Class 1 Div 2 - Seal Methods at Motors

[stuofsci02]

Long time lurker first time poster...

I am executing a project for a mobile skidded piece of equipment that could be used in Class 1 Div 2 areas.

We are utilizing a Bebco Purge on our Control Panel.

In the field, all of our four motors are XPFC Enclosed and approved for Class 1 applications.

Coming out of the purged panel I intend to use a seal fitting like the Hubbel Killark ENY-3 with the appropriate Sealing Compound and Fiber, and then go into threaded RMC. My understanding is that once I am past the seal I can use standard RMC fittings.

Once I am close to the motor I want to switch to Liquidtight flexible conduit rated for class 1 div 2. Since I am going to a XPFC motor, do I need to seal it at the motor end with another conduit seal? If I do have to seal it there, does the seal need to go right onto the motors wiring box, or can it go where the transition from RMC to Liquidtight is made so long as it is within 18" of the motor?

Thanks for any help!

 

[rbalex]

Is the motor required to be explosionproof?

 

[stuofsci02]

No it is not, but this is what we have already built onto the skid.

My gut feel tells me that since I have an EXP motor that I need to seal at the motor with a conduit seal (to maintain the EXP rating of the motor wiring box), and then switch to liquidtight flex conduit.

If I had just a TEFC motor with Class 1 Div 2 marking would I be able to do something different?


Thanks,

Stuart

 

[rbalex]

I noticed you are in Canada. There are some subtle differences between the NEC and the Canadian Electrical Code (CEC) in hazardous locations. It’s been since the late 1990’s that I worked with the CEC.

The NEC doesn't generally require motors to be listed at all. It requires motors for Division 1 to be identified for Division 1 and listing is usually the simplest method. The NEC doesn’t require motors to be marked for Class or Division in Division 2. In fact. very few domestic motors are UL listed for Division 2. Those few that are are for highly specialized applications. Some are CSA listed for Division 2, but that is irrelevant since it's not a requirement. (It still a good way to "identify" them though) See NEC Section 501.125(B); especially the last two sentences. As I mentioned, I haven’t “worked” the CEC for some time. At the time, motors were CSA listed for Division 2 but not necessarily required to be.

All that said, I believe there is still enough similarity between the NEC and CEC that explosionproof motors would not need to be sealed at all since they are not required to be explosionproof.

 

[stuofsci02]

Thanks for your quick response!

I am in Canada, but this piece is designed for the U.S. so NEC is good.

Am I making this more difficult then it needs to be :?

We normally wire this same style skid with TC-ER cables. Can I do the same with this skid using class 1 div 2 cord grips with class 1 div 2 TC-ER cables.

We also have on the skid some NEMA 7 & 9 rated solenoids, an Intrinsically safe level probe, and a non-incendive 120V flow meter.

Since this is div 2 my understanding is that we are trying to limit ignition sources as opposed to limiting fuel sources.

Thanks!

 

[rbalex]

Thanks for your quick response!

I am in Canada, but this piece is designed for the U.S. so NEC is good.

Am I making this more difficult then it needs to be

We normally wire this same style skid with TC-ER cables. Can I do the same with this skid using class 1 div 2 cord grips with class 1 div 2 TC-ER cables.

We also have on the skid some NEMA 7 & 9 rated solenoids, an Intrinsically safe level probe, and a non-incendive 120V flow meter.

Since this is div 2 my understanding is that we are trying to limit ignition sources as opposed to limiting fuel sources.

Thanks!

Again with the subtle differences.

I was one of the major TC-ER proponents in the US. It’s really good stuff; however, the NEC doesn’t like it quite as much as I do. Depending on how you intend to get your skid identified, TC-ER would probably be accepted as a manufactured package product [See Section 90.7,Second paragraph] but it may have some problems with the literal requirements of Section 336.10(7), which is the only Section that specifically permits its manner of use in the NEC. It should be suitable [See Section 500.8(A)] but I’d check with the installation location's AHJ for confirmation.

The solenoids, level probe and flow meter, shouldn’t have any problems, packaged unit or not.

 

[petersonra]

Again with the subtle differences.

