Enclosure with all C1D2 rated equipment

[chrisplusian]

I am dealing with a design which will have all C1D2 rated pneumatic valve assemblies (actuated via a relay controlled solenoid located on top of the valve) in a C1D2 area in one enclosure, and a second enclosure which will have controls equipment all rated C1D2. I am trying to understand if all the equipment located inside the enclosure is C1D2 does the enclosure need to be purged and pressurized because of the power feed to the panel?

500.8(B)(3) gives provisions for a non-explosion proof enclosure, and 501.10(B)(4) agrees. There is an issue I don't understand and that is 501.10(B)(4) points to 501.105(B)(2) as well as 501.150(B)(1). Both of the later sections deal with:

Switches, circuit breakers, and make-and-break
contacts of pushbuttons, relays, alarm bells, and horns shall
have enclosures identifed for Class I, Division 1 locations in
accordance with 501.105(A)

But the exceptions are different. 501.105(B)(2) exception allows things listed for division 2 locations, while 501.150)(B)(1) does not. Confusing is that 501.105 is for "Meters, Instruments, and Relays" while 501.150 is for "Signaling, alarm, Remote-Control, and Communications". Oddly enough I typically consider alarm bells, and horns to fall in the category of signaling or alarm, and relays to fall into the category of remote-control. I have always been able to place my panels outside the Hazardous areas in the past, so this is the first time panels will have to go in a Class 1 Divsion 2 location. I thought the panel would need to be purged and pressurized because it has a 10 amp feed coming into the enclosure by means of TC-ER-HL cable. I realize that 500.8(B)(3) uses the word normal which is not defined in the NEC.

I have two questions I seek to answer in general:
1) Does a panel which only contains equipment rated for class 1 division 2 locations not have to be purged and pressurized or explosion proof when the branch circuit feeding it is rated 10A @120VAC, or 10A @24VDC (obviously not IS or NI)?

2) Why does 501.105(B)(2) allow for division 2 equipment in the exception and 501.150(B)(1) does not?

 

[petersonra]

In general, devices that do not spark when they are actuated can be used in a C1D2 environment without any special protection means, although they may need to be listed for use in the area.

Things like relays, switches, and other devices that can create a spark when they are actuated cannot, unless you use a hermetically sealed version.

The actual voltage on the panel is not an issue. You can have TEFC motors in a C1D2 area that are 480 V with no special protection.

BTW, this is not an exhaustive list of what you can and cannot do. There are a lot of gotchas along the way that you have to pay attention to.

 

[chrisplusian]

In general, devices that do not spark when they are actuated can be used in a C1D2 environment without any special protection means, although they may need to be listed for use in the area.

Things like relays, switches, and other devices that can create a spark when they are actuated cannot, unless you use a hermetically sealed version.

The actual voltage on the panel is not an issue. You can have TEFC motors in a C1D2 area that are 480 V with no special protection.

BTW, this is not an exhaustive list of what you can and cannot do. There are a lot of gotchas along the way that you have to pay attention to.

I guess my first question is really related to the portion of wiring that goes up to the device location, not the device itself.

In regards to your statement about motors.... they require a disconnect in sight, or a lockable controller disconnect that is readily accessible. Pretty hard to accommodate either of those without explosion proof wiring methods, unless I am missing something.

 

[retirede]

If the devices you plan to put in the enclosure are installed in a manner that would be C1D2 compliant with no enclosure at all, the there should be no special requirements for the enclosure.

Having your disconnect “readily accessible” does not infer that it must necessarily be located in the classified area.

 

[chrisplusian]

If the devices you plan to put in the enclosure are installed in a manner that would be C1D2 compliant with no enclosure at all, the there should be no special requirements for the enclosure.

Having your disconnect “readily accessible” does not infer that it must necessarily be located in the classified area.

I agree with what you said about readily accessible. Just with the installations I have done in the last 5 or 6 years it has not been possible to pull it off.

