What about can I expect from panels on a cloudy day?

[SunEagle]

It's 12V stuff except for the red/green 120V display which is hooked to an arc fault/gfci breaker.

Certainly you both aren't asserting airplane instrument panels, vehicle dashboards and equipment like excavators and the like are made of cement tile backer board.

You are correct. If all of the voltages are DC and below 50V then you should have nothing to worry about. But if any source is AC and above 50V look out.

[SunEagle]

This is just silly. Metal conduit and boxes come to mind as well as almost every household appliance. They do not use "non-conductive" materials. They use EGC to ensure the breaker comes into play should the metal surfaces become energized.

This reminds me of people that think bathroom outlets can't be too close to the sink.

This forum is full of people using charge controllers and inverters that are not UL listed and do not really have proper protection inside the units. This stuff poses far more fire or electrocution danger than mounting 12V equipment to an aluminum sheet.

As I have said if the voltage is DC and below 50V then you have nothing to worry about. As for others that perform a DIY electrical installation not using UL listed or over current protection is a gamble. Most people do not just use battery voltage to power their loads. The have some type of inverter that not only boosts the voltage but inverts it to AC. Those are the ones that I try to steer away from what they are doing or at least get some professional electrical help.

[SunEagle]

120V stuff is in a little Eaton panel fed with 30 amps.

Looks good to me

[Ampster]

Looks good to me

I don't see a problem either. I don't know what all the fuss was about.

[Mike90250]

I don't see a problem either. I don't know what all the fuss was about.

The fuss is all about thinking ahead. Voltage. Insulation. AC DC insulated components. What if this goes wrong?

Some people want to be validated for bad work. Now there appears a 120VAC breaker panel next to the metal plate. Which wires cross where? I say I don't like it because I have lots of questions. Someone else is happy if it's DC <50V

The fuss is 40 years of spacecraft engineering experience where all things get considered. That does not go away lightly,

[Ampster]

The fuss is all about thinking ahead. Voltage. Insulation. AC DC insulated components. What if this goes wrong?
..........

The poster asked a number of ways what could go wrong and did not get a clear answer about mounting on metal. He was not building a Spacecraft so why would those standards apply? He did asked why airplanes can mount electronics on metal and got no response from the Spacecraft Engineer. That was what I meant by fuss. Anybody can say the sky is falling, the value of forums like this are that people can get valuable feedback.
To be clear I am not advocating unsafe practices. As several well respected members posted, there is a lot of electronics that comes in metal cabinets.

[sdold]

Those are panel-mounted components so the metal panel makes sense, but using a road sign looks really odd. It makes one wonder why you didn't at least turn it over and use the bare metal side. That equipment looks like it belongs in at least a NEMA 4 rainproof cabinet, are you sure it's OK where it is, exposed like that?

[Mike90250]

As several well respected members posted, there is a lot of electronics that comes in metal cabinets.

And those are generally Rated Cabinets, well engineered, with proper knockouts and mounting hardpoints.