Wet Well Seal-Off

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector
I have sewage pump wet-well classified by an engineer as Class 1 Div 1
I have 2" PVC Conduit encased in concrete 24" deep with terminal ends flush with the interior of the wet well.
The PVC transitions to PVC Coated aluminum conduit and terminates in a 36 x 36 non-explosion-proof box with terminal strips.
The j box has other entries to a control cabinet with seal-offs in that run.
The design is supposed to eliminate the need for a seal off of the pump cables.
It seems to me the 2" conduits (from the wet well) would need a boundary seal before entering the j box.
Even if the j box is explosin proof the fact that the conduits are 2" would require seals per 501.15(A)(2)
Input desired !!!
 

nhee2

Senior Member
Location
NH
If the area is Class I, Div 1 and the enclosure penetrations are 2" or greater then I agree the box needs a seal within 18" (501.15(A)(2)).

As far as the boundary seal, does 501.15(A)(4) exception 2 apply, allowing the seal to be installed as fitting where conduit emerges from ground? Otherwise I think you need seal in the well, as first fitting. I've spec'd GUAB fitting with sealing cover for this type of penetration/first fitting in other applications (although not in a wet well, so not sure if it would work).
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector
Thanks for the rely.
We did allow the 501.15(A)(4) Exception but, in the the j box is Nema 3R, we are requiring a seal-off where the conduit emerges from the ground entering the j box (terminal box).
The install (without the seal-off) has become commonplace around here mainly due to the pump operators not wanting to chip out chico in order to change the pump.
When we ran it by the design engineer he came back and added the seal-off.
I understand there frustration and was in hopes I had overlooked something and could allow it.
It is a little un-nevring that earlier installs passed and when I questioned the answer was "an engineer drew it so we accepted it".
 

tom baker

First Chief Moderator
Staff member
There is a very simple method that avoids the seal off and is code compliant
I will send sketch later.
There have 2 posts about lift station wiring in the last 6 months would be worth finding those.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector
There is a very simple method that avoids the seal off and is code compliant
I will send sketch later.
There have 2 posts about lift station wiring in the last 6 months would be worth finding those.
I read those and noted the solutions to the contractor but they are insistent on this plan.
 

tom baker

First Chief Moderator
Staff member
See attached. Our moderator RBAlex prefers this method. No chico, no sealoffs. Any seals or GUAs in the wetwell won't last.
The key is the sleeve does not connect to the SS J box. if it does then seal offs are needed. this is the standard way our liftstations are done where I used to work.
Perhaps the design engineer could go with the crews some rainy day when they have to swap out a pump. Have him chip out the chico
 

Attachments

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector
That has been presented as an alternative.
IN this case the there is no building and the j box has solid legs on each end so we recommended an expanded metal protection shield (removable) in lieu of the shield to allow air flow..
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector
I feel like "sting" continuing the thread (except I have no napkin for sketches)..
Would there be any concern about the cords allowing gases into the j box ??
 
  • Like
Reactions: MTW

nhee2

Senior Member
Location
NH
Thanks for the rely.
We did allow the 501.15(A)(4) Exception but, in the the j box is Nema 3R, we are requiring a seal-off where the conduit emerges from the ground entering the j box (terminal box).
The install (without the seal-off) has become commonplace around here mainly due to the pump operators not wanting to chip out chico in order to change the pump.
When we ran it by the design engineer he came back and added the seal-off.
I understand there frustration and was in hopes I had overlooked something and could allow it.
It is a little un-nevring that earlier installs passed and when I questioned the answer was "an engineer drew it so we accepted it".
Sorry I mis-read your original post, it said 'non-explosionproof, outside the wet well' but I read 'explosion-proof, inside the well'. I guess it is good we don't do wet well work.
 
Top