Ex 'e' Enclosure on Class I Div 2

Status
Not open for further replies.
L

Lemoca

Member
Location
Bloomfield, NJ
On NEC the enclosure doesn't always have to be explosionproof unless as required by 501.105(B)(1), 501.115(B)(1) AND 501.150(B)(1). Which on my understanding states that as long as my equipment rating is good for Class 1 Div 2 Group B, I can have them inside of on non-pressurized NEMA 4 enclosure for instance.

However, the fact that I sub this NEMA 4 enclosure by a EX 'e' NEMA 4X enclosure (Increased Safety) won't mean that now I can put non rated electrical equipment inside, the components inside will still have to Class I Div 2 group B rated. Am I correct? I am getting little confused with what would be the advantage of using a Increased Safety Enclosure if at the end all my components will still have to be zone 2 rated.

Another question, does a increase safety enclosure has to be on stainless stell? Because some of the vendors that I consulted only had this option.

Can anybody help me on this confused topic.

Thanks,

Lemoca
 
Are you confused by the difference between a NEMA 4 enclosure and a NEMA 4X enclosure and how this impacts their suitability in a Class 1, Div 2, Group B location? A NEMA 4X enclosure is functionally the same as a NEMA 4 enclosure and they meet the same performance specifications. The difference is that a NEMA 4X enclosure is required to be constructed of corrosion resistant materials - generally interpreted to mean that it is stainless steel construction rather than painted or powder coated steel.


The difference between NEMA 4 and NEMA 4X is irrelevant from the perspective of Article 501. The reason some manufacturers don't sell NEMA 4 and only have NEMA 4X enclosures for hazardous locations is that many companies, including mine, have specs that only allow stainless steel enclosures outdoors, whether in a hazardous location or not.

as long as my equipment rating is good for Class 1 Div 2 Group B, I can have them inside of on non-pressurized NEMA 4 enclosure for instance.
Click to expand...
I think you are correct if I understand what you are saying. You can have a non-pressurized NEMA 4 enclosure in a Class 1 Div 2 location as long as there are no "arcing or sparking" devices inside. This means a NEMA 4 enclosure can be used for a pull box or used to enclose factory sealed devices. These factory sealed devices may be what you are referring to as "equipment rating is good for Class 1 Div 2 Group B."

What do you mean by an "increased safety enclosure?"
 
An enclosure may be marked for multiple types. Each mark is independent so it only affects the enclosure?s use and not another other mark.

For example, an enclosure marked only ?NEMA 3R? could be used outdoors but would not be suitable for Class I, Division 1. An enclosure marked only ?NEMA 7? could be used in Class I, Division 1 but would not be suitable for outdoor use. An enclosure with both marks could be used outdoors in Class I, Division 1.

The concept also applies to marking systems, such as UL/NEMA or CENELEC/IEC. Each mark applies to the relevant system. The NEC does make some limited provisions in Section 501.5 to let equipment marked for NEC Zones under 505.9(C)(2) to be used in NEC Division classified locations. In Section 505.9 there is a general permission to automatically mark certain Division marked equipment with NEC Zone markings. It doesn?t mean it will actually be marked that way, but it?s a freebee for manufactures, so most do.

You should also note ?explosionproof? is not one of the recognized protection techniques for Zones listed in Section 505.8; nevertheless, it is mentioned throughout the Article.

?Ex? alone means nothing in either NEC classification system. To be recognized by the NEC, the mark must be ?AEx? per Section 505.9(C)(2)(3). So basically, the ?Ex? alone can be ignored since it only applies to IEC usage and, for NEC purposes, the enclosure mentioned in the OP is simply NEMA 4X and may be used in Divisions or Zones where ordinary location equipment is otherwise permitted.
 
Thanks for your replies.

I just want to clarify my question, in my company we've been using a Class I, Zone 1 AEx e II T6 Junction boxes which contain intrinsically safe circuits inside. Then I can see why we using such rating on the junction box.

Now, we are creating a module that will have a small enclosure that would only contain a few distributed IOs, relays and terminals, all of them rated Class I, Zone 2 GP Zone 2 IIC T4 and they also have a EX approval - II 3 G EEx nA II T4.

And someone at my office said that we had to have a Increased Safety enclosure just like the small junction box I just mentioned (AEx e rating). However, I don't see why it has to be an AEx 'e' rated enclosure, because the Increased safety rating ('e') still requires non arcing and/or non sparking devices inside, and since the components I have have a non-incendive method of protection according to their EX approval, I just can go by article NEC 501.15(4)(b) that tells me that I shall not be required to use explosionproof enclosures.

So, if my enclosure is out on a Class I Zone 2 IIC, the inside of it will also be rated as the outside, but if my components are rated for such harzadous area, I wouldn't need any type explosion protection for my enclosure - such as Increased Safety, Flameproof or Pressurized and Purged.

Thanks Again,

Lemoca
 
I?m still having a problem uinderstanding your mixing and matching the two NEC Class I, classification systems.

First, if the location you are installing in is classified under the Zone system (Art. 505) as you indicated in your second post, then citing 501.105(B)(1), 501.115(B)(1) and 501.150(B)(1) as you did in your OP is meaningless. I have no idea what you are meant by ?NEC 501.15(4)(b)? in your second post, but it doesn?t matter either since Article 501 is not directly applicable to Zone classified locations.

You would need to justify using a NEMA 4 enclosure without an ?AEx? marking in a Class I, Zone 2 classified location with a citation from either Section 505.15 (C)(1)(g) or Section 505.20 (C) or one of its Exceptions. (You can do it :D)
 
Status
Not open for further replies.
Top