Can I "wall-mount" to a metal backing?

Wood doesn't last well in my climate. Cement board doesn't seem designed to carry much weight. Plywood, if obtainable, quickly falls apart in the humidity. Concrete walls exist, but are not very portable. The whole system is expected to be moved to a different building within two years, so having the main units "easily" transportable would be nice.

I'm thinking about mounting my charge controllers, inverter, breaker boxes, etc. to either a welded frame (e.g. from square tubing), or to a piece of thin metal plate. My concerns have to do with the risks of shorting and/or grounding with components directly attached to a conductor. Has anyone tried this, or would it be too foolish?

Additionally, the powerwall battery weighs in at around 115 kilograms--no featherweight to be sure, and I'm not even sure the block wall would support it (concrete blocks are only three inches thick in this country, yes, just 3" thick, and the masonry work is rarely perfectly square and level).

Possible advantages to having a steel backing would include termite resistance, heat dissipation, and no issue with weakening of the material due to softening glue (plywood) or mildew, etc. But if the conductivity would be a problem, this might not be workable.

Thoughts, especially from the electrical experts, are most welcome.

I work at a laser cutting shop, and did exactly what you want, but in my enclosed trailer, so its constantly bouncing around and wanting to rip off the wall. I mounted a 200ah 48v Battery (Over 200lbs!) and a Deye 8k inverter on the wall to a 12ga 304 Stainless Steel Sheet. I documented it on my YouTube Channel: https://www.youtube.com/@McKenzieHobbies

For what its worth, I have also mounted 80-100lbs inverters to 1/2" Hardie Board before, and it was more than strong enough.

All of your metal enclosures, like inverter and electrical panels, should be bonded together with a ground wire and to a ground rod. PV panels are sometimes mounted on metal ground mounts or metal roofs.

No problem that the structure is metal too. At least here in the US, metal in a building including water pipe, gas pipe, and steel in the concrete foundation should also be bonded to the grounding system.

Don't leave the metal structure ungrounded. If a wire was abraded and contacted the structure, you want it to have a path back to inverter chassis.

"thin metal plate", if too flexible it will bend under weight. But if it has a couple bends, forms a structure that is rigid. As a flat sheet, could serve to distribute weight over many screws. Some brands of equipment have mounting plates. You'll have to deal with all the weight at once to move together, but maybe high frequency inverter etc. won't be too much. Only have to disconnect battery.

Your thin masonry could work if used to form a right angle, like corner of a building. Our structural concrete blocks have rebar running inside horizontal and vertical.

Some plywood is waterproof glue. Of course it could still rot if not painted. Boats of made of wood.

Hedges covered it. Bonded and grounded.

I used something we call strut. Aka super strut, unistrut, channel strut. Very strong. Corrosion resistant. Easy to assemble and take apart. Somewhat expensive for the specialized fittings. Square metal tube would work as well.

Coastal Texas is pretty warm and humid as well. But I can’t see why exterior plywood, properly painted, wouldn’t last if kept out of the elements (rain).

Edit to add-you could also cover the grounded and bonded metal plate with a non-conductive sheet of something.

I don't think we have such a thing as "hardie board" here; at least, I don't remember seeing any. We do have one type of plywood that is somewhat protected from the humidity by being inside a plastic sandwich. The edges are still exposed, though. I've bought a piece of plywood that I had intended to use for nest boxes for the chickens, but as I did not make them immediately, within just two or three months, the plywood was already unusable. The layers were all coming apart--it was not the plastic sandwich variety. Lesson learned. I definitely do not wish to use standard plywood for this solar project.

The plasticated plywood (I really don't know what to call this stuff...I never saw it in America, but perhaps they have it there now?) might work, but I'd be a little concerned that if there were some electrical hot spot, the plastic could catch fire more readily than wood would.

I've thought a bit about whiteboard--the stuff used for classrooms: it has a nice smooth surface. But the problem with it is that it still has a type of composite wood backing, and ants love to chew through it and nest in it. Been there. Unfortunately, ants are going to be a problem anywhere in this country, and some types like to nest in electronics, too. I've watched ants eat roofing paint that had been painted as lettering on top of standard exterior latex. They didn't bother the latex, just the oil-based stuff on top. You just never know what they'll do next!

My fear with grounding is that it might attract lightning. Almost nothing around here is grounded, and it's an awful thing to have the best ground for a kilometer around.

That’s a whole topic on grounding and lightning. Not sure it works the way you think it does. All the ground is grounded.

Bluedog225 said:

That’s a whole topic on grounding and lightning. Not sure it works the way you think it does. All the ground is grounded.

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In theory, yes, you're right. But in practice, the kind of soil we have, which is largely clay, is not very conductive. This means if one creates a good ground somewhere, it will have superior conductivity, perhaps even better than the nearby tree. Again, I have personal experience with this. The very first storm we had after I had carefully grounded my inverter system knocked out my UPS. I never connected to ground again, and never had a problem again. I posted the full story once here somewhere.

