Seals on Conduit from Gasoline Dispenser

[Jon456]

We have conduit running out from the sump under a fleet gasoline dispenser. There are seals on the conduit inside the sump as the first fittings just before the conduit leaves the sump. After leaving the sump, the conduit passes under the concrete dispenser island for a lateral distance of ~4 feet. Beyond the island, the conduit is buried under earth. It travels laterally ~2 feet and then turns to follow the concrete foundation of an adjacent metal building. It then runs laterally along the foundation, still buried under earth. Approximately 10 feet from the dispenser island, the conduit will stub-up out of the ground, running vertically up the side of the metal building. There will be conduit seals at this stub-up location. After the seals, conduit will continue vertically to junction boxes ~8 feet high on the building's exterior wall. All the conduit from the seals in the sump to the seals on the stub-ups will be PVC-coated RMC.

Questions:



1. What is the min and max distance above the ground for the conduit seals after the RMC exits the ground at the stub-ups on the side of the building? Attached is an image from the Crouse-Hinds Code Digest that suggests that the seals should be exactly within the 18" Class 1, Div 2 boundary. It seems unlikely that such precision can be had in practice when working relative to bare earth.

1.(a) Can the seals be below the 18" boundary? If so, by how much? And would that prevent the use of EMT conduit on the vertical run above the seals?
1.(b) Can the seals be above the 18" boundary? If so, by how much? And would that allow the use of EMT conduit on the vertical run above the seals?
​

2. How deep must the RMC conduit be buried under the earth between the concrete dispenser island and the stub-ups on the side of the building. This earth area is a narrow alley between two metal buildings with no possibility of any vehicular traffic.

3. It's my understanding that the junction boxes on the side of the building (well above the Class 1, Div 2 boundary) can be regular weatherproof boxes without any special ratings for hazardous locations. Is that correct?

 

[rbalex]

1. It depends on how the boundaries are established but basically a seal within 10' of emergence from grade and no other fittings between it and the boundary will do.

2. Burial depth(s) are still controlled by Section 300.5.

3. As long as the junction box is located outside the classified envelope it can be any Type otherwise suited for the location.

 

[Tom the lectrician]

Ok, I used to be in that field, so here it is. Yes you have to have a seal off within 18" after exiting the ground. They must be the first fitting out. Packed and poured..Thanks K&K..miss you guys, all is well with me , you'd know who it is. Also you must go by the manufacturers instructions. Anything that went through the ( and that's class 1 division 1 btw) area is to be sealed at both ends, first fitting out of the ground, up to 18". Burial depth is upheld by typical codes of 18" if below concrete, but not in a driveway. 2' deep if auto traffic area. Yes outside of the 20' hazard area, after the seal off, and the grounding bushing of course,you can use anything you want so long as yoire grounded up to the point of your gutter. ( what we usuallu set after exiting the ground
)compliant with code, to complete your run. Weatherproof boxes and pipefitings are fine. Use pvc if you want...cheaper, faster and legal. Make it look good, paint it before you hang it up. Sorry if I made any mistakes and used all experience with no code references. But I remember everything I learned. Section 500 if I'm remembering correctly.

 

[Jon456]

So at the stub-up, the seal must be between the ground and 18" above the ground? That puts the seal within the Class 1, Div 2 zone. So what type of conduit is permitted above the seal? It seems to me that the conduit connection above the seal will still be within the Class 1, Div 2 zone unless you get the body of the seal fitting to actually cross the boundary.

From Table 300.5, the RMC must be at least 6" below grade when covered in earth. Under the 4" thick concrete island, Table 300.5 specifies that RMC must be covered by at least 4" (to within 6" of the footprint of the concrete). I assume that cover means the same 4" of concrete, and not an additional 4" of soil below the bottom of the concrete slab. Correct?

 

[rbalex]

I apologize for not originally referencing Section 514.8. It substantiates my responses to questions 1 and 2.

You may need to reconsider the 6" cover. Most (not necessarily all) AHJs consider the run as being beneath a trafficked location. [See the fifth line of Table 300.5.] Trafficked locations can cause cable creep although it's not usually a great concern for lighter conductors as typical in your application. The minimum depth can vary over the total run though. The Table's fourth line doesn't require additional earth coverage, but only applies to non-trafficked areas.

