Overhead service

[Roddick]

Helloo
I will do soon do an 200Amps overhead electrical service.I will use 3" conduit riser through roof.I had an inspector on a job and he said that Comed doesn't accept roof attachment any more.He advice me to use aluminium conduit which is fine for me.But there is a note in the comed red book that riser is "rigid steel conduit".On web of americanconduit.com I found this notes:"If you’re not familiar with aluminum conduit, you might be wondering, “Does rigid aluminum conduit meet the same code requirements as rigid steel conduit?” The answer is yes – it definitely does".
So may I use an aluminium 3" conduit as a riser?Thank you.

 

[LarryFine]

You may.

 

[kwired]

Rigid aluminum is covered in same article as all Rigid metal conduits.

I really doubt it will have the same physical strength characteristics as rigid steel conduit of same size.

NEC has no details on how to determine what the mechanical load will be on such a service mast, and AFAIK doesn't exactly require it to be RMC, just that it needs to be able to withstand the mechanical load imposed on it. Some POCO's are very adamant about it being RMC and or have a minimum size and somewhat go by that even when the load is obviously not much. Like say when you have a drop from the pole to a building that is only 10 feet from the pole and only has say #4 o4 #2 aluminum triplex for a drop cable - a 1" EMT likely could more than handle the mechanical load but some POCO's will still want minimum of 2" RGS or they won't connect it.

 

[suemarkp]

Why 3" for a 200A service? Will the meter enclosure take a 3" conduit (my 200A meter will only take a 2.5" max). If you want provisions for a 320/400A service, then a 3" mast makes sense and use a 320/400 meter base. If you looking for more strength, a leg kit helps more than anything. Conduit isn't very resistant to bending, as it is intended to be easy to bend with benders. But certainly, increasing the diameter increases the bending force to bend it.

 

[infinity]

.I had an inspector on a job and he said that Comed doesn't accept roof attachment any more.He advice me to use aluminium conduit which is fine for me

What do you mean when you say they do not accept roof attachment?

 

[don_resqcapt19]

Helloo
I will do soon do an 200Amps overhead electrical service.I will use 3" conduit riser through roof.I had an inspector on a job and he said that Comed doesn't accept roof attachment any more.He advice me to use aluminium conduit which is fine for me.But there is a note in the comed red book that riser is "rigid steel conduit".On web of americanconduit.com I found this notes:"If you’re not familiar with aluminum conduit, you might be wondering, “Does rigid aluminum conduit meet the same code requirements as rigid steel conduit?” The answer is yes – it definitely does".
So may I use an aluminium 3" conduit as a riser?Thank you.

Assuming that the service drop will be attached to the riser, I doubt that the utility will permit the use of aluminum conduit. The following is from ComEd's 2022 Service and Meter Requirements manual. (C7820, page 1 of 6)

RIGID STEEL CONDUIT - 2-1/2" FOR 100 AMPERE OR SMALLER, OR 3" FOR LARGER SERVICE ENTRANCE EQUIPMENT, OR METALLIC RACEWAY OF EQUIVALENT STRENGTH MAY BE USED.

I would not see 3" aluminum as having equivalent strength as 3" rigid steel conduit.

Aluminum does meet the same code requirements as rigid steel conduit, but there is no code requirement that covers the strength of the two conduits where used to support a service drop. The code simply says the raceway used to support a service drop must "be of adequate strength or be supported by braces or guy wires to withstand safely the strain imposed by the service-drop..."

 

[John A]

Here in NJ, the utility rules govern the sizes, and type of conduit to be installed for a 'mast' service. 2-1/2" minimum RGS.

 

[infinity]

Here in NJ, the utility rules govern the sizes, and type of conduit to be installed for a 'mast' service. 2-1/2" minimum RGS.

I've installed a few with 2" RMC here in Northern NJ. Orange & Rockland Electric has a minimum mast size of 2". PSE&G has a 2" minimum and a 3" maximum.

 

[John A]

I stand corrected. 2" max 2feet above roof penetration; 2 1/2" max 4 feet above penetration; 3" max 7 feet above penetration.

I have not come upon a 2" mast service in a long time.

 

[kwired]

I stand corrected. 2" max 2feet above roof penetration; 2 1/2" max 4 feet above penetration; 3" max 7 feet above penetration.

I have not come upon a 2" mast service in a long time.

distance to point of attachment is what really matters, do they consider that or is those their max distances out of the roof period?

 

[g-and-h_electric]

Being a "Chicago area" electrician for 40 years (including carrying a Chicago license). I can tell you for absolute certain, if the "ComEd" redbook tells you a specific method that is all that they will accept. I have had Com Ed inspectors and engineers out to jobs, and if their book says it they will accept nothing different. (learned that lesson the hard way, as did my current boss)_

Additionally I know for a fact that aluminum heavywall bends a whole lot easier than "rigid" or IMC. I know aluminum is lighter to shove up or down for the mast, but if a branch or tree falls on the service drop it will bend guaranteed. I have seen the old Garvin square mast kits (which I dont think they make anymore) bend like a wet noodle and kinking from a large branch hitting the drop.

 

[kwired]

Being a "Chicago area" electrician for 40 years (including carrying a Chicago license). I can tell you for absolute certain, if the "ComEd" redbook tells you a specific method that is all that they will accept. I have had Com Ed inspectors and engineers out to jobs, and if their book says it they will accept nothing different. (learned that lesson the hard way, as did my current boss)_

Additionally I know for a fact that aluminum heavywall bends a whole lot easier than "rigid" or IMC. I know aluminum is lighter to shove up or down for the mast, but if a branch or tree falls on the service drop it will bend guaranteed. I have seen the old Garvin square mast kits (which I dont think they make anymore) bend like a wet noodle and kinking from a large branch hitting the drop.

When a tree falls on a drop often something on the drop will fail before the mast will bend with GRC, but I can recall at least one time where the drop held up pretty well and folded a 2" GRC mast.