Sewer wet well conduit for submerged pumps.

kwired

Electron manager
Location
NE Nebraska
Thank you. From your understanding of what I wrote, would you pass the job if you were inspecting it? (I would)
I would pass it based on my own knowledge at this point anyway. If my employer didn't want such installs to pass, I would be asking questions at very least.
 

rbalex

Moderator
Staff member
One of the most commonly misunderstood concepts of electrical area classification is NEC Divisions are defined in terms of possibilities, rather than probabilities, [See Section 500.5 and read it carefully] This is a significant difference between the NEC Divisions and IEC Zones which are defined in terms of probability. (NEC Zones are a forced fit hybrid of the two systems with possibilities taking a stronger emphasis).

I have told people over the years, if they ignore my warnings, the odds may be in their favor BUT if they have a problem it will be a big one and they will have virtually no defense in an OHSA investigation. Of course, there is very little defense with OSHA in the first place, but it may make the difference in a fine or jail time.
 

oldsparky52

Senior Member
One of the most commonly misunderstood concepts of electrical area classification is NEC Divisions are defined in terms of possibilities, rather than probabilities, [See Section 500.5 and read it carefully] This is a significant difference between the NEC Divisions and IEC Zones which are defined in terms of probability. (NEC Zones are a forced fit hybrid of the two systems with possibilities taking a stronger emphasis).

I have told people over the years, if they ignore my warnings, the odds may be in their favor BUT if they have a problem it will be a big one and they will have virtually no defense in an OHSA investigation. Of course, there is very little defense with OSHA in the first place, but it may make the difference in a fine or jail time.
So Bob, how would you connect 2 pump cords and 3 float switch cords from this pit to a controller mounted above ground and adjacent to the pit, where you only have one 2" opening to exit the structure? You know, seals and such. My gut says you don't approve of the installation I described and I would love to understand the fallacy of my thinking if I am reading you correctly.
 

rbalex

Moderator
Staff member
C1D1 in the wetwell and if a vault with piping, meters, etc C1D2, if I remember and I no longer have a copy of 820
NFPA 820 may be referred to (with great difficulty) here.

Another caution I often make is electrical area classifications cannot usually be determined directly from the NEC except for installations subject to Articles 511 to 516. Otherwise, Standards listed in Section 500.4(B) IN No. 2 should be consulted. NFPA 820 is one such Standard. There are a few other Standards, such as AGA XF0277 that I find generally acceptable for installations specific to their respective industries. NFPA 497 and API RP500 or RP505 are the most general Standards.
 

rbalex

Moderator
Staff member
So Bob, how would you connect 2 pump cords and 3 float switch cords from this pit to a controller mounted above ground and adjacent to the pit, where you only have one 2" opening to exit the structure? You know, seals and such. My gut says you don't approve of the installation I described and I would love to understand the fallacy of my thinking if I am reading you correctly.
I generally try to avoid telling folks what to do specifically - it's like engineering DIY assistance. I try to refer to the appropriate Standards, NEC Articles, Sections, etc., and, if necessary, help to interpret them. It's always important to classify first [as required by Section 500.4(A)] THEN select the appropriate equipment and wiring methods.

As noted elsewhere, open raceways or sleeves from a Class I location creates a vent in the unclassified location that needs to be dealt with

A possible consideration is in NFPA 497 [2017], Part 5.6
 

wandwwonly

Member
Location
US
Occupation
electrician
3M makes re enterable products for the seal offs that really works well. Cable gland fittings are also an acceptable boundary into a tjb with nothing but terminals no arcing potential.

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wandwwonly

Member
Location
US
Occupation
electrician
Who classified your stations? Unless commercial or combined use drainage and sewer should be class 1 division 2.

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oldsparky52

Senior Member
Who classified your stations? Unless commercial or combined use drainage and sewer should be class 1 division 2.

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The classification is everything, especially the boundaries.

It seems that (like Bob said) the people qualified to make these determinations are saying (like that old George Hamilton song) "if you don't know I ain't gonna tell you".
 

wandwwonly

Member
Location
US
Occupation
electrician
The classification is everything, especially the boundaries.

It seems that (like Bob said) the people qualified to make these determinations are saying (like that old George Hamilton song) "if you don't know I ain't gonna tell you".
I agree boundaries are everything and I'll try not to step over any ol' sparky. New to the forum. This subject comes up ever 4 or 5 years. I never have quite understood why. The environment doesn't warrant it. 95 precent of the process is water. I know someone could dump gasoline in the wetwell but who could afford that. The largest concern is migration of corrosive vapors that reek havoc My recollection is NFPA classify's community station wetwells C1D2 and mixed flow stations C1D1. There rated submersible pumps with hard usage cables for removal without entering the wet well 501.140a 3. Across three county's we have used many different construction methods all of them allow easy removal of the pump cables. It seems the AHJ is being unreasonable. Not knowing anything about the assembly i would consider removal of the seal off and enter with listed cable glands 501.140 B4.

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kwired

Electron manager
Location
NE Nebraska
Typical swine barn has slat floors with a collection pit under a great portion of the floor or even entire floor in some instances. Basically no different than a municipal sewer lift station from perspective of being able to give off methane. We don't use classified location wiring in those. Sure there is ventilation mostly for the sake of the animal's health. Cold winter days that ventiltion becomes somewhat minimal.
 

oldsparky52

Senior Member
This subject comes up ever 4 or 5 years. I never have quite understood why.
Because someone keeps running into a situation where x-proof seals are asked for or they have to change out a pump or float switch and run into an installation that has x-proof seals and they have to break it out.

I think lawyers have scared people into cover their behinds instead of using their heads.
 

Bwas

Member
Location
Florida
You either have to run the cables in free air somewhere or accept the liability of not re-sealing the conduits. Or get an engineer to sign and seal a letter that explains why the seal offs aren't required.
 

WKB PE

New User
Location
Central Illinois
Occupation
Professional Engineer
Sorry to open this up again but I guess I don't understand the problem. A sanitary sewer wet well is typically a Class 1 division 1 or 2 area per NFPA 820 depending if it is ventilated or not. I was taught and I believe it to be NEC compliant to bring the pump cables (furnished with the submersible pump) up into a junction box in conduit, splice the pump conductors to THHN/THWN in the junction box on terminal strips or wire nuts and put the seal on the conduit with the THHN/THWN going to the starter/vfd or motor service disconnect. No seal is required between the pump and the J-box as the J-box does not have any arcing equipment in it.
 

augie47

Moderator
Staff member
Location
Tennessee
Rbalex can confirm if this is Code compliant, but in line with your original post I would think you could do as you suggest but the "C" fitting would have to be explosion proof. You cold still remove the cap and catch the chips.
 
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