Conduit seal for lighting conduit in Class I Div 1?

[greenspark1]

Hi,
I have a simple scenario- conduit run from a light switch to a light in a small Class I Div 1 room. All the components are in the hazardous area.

I believe I need a conduit seal within 18" of the switch since it could produce a spark. Do I need another seal within 18" of the light? If the switch is fed from the bottom and feeds the light from the top, do I need a seal on each side? I'm looking at 501.15 but lights especially aren't clear. Any change if this is Div 2? Thanks for any clarification!

 

[rbalex]

It ain't rocket science but your scenario isn't quite as simple as you may think. In fact, you may need anywhere between 0 and 3 seals.

The following assumes the raceways are less than 2".

With respect to the pushbutton, sealing will depend on whether or not it is "factory sealed". If it is, no seals are required (0 seals) for the pushbutton itself. If it isn't, then each conduit entering it will require a seal (2 seals). Likewise, the luminaire will require 0 or 1 seal, depending on how it is identified for Division 1. If it is explosionproof (the most likely), a seal is required (1 seal). Other luminaires identified for Class I, Division 1 may or may not require a seal (0 or 1 seal).

If seals are required and there is a common seal within 18" of each enclosure along the length of the common raceway it can serve for both enclosures.

 

[greenspark1]

Hmmm, sounding more and more like rocket science I appreciate the explanation though.

I just looked into the switch we're using, and wouldn't you know, it's factory sealed! LINK. I guess I don't need any seals for it. I'd like to understand how this works, is the switch mechanism itself encapsulated in some sort of gas- proof compound? Obviously the switch has to be taken apart to wire it up.

For the light: I'm using an explosion-proof fixture such as this: http://www.cooperindustries.com/con...pdfs/lighting/evi-incandescent-luminaires.pdf
It DOES say that it's factory sealed, so wouldn't require anything extra. I'm not sure exactly how the fixture is sealed, but I will trust the literature. Similar to the light, it is sealed with pigtails? However, I cannot sole source so they may install a different light. I would hope that all Class I Div 1 lights are factory sealed, but sounds like I need to check the cutsheet to make sure. Too bad this isn't simple stuff.

Next on my list is to determine if various temperature transmitters, flow meters, etc need sealing. Digging in the weeds. Thanks again rbalex.

 

[jap]

It ain't rocket science but your scenario isn't quite as simple as you may think. In fact, you may need anywhere between 0 and 3 seals.

The following assumes the raceways are less than 2".

With respect to the pushbutton, sealing will depend on whether or not it is "factory sealed". If it is, no seals are required (0 seals) for the pushbutton itself. If it isn't, then each conduit entering it will require a seal (2 seals). Likewise, the luminaire will require 0 or 1 seal, depending on how it is identified for Division 1. If it is explosionproof (the most likely), a seal is required (1 seal). Other luminaires identified for Class I, Division 1 may or may not require a seal (0 or 1 seal).

If seals are required and there is a common seal within 18" of each enclosure along the length of the common raceway it can serve for both enclosures.

Why would a seal be required for the light fixture?

 

[rbalex]

Both the pushbutton and luminaire essentially use dual explosionproof chambers with a common seal between them. The arcs, sparks and heat (ASH) occur in one chamber and terminations are made in the other.

 

[rbalex]

Why would a seal be required for the light fixture?

Some do some don't. It depends on whether they are a single or dual chambered design. A single-chambered unit needs to be sealed unless the tested value of the internal components is below the "T-code" of the relevant materials.

 

[rbalex]

Hmmm, sounding more and more like rocket science I appreciate the explanation though.

I just looked into the switch we're using, and wouldn't you know, it's factory sealed! LINK. I guess I don't need any seals for it. I'd like to understand how this works, is the switch mechanism itself encapsulated in some sort of gas- proof compound? Obviously the switch has to be taken apart to wire it up.

For the light: I'm using an explosion-proof fixture such as this: http://www.cooperindustries.com/con...pdfs/lighting/evi-incandescent-luminaires.pdf
It DOES say that it's factory sealed, so wouldn't require anything extra. I'm not sure exactly how the fixture is sealed, but I will trust the literature. Similar to the light, it is sealed with pigtails? However, I cannot sole source so they may install a different light. I would hope that all Class I Div 1 lights are factory sealed, but sounds like I need to check the cutsheet to make sure. Too bad this isn't simple stuff.

Next on my list is to determine if various temperature transmitters, flow meters, etc need sealing. Digging in the weeds. Thanks again rbalex.

While you may not specify a proprietary manufacture, you can specify the design be "factory sealed". Many but certainly not all instrumentation devices are factory sealed but it is a little tougher to specify that feature.

 

[jap]

What in the termination point of an explosionproof fixture would be considered arc producing?

 

[rbalex]

What in the termination point of an explosionproof fixture would be considered arc producing?

"Arcing" isn't the only criterion; sparks and high temperatures must also be considered. See 501.15 (A)(1)(1).

 

[greenspark1]

Thanks again rbalex. I learn something new every day, keeps this field interesting.

 

[jap]

"Arcing" isn't the only criterion; sparks and high temperatures must also be considered. See 501.15 (A)(1)(1).

What does an explosion proof luminaire have inside its termination point that would cause sparks or high temperatures?

 

[rbalex]

What does an explosion proof luminaire have inside its termination point that would cause sparks or high temperatures?

Reread - and spend some time comprehending - post #6. Otherwise, I'll just have to chalk this up to a case of 90.1(C).

 

[jap]

Reread - and spend some time comprehending - post #6. Otherwise, I'll just have to chalk this up to a case of 90.1(C).

I'd have to agree since the OP was talking about a light switch and not a pushbutton.