I was one of the major TC-ER proponents in the US. It?s really good stuff; however, the NEC doesn?t like it quite as much as I do. Depending on how you intend to get your skid identified, TC-ER would probably be accepted as a manufactured package product [See Section 90.7,Second paragraph] but it may have some problems with the literal requirements of Section 336.10(7), which is the only Section that specifically permits its manner of use in the NEC. It should be suitable [See Section 500.8(A)] but I?d check with the installation location's AHJ for confirmation.

The solenoids, level probe and flow meter, shouldn?t have any problems, packaged unit or not.

Just curious what part of 336.10() would prevent the use of TC-ER as long as it came out of a cable tray and went right to the end device? i thought that was pretty much what it was for, so you could avoid running cable tray out to the device.

 

[rbalex]

Just curious what part of 336.10() would prevent the use of TC-ER as long as it came out of a cable tray and went right to the end device? i thought that was pretty much what it was for, so you could avoid running cable tray out to the device.

That's sort of the point. As I recall, the CEC doesn't require any part of the TC-ER to be in cable tray. (The NEC shouldn't either) Another bit of subtle difference info: the CEC considers most common forms of cable tray as raceway.

 

[stuofsci02]

Thanks Gentlemen,

So what would be a good general practice for what I am trying to do. I don't want to over complicate the situation. If I can use simple methods that would be great.

I am still confused what fittings I need to use at the field devices and purge panel.

Do I need to go RMC with seals at the purge panel?

Thanks,

Stuart

 

[rbalex]

Since this would be a "Type Z" purge, almost anything that keeps the pressure up (including duct seal) is suitable. Technically, no seal at all is required if you were willing to provide enough air to maintain pressure. [See Section 501.15(B) Exception 3.] I confess I don?t usually recommend this unless you are dealing with a very small volume.

 

[stuofsci02]

Since this would be a "Type Z" purge, almost anything that keeps the pressure up (including duct seal) is suitable. Technically, no seal at all is required if you were willing to provide enough air to maintain pressure. [See Section 501.15(B) Exception 3.] I confess I don’t usually recommend this unless you are dealing with a very small volume.

Bob, thanks for directing me to that.

This panel has 12 cu.ft volume.

I would really love to use TC-ER to wire this up, but it sounds like it could be a grey area. I wonder then if our non-hazardous location skid is in that grey area too. We have not had any issues with it passing any electrical inspection, so I guess so far so good.

It sounds like if I use RMC then I should seal all my panel penetrations with a conduit seal and seal compound if nothing more then to maintain pressure in my enclosure.

I am still confused on how to enter my field devices except for the motors (which you clarified for me).

My NEMA 7 solenoids have 24 inch leads coming out of a 1/2" Exp-Proof female threaded conduit. In class 1 div 2 is the correct method to install a conduit seal directly to the solenoid and then pull the leads through the seal and make the terminations inside a standard pull/splice box? Or do I need an explosion proof box to make my splice in and then seal that from the conduit?

I have NEMA 7 pressure switches that have termination point inside the pressure switch enclosure. For this is the correct method is to put conduit seal directly onto the enclosure of the pressure switch before transition back to RMC?

Thanks again!

 

[petersonra]

That's sort of the point. As I recall, the CEC doesn't require any part of the TC-ER to be in cable tray. (The NEC shouldn't either) Another bit of subtle difference info: the CEC considers most common forms of cable tray as raceway.

I don't deal with the CEC.

I have often thought TC was a good option in lieu of conduit for wiring up stuff in the field. But, the support requirements make it tough to use.

 

[rbalex]

Bob,thanks for directing me to that.

This panel has 12 cu.ft volume.

I would really love to use TC-ER to wire this up, but it sounds like it couldbe a grey area. I wonder then if our non-hazardous location skid is in that greyarea too. We have not had any issues with it passing any electrical inspection,so I guess so far so good.

It sounds like if I use RMC then I should seal all my panel penetrations with aconduit seal and seal compound if nothing more then to maintain pressure in myenclosure.

I am still confused on how to enter my field devices except for the motors(which you clarified for me).

My NEMA 7 solenoids have 24 inch leads coming out of a 1/2" Exp-Prooffemale threaded conduit. In class 1 div 2 is the correct method to install aconduit seal directly to the solenoid and then pull the leads through the sealand make the terminations inside a standard pull/splice box? Or do I need anexplosion proof box to make my splice in and then seal that from the conduit?

