Hazardous room boundary

[alphaX]

Hello, I am working on putting a fire rated automatic sliding door for a Class I Div II room. The PTO switches and overide for the door inside the rooms are XP rated. Now the proximaty sensors mounted above the rail of this doors which are outside the room and in the corridor wall space are neither XP rated nor do they have intrinsically safe circuiting. Do I have to mount these sensors outside the 3 feet boundary from the Door frame to comply with code requirements for the 3 feet boundary restriction from the opening of a Class I div II room? Though, I am mounting these sensors outside the room and the room is negatively pressurized to the corridor. I did not get the idea why I cannot mount switches or sensors with 24V wiring within the three feet boundary outside the room from the door frame. Would really appreciate any comments or feedbacks.
regards,
AP

 

[bsh]

It takes very little energy to create a spark large enough to cause an explosion. I went to a seminar once and the speaker said there was enough energy released from a fly walking up a wall to create an explosion. Anyway, the spark from 24 volts could do it (turn on your car lights and remove the battery cable from the post and see what happens). The voltage is not the issue, it's the energy released from the switch operation that's the problem. If you can put the switches through an intrinsically safe barrier located outside the hazardous area that would work. Also if the presurization were monitored to shut down the electrical equipment inside the XP zone that would work too.

 

[alphaX]

HB

HB

Thanks for your coment, BSH. So there is a three feet boundary restriction outside around the opening (the door frame) of a class I Div II room ? And if that holds, I won't be able to mount any sensors or switches within the three feet boundary of the edge of the door frame even if I am mounting them outside the Xp room and the room itself is negatively pressurized. No I am not monitoring the pressurization of the room. Please clearify the three feet boundary restriction outside the opening of a class I div II room and would appreciate if someone can point out the artile of the code it's comming from.
regards,
AP.

 

[don_resqcapt19]

The NEC does not set the classified are boundries. They are set by the design engineer.
Don

 

[alphaX]

HB

HB

Thanks for your comment, so there is no restrictions in code requiring the consideration of a 3 feet class I div II boundary outside the room starting from the edge of the door frame and along the wall of the corridor outside the XP room. My understanding is I did not see any safety issues to put Proximity sensors along the rail where the sliding door hangs from the top wall in the corridor area. As the room is negatively pressurized and the room on the opposite side of the door is a class I div II, I don't know how if any flammable gas will come outside the room, then accumulate outside the room in the corridor and endanger anything. Would appreciate feedbacks.
regards,
AP

 

[Natfuelbilll]

The code allows "non-incendiary" installations in C1 and 2, Division 2 locations.

The distances which you are looking for may be found elsewhere. What is the gas? You may be able to investigate NFPA or industry documents for your questions.

 

[Cody K]

In my natural gas application, all of our switches and transmitters are labeled "class 1 div 2". I am assuming that means they are nonincendive. You should have little problem finding prox switches that meet this criteria.

 

[don_resqcapt19]

Cody,

In my natural gas application, all of our switches and transmitters are labeled "class 1 div 2". I am assuming that means they are nonincendive.

No...it just means that they can be used in a Class I, Division 2 area.
Don

 

[Cody K]

Cody,

No...it just means that they can be used in a Class I, Division 2 area.
Don

Don, I appreciate your correction. So what you are saying is the devices I wrote of can actually produce a spark?

 

[don_resqcapt19]

Don, I appreciate your correction. So what you are saying is the devices I wrote of can actually produce a spark?

Yes, that is possible. Many items listed for use in Class I Division 2 areas have spark producing contacts or other ingnition sources. These devices are in explosionproof enclosures and in many cases will require the use of seal-offs.
Don