Class I, Div. 2 item in Div. 1 area 2

[elm383]

Hello esteemed engineers,

I am looking for a second opinion regarding the following matter. This is because I'd like to clarify any bias since the parties that have advised me so far have vested interest in promoting their solutions.

I am looking into locating a certified Class I Div.2 area equipment (i.e. PLC) into a Class I Div. 1 area, and have been told that the only way to achieve this is to either use a EEx-d (explosionproof) enclosure or use EEx-p (purging) enclosure. It's a pity since if EEx-d or EEx-p is used, I might get away with a more common equipment which is more cost effective (subject to EEx-d & EEx-p limitations). Right now, I already have a Class 1 Div.2 area certified equipment and if possible would like to utilize the available certification.

Your advise is truly appreciated. Thank you always.

 

[controlnovice]

If you already have a PLC with Class I, Div 2 rating...

[ul]
[li]The best (and only solution for me) is to place it in a Class I, Div 2 or Non Classified area.
I would not approve placing this in a Class I, Div 1 area, even with the correct enclosures.[/li]
[li]If you truly don't have a choice, then go with a purged enclosure. You will need a type X or Y enclosure.
These are best for the ability to maintain the devices inside.[/li]
[li]While it might be to code, I don't recommend an explosion proof enclosure at all. (mainly for maintenance purposes)[/li]
[/ul]

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This is normally the space where people post something insightful.

 

[elm383]

controlnovice,

Thank you for the advice. In this case, I would have to go forward with the Class I Div 2 PLC in a purged enclosure (I'll have to study type X and Y suitability).

However, for future implementations, does it make sense to go with unclassified components and put it in a type X purging enclosure instead?

 

[controlnovice]

For future PLCs....place them in Non Classified areas! Although, many of them are becoming rated for Class 1, Div II areas and can be placed there. I would try to avoid putting a PLC in an X, Y or Z purged enclosure or explosionproof enclosure. I have placed HMI screens in purged enclosure where the customer wanted the operator to have access on the plant floor, but the HMIs were rated for such and touch screen.

You'll have to look up the definition of X and Y purging...I don't have access right now to my documents. In one of them, you cannot place a non-classified in a Class 1, Div 1 area...you can only drop one level. So you can place a device rated for Class I, Div II but not a Non Classified device in the enclosure in a Class 1, Div I area.

I don't have the documents on X, Y and Z type enclosures. Just be careful. You may have to measure and track the pressure of the enclosure and if you loose pressure, you have to shut off the electricity to the X, Y or Z panel (I don't remember which type enclosure this is for)...I'd have to look it up.

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This is normally the space where people post something insightful.

 

[roydm]

OOpps I meant to give a star to Controlnovice, excellent advice.
As you say avoid explosion proof at all cost, makes it almost impossible to maintain.
I have used Z purge in Class 1 Div 2 but never in Div 1

 

[elm383]

Rough explanation on types of purged enclosure. Just for info if anyone else parses through this thread.

[ul]
[li]Type X would reclassify internal enclosure area from zone 1 to unclassified or non-hazardous.
Meaning that the enclosure can be installed in zone 1 and the internal components does not necessarily have to be certified to any zone.

[/li]
[li]Type Y would reclassify internal enclosure area from zone 1 to zone 2.
Meaning that the enclosure can be installed in zone 1, but the internal components must be at least certified zone 2 components.

[/li]
[li]Type Z would reclassify internal enclosure from zone 2 to non-hazardous.
Meaning that the enclosure can only be installed at zone 2 (or safe/unclassified area. Doesn't make financial sense, but you can), but the internal components must be at least certified zone 2 components.

[/li]
[/ul]

Let me know if it's not accurate.

--Edit--

By the way:

Zone 1 is similar to Class I Div. 1
Zone 2 is similar to Class I Div. 2

 

[elm383]

Can I conclude that, always find someway to locate the items within its classification area first, and give consideration for explosionproof and purging enclosures only if there is no other way?

 

[themoke]

[Can I conclude that, always find someway to locate the items within its classification area first, and give consideration for explosionproof and purging enclosures only if there is no other way?]

Yes, ideally you will specify equipment certified for the area that it will be installed. Purged enclosures require maintenance, consume inert gas, and in many cases consume I/O for alarms. Explosion-proof enclosures are heavy, costly, and difficult to get in and out of. A third option you have, that wasn't discussed, is to provide a gas detection system (or possibly utilize one that already exists) that will trip power to your panel upon detection of the specific gas in your C1D1 area. See NEC article 500.7(K) for more information on this option.

Hope this helps.

Kind Regards,
Mike H.