5kV switch in a Class I, Div 2 Area
5kV switch in a Class I, Div 2 Area
(OP)
I am trying to spec a 600A 5kV fused disconnect switch to be installed in a Class I, Div 2 hazardous area.
The two options I am currently aware of are:
Seal up the enclosure and pressurize it per NFPA 496, since this would be a 4 section switch that is an awful big enclosure to pressurize and monitor for leaks.
Use a gas insulated load break type switch. I don’t know a lot of SF6 but it seams to be the way to go, It just seems a bit pricey.
Any other idea or tips?
The two options I am currently aware of are:
Seal up the enclosure and pressurize it per NFPA 496, since this would be a 4 section switch that is an awful big enclosure to pressurize and monitor for leaks.
Use a gas insulated load break type switch. I don’t know a lot of SF6 but it seams to be the way to go, It just seems a bit pricey.
Any other idea or tips?






RE: 5kV switch in a Class I, Div 2 Area
RE: 5kV switch in a Class I, Div 2 Area
RE: 5kV switch in a Class I, Div 2 Area
RE: 5kV switch in a Class I, Div 2 Area
Several manufactures make devices that are “factory-sealed” and fit in or on otherwise non-explosionproof boxes, that's an option. Enclosing your equipment maybe the best as far far as safety is concerned. This setup would provide the safety necessary AND remove the need for other seals in the electrical system since the boundary is now the wall.
hold6448, Piping "clean air" is the same as "pressurizing per NFPA 496".
davidbeach, Section 500.4(A)NEC requires the electrical area classification be documented. Since you have to “draw the line” somewhere and it is Division 2, suggest electrical equipment located inside interior walls (enclosed). That would place most of the electrical system outside the classified area.
My $0.02!
RE: 5kV switch in a Class I, Div 2 Area
RE: 5kV switch in a Class I, Div 2 Area
Change the switch location.
Revisit the area classification and see if the area around the switch can be safely defined as "non-classifed" (Sometimes blanket classifications extending out to the unit boundary limits are more stringent than necessary.)
Elevate the switch and switchgear to the second floor. In refineries with heavier-than-air vapors the classified area may only extend 10-25 feet above grade. An enclosed Power Control Building on stilts is a solution some plants use.
As others have suggested placing the equipment in an enclosure with a pressurized air intake ducted from a safe location (25 feet off the ground) is a common solution.
RE: 5kV switch in a Class I, Div 2 Area
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RE: 5kV switch in a Class I, Div 2 Area
I still say that the best solution is to move the switch, there is certainly a better location.
RE: 5kV switch in a Class I, Div 2 Area
My point is basically to "separate" the equipment from the classified area, not placing the equipment inside a "wall cavity".
The reason I registered to this forum is simply because I know there are other people here who knows more than I do (and vice versa)! Having said that, I take every post well and think it over if these posts/ replies have truth in them! Please go easy on me, will ya?
First and foremost, "respect".
RE: 5kV switch in a Class I, Div 2 Area
Anyone who comes in expecting that others will "go easy on me" is bound to be disappointed. The crew of regulars don't "go easy" on anybody, including the most veteran members. Questions which show that the asker has put effort into trying to determine the answer will be treated with respect and answered with much good information, whether from a first time poster or someone who has been here for years. Statements that fly in the face of long experience can be expected to be received with less than warm hospitality.
Even some members who are now recognized as important contributors had some really lousy newby posts, but they saw how the give and take worked and figured out how to fit in.
As I said, nothing personal. Ask good questions with lots of background and you will get good results. Make statements that aren't well supported and you'll get called on it. Ask questions that resemble a fishing expedition and you won't get much help until you refine the question. All are welcome, but those who "play by the rules" are certainly more welcome.
Enjoy and learn.
RE: 5kV switch in a Class I, Div 2 Area
To answer a few questions the switch can not be located outside the hazardous area because we are reworking/refeeding a few existing 4160V-480V transformers that are smack dab in the middle of the plant.
I am still waiting on a price quote from the local G&W rep, but it would appear that the SquareD HVL/cc switch is the way to go. A lineup of 3 HVL/cc switches is a little over half the cost of the conventional HVL switches with a custom purged enclosure.
Thanks again,
Erik
Link to the HVL/cc switch:
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RE: 5kV switch in a Class I, Div 2 Area
RE: 5kV switch in a Class I, Div 2 Area
I was referring to a constantly purged box which is different than a pressurized box. I believe an enclosure may be either purged or pressurized per NFPA 496. Maybe I am confused.