I have NEMA 7 pressure switches that have termination point inside the pressureswitch enclosure. For this is the correct method is to put conduit sealdirectly onto the enclosure of the pressure switch before transition back toRMC?

Thanks again!

I like the TC-ER option; I just think you should lay out your groundwork with the local AHJ depending on how you intend to get the skid listed. (If I were the AHJ, I wouldn’t hesitate to accept it as part of a factory installation) You could use TECK-90 as an alternate. It is recognized as Type MC in the US and generally acceptable in Division 2. There are several brands of cable seals available too. BUT – if you insist on RMC you already know what to do although the seal still doesn’t have to be explosionproof. [See Section 501.15(C) Exception]

The solenoids aren’t required to be explosionproof. [See Sections 501.105(B)(3) and 501.120(B)(2)] They don’t require seals.

Sealing the pressure switch is will depend on whether it is “factory sealed” or not. If it isn’t then what you described is acceptable. See Exception to Section 501.15(A)(1)(1)part (3).

 

[stuofsci02]

I like the TC-ER option; I just think you should lay out your groundwork with the local AHJ depending on how you intend to get the skid listed. (If I were the AHJ, I wouldn?t hesitate to accept it as part of a factory installation) You could use TECK-90 as an alternate. It is recognized as Type MC in the US and generally acceptable in Division 2. There are several brands of cable seals available too. BUT ? if you insist on RMC you already know what to do although the seal still doesn?t have to be explosionproof. [See Section 501.15(C) Exception]

The solenoids aren?t required to be explosionproof. [See Sections 501.105(B)(3) and 501.120(B)(2)] They don?t require seals.

Sealing the pressure switch is will depend on whether it is ?factory sealed? or not. If it isn?t then what you described is acceptable. See Exception to Section 501.15(A)(1)(1)part (3).

Thanks,

I also like the TC-ER cables idea as well. Since this will be a travelling skid the AHJ will change from place to place, but I am sure a precedent could be set.

I said this was for the U.S. but I guess it could go to Canada also with a 460/575 TX. The TX won't be in the C1D2 area. It sounds like the CEC is more open to the TC-ER cable. Any reason you think this would be a problem?

For the TC-ER cable, we typically secure this to our 4" stainless steel skid structure. Does this violate any code? It is not a true cable tray or angle, but it is out of hazards way and is a very rigid support. We use impact resistant TC-ER.

Thanks,

Stuart

 

[rbalex]

Thanks,

I also like the TC-ER cables idea as well. Since this will be a travelling skid the AHJ will change from place to place, but I am sure a precedent could be set.

I said this was for the U.S. but I guess it could go to Canada also with a 460/575 TX. The TX won't be in the C1D2 area. It sounds like the CEC is more open to the TC-ER cable. Any reason you think this would be a problem?

For the TC-ER cable, we typically secure this to our 4" stainless steel skid structure. Does this violate any code? It is not a true cable tray or angle, but it is out of hazards way and is a very rigid support. We use impact resistant TC-ER.

Thanks,

Stuart

FYI Transformers are generally permitted to be in “general purpose” enclosures in Division 2. See Section 501.100(B). NOTE: Sections 450.21 to 450.27 refer to various types of installations that are acceptable in unclassified locations. Of course, any disconnecting means may need attention, but see Section 501.115(B)(2).

The CEC is more open to TC-ER because the rules making body covering it are not dominated by raceway, cable-tray and Type MC cable manufacturers.

Support from the structure should be acceptable if the cable is not installed in an otherwise “prohibited” manner. See Section 336.12; especially 336.12(1). All TC-ER is “impact” resistant by definition. See Section 336.10(7).

 

[stuofsci02]

Thanks!

 

[petersonra]

I think you will be Ok in most of the US if you include a short section of cable tray that the tray cable hangs out of.

You can get some really cheap and low end cable tray, and then you won't have to worry about it if it goes to the US.

 

[rbalex]

I think you will be Ok in most of the US if you include a short section of cable tray that the tray cable hangs out of.

You can get some really cheap and low end cable tray, and then you won't have to worry about it if it goes to the US.

I have no problem with this solution either although it demonstrates how silly the current requirements are.