double locknut versus hub

[petersonra]

What do you guys think?

Is a double locknut arrangement an acceptable way to connect conduit to an enclosure in lieu of a screw type hub?

What about in wet areas if sealing washers are used?

 

[raider1]

Yes, a double locknut arrangement is acceptable for connecting a threaded raceway.

Using a sealing locknut would be acceptable for raceways installed in a wet location.

Chris

 

[petersonra]

I guess it is acceptable as far as it being code.

i was thinking more along the lines of whether it is acceptable to your own standards of quality.

I have seen enough of these that loosen up over time that I distrust them.

 

[iwire]

I see no reason to believe a hub is more or less likely to loosen up then lock nuts.

 

[raider1]

I see no reason to believe a hub is more or less likely to loosen up then lock nuts.

Agreed.

Chris

 

[petersonra]

I see no reason to believe a hub is more or less likely to loosen up then lock nuts.

So why have I seen far more double lock nutted joints loose than joints made up with hubs?

And why do so many engineering specs prohibit them?

 

[rbalex]

So why have I seen far more double lock nutted joints loose than joints made up with hubs?

And why do so many engineering specs prohibit them?

I can't speak to your personal experience or why other engineers do what they do.

My own bias is based on the restrictions in Section 501.30 and analogous Sections in other Classified Location Articles.

I tend to use the “brute force” approach (i.e., I usually ignore the Exception) in non-classified locations just to make sure “Such means of bonding shall apply to all intervening raceways, fittings, boxes, enclosures, and so forth between Class I locations and the point of grounding for service equipment or point of grounding of a separately derived system” is observed. Obviously, it isn’t an absolute necessity, but it’s one of the few things I do for the “warm-fuzzies.”

 

[iwire]

So why have I seen far more double lock nutted joints loose than joints made up with hubs?

How could you tell if a Hub was loose?

And why do so many engineering specs prohibit them?

Of course I do not know why but I think the finished product using hubs looks more professional.

 

[GUNNING]

Tricks!

Tricks!

I have seen where you use a long threaded piece of pipe and a coupling with a lock nut on each side of the coupling replacing a myers hub.
You over thread one side of the pipe. Put a lock nut on the pipe. Thread the coupling down to almost all the way through the coupling. Put a lock nut on the other piece of pipe threaded down. Then match up the pipes threading the coupling onto the new piece of pipe till its halfway down. then lock nut tight the ends. Replaces a $20 hub with a $1.50 coupling.
Its a neat trick and in the American Electricians Handbook.

 

[tkb]

I have seen where you use a long threaded piece of pipe and a coupling with a lock nut on each side of the coupling replacing a myers hub.
You over thread one side of the pipe. Put a lock nut on the pipe. Thread the coupling down to almost all the way through the coupling. Put a lock nut on the other piece of pipe threaded down. Then match up the pipes threading the coupling onto the new piece of pipe till its halfway down. then lock nut tight the ends. Replaces a $20 hub with a $1.50 coupling.
Its a neat trick and in the American Electricians Handbook.

Good idea except it is a code violation.
It's called a running thread.

 

[petersonra]

Good idea except it is a code violation.
It's called a running thread.

Conduit thread is pipe taper. How do you make a running thread work that way?

 

[GUNNING]

Just thread a peice of rigid as long as the coupling on one side, the other side has a normal thread length.

 

[xformer]

Good idea except it is a code violation.
It's called a running thread.

I agree with you Tim.

 

[tkb]

Conduit thread is pipe taper. How do you make a running thread work that way?

It is tapered for the length of the die. If you keep threading it becomes a straight thread after the length of the die and the couplings have a straight thread.