Solenoids in Class II Div 2

RTMintus

Member
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?
 

rbalex

Moderator
Staff member
See Table 110.128, Informational Note No. 1.

This emphasizes that not all NEC answers are in one location.
 

powerpete69

Member
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?
I read the code section you referenced. Confusing as always.
It says dusttight or otherwise identified for the location.
Here some thoughts that might induce some thought.
Nema 4/4X is dust tight, but not rated for Class II, division 2 per my perception.
Class II, division 2 generally requires Nema 9 enclosures. Also keeps heat inside.
A nema 9 will contain an interior explosion, a Nema 4/4X will not. Nema4/4X not rated for group E, F and G.

The link below gives a wonderful explanation of the difference between Nema 4/4X and Nema 9.

In the end, if there is a spark, will there be an explosion inside the enclosure (good) or an explosion outside the enclosure (bad)? Is your enclosure heat rated?

Doesn't Class II, Division 2 also require rigid conduit with at least 5 threads and seals?

Please correct me if someone knows better.
 

rbalex

Moderator
Staff member
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.

Only explosionproof enclosures have the five thread engagement requirement. [Section 500.8(E)(1)] See Section 502.10(A)(3) for some specific Class II, Division 1 requirements though. Also see Section 502.5 for some insights with respect to explosionproof equipment in Class II locations.

Basically, it is impossible to reliably prevent vapors and gases from entering most Class I enclosures. Dust entry and thus internal ignitions, are relatively simple to avoid in Class II. This is why the sealing requirements are substantially different as well. [Section 502.15] Note they are virtually identical for both Class II, Divisions 1 and 2
 

powerpete69

Member
Great corrections. Always a pleasure to be corrected by someone with more knowledge and experience.
I see the table now, should have similar information to my Eaton link above. Although I don't see Nema 7 or 9, likely because they are in the explosion proof Article 500 section of NEC.

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?
 

RTMintus

Member
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:

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.
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...
 

rbalex

Moderator
Staff member
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?
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.

With respect to the OP, the assembly, including the coil, would need a "T-code" consistent with Section 500.8.(C)(4). The enclosure would need to be dusttight or otherwise identified for the location. Type 4/4X is not alone dusttight, but odds are it will have an alternate rating that is.
 

powerpete69

Member
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.

Type 4/4X is not alone dusttight, but odds are it will have an alternate rating that is.
An alternate rating like Nema 9 for example?
 

rbalex

Moderator
Staff member
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...
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."

BTW note neither NEMA nor UL are references to Types. Both are obsolete.
 

rbalex

Moderator
Staff member
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?
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.
 

powerpete69

Member
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.
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?
My little Eaton link above says that Nema 7 is explosion proof. Oh boy.....
 

rbalex

Moderator
Staff member
Odds are I would use explosionproof in Division 1, but there are alternatives [See Section 500.7]. There are many options in Division 2 depending on the contents. [See Section 500.7 as well]
 

RTMintus

Member
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.
 

powerpete69

Member
Class II, Div. 1—are those
where dust is suspended in
the air under normal
operating conditions, in
quantities sufficient to
produce explosive or ignitable
mixtures.

Class II, Div. 2—are those
where such dust is not
normally in the air, but where
deposits of it accumulating on
the electrical equipment will
interfere with safe dissipation
of heat, causing a fire hazard.

The second would clearly explain why you don't need explosion proof in Class II, Division 2.
 

Ragin Cajun

Senior Member
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..
 

rbalex

Moderator
Staff member
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.
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.
 

rbalex

Moderator
Staff member
It appears the actual change did, in fact, occur in 2017, where the definition of Dustight in Article 100 was revised to include 4 and 4X. However, as far as I can tell it cites a NEMA Standard improperly. I no longer have access to the latest Standards.
 

RTMintus

Member
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..
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?
 

rbalex

Moderator
Staff member
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?
The insulation class is not quite the same as the T-code or temperature rise. [Section 500.8(C)(4)] It is, however, a pretty good indicator of the maximum temperature anticipated. See also Section 500.8(D)(2) and its IN reference to NFPA 499. Actually, NFPA 499 is a wealth of information.
 

RTMintus

Member
Based on that, it sounds as if there is no option to use a "general purpose" solenoid or motor (because there is no T-code or max temp)... Correct?
 

rbalex

Moderator
Staff member
Based on that, it sounds as if there is no option to use a "general purpose" solenoid or motor (because there is no T-code or max temp)... Correct?
You already cited the correct Section for solenoids in the OP. For motors, it's Section 502.125(B). You may wish to review Sections 500.8(A), especially 500.8(A)(3), and 500.8(C)(6)(b) as well.
 

RTMintus

Member
I've read them numerous times. It would appear that a general purpose motor and solenoid can be acceptable for use in a Class II Div 2 environment without labeling and should not exceed the 165C temp under normal operation...
 

rbalex

Moderator
Staff member
I've read them numerous times. It would appear that a general purpose motor and solenoid can be acceptable for use in a Class II Div 2 environment without labeling and should not exceed the 165C temp under normal operation...
It looks like you interpreted it properly.
 
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