Service Entrance

[kwired]

If the right angle end of the LB is inside the wall and sealed at the wall surface, you would not need the EMT connection to be watertight.

I agree and that did cross my mind when posing before. Not every time is the end within the wall though, or you get guys that need to use a RMC out of top of meter for a mast that will support a service drop but they don't have a threader for 1.25 to 2 inch and want to instead run EMT out the load side of meter, then they would be using EMT in both sides of the LB.

I realize this taper thread and straight thread thing is maybe technically wrong, why did they make these things interchangeable in the first place if they are not intended to be used together?

Biggest concerns brought up are water tightness or bonding effectiveness. Does anyone have any indisputable proof of either being a problem? By indisputable I mean can you prove the water inside a raceway came through the threads or possibly from condensation or other entry point, or that a failure of bonding was because of a mismatch in threads and not that a fitting wasn't ever tight in the first place.

 

[Sierrasparky]

Not that I know of but I doubt the OP needs that.

Out here on the west coast, we us all in one combos so that is not usually a issue.

 

[mopowr steve]

It's been my understanding that all electrical fittings are straight threaded only plumbing fittings are tapered.

So are you using the correct straight thread dies in your threader?

 

[iwire]

It's been my understanding that all electrical fittings are straight threaded only plumbing fittings are tapered.

So are you using the correct straight thread dies in your threader?

Our conduit and nipples use tapered threads. We use the same NPT threading dies as plumbers.

However you are correct about fittings, they use straight threads.

 

[mopowr steve]

Our conduit and nipples use tapered threads. We use the same NPT threading dies as plumbers.

However you are correct about fittings, they use straight threads.

Ah , but this is where you are wrong; you should be using rigid galvanized conduit which has straight threads and when buying nipples they to should be conduit nipples. And your threading machine should have straight thread dies.
NPS dies.

 

[iwire]

Ah , but this is where you are wrong; you should be using rigid galvanized conduit which has straight threads and when buying nipples they to should be conduit nipples.

That is a no.

Electrical conduit has tapered threads as do electrical conduit nipples.

Go take a look, I'll wait.

And your threading machine should have straight thread dies.

Nope, that would be an NEC violation.

344.28 Reaming and Threading. All cut ends shall be
reamed or otherwise finished to remove rough edges. Where
conduit is threaded in the field, a standard cutting die with a
1 in 16 taper (3/4 in. taper per foot) shall be used.

 

[kwired]

Ah , but this is where you are wrong; you should be using rigid galvanized conduit which has straight threads and when buying nipples they to should be conduit nipples. And your threading machine should have straight thread dies.
NPS dies.

Even the factory threaded ends of RMC have tapered threads. The couplings have straight threads. The coupling gets tight when the taper is inserted enough into the coupling to start jamming threads. There is kind of a mixture of straight and tapered threads in hubs, conduit bodies, FS boxes, etc. though.

But only one side nee be tapered to have it tighten. If both sides are straight thread it doesn't tighten, it bottoms out, which only takes a slight backing off and it is loose, where if a tapered thread is involved it takes more backing off before it is loose.

 

[Sierrasparky]

What abount running thread conduit! hmy:

 

[GoldDigger]

As long as it gets inserted into tapered females, it should work, but is not likely to be as water or vapor tight.
And if necessary it is relatively easy to clean up the ends with a tapered die.

 

[mopowr steve]

OK I'm wrong thanks for the clarification. I was going off something told to me years ago that related to tapered threads on a piece of conduit would not allow it to fully seat in couplings leaving exposed internal threads that could damage conductors. Same reason it's not listed to use a coupling and connector to change wiring methods rather a connector listed for the use makes the transition without exposed internal threads.
None-the-less I've used the standard die to make threads so I haven't been violating 344.28 anyway.
I will though have to get back with you on the difference between electrical conduit nipples and standard galvanized nipples having different thread types. As if I remember right I get electrical conduit nipples for the fact they do fully seat in couplings.

 

[ActionDave]

OK I'm wrong thanks for the clarification. I was going off something told to me years ago that related to tapered threads on a piece of conduit would not allow it to fully seat in couplings leaving exposed internal threads that could damage conductors.....

I want to see the threads in a coupling that can damage a conductor or its insulation. They must be animated or cut from some kind of steel I have yet to encounter.

 

[iwire]

I want to see the threads in a coupling that can damage a conductor or its insulation. They must be animated or cut from some kind of steel I have yet to encounter.

I want to see conductors deflect that much in a 1/2" to 3/4" gap.

 

[kwired]

As if I remember right I get electrical conduit nipples for the fact they do fully seat in couplings.

So does a field threaded piece of RMC. The coupling has straight threads, the smaller end of the taper is inserted first, when the larger end of the taper starts to fit tighter there is little or no exposed thread left outside the coupling. Exception would be on a straight thread fitting where the pipe begins to bottom out before the larger end of the taper is fully threaded in. Your conduit nipples have the same taper on the threads.