Questions on Installing Unistrut for Solar Panels

[PNW_Steve]

I am missing something as far as the shims go.

It looks to me like attaching the Unistrut directly to the roof would have the two outside runs canted away from the bus. It appears to me that a tapered shim at each point of attachment to the roof may be the solution.

We're you able to "level" the outer runs of Unistrut? If so, could you share a little more detail on the shims?

Thank you

S.

[ComfortEagle]

Originally Posted by PNW_Steve

...It looks to me like attaching the Unistrut directly to the roof would have the two outside runs canted away from the bus. It appears to me that a tapered shim at each point of attachment to the roof may be the solution.

Were you able to "level" the outer runs of Unistrut? If so, could you share a little more detail on the shims?

The shims are made from pieces of composite decking. Below is a close up of one of the shims. They were lathered up with Proflex RV sealant prior to installation.


After the above photo was taken the bolts were coated with Dicor self-leveling sealant, and the shim edges were sealed with Dicor non-leveling sealant and then coated with a couple coats of paint.


To level the three section of unistrut I mounted some strut perpendicular to the long runs to keep them level while designing and installing the shims.


wrenchtech, I am concerned I may be hijacking your thread. Say the word and I will cease and desist...

[JDSquared]

Originally Posted by ComfortEagle

The shims are made from pieces of composite decking. Below is a close up of one of the shims. They were lathered up with Proflex RV sealant prior to installation.





After the above photo was taken the bolts were coated with Dicor self-leveling sealant, and the shim edges were sealed with Dicor non-leveling sealant and then coated with a couple coats of paint.





To level the three section of unistrut I mounted some strut perpendicular to the long runs to keep them level while designing and installing the shims.





wrenchtech, I am concerned I may be hijacking your thread. Say the word and I will cease and desist...

This is great info thank you.

[RLVmann]

That looks really good. Was exactly what I was envisioning. I hadn't thought of the shims. Thanks again for sharing!

[o1marc]

Originally Posted by RLVmann

That looks really good. Was exactly what I was envisioning. I hadn't thought of the shims. Are they just flat or have a angle / wedge to them? Thanks again for sharing!

Pretty clear close up pic of the tapered shim in the post right above yours.
I see you posted within a minute of that post so may not have seen it.

[RLVmann]

Yup. I just revised mine. Thanks. Did you cut those shims yourself?

[TheHubbardBus]

When I shamelessly rip off Comfort's unistrut mounting method, I'm going to give these shims a shot:

https://www.amazon.com/Pro-Project-N...4901294&sr=8-1

[RLVmann]

I have some of those I've used for other things. I only worry it would take multiple shims to achieve a level surface. I guess you could glue them together

[o1marc]

Originally Posted by RLVmann

I have some of those I've used for other things. I only worry it would take multiple shims to achieve a level surface. I guess you could glue them together

That will work, but if you had a foot of composite deck boards you could make custom ones like his.

[Ak3Spirit]

FYI: I’d sleeve the panel tie down bolts with PEX tube or like kind to protect solar panel frames. Sandwich a Teflon piece between the strut clip and frame for dissimilar metals. Lastly use Locktite on the bolt to spring nut connection and still run a torque wrench check as part of my scheduled maintenance.
FOOD 4 Thought:
I’d like my panels to be “lids” on roof storage bins. Been thinking of camed or pivot hinge system using HVAC actuators to open/close via remote control app that adjusts panels for greatest exposure (Watt Hrs). I viewed a YouTube vid of a van setup and the gain is substantial.
Good design on the strut rack!

[Chram]

So helpful! Would you be able to explain how you did the shims, and what you used for them?

[Tcbitt_PNW]

@comfort eagle, thanks for posting those pics, thats super helpful. I'm about to do my solar mount as well and think im going the unistrut route as well.
Question for those of you that have used unistrut, have you experienced any galvanic corrosion with cold galvanized against aluminum panel frames, or am I overthinking it?

[magnakansas]

Experience and published metallurgy articles all indicate little to no measurable activity between these two in contact with each other.

William

[Tejon7]

What he said ↑

And besides that, galvanic corrosion requires direct contact of dissimilar metals as well as an electrolyte (rainwater in our case). Most solar racks inherently minimize both by smooshing sealant around the roof penetrations and/or using shims like ComfortEagle, plus creating a rain-protective "roof" of solar panels overtop the strut.

You can get aluminum strut channel, but unless you're converting your bus into a submarine the regular 'ol zinc should be fine. The extra cost for aluminum strut might be worth it for weight savings, but not for corrosion prevention IMO.

Edit: Tcbitt_PNW, sorry, I didn't read your post correctly the first time. I thought you were talking about steel strut on aluminum roof, but you meant aluminum solar panels on steel strut. My original reply doesn't make perfect sense, but I'm leaving it out of laziness

[DeMac]

Aluminum bolted to the non zinc coated factory steel yields a different result.







These are the factory installed aluminum strut that supported the rear condenser, over the RE. Bus was 12 years old at the time of picture.

Note: more rust where the most pressure a was, not where the bolts penetrated

[HamSkoolie]

Originally Posted by DeMac

Aluminum bolted to the non zinc coated factory steel yields a different result.


These are the factory installed aluminum strut that supported the rear condenser, over the RE. Bus was 12 years old at the time of picture.

Note: more rust where the most pressure a was, not where the bolts penetrated

Removed the pics for brevity....
1) That looks like the evaporator mounts on the exterior of a roof mount.

2) My 1996 had the condenser mounted the same way and there was almost zero corrosion but my roof is galvanized or galvannealed.

[HamSkoolie]

Originally Posted by magnakansas

Experience and published metallurgy articles all indicate little to no measurable activity between these two in contact with each other.

William

On the F-4 Phantom and F-18 Hornet both of which used large quantities of aluminum, our steel hardware was zinc chromated on the surface and while in a salt environment we were always battling corrosion somewhere on the aircraft, the zinc chromate to aluminum fixtures, were rarely an issue.

[DeMac]

Originally Posted by HamSkoolie

Removed the pics for brevity....
1) That looks like the evaporator mounts on the exterior of a roof mount.

------------
Yes. The, Evaporator not Condenser.

[HamSkoolie]

Originally Posted by DeMac

------------
Yes. The, Evaporator not Condenser.

Okay, had mine patched with packing tape for the winter after pulling the evap. They're now sealed with 16ga galvanized patches riveted on with zink coated steel rivets and sealed with polyurethane PL 3X adhesive. The patches were cut from the removed window surround panels and the harbor freight 16ga rated metal shears cut that metal quite nicely.