I'm in WA state. PoCo is Mason PUD #1. AHJ is WA L&I. I recently had my first inspection after upgrading meter box from 200A service to 400A service. Only flunked for 7 things. One of them was "add guy kit on service mast". The roof is metal. Inspector said since the mast is more than 2' above the roof (I wanted separation between service wires and metal roof. It's probably 3-3 1/2') and is a 3" mast and will have heavy wires attached, it needs a guy wire (or wires?).

I'm picking up an MK-3 from Platt: https://www.platt.com/platt-electric-supply/Mast-Guying-Kits-w-Wire/Nichols/MK-3/product.aspx?zpid=43927. I suspect it won't come with directions. I'm wondering if someone can provide guidance on how to install it. E.g., how high up should the wires be attached to the mast? What directions should the wires head away from the mast? Is there a distance away from mast or angle down I should aim for when determining where the roof attachments go?

I've attached a picture of the mast. If it'll help, I can get a better shot next time I'm on site (if the rain lets me). The power pole is currently about 15' beyond the right end of the house and about 10' in front of the front of the roof line. With that said, though, I hesitate to add guy wires based on that. PoCo wants to upgrade service wires in the neighborhood. They may move the pole elsewhere. They may even go underground (in which case, at some point, this all becomes moot). But, I should probably add the guy wires that make sense now, and worry about the future when it happens.

enter image description here

  • The service drop (wires from pole to masthead on your house, or underground wires) is not yours. Any repairs are the responsibility of the power company. – Gunner Oct 9 '20 at 20:14
  • I'd wait until the power company is finished with their work. The guy you'll be installing is to support the mask from the tension of the cables coming from the pole to your weather head. It should be inline with those cables. Is there a third wire coming out of your weather head? – JACK Oct 9 '20 at 20:27
  • That mast is about to have a HUGE amount of side-force from the power company's wire drop, which is both heavy and taut. How to transfer that to the building structure isn't an electrical question, it's an architectural one. – Harper - Reinstate Monica Oct 9 '20 at 20:33
  • The MK3 is a two-wire guy kit, per nicholsmanufacturing.com/catalog.pdf so you would aim for rafters (or purlins, depending on roof structure) either side of the direct line to the pole/transformer. If they change it later, you or they worry about that, then. You want the mast clamp as high as possible (just under the weatherhead.) Within the limits of roof structure and supplied cables, longer is better for the cables. – Ecnerwal Oct 9 '20 at 21:22
  • @Gunner and JACK, I'm sure you're right, but the AHJ won't allow the PoCo to do any work until I've made the correction AHJ called for. JACK, yes, there is a third wire. It's 250 MCM and only about 18" long, so harder to see. – Tom Getzinger Oct 9 '20 at 23:42

The reason you need guy wire is to support the mast place strap at the top of the mast then extend the wire behind the mast so when you pull the wire tight you look down the wire and the pole and mast line up with each other. I like my anchor into the roof to be as high as possible because higher up on the roof there is less water and leaves to hang up as they go down. Next is to find a rafter to screw into I usually use 1/4 x3” lag bolts and that is plenty for a 40’-60’ span the normal range I see houses set back from the lines. When I was an apprentice I was taught to site to the top of the transformer to the top of the mast and put my anchor in on that line but many times that did not end up on a rafter and that angle really did not help as much as a longer run. With a longer run of wire or cable usually you will cross a rafter and that is just right because the rafters are the strong points in your roof.


how high up should the wires be attached to the mast?

As high as is practical, the higher it is the less lever effcet is multiplying the tension in feed wire.

What directions should the wires head away from the mast?

In the the opposite direction that the supply cable is coming from, but slightly to the side. (eg 30 to 45 degrees off directly behind the feed, but you'll be constrained by what is available to bolt to)

Is there a distance away from mast or angle down I should aim for when determining where the roof attachments go?

That kit comes with fixed length 6' cables with only a little adjustment in the bracket so you need to find hardpoints on the roof (like a rafter or purlin) that you can bolt through. that are the correct distance from the pole.

Running the guy cable flat is allowable, sloping down to the roof is normal, sloping the other way is probably not a good idea, as the cable would then carry extra rain water to the pole.

If the guy cable is steeper than 45 degress you should probably use a longer cable instead

After writing the above I found this picture in the Nichols catalog (linked from the page you linked) it seems to cover all the points I made above. enter image description here

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