Myers Hub and LFMC Connector Assembly Causing Loose Sealing Gaskets

[Nils]

Hello, I am dealing with a Solar project to where the specs and design call for outdoor NEMA 4X enclosures having conduits entering on the bottom to use a combination of a Myers Hub AND and LFMC connector assembly for flexible conduits. The issue I am having is the the tapered internal threads of the Myers Hub and the threads of the LFMC connector are more than 5 fully engaged and are watertight, however the yellow sealing gaskets of the LFMC connector are loose. The LFMC connector is as tight into the Myers hub as possible, our installer used a RIDGID tristand chain vise and a pipe wrench to ensure the maximum threads possible are engaged without damaging the assembly. However, we have a round a 5/16” gap of threads between the Myers Hub and LFMC connector, causing the 1/8” yellow sealing gaskets from the LFMC connector to be visibly loose. The local AHJ and a 3rd Party Mechanical Completion Inspector have passed the assembly as is, stating that the gaskets are now redundant and not necessary due to the fully engaged threads of this particular assembly. We even had a “WET TEST”, where every inch of our system was thoroughly soaked with a water based solution, and then tested for short and inspected for moisture intrusion. We passed this test 100% and every enclosure on site was bone dry.

Now here is our problem, I have a 3rd Party Commissioning Agent with absolutely no field experience and very little understanding of the NEC basically telling me “it doesn’t look like the picture in my book” regarding the loose yellow sealing gaskets. Of course the picture he is using does not have a Myers Hub in it, the LFMC connector in that photo is fully seated directly to the enclosure with a tight yellow gasket. Once it was explained to him, his response was “I don’t care”

Does anyone here know of any aesthetic quick fixes for this situation. We are not going to cut and remove the gaskets, we are passed that now, and we are trying to avoid un-terminating cables and pulling the cable back through to replace the existing gaskets with thicker gaskets. Does any one know of any type of external weatherproof collar of something like that that may suffice once presented as a solution. This one silly issue is holding up COD on the project. Any assistance possible here would be greatly appreciated.

Thank you,

 

[tthh]

This isn't something I am too familiar with, but isn't this an either/or situation -- Myers Hub Or LFMC connector into the box?

 

[LarryFine]

Welcome to the forum.

Of course the picture he is using does not have a Myers Hub in it, the LFMC connector in that photo is fully seated directly to the enclosure with a tight yellow gasket.

In my opinion this is what should be done. A bottom entry in particular does not need a Myers hub.

 

[texie]

Welcome to the forum.


In my opinion this is what should be done. A bottom entry in particular does not need a Myers hub.

I agree. I would also point out that the spec is wrong in the first place to call for a LT connector to be attached to a hub. The hub is only listed for use with threaded rigid or IMC conduit. The LT connector is only listed to be used with a locknut. You can't use a connector into a hub and be compliant.
That said, we all know this is done all the time and the sealing washer is just discarded. Doing it the compliant way without the hub and using the sealing washer and locknut is not great either as we all know those washers are worthless as they just squish out.

 

[don_resqcapt19]

The LFMC connector threads have not been evaluated for use with any fitting having female threads. It is a common practice to use the connectors for that purpose, but that use is outside the product standard specifications for both products.
From the UL Guide Information for " Conduit Fittings (DWTT)"

Male fittings not provided with a locknut, intended for securement to a threaded hub, are marked on the smallest unit shipping carton, "For securement to a threaded hub only," or the equivalent.
Male fittings provided with a locknut, also intended for securement to boxes with threaded entries, hubs or fittings with internal female threads (e.g., conduit bodies, couplings), are marked on the smallest unit shipping carton, "For securement to a threaded hub," or the equivalent.
Male threaded fittings provided with or without a locknut and intended for securement to boxes with threaded entries or fittings with internal female threads (e.g., hubs, conduit bodies, couplings) are provided on the smallest unit shipping carton with installation guidance to install into a box with a threaded entry or hub.
Fittings with internal female threads (e.g., hubs, conduit bodies, couplings) have only been investigated for use with threaded rigid conduit.

As far as I know there are no connectors that are so marked as the product standard does not provide for any type of testing that would permit that marking.
Even the use of a sealing lock nut may be outside the provisions of the listing standards.

Sealing (Liquid-tight) Locknuts — Sealing locknuts are intended for use with threaded rigid metal conduit and intermediate metal conduit with one sealing locknut in the outside or the inside and either an ordinary locknut or sealing locknut on the inside of the enclosure for wet locations or liquid-tight applications. Sealing locknuts may also be used with certified wet location or liquid-tight fittings where so marked on the fitting carton and used on the inside of the enclosure.