Small Solar Array (2 120Watts panels) mounted horizontally atop of fence posts

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tk3000

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Hello Folks,

Few months ago, I bought a house. In the past, in another house, I installed two small sollar arrays in the house' and in a detached garage's roof. Currently, I am looking into install a very small solar array (two 120Watts solar panels in series) on top of two fence posts (4x4).

The install would not be vertical, but horizontal and above the fence posts. The panels would have a small wood frame (red cedar) which would then be supported primarily by two fence posts.

Initial problem is due to the posts dimensions. Upon measuring the posts, it was found out that it measures about 3.9” by 3.9”. I then assumed that it was a 4x4, but turns out that a 4x4 measures 3.5” by 3.5”. The pic below depicts the issue:

FORTWAYNE_HOUSE_FENCE_SOLAR_INSTALL1.jpg


An overview of the spot whereby the small array would be located:

FORTWAYNE_HOUSE_FENCE_SOLAR_INSTALL2.jpg


Would frame pre-assembly:

FORTWAYNE_HOUSE_FENCE_SOLAR_PANELS_WOOD_FRAME_PREASSEMBLY.jpg

That is the ideal spot given my circumstances. It is very small array, so it should not put much stress in terms of weight bearing on the posts. Primarily, it would be used to feed power for two cameras, some low voltage and low intensity lights, and few small pumps (5 or 12DVC) used in an small irrigation system.

Could not find out the timber/lumber with the right dimensions to extend the posts at local home centers. Maybe they were custom made? Any insights would be appreciated.
 
Last edited:
Hello TK3000!

I think snow and wind loads are important to consider. I suppose those loads eliminate dowels, hanger bolts or biscuits.

In the interest of strength, here some ideas for your consideration:
Maybe lay a piece of 3.5" x 3.5" piece on the top of the post and countersink rather deeply. Then screw it down into the top of the existing post with long screws. (Stainless if cedar) This assumes that the end of the existing post is tight and good wood.

Another idea is to take a couple of mending plates, perhaps 10 gauge and jog them like a Z-Bracket. (Drawing below)

Plan C:
Perhaps you can cut slot "pockets" in the top of the existing post with an oscillating tool. Next push the bracket shown in your photo into the pockets. Then screw in from the sides of the post to capture the bracket.

Expensive, but strong is a piece of Unistrut on the top of the existing post with strut-nuts & strut angle brackets to attach the new wood will give you a very strong and adjustable bracket.

I think wandering around a home center might provide inspiration. Electrical and plumbing items are magical for "How am I going to attach this" projects.

Paul
 

Attachments

  • Z Bracket.pdf
    21.4 KB · Views: 0
Forgot an idea-
Notch out the existing post so that the bracket in your photo will fit. A wood chisel will work very well on the post, as will a router. That notch will also help keep the bracket from tilting.
Paul
PS: I also suggest perhaps some adhesive, caulk or a rubber sheet between the woods so water doesn't pool in there and freeze in winter, pushing up on the upper post.
 
tk3000 said:
Hello Folks,

Few months ago, I bought a house. In the past, in another house, I installed two small sollar arrays in the house' and in a detached garage's roof. Currently, I am looking into install a very small solar array (two 120Watts solar panels in series) on top of two fence posts (4x4).

The install would not be vertical, but horizontal and above the fence posts. The panels would have a small wood frame (red cedar) which would then be supported primarily by two fence posts.

Initial problem is due to the posts dimensions. Upon measuring the posts, it was found out that it measures about 3.9” by 3.9”. I then assumed that it was a 4x4, but turns out that a 4x4 measures 3.5” by 3.5”. The pic below depicts the issue:

View attachment 33001


An overview of the spot whereby the small array would be located:

View attachment 33002


Would frame pre-assembly:

View attachment 33003

That is the ideal spot given my circumstances. It is very small array, so it should not put much stress in terms of weight bearing on the posts. Primarily, it would be used to feed power for two cameras, some low voltage and low intensity lights, and few small pumps (5 or 12DVC) used in an small irrigation system.

