Seal offs

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mannyb

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Florida
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Electrician
We are wiring 3 uderground storage tanks fuel sump pumps and sensors. The sump motors are wired with seal offs. rigid conduit and EP boxes one conduit to each motor. The sensor wiring is ran in seperate rigid conduit seal off, and EP J box as it enters boundry then it homeruns to each sump sensor. The sensors are located within classified area. Does each conduit with sensor wiring need to have seal offs going out to each sump and another seal as it enters the sump pump area for each tank?? I can see where its required for enclosures and dispensers but not a J box. If anyone has experience or knowledge I appreciate your help
 
Do the home runs for the tank sensors all come up from underground at one place to meet the sensor jbox?
 
You need to consult the area classification drawing that is required by 500.4 before thinking about doing any work associated with classified areas.
 
The #1 answer we give on this forum is 500.4. All your work is defined by the area classification drawing. Omitting a seal ix a expensive mistake.
 
Having seen his other posts on here I suspect Manny has read the code, if its a gas pump change out he may be the one making the classification drawing, hence the question.
In either case a diagram would help.
I think he might be asking about daisy chaining sensors tank to tank underground, vs all coming up at a gutter with seal offs, but we'll see if he elaborates.
 
tortuga said:
Having seen his other posts on here I suspect Manny has read the code, if its a gas pump change out he may be the one making the classification drawing, hence the question.
In either case a diagram would help.
I think he might be asking about daisy chaining sensors tank to tank underground, vs all coming up at a gutter with seal offs, but we'll see if he elaborates.
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Yes. There is one conduit for sensor wiring that will, homerun, or daisy chain to other Fuel monitors from the EP J box. Im asking if i would still need to provide seal offs as they leave the J box and I start to daisy chain? Is the one seal off as it enters the boudry enough. We are currently putting seal offs as they exit the J box but I think its really not necessary but I just
oldsparky52 said:
See 504.20 and 504.70

Actually you should read all of 504
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504 instrinisically safe systems. I read the article but I dont see any reference to my question. I have a seal as it enters the boundry but If I am to daisy chain the senors in the boundry is it still required to add seal offs. The dispensers and enclosures are very clear about it but I can see any refernce to pull boxes or J boxes. We are putting the seal offs either way but I was trying to find out if its even necessary sense we already have one at the boudry.
 
mannyb said:
Yes. There is one conduit for sensor wiring that will, homerun, or daisy chain to other Fuel monitors from the EP J box. Im asking if i would still need to provide seal offs as they leave the J box and I start to daisy chain? Is the one seal off as it enters the boudry enough. We are currently putting seal offs as they exit the J box but I think its really not necessary but I just


504 instrinisically safe systems. I read the article but I dont see any reference to my question. I have a seal as it enters the boundry but If I am to daisy chain the senors in the boundry is it still required to add seal offs. The dispensers and enclosures are very clear about it but I can see any refernce to pull boxes or J boxes. We are putting the seal offs either way but I was trying to find out if its even necessary sense we already have one at the boudry.
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Seals are required in the same locations for raceways that contain IS circuit as they are for power circuits, but they are not required to be explosionproof seals. See 504.70
 
tortuga said:
Having seen his other posts on here I suspect Manny has read the code, if its a gas pump change out he may be the one making the classification drawing, hence the question....
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It i a rare engineer or electrician who is actually qualified to create area classification drawings.

That is one of the reasons that Article 514 spells out the classified areas for fuel dispensing occupancies.
 
Let me try wording my question again

I have 3 tanks within class 1 div1 and class 1 div 2boundries. We also have fuel monitor sensors in the boundries. The sensors are ran within conduit, seal off, and EP J box. We are going to home run the sensor wires to each tank sump area. woould it be required to install a seal off as it leaves the Jbox to other area within the boundry? I can find where it mentions it for dispensers and enclosure or it I was leaving the classified area but not within the area. We are installing the seal offs either way.Im not trying to reclassify the area. I thought I might be missing something that would help with the installation. Thanks for help. I can find all kinds of info on everthing else but this question.
 
My answer would be no, the seals are not required if not leaving the boundary.

The way I used to wire these is to send one conduit (PVC) to a tank probe riser manhole with a 6x6x4 PVC box (face up). Then come out of that box to the stp sump, the fill bucket sensor, interstitial sensor.

When I stubbed into the STP sump, I would do so with rigid conduit and sealoff to a bell box. Pour the sealoff normally, not for x-proof reasons but because we have a problem with water intrusion inside the conduit around here and that poured sealoff puts a stop to that. No sealoffs at the probe riser but one at ever sump entry.

I would pour the sealoff at the building too.
 
oldsparky52 said:
My answer would be no, the seals are not required if not leaving the boundary.

The way I used to wire these is to send one conduit (PVC) to a tank probe riser manhole with a 6x6x4 PVC box (face up). Then come out of that box to the stp sump, the fill bucket sensor, interstitial sensor.

When I stubbed into the STP sump, I would do so with rigid conduit and sealoff to a bell box. Pour the sealoff normally, not for x-proof reasons but because we have a problem with water intrusion inside the conduit around here and that poured sealoff puts a stop to that. No sealoffs at the probe riser but one at ever sump entry.

I would pour the sealoff at the building too.
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Thanks for your answer. Thats the way I have seen at many other locations but still hesitant on application. I see where I needed the seal at probe riser but wondered if I needed one leaving the J box to the other stp pumps because its a classified area. We also put seals inside STP SUmp. Would the probe sensors be ART 504 IS and thats why I could use a pvc box? Would you use PVC leaving the PVC box?
 
I would stub down from the building with RGS and switch to PVC. Turn up at the inventory probe into the back of a PVC box with the opening looking up. Then from there to the other places I needed to hit. The reason for this was if you loop sump to sump it's a pain to pull through all those boxes, much easier to just pull through the one box at the inventory riser. I used box adapters to connect the PVC to the PVC box at the inventory riser in order to avoid steel locknuts. (Don't forget to drill a 7/8" hole in the side of the box before backfilling for the probe cable, much easier than after concrete is poured).

504.20 allows me to use PVC in/out of that box at the inventory probe riser.

504.70 allows me to use ductseal in that PVC box.

I've never been turned down by an inspector doing it this way. I know some on this site will argue that ductseal is not listed for this, but so far no AHJ has turned it down (and since I quit working I guess I will never be turned down :) ).
 
wallyworld said:
Is it an actual fitting or do you stuff the conduit full of some compound?

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Some AHJs will permit you to seal the end of the raceway, or to pack a conduit body full of some type of sealant. Some times, an actual seal is used, but filled with duct seal in place of being poured like you do for an explosionproof seal.

This is really a question as to what YOUR AHJ will permit for this application.
 
don_resqcapt19 said:
Some AHJs will permit you to seal the end of the raceway, or to pack a conduit body full of some type of sealant. Some times, an actual seal is used, but filled with duct seal in place of being poured like you do for an explosionproof seal.

This is really a question as to what YOUR AHJ will permit for this application.
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I agree on what my inspector would allow. I generally use rigid and a sealoff. Never seen anyone use pvc into a tank area where it would emerge into a sump or manhole. I have used liquid tite in that area . I think control drawings by Veeder root or Incon may eliminate plastic boxes in some cases not sure on pvc pipe in classified areas.

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