NEMA Enclosure 1G

[dasarmin]

I found a previous posting about NEMA enclosure 1A to 1G, but it didn't really give an explanation of a 1G enclosure.
I?d specified a NEMA 12 Drive enclosure and was quoted a NEMA 1 G (gasket). Is the 1 G comparable to a 12?

 

[jim dungar]

The official enclosure is NEMA 1.

Many years ago, some Motor Control Center manufacturers started to put gasketing around the doors of the individual starter buckets. This made the starters gasketed, ala NEMA12, but the structures were still NEMA 1, hence the creation of marketing terms like NEMA 1G, NEMA1 Gasketed, and NEMA 1A.

A NEMA 1 with gasketing is not the same as a NEMA 12, it is simply a NEMA 1 with doors that don't rattle.

 

[petersonra]

If you look at a typical type 1 MCC that has gasketed doors, it superficially appears to be pretty comparable to a type 12. My guess is that for most purposes it is pretty close.

the gaskets do keep the doors from rattling as Jim mentioned, and they reduce the amount of dust that gets into the compartments.

However, it is not really type 12 and if you need that level of protection a type 1 with gaskets is not the answer.

Having said that, a lot of people are buying the gasketed type 1 style MCCs because they cost very little over a type 1 and add significant dust resistance.

Not as useful on buckets that have VFDs in them though as they are often vented.

 

[jim dungar]

... add significant dust resistance...

Yes, for the individual starters. But in gasketed MCCs the wireway doors and covers are not sealed so there can still be quite a bit of dust ingress.

For stand alone devices NEMA 1 Gasketed may just mean the manufacturer never submitted it to, or it could not completely pass, a full Type 12 testing. After all, technically as soon as you punch any hole into a UL Listed enclosure, it becomes a Type 1 unless they 're-certify' it.

 

[petersonra]

Yes, for the individual starters. But in gasketed MCCs the wireway doors and covers are not sealed so there can still be quite a bit of dust ingress.

For stand alone devices NEMA 1 Gasketed may just mean the manufacturer never submitted it to, or it could not completely pass, a full Type 12 testing. After all, technically as soon as you punch any hole into a UL Listed enclosure, it becomes a Type 1 unless they 're-certify' it.

the rest of the structure tends to be more dust resistant than the compartments are without the gaskets.

 

[Jraef]

The reason why some VFD mfrs are adopting the NEMA "1G / 1A" terminology is because if you must ventilate a box, there is NO WAY it passes type 12 (or 4) test requirements. When the enclosure ratings were just supported by NEMA and compliance was voluntary, peoplee used to use the term NEMA "12-V" for Vented. This is a complete oxymoron, you cannot have a box that is sealed and vented at the same time, no matter how good you think your filters are.

Once UL took over the specifications and testing of enclosure type ratings, the concept of "12-V" was of course exposed as a fraud, and eliminated. So now the ONLY rating you can get on ANY enclosure that has any type of exposure to free air exchange is Type 1. So even if you start with a Type 4X stainless steel enclosure, if you put vents in it, the UL rating reverts to Type 1. So now when people ask for type 12 but vents are needed because it is a VFD, the only thing the mfr can safely say without it being a lie that could jeopardize their UL listing is to say it is Type 1, and they add the "A" or 'G" like the MCC people do to indicate that it is still gasketed.

 

[petersonra]

The reason why some VFD mfrs are adopting the NEMA "1G / 1A" terminology is because if you must ventilate a box, there is NO WAY it passes type 12 (or 4) test requirements. When the enclosure ratings were just supported by NEMA and compliance was voluntary, peoplee used to use the term NEMA "12-V" for Vented. This is a complete oxymoron, you cannot have a box that is sealed and vented at the same time, no matter how good you think your filters are.

Once UL took over the specifications and testing of enclosure type ratings, the concept of "12-V" was of course exposed as a fraud, and eliminated. So now the ONLY rating you can get on ANY enclosure that has any type of exposure to free air exchange is Type 1. So even if you start with a Type 4X stainless steel enclosure, if you put vents in it, the UL rating reverts to Type 1. So now when people ask for type 12 but vents are needed because it is a VFD, the only thing the mfr can safely say without it being a lie that could jeopardize their UL listing is to say it is Type 1, and they add the "A" or 'G" like the MCC people do to indicate that it is still gasketed.

there are now fans and grills that are UL listed as type 12 so it is indeed possible to ventilate a type 12 cabinet.