Could not find out the timber/lumber with the right dimensions to extend the posts at local home centers. Maybe they were custom made? Any insights would be appreciated.
Click to expand...
You might like to familiarize yourself with the several different milling standards of milled lumber, which are, S4S, surfaced 4 sides, RS, rough-sawn & RE-SAWN, each of which have different finished dimensions, and in keeping with that, SIMPSON, in general, offer connectors designed to transition from each to the other, some, not all, will be carried at hrdw. outlets.

Also, in keeping with PJB12'S post, generally you'll find the increasing a fence height above 6' requires it to be an engineered product, because anything above 6' in height is subjected, adversely, by wind, and requires an altered footing, to resist.
 
PJB12 said:
Hello TK3000!

I think snow and wind loads are important to consider. I suppose those loads eliminate dowels, hanger bolts or biscuits.

In the interest of strength, here some ideas for your consideration:
Maybe lay a piece of 3.5" x 3.5" piece on the top of the post and countersink rather deeply. Then screw it down into the top of the existing post with long screws. (Stainless if cedar) This assumes that the end of the existing post is tight and good wood.

Another idea is to take a couple of mending plates, perhaps 10 gauge and jog them like a Z-Bracket. (Drawing below)

Plan C:
Perhaps you can cut slot "pockets" in the top of the existing post with an oscillating tool. Next push the bracket shown in your photo into the pockets. Then screw in from the sides of the post to capture the bracket.

Expensive, but strong is a piece of Unistrut on the top of the existing post with strut-nuts & strut angle brackets to attach the new wood will give you a very strong and adjustable bracket.

I think wandering around a home center might provide inspiration. Electrical and plumbing items are magical for "How am I going to attach this" projects.

Paul
Click to expand...
Hi Paul!

“ I suppose those loads eliminate dowels, hanger bolts or biscuits.”

=> That is very true. You are bringing me memories of my woodworking/joinery times, for most part I used pocket screws though (I have to get back to it).

“Maybe lay a piece of 3.5" x 3.5" piece on the top of the post and countersink rather deeply. Then screw it down into the top of the existing post with long screws. (Stainless if cedar) This assumes that the end of the existing post is tight and good wood.”

=> Overall, the post is in good shape, but I would say that the top of a post that has been exposed to the weather is its weakest link (assuming its bottom is no bad near the ground).

The mending plates is something I did consider, and sounds like a good option. But, I was cogitating the use of two or three simpsons plates (galvanized heavy tie plate). Couldn’t simpsons heavy duty ties be used as well?

“Expensive, but strong is a piece of Unistrut on the top of the existing post with strut-nuts & strut angle brackets to attach the new wood will give you a very strong and adjustable bracket.”

=> This one is a good way and the being able to adjust (however small) afterwards is a plus. I have to take a closer look on the top of the post. And it is a little difficult for to work there on a ladder because the terrain is sloped and the ground is covered with rocks.

“I think wandering around a home center might provide inspiration. Electrical and plumbing items are magical for "How am I going to attach this" projects.”

=> I hear you! I am the same way and can see value in lots of things. Often, I buy things that I don’t necessary need now, but may have some future potential use.

The Z-Bracket looks like a winner! If it fits and has the right dimensions, I will use them. Thanks for the drawing!
 
You mentioned Simpson. Good Idea!
Their plates can be more easily bent into a Z-Bracket than the thicker mending plate I suggested.
I recently used some TP39 plates that are 3-1/8" x 9". Perhaps a pair of those would work. I think they are 0.030" thick, or close to it.

Of all the choices, I do think slots in the existing post to slide your photographed bracket's legs into with long screws to go through it might be strongest. But, it's not good if you don't have the tools or good wood.

Is it feasible to skip the existing post & make something new to support the panels? This way, the load of the panels won't cause the fence to tilt. Perhaps new wood posts into the ground, or driven pipes. Just mind wandering...
 
