Interpretation: NEC for installation of rigid conduit in wet locations 1

[ckoen]

Could someone help me find an interpretation of a code somewhere which states the proper installation techniques or practices for stubbing up conduit outside in wet locations. Also, if a conduit (with medium voltage/high voltage wire suitable for underground installation) that is stubbed up in a concrete trench with a metal tray cover enclosing it requires any type of sealing bushing to prevent entry of water into conduit.

Here's my situation, we are building a power plant and the contractor has stubbed up all the conduits outside, whether under the specific devices or buildings or as mentioned above in concrete trenches. All conduits runs are enclosed in concrete.
Is there a specific height requirement for the stub up?
Is there a specific requirement for sealing the conduits? (as of right now they are not in a hazardous location, but I'm still checking on that)

Also the wires leave the conduits and are installed in metal raceways. when the wire changes direction from the horizontal run to go vertical into the building there is no raceway or support devices for the wires. the approximate length of the vertical run is 3 ft.

Should that wire be supported in some fashion, rather than just let it hang?? Charles Koen
Combustion Turbine Technical Manager
Calumet Energy Team

 

[REDDOG]

Only the Electrical Inspection Authority can interrupt the Code. What is the Electrical Inspector position on this installation?
Rigid Metal Conduit is not water tight. Conductors installed in underground raceways must be approved for this purpose.
Vertical support is required for runs greater than 35 feet for conductors sizes over 750 MCM Copper.
What do the approved drawings call for?
As to Classified Areas, what do the drawings call for?

 

[ckoen]

The position of the inspector for the project on site is: he agrees that metal conduit is not watertight to begin with so he feels that there is no reason to seal the end of the conduit that is filling the conduit with water. his feeling is that even though the conduit is enclosed in concrete it will fill with water anyhow over time due to the very high water table we are in.
my position, as well as my interpretation of the code, is that we should take every precaution necessary to maintain the integrety of the conduit dry by at least installing a water-tight bushing on the end of the conduit that is exposed to the open water. Charles Koen
Combustion Turbine Technical Manager
Calumet Energy Team

 

[REDDOG]

If this is YOUR POSITION then issue a change order for a sealing devise that can be filled with duct seal.
Are these conduits riser stubbed up outdoors or within a pull box or enclosure? If outdoors then the end is exposed to weather and a approved fitting is required. If conduit terminates within an enclosure above the water level, what is the point. If conduit passes thru a classified area then a sealoff is required. What do the drawings and specifications require?

 

[ckoen]

Before I add it to our punch list or change order list, I need to know if it was wrong to begin with.

I am the owner, once the plant is turned over to us. Right now it belongs to the contractor.

The conduit is stubbed up inside a concrete trench that the contractor made because the physical location of the transformer that it terminates in was moved back 6 feet from its design on the prints due to lack of acessibility according to code. They covered the trech with a metal cover. Both the transformer and the trench are outside. The bottom of the trench is approx. 2 ft. below grade. The stub is approx. 6" above the floor of trench.

This was an OPPS! on the contractors side and the engineerig firm that made the spec. If the transformer would not have had to be moved, the conduit would have stubbed up inside the transformer and there wouldn't have been an issue...They did it this way so they wouldn't have to run new conduit. I don't have athority to make them change it unless there is a code that specifically states it should be sealed. It is not in a hazzardous environment, so a seal-off is not required. Charles Koen
Combustion Turbine Technical Manager
Calumet Energy Team