Intrinsically Safe Wiring Methods

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JW 569

JW 569

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San Diego, CA
I am writing a site survey report on an existing installation in a Class I Div. 2 area. There is intrinsically safe circuits in CMP rated cable that leave an enclosure and run as open wiring to various simple apparatus. (Does apparatus have a plural form?):roll: The cable are spliced to the apparatus leads and there is no enclosure.

I personally don't like the installation, as there is no reason that these cables cannot be in conduit and the splices in an enclosure. I can't seem to find a specific article that prevents this. Art. 725.61(3) refers back to 501.10(B)(3) and I haven't found a definite answer in any other articles either.

I don't want to tell the customer its OK if its not. I also don't want recommend repairs that they don't need.

Any help here would be greatly appreciated. Thanks.
 
Wow! There it is in black and white. I've been working so hard on this report that I've gotten writer's block and apparently I now have reader's block.

Thank you!

If the customer has the control drawings as required this would have been an easy call.

I have issues with open wiring in industrial installations as it seems to be a constant in regards to reliability problems. I think that I have found the middle ground,though. The simple apparatus have threaded entries and it seems that 500.8(D)(1) requires a fitting regardless of the wiring method. I will at least suggest that they install an outlet box for the splice and a strain relief connector for the cable.

Does that sound OK?
 
JW 569 said:
Wow! There it is in black and white. I've been working so hard on this report that I've gotten writer's block and apparently I now have reader's block.

Thank you!

If the customer has the control drawings as required this would have been an easy call.

I have issues with open wiring in industrial installations as it seems to be a constant in regards to reliability problems. I think that I have found the middle ground,though. The simple apparatus have threaded entries and it seems that 500.8(D)(1) requires a fitting regardless of the wiring method. I will at least suggest that they install an outlet box for the splice and a strain relief connector for the cable.

Does that sound OK?
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Do you have an installation drawing for the device, by the Manufacturer? There should be one if it is a listed and labeled device. It seems to me that you should be able to terminate the cable with a cable gland into the device's threaded opening and make the splice/wirenut connections inside the device itself. If you have and 'extra' box, it need to be supported independently from the device and appropriate conection made between it and the device.
 
I am trying to get installation drawings for the customer. When they purchased this facility, there were no documents or drawings transferred from the seller. I am finding that it is difficult to get drawings from manufacturers that are not located in the U.S. Apparently the FTC requires American manufacturers to provide documentation at no charge, but either can't or doesn't make Foreign manufacturers do the same.

These devices are sealed units with threaded connections and pigtails.

I should have been a little more specific when I said "box". In my mind, I was picturing something like an Appleton GU style box. It may be overkill but there's just something about this facility that screams "The minimum requirements probably aren't good enough."
 
JW 569 said:
I am trying to get installation drawings for the customer. When they purchased this facility, there were no documents or drawings transferred from the seller. I am finding that it is difficult to get drawings from manufacturers that are not located in the U.S. Apparently the FTC requires American manufacturers to provide documentation at no charge, but either can't or doesn't make Foreign manufacturers do the same.

These devices are sealed units with threaded connections and pigtails.

I should have been a little more specific when I said "box". In my mind, I was picturing something like an Appleton GU style box. It may be overkill but there's just something about this facility that screams "The minimum requirements probably aren't good enough."
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If it is listed and labeled as intrinsically safe then you should have the installation drawing on hand as installing the device without the manufacturers instructions may put you in danger of voiding the listing. (I am not sure, but I would think that it also would be part of the control document.)

GU is explosionproof and it is an overkill.

In hazardous location the overkill sometimes bring dangerous results. The misapplication of fittings can lead astray installers who are not throughly familiar with hazardous area installation requirements - most of them are not - and leads to inconsistency, misapplication and eventually to hazardous conditions.
 
I see your point, and I agree.

You have to understand that in this facility where the devices are located, the hazard doesn't come from the switch itself. If the connections to the switch were to come apart during the process cycle there could a hazardous situation created elsewhere in the facility. This, of course, leads me back to the control drawings that would, if they existed, provide for these cable to be protected if they present a hazard when damaged.

This customer, unfortunately was sold a huge liability when they bought this place. This will eventually end up in litigation and I am just trying to give them an idea of what it would cost to make repairs, under the assumption that this intrinsically safe system is an engineered system.

From my standpoint, these are just hypothetical repairs, as I feel this facility will ultimately be shut down.
 
JW 569 said:
I see your point, and I agree.

You have to understand that in this facility where the devices are located, the hazard doesn't come from the switch itself. If the connections to the switch were to come apart during the process cycle there could a hazardous situation created elsewhere in the facility. This, of course, leads me back to the control drawings that would, if they existed, provide for these cable to be protected if they present a hazard when damaged.
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The wiring is still protected by the barriers. I don't see any hazard.

Now if the claim is that the mere disconnection of the switch, IS or not, creates a hazard, you have a major flaw in the design of the control system, but its not a wiring issue. It would be just as fatal if the switch itself happened to fail.
 
JW 569 said:
I see your point, and I agree.

You have to understand that in this facility where the devices are located, the hazard doesn't come from the switch itself. If the connections to the switch were to come apart during the process cycle there could a hazardous situation created elsewhere in the facility. This, of course, leads me back to the control drawings that would, if they existed, provide for these cable to be protected if they present a hazard when damaged.

This customer, unfortunately was sold a huge liability when they bought this place. This will eventually end up in litigation and I am just trying to give them an idea of what it would cost to make repairs, under the assumption that this intrinsically safe system is an engineered system.

From my standpoint, these are just hypothetical repairs, as I feel this facility will ultimately be shut down.
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Seem to me that the operation is not designed to be fail safe, if the opening of a switch will create a hazardous condition.

IS for a Cl.I, Div. 2 location is an overkill to begin with. In most cases, even if you violate the 'by-the-book' instalaltion of the IS circuit, if your barrier is in place, you will not likely to create an ignition source simultaneously with the random presence of an ignitable mixture.

By no means am I saying that you are OK with the installation, just pointing out that I would think the proper ionstallation of an IS circuit in a Cl.I, Div. 2 area seems to eb the least of your problems.
 
There are two methods for the design, installation and maintenance of IS circuits. 1 is the Entity method, a qualified individual selects individual components listed and designs the entire IS circuit and develops the control drawing defining all IS parameters defining the circuit and it's installation. The other is the Loop method, typically a manufacturer defines the entire IS circuit and supplies a control drawing defining all IS parameters. Both require a control drawing per the NEC 504.

Specifically to the open splices, I would not allow based upon general wiring suitablity requirements for hazardous area locations. The wiring still has to meet general wiring practices for the environment it's installed in. Physical protection minimally required in a harsh environment.
 
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