I read the code section you referenced. Confusing as always.For solenoids in class II, Div 2, they are required to be compliant with 502.120(B), which only requires them to be in an enclosure that is dusttight or otherwise identified for the location. That said, is a coil with a Nema 4/4X rating acceptable?
Informational Note 1 for Table 110.28 states: The term dusttight is typically used in conjunction with Enclosure Types 3, 3S, 3SX, 3X, 4, 4X, 5, 6, 6P, 12,,12K and 13.Actually, Type 4/4X enclosures are not dusttight. [See Table 110.28 IN No.1 as noted above (My error referring to it as 110.128)] However, many 4/4X enclosures are multi-rated with additional dusttight ratings as well.
Technically Type 7 is explosionproof and Type 9 is dust-ignitionproof. For all practical purposes, with proper observation of Sections 502.10 and 502.15, dusttight is a sufficient alternative to dust-ignitionproof and it has virtually disappeared as an enclosure Type. (Unconfirmed, but it is my understanding that NEMA will eventually eliminate NEMA 7) A few specific applications mentioned in Section 502.100 and following may (only may) require identification for Class II. This is especially true for Group E, which can only be Division 1.All that being said, does he need to use the Nema 4X or Nema 9 enclosure for his specific case? Or is he asking about the rating of the coil itself?
An alternate rating like Nema 9 for example?Type 4/4X is not alone dusttight, but odds are it will have an alternate rating that is.
Are we reading from the same NEC Edition? I'm referring to 2017 which states, "The term dusttight is typically used in conjunction with Enclosure Types 3, 3S, 3SX, 3X, 5, 6, 6P, 12, 12K and 13."I was actually referring to the coil itself, which is epoxy encapsulated with a multiple NEMA rating that includes 4 and 4X. I do have a question about Bob's comment:
Informational Note 1 for Table 110.28 states: The term dusttight is typically used in conjunction with Enclosure Types 3, 3S, 3SX, 3X, 4, 4X, 5, 6, 6P, 12,,12K and 13.
I'm trying to see how these line up...
ACK-Too many things going on. Dust-ignitionproof (NEMA 9 reference) not explosionproof (NEMA 7) is apparently on the chopping block. As I mentioned, it is an unconfirmed rumor, but it was reported by a NEMA field rep.It would be hard to believe that nema 7 goes away. But perhaps.
NEMA 7 enclosures are designed to contain an internal explosion without causing an external hazard. These enclosures are intended for indoor use in hazardous locations classified as Class I, Division I, Groups A,B,C, or D.
Tire manufacturers and paint plants to name a few use the explosive gases listed above. Butadiene, Hexane, Isoprene, Styrene are the main tire manufacturer chemicals that are heavier than air and are explosive. All the gases head towards the floor.
Hydrogen is a whole other ballgame. Hydrogen is lighter than air and heads for the ceiling. We got involved in a hydrogen study last year, really strict rules especially with the ventilation.
An alternate rating like Nema 9 for example?
Ok. Moving forward, if you have an electrical enclosure within the hazard of a Class I, Division 1 or 2 source, what kind of enclosure would you buy?ACK-Too many things going on. Dust-ignitionproof (NEMA 9 reference) not explosionproof (NEMA 7) is apparently on the chopping block. As I mentioned, it is an unconfirmed rumor, but it was reported by a NEMA field rep.
Well, this is interesting. I see the addition with no indication that it is new. I also reviewed the 2020 "First Draft" and which did indicate the change, but the Public Inputs did not indicate the Substantiation as fas as I could tell. It's not a big deal since most Type 4/4X enclosures also have some form of "Type 3" rating as well.Sorry about that, Bob. I was looking at the 2020 version, which now includes 4 and 4X in note 1. For what it's worth, the coils also are rated 3 and 3S.
The standard solenoid coils are rated for 155C, which is below the temperature limit of 165C. We were likewise looking at a motor that is also similarly rated (both are class F insulation). Will these be acceptable?For a simple solenoid, you generally do NOT need to go "explosion proof". Coils are not normally "sparking" devices like a contactor. Unless the operating temperature of the coil is above the ignition temperature of the dust, gas, etc. you are fine.
Div 2 means you are allowed one failure, EITHER a failure of the coil or the "unusual" presence of the flammable element. One failure will not result in a conflagration. BTW, an induction motor is also fine in Div 2 unless it's temperture is too high..