Sewer Lift Station

Many of the Lift stations I maintain only have LFMC going from the control cabinet to the well, just like the one in the picture. I have several concerns:

Do I need to install RMC coming from the ground with explosion-proof fittings to keep gases out of the cabinet? As is, duct-seal is stuffed into the incoming openings of the connectors. The reason they were installed this way is to avoid chipping out Chico every time a pump or float would have to be taken out and repaired and/or replaced. The floats are changed more often than the pumps are taken out but the pumps are removed completely at times in order to take back to the shop for maintenance.

I’m just at a loss of what to do to make these systems safe, legal, and convenient to maintain. I should also add, that the gases do deteriorate components over time, so the duct-seal is not a good substitute. I just want to do things correctly but I’m not sure how to go about it.
 

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petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Many of the Lift stations I maintain only have LFMC going from the control cabinet to the well, just like the one in the picture. I have several concerns:

Do I need to install RMC coming from the ground with explosion-proof fittings to keep gases out of the cabinet? As is, duct-seal is stuffed into the incoming openings of the connectors. The reason they were installed this way is to avoid chipping out Chico every time a pump or float would have to be taken out and repaired and/or replaced. The floats are changed more often than the pumps are taken out but the pumps are removed completely at times in order to take back to the shop for maintenance.

I’m just at a loss of what to do to make these systems safe, legal, and convenient to maintain. I should also add, that the gases do deteriorate components over time, so the duct-seal is not a good substitute. I just want to do things correctly but I’m not sure how to go about it.
It does not appear that any of the equipment you have in the picture is explosion proof. where are the boundaries?

IMO, duct seal is an adequate seal for a div 2 boundary seal. It is not required to be a listed explosion proof seal like it is within a div 1 area.
 
Well, then I guess that’s a good thing. I was trying to figure out how to make it right because I thought it was wrong. Now if I can just figure out a better way to block the H2S that destroys components and terminals.
 

tom baker

First Chief Moderator
Staff member
How many similar WWLS do you have?

Yes a WWLS is classified as a C1D1 location. I have a few suggestions

1.The NEC requires in 500.4 Documentation, that all areas designated as hazardous shall be properly documented. This documentation is required to be available to those authorized to inspect, maintain or operate electrical equipment.
Its not your job to ask what the classification is, that needs to be done for you, I would seek out a qualified engineering company to do area classification drawings and have those stamped.

Next, change your installation standard to incorporate the correct wiring methods, so future installations are in compliance. Have a good set of detail drawings to use for bidding, etc

2 . Become knowledgeable about chapter 5, Mike Holts Understanding the NEC is a great place to start here is Vol 1 https://www.mikeholt.com/productite...rchtext=&product_type=Book&category_from=Book
I would also get Vol 2

3. the Crouse Hinds code digest is an excellent review of hazardous locations, and its free (CH makes haz locations fittings, etc) https://www.crouse-hinds.de/download/1/Crouse-Hinds Code Digest 2017.pdf

4. Who ever does your area classification in item 1 will likely use NFPA 820 Standard for Fire Protection in Wastewater Treatment and Collection Facilities, you'll want a copy https://www.nfpa.org/codes-and-stan...s/list-of-codes-and-standards/detail?code=820

You have taken on quite a project and to correct this will require more than duct seal
 
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tom baker

First Chief Moderator
Staff member
Your installation has some issues....
Who inspects your WWLS?
The long length of LTFMC from the meter to the electrical panel is violation and could be easily damaged. I would run rigid down from the meter, across the slab and up to the panel.
The LTFMC from the control panel to the enclosure on the left needs to be secured
And any explosive gas can make its way up into the control panel and be ignited.
There is a way to isolate the sewer gas from the control panel, and allow for an easy way to change out the submersibles.
I think I will do a sketch and attach it later.

I once saw a WWLS manhole cover thrown across the street in an explosion, gasoline had gotten into the sewer and there was an explosion at a lift station.
 
— I have 76 lift stations I am responsible for.
— Many of my stations don’t have inspections because they’re located in the county, which is why I thought I’d take it upon myself to make them right.
 

tom baker

First Chief Moderator
Staff member
The reason they were installed this way is to avoid chipping out Chico every time a pump or float would have to be taken out and repaired and/or replaced. The floats are changed more often than the pumps are taken out but the pumps are removed completely at times in order to take back to the shop for maintenance.
yes there is a simple way to avoid chipping out the Chico. More later
 

tom baker

First Chief Moderator
Staff member
I am in Seattle area, very smoky here so stuck inside, a little more time on the forum...
On your floats, are they IS?
If you use IS floats, then you don't have to use haz location wiring. But still need to seal the conduit.
This would require an IS relay/barrier in the control panel, probably a bigger control panel
See Article 504 in the NEC.
I've worked on a lot of WWLS and floats, back in the day we used mercury floats, they lasted forever.
Now the mechanical floats don't last as long
 

oldsparky52

Senior Member
IMO all that equipment in your picture is out of the classified area (it's above it). If your circuits are the cable that comes with the float switches and pumps, then you can install them w/out splices to the control box. The problem in your picture is your conduit system exits a classified area and enters the control cabinet. That is a no no.

I have the opinion that if you cut that conduit off near grade (low enough that it does not exit the classified area) and call it a chase to install your cable that does not require a raceway, then you are good to go. Logic being that the raceway does not pass through a classified area to a non classified area so it does not need to be sealed.

Your cable does not pass gasses so it does not need x-proof sealing (you should use the proper cord grip in the bottom of the control panel).

The argument that you are installing another vent might be made and is valid, and IMO ductseal or other means can be used to seal off that conduit (w/out a hardened seal preventing replacement of cables).
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
In a lot of lift stations I have worked on that look like that, there is another j-box under the access lid where the connections from the floats and motor are made, and the conduit from THAT box up to the surface has the EYS fittings. Sometimes the EYSs are above grade, sometimes below. But either way, that extra box is there so that they don't have to break out the sealant in the EYS every time they change floats, which can be quite often.
 

oldsparky52

Senior Member
In a lot of lift stations I have worked on that look like that, there is another j-box under the access lid where the connections from the floats and motor are made, and the conduit from THAT box up to the surface has the EYS fittings. Sometimes the EYSs are above grade, sometimes below. But either way, that extra box is there so that they don't have to break out the sealant in the EYS every time they change floats, which can be quite often.
I wonder how much of the float change out is due to the bad connections in that junction box.

Isn't that box in the C1D1 area, so doesn't it need to be x-proof?

IMO this is the least desirable way to install this. There should be no junction box in the well.
 
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