Mast height on residential

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TOOL_5150

TOOL_5150

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bay area, ca
I got into a conversation with someone about the mast height on a house. He said that it can not be more than 24" high, otherwise it needs to be back guyed. Here in CA, our POCO told me it can be up to 3'. Now, the question is why does the total height of the mast matter, when the service drop will not be hanging from the weather head [ideally :grin:], but the drop will be connected to the insulator lower on the mast. If the mast was say 5', but the drop was connected 18" up the mast, would it need to be back guyed still? Im not near my code book, and this has been bugging me ever since.

~Matt
 
Matt.,,

The reason why majorty of POCO want the mast at 24 inch [600MM] or higher due the span from the POCO post to the mast some canbe pretty long distance and it can cause alot of strain on the mast.

Try to weight the common #1 alum ACSR cable [ common for 200 amp service] something like 120 feet you will get the idea then add weight of ice build up that can really add up very fast IIRC a quarter inch [ 8MM] of ice with 120 feet span and i am talking about little over 1200 LBS very easy.

Somthing like in my area we are required all the mast over 600MM have to be backguyed keep in your mind there are pretty good percentage of area where ice will encounter here and yeah we do get it from time to time.

Also the height of mast can make the diffrence of drop of span some case I have to use much higher mast to clear the area if the sisuation called for.

Merci,Marc
 
TOOL_5150 said:
I got into a conversation with someone about the mast height on a house. He said that it can not be more than 24" high, otherwise it needs to be back guyed. Here in CA, our POCO told me it can be up to 3'. Now, the question is why does the total height of the mast matter, when the service drop will not be hanging from the weather head [ideally :grin:], but the drop will be connected to the insulator lower on the mast. If the mast was say 5', but the drop was connected 18" up the mast, would it need to be back guyed still? Im not near my code book, and this has been bugging me ever since.

~Matt
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What you say makes perfect sense. Here, I have never seen a mast that was guyed. And the POCO is pretty relaxed as far as height. They do have specs, of course, but don't turn many down. We don't have much snow here though. I bet an engineer would agree with your way of thinking.
 
M&W makes a pretty neat fitting to back-guy a mast if you're dealing with a shingle roof. I can't seem to find a picture of it. It's a tab you fasten under one of the shingle tabs, and a loop sticks out from under the shingle tab. I've seen some pretty hairy other methods guys have come up with, which vary from an eye bolt screwed into the deck and tarred around, up to a one-hole strap screwed into the deck with no tar.
 
Our requirements are dictated by the POCO here. POAs have the be 12' at minimum per 230.24.B. If the distance between the eave brace and the POA is 36" or less (with 2" IMC), then stiff legs are not necessary. If the distance is greater than 36" (which is usually the case), then we have to use them.

The stiff legs (guys) we use are 3/4" EMT anchored with 3/8" all-thread through the trusses of the roof.
 
In AZ it is regulated by the POCO's.


30 or 36 inches (depending on POCO) from mast brace to point of attachment without back brace. (POA is 6" below weatherhead)

They recently instituted a 6" max from the roof to point of attachment so their guys don't have to climb a ladder on the roof.



The stiff legs (guys) we use are 3/4" EMT anchored with 3/8" all-thread through the trusses of the roof.
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Damn I HATE doing that. Besides being very difficult, it is a roof leak waiting to happen. Fortunately they are not very stict on the 12" POA height or almost every one would have to be backbraced as the eave brace is about 9' max which leaves you a bit short.
 
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220/221 said:
In AZ it is regulated . . . Damn I HATE doing that. Besides being very difficult, it is a roof leak waiting to happen.
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LOL - Getting the 3/4's end mashed at the right orientation was one of the hardest things to learn. :roll:
 
Getting the 3/4's end mashed at the right orientation was one of the hardest things to learn.
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Mostly because you generally can't do it on the roof. Up and down the ladder gets harder every day. Flatten/bend one end, carry it up, mark the orientation, climb down, do the other end, climb up and "adjust" with channel locks :grin: You can get quite a bit of twist if needed. Also, I use carriage bolts instead of all thread. It's a little cleaner.

The hardest part for me is finding EXACT CENTER of the rafters. I usually end up getting close with a chaulk line off the rafter tails, then running a long drywall screw in to feel for the edges.

Tile roofs are a joy also.

Did I mention I hate the backbrace? It ususally has to be done to clear an illegal structure.
 
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