EMT COUPLERS

[iwire]

Anyone know the resistance of 1/2 inch emt per foot ?

Its less than the per foot resistance of 12 AWG copper. 8)

 

[Jim W in Tampa]

Now factor in the resistance of couplers ,connectors,locknuts for the emt and wire nuts for the thhn.Considering the thickness of emt it should be lower.

 

[Jim W in Tampa]

Perhaps emt then is safer than romex.

 

[iwire]

Considering the thickness of emt it should be lower.

That is the key, a 1/2" EMT has a lot more matrial per foot than 12 AWG copper.

 

[ron]

It would be interesting to compare the impedance of EMT to a copper conductor. Although there is more EMT, the addition of couplings and the natural impedance of the EMT vs copper, it would seem to be a real close competition. I cannot find a source of impedance values for EMT, especially with couplings.
Although not #12 CU and not 3/4"EMT, the following article implies that the impedance of the conductor may be less than the EMT.
http://bg.ecmweb.com/ar/electric_code_forum_4
Also keep in mind that impedance during a ground fault is different than impedance during a test with a multimeter, due to the heating effects and vibrations imposed during a short circuit.

 

[iwire]

Ron there is a place, I am in a hurry now but I think it is at the "Steel tube institute' or something like that.

Maybe Don or Tom will jump in with the address.

I believe it has been stated that EMT is good for about 300' before it becomes an ineffective ground fault path.

Bob

 

[don_resqcapt19]

Jim,

Perhaps emt then is safer than romex.

In code compliant installations, both are safe, but in my opinion the extra protection provided by the steel makes the EMT safer than the NM.
Don

 

[don_resqcapt19]

The Steel Tube Institute funded research at George Tech that resulted in the GEMI software.

 

[stew]

under no circumstance may you install more couplings in a run than you have in the truck at the time of the original installation. NO EXCEPTIONS!!!

 

[LarryFine]

under no circumstance may you install more couplings in a run than you have in the truck at the time of the original installation. NO EXCEPTIONS!!!

So the ones in my pocket from the last job cannot be used?

 

[stew]

you were in your truck when you started so the pocket inventory may also beused with vilolation of the fundamental truck rule.

 

[Jim W in Tampa]

There is an exception if your going back to the job in the morning or big orange is near where you go to lunch.Sorry forgot the article number but its in there someplace :lol:

 

[macmikeman]

We need an umpire ruling here since the box of couplings on the truck always has two in it that have lost one of the set screws.

 

[ramdiesel3500]

Couplings with missing set screws are not considered true couplings. The are called "partial couplings" and cannot be included in the truck inventory quantity! However, in the case of multiple "partial couplings" it is permissible to combine parts in order to "field assemble" true couplings from the trucks inventory!

 

[Jim W in Tampa]

Couplings with missing set screws are not considered true couplings. The are called "partial couplings" and cannot be included in the truck inventory quantity! However, in the case of multiple "partial couplings" it is permissible to combine parts in order to "field assemble" true couplings from the trucks inventory!

Only if the exact same brand and screw size.Otherwise we don't have a listed coupling.Inspectors check for this as it happend a lot.Also note that all screws must line up with the emt.