service mast through the roof

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wire monk

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Do you have to use rigid conduit are can you use IMC for the power co to attach the service drop to??? For a service mast..
 
Depends on how the serving electric utility calculated the lengths of the permitted service drops. That question can only be answered by the serving electric utility. The through the roof raceway will be for the support of their service drop and they are not going to attach it if it doesn't meet their standards. :smile:
 
The NEC does not specify, other than the "mast must be capable of supporting equipment". As others have said, your local poco will provide specs. on their requirements. Welcome to the forum!:smile:
 
Curt read carefully from your link. :smile:

Allied’s method of manufacture increases the average tensile strength of IMC to such an extent that its wall strength is over 50% greater per
unit of thickness than that of representative samples of GRC measured by Allied.
Click to expand...

So the metal itself is stronger, but RMC having a thicker wall section is still stronger over all.
 
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Bob

I guess stronger was the wrong word. If you look at the various testing charts including the ?Service Mast Cantilever Beam Test? IMC outperforms rigid.
 
It all depends on the local PC. In some counties here (Tenn) its 2'' in others its 2.5'', both RMC. Myself, I think 2.5 is overkill, but to each there own.;) But you will need to contact the local PC if your not sure, that can be a costly mistake and one big headache, not to mention the embarrassment from the local AHJ.
 
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Up here in the mountain areas we have wind load, snow/ice load, and falling tree branches on the overhead drops. We use 2" minimum IMC or Rigid and, even more important we attach the pipe very securely to the building using strut and 3/8" lags into solid lumber. If the riser is over 3' above the roof penetration we also install back stays using 1/2" EMT lagged in behind the pipe in line with the drop. Sometimes that isn't even enough. Our poco wants the riser to be stronger that the drop cable.
 
curt swartz said:
Bob

I guess stronger was the wrong word. If you look at the various testing charts including the ?Service Mast Cantilever Beam Test? IMC outperforms rigid.
Click to expand...

From your link, bottom of page 7

Force to yield 2" IMC 5,200 Lbs

Force to yield 2" RMC 6,083 Lbs

I guess we could go back and forth all day long as I do see figures on the bottom of page 8 that show IMC having higher numbers.

I am not trying to give you a hard time, only the sales and marketing people that put the info together.
 
Bob

I got directed to that link a while back when debating the issue. In reality I have never been a fan of IMC and probably only used few sticks during the 24+ years in the trade just because that is what I had available. Even if my supply houses stocked it I doubt I would buy it. I would never think of burring IMC since even rigid rusts our in a few years in my area. IMC is also a PITA to bend compared to rigid.
 
3 inch rigid here most of the time unless its 18" or less thru the roof.
i can tell if its imc by the finish its not like rmc. at least all i've used is
 
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