EYS on which side of the junction box lift station

[Bjenks]

In Florida engineers are now required to sign and seal government designs. In this case a county lift station drawing has been given to me to not only design the one-line and grounding but to actually sign their standard design. My dilemma is that they show the conduit coming from the grinders out of the ground into a stainless steel junction box then to the seal-offs and then into the control panel.

My standard design is to put the seal-offs before any electrical connections including a junction box. My thought is that I am trying to eliminate any arcing going into a methane gas chamber. If there is ignition then I will supply a path for the explosion and gasses away from any other sources of arcing. I also don't want to use the junction box as part of a seal off system.

However, I noticed that many government systems say the seal-offs must be between the junction box and the control panel. This doesn't seem to make sense to me unless someone can explain why. Also I normally don't allow any type of PVC between the grinder and the seal-off because of explosion issues. I require coated galvanized steel for corrosion and explosion protection, is this off and if so your reasons.

Thanks

 

[KentAT]

However, I noticed that many government systems say the seal-offs must be between the junction box and the control panel. This doesn't seem to make sense to me unless someone can explain why.

I am not at all familiar with lift station area classifications, but I would say it all depends on the area classification(s) as specified on the Hazardous Area Classification drawing and whether the conduits are crossing a boundary from Class 1, Div 1 to Div 2, or from Div 2 to unclassified.

My thoughts are that if the conduit exiting the ground enters a different classification, a boundary seal is required per 501.15(A)(4) or 501.15(B)(2), and there can be no junction box between the boundary and the seal. If the boundary seal is also within 18" of the enclosure, it can serve as both the boundary and the enclosure seal.

If there is no change in the area classification as it exits the ground, the seals required by the government are primarily to satisfy the enclosure sealing requirements. The junction box would be acceptable as long as it is rated for the haz. location and does not contain any ignition source.


Others will add to or correct my thoughts...

Kent

 

[Bjenks]

Good feedback. I should have mentioned that in my specs I alway put in that the seals must be at least 18" below the control panel. The junction box is usually speced out as a Stainless Steel box with a DIN rail and connectors for the floats and motor cables, no manufacture or further spec. That way the motor cables and float conductors are part of a UL listed system and just connected at the DIN Rails. This gives it a practical reason for putting the seals on the other side of the box so that when you replace the floats or motor you don't have to redo the seals, but seems to take away some of the reason for the seals.