Sewage Lift Stations / Methane Gas

[pdr]

Looking for a straight answer. Are seal offs required at the control panel? Please provide the code article. Thanks, PDR.

 

[kwired]

If it has been determined to be a classified area yes.

Maybe your real question is whether or not it is classified area.

There may be other factors to determining this that are beyond the NEC - the NEC requirements do determine what the wiring methods will be once the classification is determined.

 

[pdr]

Sewage Lift Stations / Methane Gas

Please expand on your comment regarding if it is in a classified area.

We have the tank with pumps and floats, in an outside location. Approximately 6 feet from the tank is the Control Panel. We have UG PVC conduits from the tank and stubbed up under the the CP. The tank has a hatch. My concern is the methane gas entering the conduits and going into the CP. Methane is classified as Class I, Group D.

Thanks, PDR.

 

[kwired]

If it is classified you can't use PVC except for the buried portion that is deeper than 24"

The control panel is likely not in a classified area. If the raceway comes from a classified area then there needs to be a seal at the boundary of the classified area first fitting out of the ground outside the classified area is acceptable place for it. All the equipment in the tank / pit would also need rated for the classified area. Ventilation could change the classification. Again something other than NEC alone may be what determines the classification. Once you have determined the classification the NEC is fairly clear what you can and can't do in each type of classified area.

 

[spark-e-eng]

Wastewater area classification is defined by NFPA 820. It's not just methane that you need to worry about, but also hydrogen sulfide. PVC coated rigid conduit is your best bet so the H2S doesn't eat at the galvanized. Seal-offs would be required when you pop up above ground.

 

[ActionDave]

Looking for a straight answer. Are seal offs required at the control panel? Please provide the code article. Thanks, PDR,.

I just spent this summer putting new control panels in eighteen sewer lifts in my home town. Some were above grade, some were bellow; all no more than four feet away from the wet well. None of them had to be wired as classified locations. EMT and Sealtite was all we used on all of them. No seal offs in the original or in the new.

All of the original was done by a major sewer lift company.

I don't think there is a straight answer. Tomato, tamahto; potato, pahtato; your mileage may vary.

 

[hurk27]

I have posted several photos of liftstation I have done , and in this area as long as there is a vent on the wet well we don't need a seal, but we do, do a gas/vapor stop in the conduits, we always run from the wet well to a large SS JB with terminals, then to the main control panel, this acts as an extra vapor stop, the PVC pipe going back into the ground and up to the control panel is almost always full of water also acting like a P trap that also stops any gas or vapor from reaching the control panel, which also has a positive pressure fan on the cabinet to even further keep any gas out.

here are some photo's:

As you can see these are PLC controlled systems and have VFD's in the last one for single phase to 3-phase conversion. allot of electronics that could be damaged if the vapor could reach them, never had a problem. note the fan that puts a positive pressure on the control cabinet it the upper right side of the control cabinet.

 

[spark-e-eng]

Those are some nice looking panels, however I don't understand how you got around seal-offs. It is pretty cut and dry in NFPA820 what is classified based on the type of residential system/number of households and then you go back to NFPA70 article 501 for what is required. I have visited and/or designed over 50 stations in Michigan and all had seals. Some had vented cable tray, but we had it removed.

Is the fan blowing in or out of the cabinet? I would say out in order to remove the heat from the drives being in the enclosure.

 

[kwired]

Those are some nice looking panels, however I don't understand how you got around seal-offs. It is pretty cut and dry in NFPA820 what is classified based on the type of residential system/number of households and then you go back to NFPA70 article 501 for what is required. I have visited and/or designed over 50 stations in Michigan and all had seals. Some had vented cable tray, but we had it removed.

Is the fan blowing in or out of the cabinet? I would say out in order to remove the heat from the drives being in the enclosure.

Isn't it going to move heat no matter which way it is blowing. Convection means it will move easier if it is moving air upward but it will move downward with a little more resistance to movement.

Either way it needs sufficient inlet and outlet to move any significant volume, but must have less outlet than inlet to be able to have a positive pressure.