Metal objects attract lightning if tall.
Your PV array out in a field might be an issue. Hope the inverter mount isn't.
For protection, you can set a lightning rod above the vulnerable items, with a wire to conduct the strike to the ground. After which it will spread through the ground, taking lower resistance parallel path through wires and metal if available.

Maybe one should form an underground "fence" with rods driven all around the area, tied together with wire. So a nearby strike is diverted around rather than going through dirt under your system. I don't think I've seen that described underground, only overhead.

Norwasian said:

The very first storm we had after I had carefully grounded my inverter system knocked out my UPS. I never connected to ground again, and never had a problem again. I posted the full story once here somewhere.

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We prefer single point ground, but with an PV array at a distance that is difficult.

For electrical safety, all metal frames and mounts need to be bonded together. We also ground chassis, and bond neutral to ground. GFCI (RCB) are good for human safety when touching appliances, but they wouldn't protect in case of a short inside inverter or other equipment.

Hedges said:

Metal objects attract lightning if tall.

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In my case, I believe the lightning connected with the large adjacent pond. I had pounded a 2-meter copper-clad ground rod clear down to the water level to make sure I had a good ground. Too good, I guess. At that time I had no solar panels. The ground wire came into the house from that rod and went to a plug powered by my 24-volt PSW inverter coming off of about 200 Ah of flooded batts. The batts were charged by a separate, IOTA charger. The only thing grounded in the house was that outlet, and the only thing damaged was that which had been plugged to it. Nothing else in the house was affected, including many other devices which were plugged to grid power. The grid power was not grounded at the poles either (third-world country).

I guess "When in Thailand, do as the Thais do."

But you should bond PV panel frames back to inverter chassis. That will keep the at the same potential so you don't get a DC shock in the event of a fault. Or an AC shock in normal operation - many of the cheap AIO superimpose AC on PV+/- terminals, so PV panels capacitively couple that to frames. A number of people on the forum have received mild shock from that.

Hedges said:

I guess "When in Thailand, do as the Thais do."

But you should bond PV panel frames back to inverter chassis. That will keep the at the same potential so you don't get a DC shock in the event of a fault. Or an AC shock in normal operation - many of the cheap AIO superimpose AC on PV+/- terminals, so PV panels capacitively couple that to frames. A number of people on the forum have received mild shock from that.

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I'd be interested in knowing if the LVTOPSUN, apparently a rebranded model of Deye, would exhibit these characteristics. That's what I got--an off-grid hybrid model. There is no grid power in the village where I'll be installing this, so nobody is grounding anything. I don't yet know what their storms are like up there--it's a mountainous area, and I don't live there. (I'm building this for a church, actually, but it includes the pastor's house.)

If lightning strikes the panels, wouldn't that be sayonara to the inverter if they are bonded? And being at the heart of the system, it seems that would compromise the whole works.

I wish I knew what they were doing in Taiwan. It worked well. We had some of the most severe electrical storms one could imagine, and none of the buildings were ever struck. They had some kind of reverse lightning rod system that was energized in some way to create a lightning-opposing aura over the building...or so I understood via the crude explanation in English. I don't know quite what it was. But virtually every building had it--and probably needed it, because the storms were so severe. I don't think I've seen that kind of a system used anywhere else.

If panels or inverter are stuck, expect them to be destroyed.
If a nearby strike, the EM wave induces current in wires. Use SPD for that, like the Midnight brand devices with MOV.
A nearby strike also puts current through the earth, which is why multiple places with ground rods could be a problem (also required in US for multiple structures having wires between them.)

You can't repel lightning. That would require potential has high as the lightning itself, which would then discharge to the earth because V/m too high for air.

What you can do is provide earth potential at a point higher than your protected stuff, so lightning hits your lightning rod first. Could be multiple rods on or near the building, with a wire draped between them. That is supposed to create a protected volume. This gets done for buildings where explosive ordinance are handled, etc.

Don't know if the DEYE has that issue, or just cheaper brands. But bond PV frames to inverter chassis. You already have PV cells wired to inverter electronics, so a path exists but goes through delicate parts.

Hedges said:

You can't repel lightning. That would require potential has high as the lightning itself, which would then discharge to the earth because V/m too high for air.

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Now you have me curious. I don't think they were actually intending to repel the lightning itself...I understood that they were preventing the...what are they called?...runners?...for the lightning from forming which create the lightning's path a few milliseconds before the strike. If no path is created through a particular ionized field, no lightning will follow it.

Maybe there is a way to discharge before stored energy is enough to cause lightning, but I've never heard of that. I think such a system would sometimes get struck.

I've only seen info on protection by providing an easier path for lightning around the protected area. The runner is attracted to it by electric field.

This isn't my area of expertise, but have read some documentation, including for programs I was involved in some other part of.