With regard to EMT, it must be located outside the Division 2 envelope, not just beyond the seal.

 

[Jon456]

I apologize for not originally referencing Section 514.8. It substantiates my responses to questions 1 and 2.

Please, no need to apologize. You are a wealth of information and I'm always grateful for your willingness to share your knowledge.

With regard to EMT, it must be located outside the Division 2 envelope, not just beyond the seal.

I'm still not completely clear about this statement from 514.8:

"...shall be sealed within 3.05 m (10 ft) of the point of emergence above grade."

Is that lateral distance, vertical distance, or in any direction along the path of the conduit? Does that mean the conduit can emerge from grade and, for example, run up a wall for 9 feet in a continuous section of conduit prior to encountering the sealing fitting?

So in reference to the Crouse-Hinds image in my original post, with the sealing fittings placed within the Class 1 Div 2 area (as pictured), then it would not be permitted to continue the run beyond the fitting with EMT because that would mean the EMT connection to the seal would be immediately below the Class 1 Div 2 boundary. Is that correct?

But I could extend the RMC conduit to over 18" above grade before placing the seals so that the seal is outside the Class 1 Div 2 zone, and then I could continue the conduit run in EMT (outside the Class 1 Div 2 area)?

You may need to reconsider the 6" cover. Most (not necessarily all) AHJs consider the run as being beneath a trafficked location. [See the fifth line of Table 300.5.]

I suppose I wasn't clear when I called the area an alley. What we have is a dirt area about 9 feet wide between two metal buildings, and 40 feet long. At the front of this space is the concrete island with the dispenser (which is protected by bollards). At the back is where the above-ground fuel storage tank is located, protected by concrete walls, fencing, and bollards. So there is absolutely no access to this "alley" between the buildings. Even a motorcycle could not practically get into this area.

 

[rbalex]

I believe we have discussed before in other threads that Article 514 is not entirely within the control of Code Making Panel 14(CMP14). See Article 514 Title, Informational Note(IN). Also refer to Article 510 for some general information. Some parts of the Article are remnants of the original effects of the NFPA 30A Technical Committee even if it no longer indicates the reference in brackets.

...
I'm still not completely clear about this statement from 514.8:

"...shall be sealed within 3.05 m (10 ft) of the point of emergence above grade."

Is that lateral distance, vertical distance, or in any direction along the path of the conduit? Does that mean the conduit can emerge from grade and, for example, run up a wall for 9 feet in a continuous section of conduit prior to encountering the sealing fitting?
...

Any direction along the path of the conduit is intended as long as there are no other fittings between the seal and grade.

Before the 2005 NEC, below grade was considered Division 1. If you can find a copy, see Figure 514.3 in the 2002 NEC or earlier editions. Since 2005, the Figure has gone through several revisions to what it is now but below grade has been considered unclassified since 2005. This is consistent with most common practices such as NFPA 497 or API RP500. However, there is still some discomfort within the NFPA 30A Technical Committee, so an explosionproof seal is still required at both ends of the run. This can be a minor problem if the stub-up is in a Division 2 location. Theoretically, there would now be two boundaries; one at the emergence at grade and the other between the Division 2 and unclassified location. However a judiciously located seal with no fittings between it and grade serves both cases.

BTW, the 18" from grade was never a requirement except as an arbitrary ruling by some local jurisdictions. There never was a specific distance for boundary seals until API proposed it be 10', the length of a "standard" stick of RMC/IMC. I originated the Proposal as a member of API's Subcommittee on Electical Equipment.

With respect to coverage, I was just cautioning that Section and Table 300.5 still apply.