There are likely SIMPSON brackets designed and marketed that would facilitate the transition, from one milled product, to the other, no reforming required; https://www.strongtie.com/
 
PJB12 said:
Forgot an idea-
Notch out the existing post so that the bracket in your photo will fit. A wood chisel will work very well on the post, as will a router. That notch will also help keep the bracket from tilting.
Paul
PS: I also suggest perhaps some adhesive, caulk or a rubber sheet between the woods so water doesn't pool in there and freeze in winter, pushing up on the upper post.
Click to expand...

That is a good idea. I have not considered doing it. Although it would be easier to that with a router if the timber was not already installed in the ground. Could an oscillating tool be used as well in this case?

On a tangent, though a related one. Recently, I did use an oscillating tool to trim down a small deck post that helps support the deck floor. There is a small wood deck surrounding an all season room in my house, and somebody did a really repair bad job there:

FORTWAYNE_DECK_SUPPORT_BEAM_OVERSIZED.jpg

I would assume that it was a replacement for a previous post that was badly rotten. Upon installation they probably found out that it was oversized, and so be... With an oscillating tool I was able to remove material from the top of the small floor post, will then use a belt sander to even it out.

FORTWAYNE_DECK_SUPPORT_BEAM_TRIMMED.jpg
(trimmed with an oscillating tool)

Does not it look like that this post is getting rotten where it makes contact with the ground?

Also, they probably used the cheapest possible screws to build the deck. They were corroded into oblivion:
FORTWAYNE_DECK_SCREWS_CORRODED_INTO_OBLIVION.jpg
 
Build your frame separately and then lag it to the post.
 

Attachments

  • Solar Mount.jpg
    Solar Mount.jpg
    33.4 KB · Views: 0
Snoonyb said:
You might like to familiarize yourself with the several different milling standards of milled lumber, which are, S4S, surfaced 4 sides, RS, rough-sawn & RE-SAWN, each of which have different finished dimensions, and in keeping with that, SIMPSON, in general, offer connectors designed to transition from each to the other, some, not all, will be carried at hrdw. outlets.

Also, in keeping with PJB12'S post, generally you'll find the increasing a fence height above 6' requires it to be an engineered product, because anything above 6' in height is subjected, adversely, by wind, and requires an altered footing, to resist.
Click to expand...

Yeah, I got the point. As far as timber goes (don know why 4 by 4s are called timber, guess nomenclature dependes on your location). I always knew that the stated dimension of lumber often is not the real dimension (2 by 4s don’t really measure 2 by 4 inches). But, I was not familiar with 4 by 4s till recently, and I went outside to measure the dimension of the post, then found out that its dimension was almost exactly 4 inches by 4 inches; so, I assumed that 4 by 4s actually measured 4 by 4 inches. Should have done my reseach before buying it, etc, but have too many things going on lately.

Will study more about different dimensions and types of lumber in the near future, but right now the type of project I am working on does not require that (I am not building anything like a shed [future project]); I am simply tryring to extend a fence post by about 9 inches in order to obtain proper support for a very small solar array.

It is only 9 inches of extension, it can not have much of an impact.
 
PJB12 said:
You mentioned Simpson. Good Idea!
Their plates can be more easily bent into a Z-Bracket than the thicker mending plate I suggested.
I recently used some TP39 plates that are 3-1/8" x 9". Perhaps a pair of those would work. I think they are 0.030" thick, or close to it.

Of all the choices, I do think slots in the existing post to slide your photographed bracket's legs into with long screws to go through it might be strongest. But, it's not good if you don't have the tools or good wood.

Is it feasible to skip the existing post & make something new to support the panels? This way, the load of the panels won't cause the fence to tilt. Perhaps new wood posts into the ground, or driven pipes. Just mind wandering...
Click to expand...
I agree. Slots in the exist post would be the best option everything considered; less work and utilization of what I already have, besides it probably would strong enough. Bent simpsons plates could be used to complement and make it stronger.

I had a metal bender (from harborfreight), it was stolen (among other things) long time ago. Could buy another one if needed.

