Lift Station Seal Off

[joegreene]

Is an explosionproof seal off required, in the conduit system, from the wet well to the lift station control panel....IF the lift station is installed outdoors and is vented? I have seen drawings & specs from several municipalities. Some jurisdictions require explosionproof seal offs and some do not....if the wet well is vented.

Environment & installation:
Lift station installed outdoors.
Wet well is vented.
Conduit system from control panel to wet well is SCH 80 PVC

Thoughts:
I am thinking this would be a Class 1, Division 2 location [NFPA 70 Ed. 2011 500.5(B)(2)]
On a chart in NFPA 70 2011 Ed. ( 2011 NEC Handbook page 734), the chart title is "Conduit and Cable Sealing Requirements"...Class 1, Division 2..."Conduit run leaving Division 2 location"..."Within 10ft of either side of boundary. No unions, couplings, boxes, or fittings (other than explosionproof reducers) permitted between the seal fitting and the point where the conduit leaves the Division 2 location. Not required to be explosionproof seal."

What does the discussion group think? Please include code references with any response.

Thanks for the help

 

[augie47]

In reviewing a number of these stations in the past with engineers, the well simply being "vented" did not change the classification,.

 

[rbalex]

NFPA 820, Standard for Fire Protection in Wastewater Treatment and Collection Facilities [See Section 500.4(B) FPN/IN No. 2] is the basic standard for classifying.

Augie is spot on, "venting" alone is not "ventilation". (It is a common misconception)

 

[joegreene]

NFPA 820, Standard for Fire Protection in Wastewater Treatment and Collection Facilities [See Section 500.4(B) FPN/IN No. 2] is the basic standard for classifying.

Augie is spot on, "venting" alone is not "ventilation". (It is a common misconception)

Thanks for the help

Hypothetically if the wet well was designated a Class 1, Division 2 area, how would the situation in my example above be treated? Would an explosion-proof seal off be required? I don't suppose anyone has any NFPA 820 code references I could research. Again...thanks very much for the help.

 

[rbalex]

All NFPA Standards are available online for the "price" of a free registration. They are a PITA to use but they are free.

NFPA 820 has a comprehensive set of Tables similar to T514.3(B)(2) in the NEC , but MUCH larger. Generally, they are in Chapters 5 & 6.

Assuming the wet well is ventilated properly so that it is validly Class I, Division 2, then any Division 2/unclassified boundary seals may be non-explosionproof.

 

[tom baker]

What we do is run the cords from pumps to a J-box on the outside of the lift station building. The cords are sleeved in conduit that does not connect to the box, which may be a EP j-box. Over the conduit sleeve we install a SS cover.
Installing the EP j box or GUAT if I recall the type, in the wetwell, is not a good practice.
I may be able to post some pictures later this week.