, including any adhesive used in applying it. Type 4 and even 4X testing does not include that provision, so although the sealing may be superior with regard to water and other liquids, type 12, even though not as stringent in terms of the hydrostatic pressure, requires testing with oil. Specifically machine tool cutting oil which is particularly solvent for a lot of plastics and elastomeric compounds. So if you are building a machine that is going into a factory environment that will have cutting oil in the air, he is right, you cannot use a device that is strictly listed only as type 4.

That said, the major manufacturers (I'm looking at an Allen Bradley catalog right now), have indeed UL listed their pilot devices as type 3/3R/4/4X/12/13. That means, they did indeed test them for each standard individually with UL.

This all changed when UL took over the old NEMA standards for environmental ratings. NEMA was never a testing agency, it was a set of "guidelines" collectively developed by the electrical equipment industry in the US (NEMA = National (USA) Electrical manufacturers Assoc.), who mutually agreed on compliance. But when the flood of IEC components came in in the 80s and 90s, the IEC environmental standards were not the same as NEMA, yet users were still insisting on NEMA ratings. So IEC mfrs started making NEMA compliance claims that were unsubstantiated and in some cases, out and out false. Under pressure from members, NEMA licensed UL to take over the testing and approval of the standards. That's how UL 50 came to be, and it was only about 10 years ago or so.

So what you, Kiljoy, apparently have is a low-cost supplier who did NOT want to spend the money to get their components UL listed at all of the available standards, and now you are left holding the bag. Either that, or you DO have one that is UL listed to those other standards and do not know it. You can ask for a UL compliance document that will provide that detail for you, UL requires them to have it.

"Will work for (the memory of) salami"

RE: UL508a Enclosure type 12 derated to type 4??

(OP)
That makes quite a bit of sense. Thanks! It turns out our pushbuttons are type 12,13,and 4 but the vendor was kitting them for us which had the original packaging (with type rating on it) MIA. The HMI does say 4x only. Since these things are resistant to many solvents, I suspect it was an oversight, but who knows?

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