You raised a good point regarding using caulk or some other layer on top of the current posts. Previously, I considering simply painting the very top of the post with acrylic paint. In any case, I still have to better inspect the to of the current posts (a ladder there can be trick); but overall, the fence is in good shape.

I don't know how well the fence was built though. If its footing was done with concrete or gravel or something else.
 
tk3000 said:
That is a good idea. I have not considered doing it. Although it would be easier to that with a router if the timber was not already installed in the ground. Could an oscillating tool be used as well in this case?
Click to expand...
An oscillating tool will make very quick work of cutting the slots. The blade is probably about the same thickness as your Simpson bracket. (I've done similar slots with the tool and slid in Simpson brackets- with occasional light tapping if I delay putting the brackets in the slots.)

Doing that and having screws through the side of the post, into the Simpson will give very strong shear and tilt resistance if structural screws are used. (I'd use two per side for anti-tilt.)

You'll probably want to pre-drill all the way through the plate because structural screws don't pierce metal well.

CAUTION! Don't use Simpson screws. Check the shear rating: 50 pounds!
I have often used GRK RSS screws. They have a high shear and don't snap like Grip Rite do. The crazy thread pattern draws in well and holds tightly even in end grain. Bonus: They don't rust and many are rated for cedar.

Perhaps threaded rods appropriate material for the wood all the way through with acorn nuts jamming hex nuts would be even easier than screws.

Happy Solaring!
Paul
 
Last edited:
Steve123 said:
Your kidding, right ?
Click to expand...
Well, I did not do any calculation and so on... But, I would imagine that unless the frame has its own footing it would add extra weight to the post. That frame probably would better distribute the weight of the panels throughout the post which is a good thing. Actually, I don´t really know; I am just guessing.
 
If the added panels add to the height, and you elected to forgo a permit, and the wind overturns the fence, into your neighbor yard, exposing their property, having cash on hand may not be a sufficient remedy; "Also, in keeping with PJB12'S post, generally you'll find the increasing a fence height above 6' requires it to be an engineered product, because anything above 6' in height is subjected, adversely, by wind, and requires an altered footing, to resist."

Not kidding.
 
PJB12 said:
An oscillating tool will make very quick work of cutting the slots. The blade is probably about the same thickness as your Simpson bracket. (I've done similar slots with the tool and slid in Simpson brackets- with occasional light tapping if I delay putting the brackets in the slots.)

Doing that and having screws through the side of the post, into the Simpson will give very strong shear and tilt resistance if structural screws are used. (I'd use two per side for anti-tilt.)

You'll probably want to pre-drill all the way through the plate because structural screws don't pierce metal well.

CAUTION! Don't use Simpson screws. Check the shear rating: 50 pounds!
I have often used GRK RSS screws. They have a high shear and don't snap like Grip Rite do. The crazy thread pattern draws in well and holds tightly even in end grain. Bonus: They don't rust and many are rated for cedar.

Perhaps threaded rods appropriate material for the wood all the way through with acorn nuts jamming hex nuts would be even easier than screws.

Happy Solaring!
Paul
Click to expand...



Hmmm.. I havent heard the term “structural screws”, but I came across that type of screw in the past (built-in washer and part the of shaft is unthreaded). I was going to use exterior/wood/deck screws? I was considering using lag screws at one point, but then decided to use exterior #10 (maybe 3 inches) screws. Having large part of the shaft unthreaded is good to join wood together, it should strengthen the connection in my situation too (but in my case, the load is not all that large).

I probably saw Simpsons screws in the past, but I did not know them by name. Arent they similar to structural screws -- a type of structural screws, and the same would apply to grk?

As far as attaching the panel together to the red cedar board, I was considering using zinc-plated machine bolts and nuts (along with washers). The panels are going to be connected to the cedar boards via solar panels mounting brackets, the following:

https://www.amazon.com/BougeRV-Sola...8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1

“Perhaps threaded rods appropriate material for the wood all the way through with acorn nuts jamming hex nuts would be even easier than screws.”
=> I will look into that option too!

Thanks for all your insights, always a learning experience.