 

[Jraef]

Bob,
Please don't take this wrong, I respect you and your opinions here. It's just that this is a personal pet peeve of mine that I had to get into in more depth than I cared for once as a product manager responsible for UL listings of my assigned product group. Our products needed ventilation, I could not sign my name to the UL reports that said they were Type 1 and then allow Marketing to sell it as Type 12. The subject was a constant source of contentious discussion between my company president, the marketing department and me, as the only one of the bunch who applied Engineering principals to the discussion. I ultimately lost the battle, but only because the president resorted to "because I said so". So please take all that into consideration as to why I happen to be a little obsessive-compulsive over this issue. I'm not really opposing your point of view so much as spreading the truth as I see it.

there are now fans and grills that are UL listed as type 12 so it is indeed possible to ventilate a type 12 cabinet.

I don't disagree that people are selling this, and what you believe is exactly what they WANT you to believe. But that doesn't make it true. UL50, the standard for enclosures that dictates the environmental test requirements, makes no allowances that a filtered vent fan would squeeze in under. Vent fans in fact are not even mentioned in UL50 specs. So what these companies are doing is a little bit of slight-of-hand. If you look, companies like Hoffman that have a reputation to maintain, do NOT ever say that filtered vent fans are Type 12, NEMA or UL. Those that DO say it are those who appear to be trying to capitalize on Hoffman's reluctance to join the party, because by saying it (implying it really), they can attract people who want to believe it.

• The fan is UL listed under UL508A, which does NOT address enclosure ratings. But still, it's a "true" statement that it is UL listed.
• They tell you the fan is "NEMA 12", hoping you will not realize that NEMA is not a testing or listing agency, so you can say anything you like that is preceded by NEMA, there is nobody to answer to on it but your own conscience. It's less clear cut, but not blatantly false.
• Then some go so far as to say this: "Maintains a UL Tested NEMA Type 12 seal against enclosure". That means that they put a gasket around the base of the fan, then test the gasket seal against UL50 test standards. But there is NO WAY the big gaping opening on that fan itself will stop atomized water and cement dust, the test criteria for Type 12. But they didn't technically say that, they said only that the GASKET was tested. Again, not technically a lie.

UL50 Type 12 says that the acceptable level of dust or atomized water entry is ZERO. In the UL50 dust test, the Portland cement dust they use is required to have a particle mixture with no less 82% of the particles being 0.0015" in diameter (about 38 microns). Most of the filtered "NEMA 12 Fan Kits" use a filter that is at best, "G3" rated, which is essentially meant to exclude up to 80% of "coarse" airborne particles that are a mixture of "Arizona road dust, carbon black and cotton lint", but no specific size. 20% can get through, and 20% is greater than zero.

 

[petersonra]

Hoffman is one of the companies selling fans and grills that are UL listed as type 12.

http://www.hoffmanonline.com/produc...=2383&cat_3=138274&catID=138274&itemID=138532

TFP Optional Grilles and Replacement Filters
Optional grilles offer the choice of stainless steel or black ABS plastic. These grilles replace the standard RAL 7035 gray composite or stainless steel grilles on both fan and exhaust packages. Standard replacement filters are washable foam (Type 1) or disposable (Type 12). To maintain UL Type 12 rating on the enclosure, UL Type 12 filters must be used on the fan package inlet. Washable aluminum filters are also available. Aluminum filters are compatible with Type 1 systems only.
Type 12 air filters are not washable.

Pfanneberg also offers type 12 fans.

http://www.pfannenbergusa.com/filterfan

I have used both of them. I doubt either of these companies would make up a UL listing claim they could not back up.

Incidentally, this is a fairly recent development. I never bought into the arguments a few vendors made about ventilation of type 12 enclosures in the past that you have mentioned. They were obvious to me because of the ambiguous phrasing. The phrasing being used now is very unambiguous.

 

[petersonra]

By the way, AB makes a VFD (powerflex 750) that has an external heat sink with fan that they claim is UL listed as type 4X.

That is a pretty good trick in my book.

I do not think they made that listing up either.

Again, a fairly recent development.

It is one of those things that is ambiguously worded though. What I think it means is that the enclosure is still type 4X after the drive is mounted through the back of the cabinet.

I still wonder how they get around the UL508a requirement that all components have to be mounted on a back plate, since in this case they are mounted on the rear of the enclosure wall. I have sort of accepted the idea that if UL listed it, it must be OK.

