Semi DIY PV Installation. Comments Please

[nowty]

Ahhh, footprints on the panels, I didn't notice them on first look, that's a bit naughty.

[Joeboy]

send them back

Agreed. Not worth a 25 Yr hit at your expense.

[SafetyThird]

I had to zoom in on the photos but yeah, those would be going straight back if they were delivered to me.

[MoSTiE]

i'll bet there's a bun fight over it if they dont look damaged.

[smegal]

I've installed them today (pics to follow) One does have some damage, so I'll be in touch on Monday.

[smegal]

Well it's up! One thing that I am noticing is that the columns are deflecting more than I'd like (note the wooden props). By deflecting, I mean swaying when the panels are pushed moe-so than deflection in steady state. With the wooden props, all is solid.

I've looked at the data sheets for the strut and the unistrut calculator (unfortunately, the demo version only has single channel where I've used back to back) I think I can make it work for up to 70mph wind with a support back to the garage (I've got a design in mind that doesn't need fixing to the garage using a cantilever arm and rubber foot, so no drilling is needed). I'm also going to add additional cross-bracing.

Edit. Interestingly, I may be being overly conservative. Using the below wind speed calculator, I'm getting ~2kN of wind loading for the PV array. That's split between the three posts. I was applying 2 kN to one post.

https://www.omnicalculator.com/physics/ ... calculator

On Monday, I'll try and speak to Unistrut about buying access to the calculator and analysing with the back to back for peace of mind. Initial reading of the datasheets made back to back look ok under this column loading, but the eccentricity of this loading is throwing things out. Unfortunately, I should have done more analysis at the front end, but this is where I am.




I think I need to phone a structural engineer tomorrow for some advice.

[Joeboy]

Well it's up! One thing that I am noticing is that the columns are deflecting more than I'd like (note the wooden props). By deflecting, I mean swaying when the panels are pushed moe-so than deflection in steady state. With the wooden props, all is solid.

I've looked at the data sheets for the strut and the unistrut calculator (unfortunately, the demo version only has single channel where I've used back to back) I think I can make it work for up to 70mph wind with a support back to the garage (I've got a design in mind that doesn't need fixing to the garage using a cantilever arm and rubber foot, so no drilling is needed). I'm also going to add additional cross-bracing.

Edit. Interestingly, I may be being overly conservative. Using the below wind speed calculator, I'm getting ~2kN of wind loading for the PV array. That's split between the three posts. I was applying 2 kN to one post.

https://www.omnicalculator.com/physics/ ... calculator

On Monday, I'll try and speak to Unistrut about buying access to the calculator and analysing with the back to back for peace of mind. Initial reading of the datasheets made back to back look ok under this column loading, but the eccentricity of this loading is throwing things out. Unfortunately, I should have done more analysis at the front end, but this is where I am.




I think I need to phone a structural engineer tomorrow for some advice.

Looks great, nothing wrong with a bit of extra bracing. well done!

[smegal]

With a proper support replacing the wood, using the unistrut calculator, it passes as single channel, so will be ample with back to back. But the ~3m span without additional support just won't work.

[Moxi]

Smegal,

I would suggest a tie bar from the horizontal under the panel back to the vertical channel intersecting a minimum of two thirds from the base ( at the base even better ) that will dampen any flex in the vertical by transmitting the load to nearer the base.

Bracing off the garage will work but it could over time break out the mortar around the bricks as you will be cyclically compressing and releasing the pressure. Note if the mortar does break out it will be on the inner tension bearing face not the point where the brace interfaces with the brickwork on the outer face of the wall.

Moxi

[Joeboy]

With a proper support replacing the wood, using the unistrut calculator, it passes as single channel, so will be ample with back to back. But the ~3m span without additional support just won't work.

I have seen that size and layout of array on offshore installations. It would normally be mounted on a 8" dia galvanized post so you have done well with what you have. If you have offcuts of spare unitstrut fair enough, other than that i'd go with timber from the shed woodpile purely for the Womble ethos. Last thing you need is metal fatigue over time in the wind then down she goes. Is it connected yet or is that next week? (excited for you)!