Solenoid Valve Wiring in C1D2 location

[RGS]

Hello all,

First time poster here....

I have an application where I am designing a gas flow control cabinet. Basically, there are two compartments in the cabinet; one side contains all the gas controls, the other contains all the electrical. The gas compartment, housing plumbing for Hydrogen, Propylene, Oxygen, and Nitrogen, will have very little electrical in it... only one location-rated pressure switch and a number of solenoid valves. The whole cabinet is consider to be in a C1D2 location, and the gas section is also considered C1D2. The solenoid valves that I'm thinking of using are ASCO valves, rated C1D2 Group A,B,C,&D. The electrical side compartment is purged and pressurized.

I know the pressure switch will require potted seal-off fittings, and I know where I have to locate them. I have to run the solenoid coil's wiring back to the electrical compartment. I plan on using flexible sealtite. Will I need a seal-off fitting on either side of the the sealtite?

Thanks in advance,
Rick

 

[rbalex]

My first concern is how the gas side is only considered Division 2, since there are internal sources of flamable materials.

 

[RGS]

As I understand it (and I didn't give this area this designation, it was given to me by others), the area is consider Div 2 because, with this equipment, a gas leak is considered to be an abnormal situation. This equipment must undergo regular leak checks in order for the end process to run efficiently and consistently.

 

[RGS]

Oh... and I forgot to mention that the gas compartment of the cabinet is ventilated with louvers stamped into the panels where ever possible.

 

[rbalex]

I confess I’m having a tough time with this one.

You cannot ventilate one classified location from another classified location and meet the requirements for a “purged and pressurized” protection technique. See the Section 500.2 definition and NFPA 496. Conversely, common sense would say if the gas compartment were otherwise in “open air” it would be classified Division 2 and if there were a free flow of air from the same Division 2 location, it wouldn’t change it; i.e., what would one do if the “enclosure” were a chain link fence.

Note: the idea that "...a gas leak is considered to be an abnormal situation..." is irrelevant in an enclosed, poorly ventilated location. (See NFPA 496)

That being said, let us make two assumptions: the gas compartment is properly classified as Division 2 and the electrical compartment is properly purged and pressurized and is therefore unclassified.

In this case, the enclosure for the Electrical Section becomes a boundary and sealing requirements are covered in NEC 2005, Section 501.15(B)(2). Of particular relevance is Exception 3.

Note: The seal used for the pressure switch is still necessary.

Edit: Completed the Section 501.15(B)(2) citation.

 

[RGS]

I have to apologize, for my description in my previous posts wasn't very clear.

That being said, let us make two assumptions: the gas compartment is properly classified as Division 2 and the electrical compartment is properly purged and pressurized and is therefore unclassified.

I'm being told that this is correct.

Thank you for your help. I do appreciate it.

RGS