I will travel soon, so have put this project on hold. Once I am back (maybe 10 days), will follow up in this thread.
 
tk3000 said:
Hmmm.. I havent heard the term “structural screws”, but I came across that type of screw in the past (built-in washer and part the of shaft is unthreaded). I was going to use exterior/wood/deck screws? I was considering using lag screws at one point, but then decided to use exterior #10 (maybe 3 inches) screws. Having large part of the shaft unthreaded is good to join wood together, it should strengthen the connection in my situation too (but in my case, the load is not all that large).

I probably saw Simpsons screws in the past, but I did not know them by name. Arent they similar to structural screws -- a type of structural screws, and the same would apply to grk?

As far as attaching the panel together to the red cedar board, I was considering using zinc-plated machine bolts and nuts (along with washers). The panels are going to be connected to the cedar boards via solar panels mounting brackets, the following:

https://www.amazon.com/BougeRV-Solar-Mounting-Bracket-Supporting/dp/B07Z4J5JCD/ref=sr_1_1_sspa?crid=2FZXKNIUX2V19&dib=eyJ2IjoiMSJ9.f4KhGvUU1wExs_-o1Vh--i26-orVT-JSh59d3O5rxrWV9yb2J7rL3YIMjEMxNXFb9mkTKISdPmp5eOa5v5w3cd3WR0shE5AH_5Kj8w9r31ZM5ejVOnU8HNs9RTUPdP9-mXA9-8RlwAI6ykue2sgLzOXHlEVxBrzgxX96iSif-Jsga7ilzQdf09ZdYvhDd5f4xtVz7yNjK3cOFimwKbsv3NKl9wz2-hgbEpCWZP9_FBY.F9Ao-iPuQNzeh5LV57UQiGisAoBuebSijr26QdLKdqw&dib_tag=se&keywords=solar+panel+mounting+bracket&qid=1721337066&sprefix=solar+panel+mounting+bracket,aps,133&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1

“Perhaps threaded rods appropriate material for the wood all the way through with acorn nuts jamming hex nuts would be even easier than screws.”
=> I will look into that option too!

Thanks for all your insights, always a learning experience.

I will travel soon, so have put this project on hold. Once I am back (maybe 10 days), will follow up in this thread
Click to expand...

I'm not sure zinc plated steel fasteners are compatible with cedar. I suggest investigating this based on the exact fastener you wish to use.

(Next door neighbor built a dry sauna of cedar, using all hot dipped zinc plated fasteners. The cedar ate the bolts in a few months & the whole sheebang fell down in pieces. Cheap plating? Perhaps.)

I didn't think of this, but the steel bracket may benefit from either having an isolation membrane (flashing tape, shower pan liner, etc.) between it and the cedar or perhaps a heavy coat of polymeric or oil based or urethane paint. This is to keep the steel from touching the cedar.

I'm surely no expert but wanted to post some things to consider.

Paul
 
PJB12 said:
I'm not sure zinc plated steel fasteners are compatible with cedar. I suggest investigating this based on the exact fastener you wish to use.

(Next door neighbor built a dry sauna of cedar, using all hot dipped zinc plated fasteners. The cedar ate the bolts in a few months & the whole sheebang fell down in pieces. Cheap plating? Perhaps.)

I didn't think of this, but the steel bracket may benefit from either having an isolation membrane (flashing tape, shower pan liner, etc.) between it and the cedar or perhaps a heavy coat of polymeric or oil based or urethane paint. This is to keep the steel from touching the cedar.

I'm surely no expert but wanted to post some things to consider.

Paul
Click to expand...
Hhmmm… It is good to know that. It is in the planning phase yet, I will research more about that topic. But, yeah, it seems that Hot-Dipped galvanized, aluminum and stainless steel nails are all corrosion-resistant and all can be used with Red Cedar. Maybe stainless steel fasteners would be the best option.

The use a of membrane may not be important with stainless steel fasteners. Well, eventually everything fails and needs to be repaired or replaced; but, if last many years or decades, it would be good enough.
 
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