Running RMC, techniques

[electrofelon]

HD, Lowes and many hardware stores have threaders if they sell pipe. I've gone that route when I had one or two ends. Just bring your pipe and throw them a few bucks.

-Hal

I tried that once, big orange, and they said they couldnt thread RGS because it messed up their dies. I think they were full of it. If anything, RGS may be softer alloy than "pipe" to facilitate bending (thats what I heard, maybe that is BS too).

 

[K8MHZ]

They do threading at these stores, but it's done in the plumbing section, and you probably have no choice but to get tapered threads.

Why would that be a problem?

 

[K8MHZ]

I tried that once, big orange, and they said they couldnt thread RGS because it messed up their dies. I think they were full of it. If anything, RGS may be softer alloy than "pipe" to facilitate bending (thats what I heard, maybe that is BS too).

Plumbers use the same dies as we do. NPT.

 

[retirede]

Plumbers use the same dies as we do. NPT.

Yep - Ridgid sells the same equipment to plumbers and electricians.

 

[Carultch]

Since you won't be cutting and threading the RMC you can use either threadless connectors or couplings.

Most threadless fittings for RMC, are not formally rated for wet locations. The few that are, are hard to find. Most applications where I'd be running RMC, would be in wet locations.

 

[MAC702]

... tapered threads.

After a little research, it turns out our conduit is also tapered threads. It's our fittings that are straight threads. Shows you how much RMC I've run.

 

[kwired]

That was me. I'd be embarrassed to say how many times I had to do it because my bender wasn't on the job with me, but hey, I was headed to the store for pipe anyway. Small jobs, too, so bend location wasn't critical or I had the measurement with me. Heck, most of the time I remembered to bring my tape measure with me into the store. Guess what I did if I forgot?

They do threading at these stores, but it's done in the plumbing section, and you probably have no choice but to get tapered threads.

I have used tape measures from store shelf many times, then put them back. Tapered threads is about all you will find on field threaded pipe. Straight thread never tightens it just "bottoms out".

I tried that once, big orange, and they said they couldnt thread RGS because it messed up their dies. I think they were full of it. If anything, RGS may be softer alloy than "pipe" to facilitate bending (thats what I heard, maybe that is BS too).

IMC is what is harder on threaders. If you have a threader die that is questionable at all it will leave damaged threads on IMC but still threads RMC just fine.

 

[Dzboyce]

After a little research, it turns out our conduit is also tapered threads. It's our fittings that are straight threads. Shows you how much RMC I've run.

The couplers that that come on galvanized or black iron pipe are known as “ merchant couplers”. Those couplers all have straight threads. It’s only the cast couplings that have tapered threads.

 

[K8MHZ]

The couplers that that come on galvanized or black iron pipe are known as “ merchant couplers”. Those couplers all have straight threads. It’s only the cast couplings that have tapered threads.

All the couplings for RMC I have seen have straight threads.

Like this:

 

[K8MHZ]

Plumber's couplings have tapered threads.

 

[kwired]

All the couplings for RMC I have seen have straight threads.

Like this:

What about "3 piece couplings" AKA "Erickson fittings"?

 

[K8MHZ]

What about "3 piece couplings" AKA "Erickson fittings"?

It's been a long time since I have used them. The J-men that trained me would rather tear a building down than use an Erickson. From the picture, it's hard to tell, but the threads that are on the part that screws onto the conduit look straight to me.

 

[LarryFine]

From the picture, it's hard to tell, but the threads that are on the part that screws onto the conduit look straight to me.

The threads on the ring are indeed straight. The body threads may be either.

 

[AKElectrician]

Well don't think that they are 10 foot plus the couplings length, they are 10' from start of threads to end of factory coupling.

 

[kwired]

The threads on the ring are indeed straight. The body threads may be either.

Kind of been my observation as well.

I try not to use them myself, but sometimes you do need something that can be taken apart later on, other times you may be able to avoid a three piece coupling but also need to use shorter pieces of conduit and more standard couplings to get it assembled, so pick the lesser evil.

 

[infinity]

Well don't think that they are 10 foot plus the couplings length, they are 10' from start of threads to end of factory coupling.

Yup pretty dumb IMO.

 

[kwired]

Yup pretty dumb IMO.

Well a few cents of material per piece adds up, and they can still pass it off as a 10 foot piece.

 

[AKElectrician]

Can be good fun watching a EMT guy run RMC. Especially when the boss hates unions.

 

[infinity]

Well a few cents of material per piece adds up, and they can still pass it off as a 10 foot piece.

True, but I'm guessing that's not the reason why it's 10' with one coupling.

 

[LarryFine]

Can be good fun watching a EMT guy run RMC. Especially when the boss hates unions.

Last year, I ran two 2" RMC runs up the outside of an approximately-100'-tall apartment building for a roof-mounted cellular site. The only Eriksons I used were at the very bottom, where they joined two existing-but-abandoned RMC's from the old service entrance. See thumbs:

The guy who hired me ran his 1-1/4" RMC using non-threaded compression couplings at every cut. Looked really amateurish in comparison, if I may say so.