 

[Tom the lectrician]

Ok, maybe I'm off some, but

Ok, maybe I'm off some, but

Ok, I used to be in that field, so here it is. Yes you have to have a seal off within 18" after exiting the ground. They must be the first fitting out. Packed and poured..Thanks K&K..miss you guys, all is well with me , you'd know who it is. Also you must go by the manufacturers instructions. Anything that went through the ( and that's class 1 division 1 btw) area is to be sealed at both ends, first fitting out of the ground, up to 18". Burial depth is upheld by typical codes of 18" if below concrete, but not in a driveway. 2' deep if auto traffic area. Yes outside of the 20' hazard area, after the seal off, and the grounding bushing of course,you can use anything you want so long as yoire grounded up to the point of your gutter. ( what we usuallu set after exiting the ground
)compliant with code, to complete your run. Weatherproof boxes and pipefitings are fine. Use pvc if you want...cheaper, faster and legal. Make it look good, paint it before you hang it up. Sorry if I made any mistakes and used all experience with no code references. But I remember everything I learned. Section 500 if I'm remembering correctly.

Oh yeah...we stub into a dispenser sump, add a seal off, and every nipples you use to fit it up the rest of the way also gets a seal. Just make sure you can access the spout to pack and pour it. And after leaving the classidied area, we stub up adding a seal off below 18", not certain of minimal height. .But from there fit it up with nipples into a gutter. No need to worry, youre no limger in the hazard zone.Make sure all tour stubs are the same height. Once you're in the gutter, they get grounding bushings, binding everything and a divider if your intrinsically safe wiring is going into the same gutter . It's not that much, really. Just another way to pipe stuff in. Carefully, though as not to allow vapor to get through to your electrical equipment. Also, only in the hazardous location ( within 20 feet, do you need to have seals and explosion proof boxes. And of course the pipe that came out of there. But division 2, yeah I've built a part of a factory classified as that, is more or less just weatherproof boxes and fittings. That's all that was really required. To be dust proof

 

[rbalex]

Ok, I used to be in that field, so here it is. Yes you have to have a seal off within 18" after exiting the ground. They must be the first fitting out. Packed and poured..Thanks K&K..miss you guys, all is well with me , you'd know who it is. Also you must go by the manufacturers instructions. Anything that went through the ( and that's class 1 division 1 btw) area is to be sealed at both ends, first fitting out of the ground, up to 18". Burial depth is upheld by typical codes of 18" if below concrete, but not in a driveway. 2' deep if auto traffic area. Yes outside of the 20' hazard area, after the seal off, and the grounding bushing of course,you can use anything you want so long as yoire grounded up to the point of your gutter. ( what we usuallu set after exiting the ground
)compliant with code, to complete your run. Weatherproof boxes and pipefitings are fine. Use pvc if you want...cheaper, faster and legal. Make it look good, paint it before you hang it up. Sorry if I made any mistakes and used all experience with no code references. But I remember everything I learned. Section 500 if I'm remembering correctly.

You are obviously no longer in that field.

 

[Tom the lectrician]

I'm a little rusty

I'm a little rusty

Bro, been almost 10 years since I've worked on that stuff, do miss it though.And I'm no longer in the construction end of the trade, just industrial control wiring and simple troubleshooting. Easy money...and I could still pass every inspection, garun tee it. Hasn't changed that much. That's why I joined up, to kind if get back to the basics

 

[rbalex]

Bro, been almost 10 years since I've worked on that stuff, do miss it though.And I'm no longer in the construction end of the trade, just industrial control wiring and simple troubleshooting. Easy money...and I could still pass every inspection, garun tee it. Hasn't changed that much. That's why I joined up, to kind if get back to the basics

You have no idea.

 

[Tom the lectrician]

You are obviously no longer in that field.

Come on man, burial depth and seal offs? Get real bro. I always buried everything at least 18" we all do. sizing and running pipe, conductors which is pretty much laid out for you in a print?or a nameplate? Section 430 for motor overcurrent and branch circuit feeders? Correction factors and all that? 80% rules and conduit fill, annex c. I know more than enough to build anything. Now I design and wire more than all that. And I don't brag about what I know and do. I do it as well as I know, which is according to your bare minimum. . I'm willing to bet my knowledge is more than yours chief, by far. And I'm more than familiar with my rules and regs bro. Test me out. Give me a scenerio you had a hard time troubleshooting and I'll bet you I solve it before your finished explaining. Youre* And also, it's more about practical application than words. I put all kinds of things together right, and make it look good on top of that. You can put wires and pipe together , great. I passed he rookie stage a long time ago.