When you said "If the devices I plan to put in the enclosure are installed in a manner that would be C1D2 compliant wit no enclosure, there should be no special requirements for the enclosure" I would agree with that whole heartedly. My question is if running regular wiring, assuming I put a boundary seal at the C1D2 to non hazardous boundary would be acceptable to a normal enclosure with all C1D2 components?

Again I have not been in a situation where I HAD to put an enclosure inside the C1D2 boundary before. Have done Hazardous installs but this is a first where I have to put the enclosure inside the area.

Adding to my confusion is the fact that part of the code allows you to not use explosion proof if everything inside is div 2 rated, while a very similar section does not give the same exception for everything div 2 rated.

I appreciate all the feedback.

 

[petersonra]

C1D2 wiring methods are covered in article 501. Sealing requirements are also covered there.

As for the disconnect, read carefully the requirements including the informational note that suggests the exception for creating a larger hazard by having a local disconnect would include a disconnect in a hazardous area.

 

[chrisplusian]

C1D2 wiring methods are covered in article 501. Sealing requirements are also covered there.

As for the disconnect, read carefully the requirements including the informational note that suggests the exception for creating a larger hazard by having a local disconnect would include a disconnect in a hazardous area.

I started the discussion by pointing to article 501, but I am a bit confused by the requirements which is why I came here to see if anyone could help me wrap my head around what I am confused with.

I am completely familiar with the disconnect requirements.

 

[petersonra]

501.105(B)(2) allows for make/break contacts in C1D2 areas if they are protected by one of the means in the 4 exceptions listed.

501.150(B)(1) allows for the same four exceptions.

I am completely familiar with the disconnect requirements.

This is the provision requiring a motor disconnect.

430.102 Location.
(B) Motor. A disconnecting means shall be provided for a
motor in accordance with (B)(1) or (B)(2).
(1) Separate Motor Disconnect. A disconnecting means for
the motor shall be located in sight from the motor location and
the driven machinery location.
(2) Controller Disconnect. The controller disconnecting
means required in accordance with 430.102(A) shall be permitted
to serve as the disconnecting means for the motor if it is in
sight from the motor location and the driven machinery location.
Exception to (1) and (2): The disconnecting means for the motor shall
not be required under either condition (a) or condition (b), which
follow, provided that the controller disconnecting means required in
430.102(A) is lockable in accordance with 110.25.
(a) Where such a location of the disconnecting means for the
motor is impracticable or introduces additional or increased hazards to
persons or property
Informational Note: Some examples of increased or additional
hazards include, but are not limited to, motors rated in excess of
100 hp, multimotor equipment, submersible motors, motors
associated with adjustable speed drives, and motors located in
hazardous (classified) locations.
(b) In industrial installations, with written safety procedures,
where conditions of maintenance and supervision ensure that only
qualified persons service the equipment

So as long as there is a lockable controller disconnect, you are not required to have a local motor disconnect if you meet exception (a) or (b). Virtually every factory in the US should be able to meet exception (b).

 

[chrisplusian]

501.150(B)(1) allows for the same four exceptions.

This is the source of my dilemma, and your statement about the exceptions being the same is incorrect. This is directly from the NFPA 70.

 

[chrisplusian]

So as long as there is a lockable controller disconnect, you are not required to have a local motor disconnect if you meet exception (a) or (b). Virtually every factory in the US should be able to meet exception (b).

Again I am familiar with disconnect requirements. But thanks for your feedback

 

[petersonra]

View attachment 2559486


View attachment 2559487

This is the source of my dilemma, and your statement about the exceptions being the same is incorrect. This is directly from the NFPA 70.

What is the difference? The wording is slightly different but the provisions are the same.

 

[chrisplusian]

What is the difference? The wording is slightly different but the provisions are the same.

The difference is one lists Division 2 rated is an exception and the other does not. Which again goes back to my original point of confusion, and your previous statement was that both code sections allowed the same four exceptions, I then showed they don't, and you are saying the provisions are the same? I guess I don't see it that way and am truly trying to understand what is different from one section to the next, and cannot seem to grasp it. If you are clear on why the exceptions are different I would appreciate the explanation.