We are building a piece of equipment to be used in a class 1 Div 1 location. I am somewhat confused by what exactly is required to run conduit between a terminal box on the back and a bank of 6 solenoid switches on the side of the equipment. I had planned to run conduit and then short runs of sealtite from tee's to the solenoids. I believe 18" or less is allowed. If anyone can point me to where I can find more information on the requirements of running explosion proof conduit I'd greatly appreciate it.
Class 1 Div 1 Conduit requirements.
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justdavemamm
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- Rochester NY
What if the solenoid is an Intrinsically Safe device fed by an appropriate barrier / isolator ?
Or are you presuming that when the OP says "running explosion proof conduit" that XP vs I.S. wiring is being used ?
Since the OP is asking such a question, I presume he is unaware of the different types of wiring methods available for C1D1 areas, dependent upon equipment types and such.
So I'll ask: Are the solenoid I.S. or XP or ??? rated ? What voltage are they ? Is the "terminal box on the back" Nema 7 ?
What about sealing ? The OP hasn't made mention of it and I'm thinking that unless the box is made safe by purging, seal-offs will be needed.
Or are you presuming that when the OP says "running explosion proof conduit" that XP vs I.S. wiring is being used ?
Since the OP is asking such a question, I presume he is unaware of the different types of wiring methods available for C1D1 areas, dependent upon equipment types and such.
So I'll ask: Are the solenoid I.S. or XP or ??? rated ? What voltage are they ? Is the "terminal box on the back" Nema 7 ?
What about sealing ? The OP hasn't made mention of it and I'm thinking that unless the box is made safe by purging, seal-offs will be needed.
petersonra
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- Northern illinois
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- Semi-retired engineer
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- Mission Viejo, CA
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Augie answered the question that was essentially asked in context;i.e., "what do I do for an explosionproof installation?" Augie supplied the correct reference. [Section 501.10] Whether the OP should have asked about alternative wiring methods is moot. The fact is, if flexable connections were necessary (rather than just convienient), the answer is in still 501.10; 501.10(A)(2) to be specific.
It's doubtful an IS or purged system would be envisioned for the installation described unless the client had already suggested it, since they are system solutions rather than stand alone packages.
It's doubtful an IS or purged system would be envisioned for the installation described unless the client had already suggested it, since they are system solutions rather than stand alone packages.
petersonra
Senior Member
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- Northern illinois
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- Semi-retired engineer
There are a lot of packaged pieces of equipment out there these days designed for use in hazardous areas using IS or purge in lieu of XP.
IMO it is often safer, simpler, and much less costly, and avoids all the PITA problems of cast aluminum boxes.
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I neglected to mention the terminal box and solenoids are explosion proof. Thanks for the heads up where the requirements were. No sealtite for C1 D1. There is flexible wiring that can be used, but I don't think it'd would be appropriate for this particular case. Looks like I will need seals near the terminal box. use explosion proof fittings, rigid conduit with unions to the solenoids.
Am I correct to assume explosion proof fittings have tapered threads (NPT) or do they have straight threads like standard conduit?
Am I correct to assume explosion proof fittings have tapered threads (NPT) or do they have straight threads like standard conduit?
You are correct. I ignorant when it comes to C1D1 areas. I have a golf cart sized pieced of equipment that will be installed in a C1D1 area. It will have some XP motors, XP limit switches and XP solenoides that all need to got to an XP terminal box. I would be very interested to learn of cheaper/better ways than running wire thru XP conduit/fittings.
- Location
- Mission Viejo, CA
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- Professional Electrical Engineer
There's was no question that IS or purging is available; but they both require a systemic apporach. That is, the facility must be committed to them.
As a protection technique, explosionproof is passive.
If you believe cast aluminum is a PITA try a Type X purged system in a Division I location. (Remember this was the context of the OP) Where both are properly installed, the purged system has a greater probability of failure with all the active sensing and shutdowns required.
IS is also prone to failure modes that explosionproof technology isn't. Type 2 is a bit better but far more expensive - and I still don't trust non-explosionproof seals between Division 1 and other classfications.
In this forum, as much as possible, we need to answer the OP without adding speculation.
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- Mission Viejo, CA
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- Professional Electrical Engineer
See Section 500.8(E). For what it's worth also see 342.28.
My code book is somewhat out of date. It doesn't have those sections.
petersonra
Senior Member
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- Northern illinois
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- Semi-retired engineer
I can't tell you how many cast boxes I have seen all dinged up. I don't trust that anyone has inspected the integrity of the machined surfaces after opening them up. Or that when they closed them up they did not get dirt or other foreign substances on those machined surfaces.
I agree that an IS or purged system has additional failure points. I am just not real sure that makes them less safe. IS is pretty simple for the kind of thing the OP was talking about.
Purging is a little more of an issue, especially if it is a mobile system.
- Location
- Mission Viejo, CA
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- Professional Electrical Engineer
Yes; it's described in Article 504.
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
The issue is not whether IS or purging is less safe. I've used both and they are fine. The context we are dealing with is the OP - not all the failures we've seen. It's one reason I specifically mentioned assuming the installation was done correctly - no matter which method was used. Within the context, for the installation described, explosionproof would most likely be the more cost effective.
I have some "explosion proof" solenoids that the wire's are spliced in an EP junction box and then go back to a EP panel. If I read the code correctly I need all EP conduit fittings. And a seal no less than 18" from the terminal box. What I am unclear about is if I also need seals at all connections to the junction box where the wire's are spliced. If I understand the 501-5 correctly I only need the seal at the EP terminal box. I'm using 3/4" conduit. The code says I would need seals if the conduit were 2" or larger. Also my code book is slightly out dated so things may have changed. Does this sound correct that I only need a seal near where the conduit enters the panel?
- Location
- Illinois
- Occupation
- retired electrician
I thought that the definition of IS was that "under no conditions of use or misuse can a spark be created that will have enough energy to cause ignition". I don't understand how you can have enough energy to operate the solenoid and not have enough energy to create a spark that can cause ignition.
Well the understanding is essentially in your statement of not understanding it. The solenoids are engineered such that they use less energy than that of an igniting spark... so the first thing to understand is how a spark can have too little energy to ignite a combustible gas or gas-air mixture. An explanation of such is beyond the time I have alotted :roll:
... but here's a little something for reference...
http://www.tcomega.com/temperature/Z/pdf/z131-148.pdf
- Location
- Illinois
- Occupation
- retired electrician
Smart,
Thanks for the link...but it only brings up more questions for me. The information indicates that the power in an IS circuit is limited to 1 watt or less. Most of the standard solenoids that I see need 9 to 13 watts to work. If they can make one for an IS system work at 1 watt, why are we wasting all of that energy in a standard solenoid?
Thanks for the link...but it only brings up more questions for me. The information indicates that the power in an IS circuit is limited to 1 watt or less. Most of the standard solenoids that I see need 9 to 13 watts to work. If they can make one for an IS system work at 1 watt, why are we wasting all of that energy in a standard solenoid?
I don't know for certain. I believe this is where economics come into play. Compare price on some IS solenoids and their non-IS counterparts. As for the reason in price difference, your guess is as good as mine.
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