 

[petersonra]

[*]The fan is UL listed under UL508A, which does NOT address enclosure ratings. But still, it's a "true" statement that it is UL listed.

I think if you look closer you may find that the fan is listed to UL508 while the enclosures are listed to UL508a with a bypass through UL50 and some other standards that detail the actual testing methods.

For some inexplicable reason UL made up two completely different standards and gave them virtually identical numbers.

508 is for industrial control components and 508a is for industrial control panels.

On the bright side, UL is in the process of doing away with 508 and coming up with a global standard for industrial control components that will take its place in the next year or so. That should keep all the UL consultants in work for a long while. I forget what the new number will be but it won't be 508.

 

[kwired]

So now the ONLY rating you can get on ANY enclosure that has any type of exposure to free air exchange is Type 1. So even if you start with a Type 4X stainless steel enclosure, if you put vents in it, the UL rating reverts to Type 1.

I don't know what to think for certain about the rest of what was brought up on this topic, but depending on just what/where/how a vent is installed couldn't the enclosure possibly still meet 3R rating requirements? Types 4 and 12 are understandable one could lose those ratings if any air exchange is introduced at all.

 

[GoldDigger]

I don't know what to think for certain about the rest of what was brought up on this topic, but depending on just what/where/how a vent is installed couldn't the enclosure possibly still meet 3R rating requirements? Types 4 and 12 are understandable one could lose those ratings if any air exchange is introduced at all.

Hypothetically, what if instead of direct venting with filtering the air supply and return are ducted to outside the dust or moisture exposure area?

 

[petersonra]

I don't know what to think for certain about the rest of what was brought up on this topic, but depending on just what/where/how a vent is installed couldn't the enclosure possibly still meet 3R rating requirements? Types 4 and 12 are understandable one could lose those ratings if any air exchange is introduced at all.

3R often comes with louver type openings.

 

[Jraef]

I don't know what to think for certain about the rest of what was brought up on this topic, but depending on just what/where/how a vent is installed couldn't the enclosure possibly still meet 3R rating requirements? Types 4 and 12 are understandable one could lose those ratings if any air exchange is introduced at all.

Yes, the specs for 3R do not say that moisture will not enter, only that it will not get to live parts. That's why 3R enclosure need a weep hole of some sort.

 

[petersonra]

Yes, the specs for 3R do not say that moisture will not enter, only that it will not get to live parts. That's why 3R enclosure need a weep hole of some sort.

we just got a 3 door 3R enclosure in. It appears to be a type 12 enclosure with rain shields over the tops of the doors and a hole drilled thru the sides at the very bottom. the shields are just screwed on.

 

[kwired]

Hypothetically, what if instead of direct venting with filtering the air supply and return are ducted to outside the dust or moisture exposure area?

Is the ventilation invulnerable to filtration failure? If you are exchanging air and run into condensing conditions you could have a lot of water end up into the enclosure. I do realize some ventilation systems also condition the air so this risk is minimized.

Kind of going off track a little here but what if we have equipment in a complete vacuum? Ventilation would be pointless, but then so would current NEMA enclosure ratings.

What would happen to water if introduced into this vacuum? Would it remain in liquid state? I know it will boil at lower temp with lower pressure, but what would it take to make it condense again?

 

[petersonra]

The thing is that there is actually no real requirement that equipment be enclosed in an enclosure that is UL listed for anything, environmentally speaking. UL requires it be a minimum of type 1 for purposes of listing something like an MCC, switchboard, or industrial control panel.

It only has to be suitable. Most of the time indoors type 1 is quite adequate.

Whether something is type 1 or type 12 sometimes comes into play in classified areas, in an indirect way.

 

[Jraef]

Hoffman is one of the companies selling fans and grills that are UL listed as type 12.

http://www.hoffmanonline.com/produc...=2383&cat_3=138274&catID=138274&itemID=138532



Pfanneberg also offers type 12 fans.

http://www.pfannenbergusa.com/filterfan

I have used both of them. I doubt either of these companies would make up a UL listing claim they could not back up.

Incidentally, this is a fairly recent development. I never bought into the arguments a few vendors made about ventilation of type 12 enclosures in the past that you have mentioned. They were obvious to me because of the ambiguous phrasing. The phrasing being used now is very unambiguous.

Looks ad though I allowed my bias to prevent me from seeing the changes. I had looked on Hoffman's site and did not see that though. Thanks for the wakeup call.