 

[roger]

Come on man, burial depth and seal offs? Get real bro. I always buried everything at least 18" we all do. sizing and running pipe, conductors which is pretty much laid out for you in a print?or a nameplate? Section 430 for motor overcurrent and branch circuit feeders? Correction factors and all that? 80% rules and conduit fill, annex c. I know more than enough to build anything. Now I design and wire more than all that. And I don't brag about what I know and do. I do it as well as I know, which is according to your bare minimum. . I'm willing to bet my knowledge is more than yours chief, by far. And I'm more than familiar with my rules and regs bro. Test me out. Give me a scenerio you had a hard time troubleshooting and I'll bet you I solve it before your finished explaining. Youre*

You probably need to look at rbalex's profile before you dig your hole much deeper, you're actually making a fool of yourself.

Roger

 

[Tom the lectrician]

Since you're only 10 feet from the island, you're still within the 20' hazardous location distance, so everything into the building, each pipe or nipple must be sealed, packed and poured. I forgot my rules and stuff. Within 18" of the grade, seals must be installed. Also in the dispnser, only boxes or capped "L"s rated for that app. may be used. Every nipple or piece of conduit gets a seal, packed and poured with Chico compound .You will have to bury the conduit, being rigid, a minimum of 4" beneath the concrete slab. If it were a drivway it would be 2 feet, which is what we always buried to anyway. No matter what pipe or location, always buried it 2 feet. That's all really, take it all to your equipment, land it o n the contactor for the pumps, tie in your product switched legs from the dispenser. 20 feet around and 2 feet above grade. Make sure your e stops are visible and within 20 feet of the area.That's your hazardous area. As for the connections to the equipment, the pump needs to be wired with a sealant around each wire also. That's what I remember from 10 years ago. HAPPY genius?

 

[GoldDigger]

... HAPPY genius?

Happy banned member? :lol:

 

[Jon456]

I believe we have discussed before in other threads that Article 514 is not entirely within the control of Code Making Panel 14(CMP14). See Article 514 Title, Informational Note(IN). Also refer to Article 510 for some general information. Some parts of the Article are remnants of the original effects of the NFPA 30A Technical Committee even if it no longer indicates the reference in brackets.

Any direction along the path of the conduit is intended as long as there are no other fittings between the seal and grade.

Before the 2005 NEC, below grade was considered Division 1. If you can find a copy, see Figure 514.3 in the 2002 NEC or earlier editions. Since 2005, the Figure has gone through several revisions to what it is now but below grade has been considered unclassified since 2005. This is consistent with most common practices such as NFPA 497 or API RP500. However, there is still some discomfort within the NFPA 30A Technical Committee, so an explosionproof seal is still required at both ends of the run. This can be a minor problem if the stub-up is in a Division 2 location. Theoretically, there would now be two boundaries; one at the emergence at grade and the other between the Division 2 and unclassified location. However a judiciously located seal with no fittings between it and grade serves both cases.

BTW, the 18" from grade was never a requirement except as an arbitrary ruling by some local jurisdictions. There never was a specific distance for boundary seals until API proposed it be 10', the length of a "standard" stick of RMC/IMC. I originated the Proposal as a member of API's Subcommittee on Electical Equipment.

With respect to coverage, I was just cautioning that Section and Table 300.5 still apply.

Thank you again for your assistance.

 

[rbalex]

Happy banned member? :lol:

Please be civil. I want it clear that I was not responsible for the disciplinary action although I supported it after it was taken. I also want to make it clear that how Tom did things 10 years ago is not necessarily how things must be done today. Many changes have occurred in hazardous locations in the last 20 years and especially in the last 15.

I stand by my responses and will let the OP determine the value of them.

 

[augie47]

Happy banned member? :lol:

Amen !!!!
more dangerous than a cocked gun

 

[wallyworld]

Please be civil. I want it clear that I was not responsible for the disciplinary action although I supported it after it was taken. I also want to make it clear that how Tom did things 10 years ago is not necessarily how things must be done today. Many changes have occurred in hazardous locations in the last 20 years and especially in the last 15.

I stand by my responses and will let the OP determine the value of them.

All the disconnects for any and all comm wires is one of the bigger changes. Pump data, card reader data, intercom and now Cat 5. I only know of a couple of options and both add issues when trouble shooting