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#222577 06/05/24 02:36 PM
Joined: Apr 2002
Posts: 200
T
triple Offline OP
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The wet well of a lift station is class 1, division 1. The area directly above the lift station is class 1, division 2 (approx. 10' dia. and 18" high). The motor disconnects and controls box are typically set outside the division 2 radius in an unclassified area. Rigid pipe is ran under ground from inside the pit to the area directly under the disconnects and control box. Any time a pipe leaves a C1D1 area, an explosion proof sealoff WITH the proper type and thickness of sealing compound must be utilized. There appears to be no exception to this rule. However, in class 1, division 2 situations, where an exiting pipe opens to an outside environment, no sealoff is needed. A standard C-condulet stuffed with duct seal is acceptable. For some reason, this method is also standard practice when a Lift Station wet well pipe emerges from the ground. I understand that lift station cords need to be removable for servicing but where is the exception allowing the transition from C1D1 to ANYWHERE ELSE without an explosion proof seal?

Last edited by triple; 06/05/24 02:40 PM.
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Joined: Jul 2004
Posts: 9,949
Likes: 34
G
Member
I inspected a few lift stations and the RNC condolet where it emerged from the pit was plugged with duct seal. It is still removable but does seem to meet the seal off intent. I couldn't see a reason to reject it.


Greg Fretwell
Joined: Apr 2002
Posts: 200
T
triple Offline OP
Member
gfretwell,

NEC 501.15 lists all the scenarios requiring explosion proof seals WITH the sealing compound type and thickness listed for the purpose. There is only one exception to the rule requiring a seal to be explosion proof (please correct me if I am wrong). That exception is for when a C1D2 conduit leaves its defined area. I am referring specifically to 501.15(A)(4) for the C1D1 boundary and 501.15(B)(2) for the C1D2 boundary. There are only two notable differences between the first paragraph of each. The code section concerning division 2 states that IMC must be threaded at the boundary (because threadless connectors can be used elsewhere in division 2 situations) AND C1D2 boundary seals do not need to be explosion proof. Also, If you have a NEC Handbook (mine is a 2017 since it is the latest accepted edition in WI) please see Commentary Table 501.1. The same thing is described regarding the boundary requirement differences between D1 and D2: specifically that D2 does not need an explosion proof seal while that point is not made for D1. The table also says that a C1D2 pipe exiting to outside needs no seal. But no such exception is described for a C1D1 pipe.

Here is my main question for you gfretwell. Would you accept a standard condulet stuffed with duct seal ANYWHERE ELSE the code requires a C1D1 seal? If not, why not? You are allowing it at the boundary with nothing in the NEC stating that that seal should be treated any differently.

Thank you very much for your response. These types of "it's just always done that way" circumstances always seem hard to get people to engage in.

Joined: Jul 2004
Posts: 9,949
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G
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I guess I could just say I didn't know any better wink

You are right I probably should have tagged it but they probably would have ignored me anyway. It was a state job.
I still have open permits from the last century nobody ever called me back on. I had no enforcement powers against state employees although I could hold up a contractors pay. I never had trouble with them.

I was really looking at the intent of the code and this happening outside did not seem as critical as a place where the transition was from C1D1 to an interior space.
I often wondered haw many of those seals got restored if they had to crack into them anyway.


Greg Fretwell
Joined: Apr 2002
Posts: 200
T
triple Offline OP
Member
I think Mike Holt needs to add a section to his "NEC Index" titled "It's just always done that way". This could contain common practices that violate code but are deemed acceptable due to a long history of relative safety. Perhaps it could have a slogan. "As long as the death toll does not rise too high, just turn a blind eye".

After scouring the interwebs, it appears that commercial lift stations are routinely piped to the outdoors without use of a true sealoff. While most seals in a properly thought out installation do not cause future problems, the cords dropped into a wet well will occasionally be removed for inspection/testing/replacement of sensors, floats and motors. While I have never tried to demo fully cured sealing compound, I can't imagine it is a pleasant experience. I would probably quickly run through my daily quota of swear words.

I recently received the prints for a lift station refurberation at a military base. The A&E firm has illustrated the code violation of not providing explosion proof seals in the exiting pipes even though they have defined the wet well as Class 1, Division 1. I talked to the inspector and it appears he is going to allow it since "it is always done that way" and the engineers essentially signed off on it when they drew the print. I don't think the code works this way since there is no gray area here to interpret.


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