Z-brackets Recommendations for Large Solar Panel Install

[WanderingAlbatross]

We are installing a single 400 watt panel on our Class C motorhome. The plan is to use 8 z-brackets and large expanding rivets into the fiberglass overcab.

I am wondering if there are any particular extra strength z-brackets people would recommend for such an installation. Is aluminum sufficient or do I need to go with stainless steel brackets? A bonus if they are low profile (<1" offset from the surface).

Thanks!

 

[42OhmsPA]

We are installing a single 400 watt panel on our Class C motorhome. The plan is to use 8 z-brackets and large expanding rivets into the fiberglass overcab.

I am wondering if there are any particular extra strength z-brackets people would recommend for such an installation. Is aluminum sufficient or do I need to go with stainless steel brackets? A bonus if they are low profile (<1" offset from the surface).

Thanks!

My opinion. If your using 8 of them you'll be fine with whatever metal you use.
I can understand the low offset being a bonus for an RV due to clearance but it's actually a negative for panel performance, you want airflow under the panel for cooling.

 

[WanderingAlbatross]

Given 8 brackets, it sounds like we should be fine. Good to know. I am also planning to use a residential panel with a high level of rigidity (REC Alpha Pure) with a top load capability of + 7000 Pa.

Understood regarding cooling and not going with too low profile of a mount. Most of the z-brackets I have seen are in the 1 inch offset range which seems reasonable.

Slightly different question, but along the same lines, are there any fairings/skirts that come as recommended? I was hoping to put a skirt on the front edge of the panel to reduce wind noise, aerodynamic drag, tree branches getting stuck under the panel, etc.

 

[zulu]

We also used 8 Z-brackets on each of the three 365W REC N-PEAK 2 panels (69" x 41") on our Class A -- Panel Photo (before Dicor was applied to all the bracket screws).

 

[WanderingAlbatross]

Very nice. Those look like some solid z-brackets. Are you happy with how the brackets are holding down the large panels?

Also, how have you liked the REC panels?

 

[zulu]

Only installed them a few months ago, but my three RECs seem to be very efficient, especially since they've been operating mostly in the shade on my parked RV.

 

[HRTKD]

I have 320 watt panels on the top of my toy hauler. I used six standard Z brackets to hold them down to my rubber roof. Each bracket has at least one of the two fasteners in the wood truss of the roof.

If I had it to do over again, I would probably use some sort of Unistrut instead of the Z brackets.

 

[WanderingAlbatross]

Is the main benefit of the Unistrut that you get to pick the bolt locations into the roof to more easily align with the trailer's wood truss structure? Basically, does it provide greater mounting flexibility? Also, it seems like the added strength of the Unistrut would not hurt.

 

[HRTKD]

Is the main benefit of the Unistrut that you get to pick the bolt locations into the roof to more easily align with the trailer's wood truss structure? Basically, does it provide greater mounting flexibility? Also, it seems like the added strength of the Unistrut would not hurt.

With Unistrut:
1. You choose where the fasteners go
2. It's a heck of a lot easier than Z brackets
3. It's more flexible should you decide to go with larger/smaller panels
4. It's way easier to remove a panel from the room

The one reservation I have with the Unistrut is that it may mess with the drainage pattern on a roof.

 

[WanderingAlbatross]

With these larger panels, do you people often put tethers on them just in case the mounts fail?

If so, what is the preferred material? Stainless steel cable? Kevlar bridle cable?

 

[HRTKD]

If you were to use eight brackets, you would have bigger roof problems than just a solar panel if that wasn't enough to keep it secure.

Any panel affixed to a roof with adhesive should include a tether. Panels with brackets that are secured into more than just the substrate (plywood) of the roof, do not require tethers.

 

[Rocketman]

Make your own Z brackets. Just get alum angles- cut them - bolt one to the frame attach one the roof and both them together- easy.

Plus you can compensate for slightly curved roofs.

 

[WanderingAlbatross]

In our case, we would be using expanding rivets into the fiberglass front cap. The front cap looks to be a fiberglass shell over an aluminum square stock structure.

Here is a photo of the front cap and a CAD drawing of the potential layout as a reference.

 

[HRTKD]

If you're sure you can get the rivets into the aluminum frame that should work. I don't have tons of experience with rivets, so a machine screw would be my goto fastener.

 

[Bluedog225]

Yeah. Expanding rivet into fiberglass with a cyclical load seems subject to wear and failure.

 

[WanderingAlbatross]

Understood. We are considering putting aluminum backer plates behind the fiberglass to give the rivets additional strength. This would require removing the overcab headliner, but it looks to be doable.

 

[Bluedog225]

Sounds like a reasonable plan. If you are going to the trouble, I’d put a good adhesive or sealant on the backer plate to limit movement against the glass.

 

[12VoltInstalls]

Panels with brackets that are secured into more than just the substrate (plywood) of the roof, do not require tethers

We are considering putting aluminum backer plates behind the fiberglass to give the rivets additional strength

That is a requirement imho.
65mph solar panels hitting the following vehicle is more than inconvenient, there’s morality involved.

 

[HRTKD]

That is a requirement imho.
65mph solar panels hitting the following vehicle is more than inconvenient, there’s morality involved.

A panel, coming loose after being secured with 8 Z brackets into more than the substrate, is going to laugh at a tether.

 

[12VoltInstalls]

aluminum backer plates behind the fiberglass

That’s not a tether though?

 

[AmyG]

If you can remove the headliner, won't you be able to see where the aluminum frame is? If so, then at least some of your brackets could be attached with through bolts to the frame.

 

[WanderingAlbatross]

I was thinking about the implications of connecting the z-backets through the fiberglass to the aluminum supporting structure. It is a good question because that would provide a significant increase in mounting strength.

It might be unfounded, but one concern might be the flexing of the fiberglass overcab with respect to the aluminum frame. I have not removed the headliner, but if I push down on the outside of the overcab fiberglass it feels like there is about a 1/4" to 3/8" air gap between the fiberglass and the aluminum. These lightweight Sprinter-based Class C motorhomes are not especially rigid. There is a chance that bolting through the fiberglass into the aluminum could lead to the fiberglass fracturing. This concept was what led to the idea of putting aluminum backer plates on the back of the fiberglass overcab because the backer plates would move with the fiberglass as it flexed.

Does this sound like a reason issue to be concerned with? Thanks!

 

[AmyG]

My trailer has an aluminum skin so I really can't comment on the potential for fracturing the fiberglass, but the fact that it flexes that much would make me nervous about mounting panel brackets to it without anything going through to the frame, even with backer plates. I think I'd just take the headliner down if you can and see what things look like. Maybe you could add a spacer between the frame and the fiberglass to keep it from flexing over the frame where your bracket bolts will go? Some rubber bushings or washers that the bolts would go through? Hopefully somebody on the forum has some experience with mounting to this kind of overcab and can share some experience.

 

[HRTKD]

This concept was what led to the idea of putting aluminum backer plates on the back of the fiberglass overcab because the backer plates would move with the fiberglass as it flexed.

Nope, nope, nope. PV panels mounted only into the fiberglass is not going to end well.

 

[WanderingAlbatross]

I'll plan to pull the headliner and look around to see how the aluminum structure is set up. Thanks for the feedback.