Sealtight Connectors

[JasonWrenn]

I have a Vendor who has built several skids of equipment, on these skids are MOV's and Instrumentation. These skids are installed outdoors in wet locations. They have used Seal-tight to enter the devices and did not remove the lock rings from the connectors, even though each device is provided with a threaded entry. I have asked for each connection to be fixed and for them to remove the lock ring and replace the damaged O ring(which was damaged from the lock ring), they claim that their Appleton Representative told them that the lock nut is needed for a correct installation. Please give your thoughts and any references as to why this installation is correct or incorrect. I believe that NEMA Standards state the lock ring should be removed.

 

[readydave8]

looks like they took lockring off and reinstalled behind gasket washer to make better seal, right or wrong but not careless

 

[don_resqcapt19]

That is a very common installation and often the only way to get the correct orientation of the LFMC connector. If you just thread the 90° connector in, you often end up with it being very loose with the sealtight end pointing where it needs too. The locknut lets you have it secured and still pointing in the correct direction.
When I had to do that, I would typically use a sealing locknut.

 

[JasonWrenn]

Wanted to add this for reference
Reference NEMA Standards Publications FB 2.20-2021 Selection and Installation Guidelines for Fittings for Use with Flexible Electrical Conduit and Cable, Section 4.1; “Fittings supplied with locknuts are for the purpose of providing a seal at an enclosure knockout or fitting joint…These fittings can also provide a liquidtight joint when installed into a threaded entry of an enclosure. When utilized in this way, the sealing devices and locknuts are not used. Liquidtight flexible metal conduit fittings supplied without locknuts are generally intended only for use in threaded entries of enclosures.”

 

[don_resqcapt19]

Wanted to add this for reference
Reference NEMA Standards Publications FB 2.20-2021 Selection and Installation Guidelines for Fittings for Use with Flexible Electrical Conduit and Cable, Section 4.1; “Fittings supplied with locknuts are for the purpose of providing a seal at an enclosure knockout or fitting joint…These fittings can also provide a liquidtight joint when installed into a threaded entry of an enclosure. When utilized in this way, the sealing devices and locknuts are not used. Liquidtight flexible metal conduit fittings supplied without locknuts are generally intended only for use in threaded entries of enclosures.”

That is all well and good, but just does always work in the real world if you are using something other than a straight connector.

I would much rather see a sealing lock nut than the connector flopping around because it can't be made up tight in the proper orientation.

Note that if these fittings had the full 3/4" per foot of taper on the threads, this would not be an issue, but they don't have that much taper.