Using Rigid coupling for transitioning

[Davebones]

Saw article in ( IAEI ) about using rigid couplings for transitioning from say emt to liquid tight conduit . ( Transitioning Between Raceway's ) Have always seen it done this way emt connector to rigid coupling to liquid tight conduit . Is this now considered wrong and are inspectors now enforcing this ?

 

[fmtjfw]

UL 2012 White Book:

CONDUIT FITTINGS (DWTT)
USE
This category covers metallic and nonmetallic conduit fittings, such as
connectors, couplings, conduit bodies, short radius conduit bodies, expansion
fittings, locknuts and sealing (liquid-tight) locknuts for use in the
assembly of nonmetallic and metallic wiring systems. Also covered are fittings
used to provide a transition between metallic and nonmetallic wiring
systems. All fittings are intended to be installed in accordance with ANSI/
NFPA 70, ??National Electrical Code?? (NEC), and are intended for installation
and use in accordance with the following information and the limitations
specified in the appropriate conduit or tubing category.

All male threaded fittings and nipples have only been investigated for use
with locknuts.
Fittings with internal female threads (e.g., hubs, conduit bodies, couplings)
have only been investigated for use with threaded rigid conduit.

To be compliant with the UL listing, you can not use any fitting with male threads with a rigid coupling. To meet the UL listing, if for instance you want to connect EMT and PVC without using a box, you use a EMT-to-female-thread fitting, a short length of threaded rigid conduit, and a PVC-to-female-thread fitting.

Don't shoot the messenger. I came across this and asked a UL engineer who confirmed the above. I also brought it up at the last yearly seminar of the Ohio Chapter annual seminar and sat back and watched the sparks fly.

 

[qcroanoke]

We do that regularly. Never been busted for it.

 

[fmtjfw]

There appears to be a difference with what the UL listings require and what many electricians do, and what many inspectors require.

 

[Davebones]

Thats why I was asking about this as I saw a article about this at the " IAEI " site .

 

[qcroanoke]

There appears to be a difference with what the UL listings require and what many electricians do, and what many inspectors require.

Yeah, I've been in the trade for over 30 years and have never been told (other than here) that you could not do that to transition to another type of raceway.
Nothing wrong with it, it just has never been tested by UL that way.

 

[Sierrasparky]

They do make specialty fittings.
Such as:
EMT to Seal tight
EMT to rigid
Rigid to seal tight

These alone cover a lot of uses.

 

[Wilg]

Used rigid couplings for a transition many times as an electrician, never turned them down as an inspector. Makes you wonder what other standard practices in the field may not meet approval if examined closely. Always something to learn.

 

[Sierrasparky]

Seen it turned down in Los Angeles many a time. That is why most competent supply houses have those speacialty fitting on the shelf.
The supply houses in the areas where the issue not enforced don't have them on the shelf. They even give you this blank stare when you ask.

 

[Davebones]

After seeing the article about this at the "IAEI" Electrical Inspector's web site . I would like to ask the inspectors out there if they are going to be enforcing this ?

 

[kwired]

They do make specialty fittings.
Such as:
EMT to Seal tight
EMT to rigid
Rigid to seal tight

These alone cover a lot of uses.

Where is the profit in selling those fittings if you don't make a requirement to use them? Stocking those fittings that you don't use very much becomes a pain and a little expensive. A rigid coupling is more universal - but lets not make it listed for anything but rigid conduit so we can sell more expensive specialty fittings:happyyes:

 

[fmtjfw]

The problem is the threads are different

The problem is the threads are different

I being the proud owner of a set of pipe dies marked "conduit" from the 1960's found that you can't use them for water or gas piping because they do not cut tapered threads (like what is required for RMC and IMC) rather straight threads as used on make conduit fittings. The connections leak.

When you try to tighten straight male threads into a tapered female thread you find that they don't make up as tightly as when both are tapered.

