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2" svc mast #5968 12/16/01 04:41 PM
Joined: Jun 2001
Posts: 196
Cindy Offline OP
If extra support is not provided, the service conduit needs to be at least 2” in diameter. Read that somewhere, but can't find it in the 99 nec? wheresitat?

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Re: 2" svc mast #5969 12/16/01 05:11 PM
Joined: Oct 2000
Posts: 3,961
Bill Addiss Offline

It could be a local rule. Where I am the Utility requires 2 1/2" GRC (minimum) for a Service Mast.


Re: 2" svc mast #5970 12/17/01 12:33 AM
Joined: Jun 2001
Posts: 141
amp-man Offline

Min 2 1/2"? How do you install that in a house that has 2-by-4 top plates? Not much of anything left...

Do you use simpson tie plates to reinforce the top plates?

And speaking of running the pipe up, got any tricks for aligning the hole in the plate and the roof sheathing with the center of the hub? I use a plumb bob and square to line up the holes right and left, then measure from face of stud for depth.

Thanks in advance,


Re: 2" svc mast #5971 12/17/01 12:55 AM
Joined: Oct 2000
Posts: 3,961
Bill Addiss Offline

I'm not sure what you mean. I'm talking about a surface-mounted Meterpan with a 2 1/2" mast. There is nothing inside the walls. I would use a plumb-bob too when going through a soffit and roof. The only way to go!


Re: 2" svc mast #5972 12/17/01 08:32 AM
Joined: Mar 2001
Posts: 2,056
Redsy Offline
Our local utility has a "Blue Book" which contains their installation requirements for servive-related equipment. That is where our size & support criteria for service masts are found. Call your utility co. and request this info.

Re: 2" svc mast #5973 12/17/01 09:38 AM
Joined: Oct 2000
Posts: 3,961
Bill Addiss Offline
We have a similar "Red Book"

Re: 2" svc mast #5974 12/17/01 12:07 PM
Joined: Nov 2001
Posts: 280
motor-T Offline
When I run 2 1/2" pipe for a service mast I usually drill a pilot hole trough the soffet and through the roof at an angle that is plumb the hole orientation is now straight with the house.
Then cut the 2 1/2 hole with a hole saw and to start keep the drill plumb to get the hole started through the soffet then climb onto the roof and do the same. depending on the type of clamps used for the pipe determines how far from the wall of the house the hole through the soffet is. once this hole is cut, I run the pipe trhough the hole and then line up the meter-base so all is plumb and anchor the meter base. I will pre-assemble the meter base with hub and adjustable fitting, if pipe is off wrt the meter-base its a simple matter of rotating the adjustable fitting to get a good alignment.
Then proceed with the wire and mast head and roof flashing.
We have around here what is known as a mast kit that comes with the Flashing, bootie, for the pipe and the mast head for 2 1/2 inch kit this is usually for 200 amp, there is a mast kit for 2 inch. But the 2 1/2 that is usually used for a long run of tri-plex of say over 120 feet otherwise we are allowed to use 2 inch ridgid.
Generally it takes one guy about 4 hours to put up a mast complete.

Re: 2" svc mast #5975 12/18/01 10:11 PM
Joined: Oct 2001
Posts: 45
WireWrestler Offline
Our POCO requires 3" rigid for supporting overhead drops. We can use less than 3" if the mast has a guy wire.

Re: 2" svc mast #5976 12/18/01 10:41 PM
Joined: Mar 2001
Posts: 85
CanadianSparky Offline
I'm in the Rocky Mountains of Canada(very high snow loads here) and we can get away with 2 1/2 inch rigid. Just wondered what kind of load there could possibly be that would require a 3" rigid mast. Seems like overkill.

Re: 2" svc mast #5977 12/19/01 12:40 AM
Joined: Oct 2001
Posts: 597
ElectricAL Offline
The PoCo in my area allows 2" GRC up to 3' high to be unguyed. I have seen a few masts, 2" GRC, that have been stuck up in the air 8' (eight) with a single guy wire off to the structure.

As for the hole, quite a while back I picked up an extra deep hole saw (2-1/2" deep) sized for 2" GRC that came with a 2-1/2' shaft. The shaft on this unit has a 2-1/4' closed end pipe mounted to it by sealed ball bearings; this allows the shaft to turn independent of the pipe. The pipe is just a titch smaller than the cut of the hole saw.

I set up under the eave, put the hole saw pilot bit on my mark, position the pipe on the shaft parallel to the wall, eyeball the pipe on the shaft vertical from side to side, and then I run the whole thing right up through the soffit and out the shingles. The pipe on the shaft keeps the hole saw centered as the hole saw pilot bit starts into the underside of the roof sheathing.


Al Hildenbrand
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