The result is that the joint may not be water tight and may not be a good electrical grounding connection. I've often wondered why people goop up the PVC adapter going into a meyers hub on a meter box, but generally don't do so for RMC, now I know.

 

[renosteinke]

We've been over this ground before, and I'm sure nobody's going to change their minds.

IMO, UL's position is unreasonable and the logic behind it unsound.

I also maintain that requiring someone to use something simply because it exists in a catalog somewhere is an abuse of authority.

As I see it, the issue ought to be decided by the simple fact that the threads used are defined by standard. NPT is NPT is NPT. IMO, any male NPT is perfectly designed to be used with any female NPT. That's what it's designed to do ... and the threads have no way of telling what they're attached to.

Ah, you say, some of our threads are not tapered. What's your point? Plenty of fittings (such as LB's) have straight threads. It makes no sense to me that I can use a connector with an LB but not with a coupling.

After consulting with my UL-issued Ouija board, I suspect that what that adamant UL statement really says is that "when we test fittings, we use locknuts and really don't know how they work with female threads. Oh, we can 'infer,' but that's not our job, so we simply don't know."

 

[Sierrasparky]

We've been over this ground before, and I'm sure nobody's going to change their minds.

IMO, UL's position is unreasonable and the logic behind it unsound.

I also maintain that requiring someone to use something simply because it exists in a catalog somewhere is an abuse of authority.

As I see it, the issue ought to be decided by the simple fact that the threads used are defined by standard. NPT is NPT is NPT. IMO, any male NPT is perfectly designed to be used with any female NPT. That's what it's designed to do ... and the threads have no way of telling what they're attached to.

Ah, you say, some of our threads are not tapered. What's your point? Plenty of fittings (such as LB's) have straight threads. It makes no sense to me that I can use a connector with an LB but not with a coupling.

After consulting with my UL-issued Ouija board, I suspect that what that adamant UL statement really says is that "when we test fittings, we use locknuts and really don't know how they work with female threads. Oh, we can 'infer,' but that's not our job, so we simply don't know."

The threads are different and for reasons. If water resistent or grounding is a issue then we need to use the proper fittings.

 

[infinity]

They do make specialty fittings.
Such as:
EMT to Seal tight
EMT to rigid
Rigid to seal tight

These alone cover a lot of uses.

Most of those fittings are not made in larger sizes so you rigid coupling transition is the only option.

 

[Barndog]

Saw article in ( IAEI ) about using rigid couplings for transitioning from say emt to liquid tight conduit . ( Transitioning Between Raceway's ) Have always seen it done this way emt connector to rigid coupling to liquid tight conduit . Is this now considered wrong and are inspectors now enforcing this ?

I see no problem with doing this. have done it a few times myself.

 

[Cow]

What gets me is they'll allow a set screw fitting with a single screw tightened against a pipe, what are they, maybe a #12 screw? But an emt connector-rigid coup-flex conn tightened with channellocks is less reliable or not listed or not tested, etc. Does that make any sense? I'd count on that to clear a fault more than I would a set screw fitting!

But it's a moot point anyway, we don't get called on it. So I'm not worried about it.

 

[fmtjfw]

You bond a 200A panelboard with a 10-32 screw.

 

[don_resqcapt19]

What gets me is they'll allow a set screw fitting with a single screw tightened against a pipe, what are they, maybe a #12 screw? But an emt connector-rigid coup-flex conn tightened with channellocks is less reliable or not listed or not tested, etc. Does that make any sense? I'd count on that to clear a fault more than I would a set screw fitting! ...

It would be my opinion that the set screw connector connection to the conduit would be a much better path than the threaded connection with a rigid coupling. It is my experience that when you tighten the emt connector-rigid coup-flex connector combination up, that it does not take much force to untighten it, no matter what tools were used to tighten it. That does not mean that I don't use the rigid coupling to flex connector combination, because i use that all the time for sealtight connections to instruments.

 

[K8MHZ]

You bond a 200A panelboard with a 10-32 screw.

A green one, so the electrons know it's OK to go there.