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Comment by negative_zero | Hacker News Reader

EEE here. I've not looked at these in detail myself as they are illegal in my country. Off the top of my head, the big problem I see is that, since you are injecting power BEHIND the circuit breaker an end-user can overload a circuit.

i.e You have a circuit with max current 16A; clever end-user plugs in 3 x 800W panels into different sockets BUT they are unfortunately on the same circuit; now 26A can be potentially drawn through a single cable IN THE WALL without tripping the breaker. This is a BIG fire hazard.

And you can't wave this away with instructions. It has to be 100% impossible for an end-user to do this.

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That's why in Germany you are limited to at most 800 W for you house with plug-in solar.

Of course your argument still stands, but we're talking about at most 3.5 A extra current, not 10 A. Home installations seem to be adequately sized to be able to handle that load. At least I'm not aware of any reported incidents, and people have been putting them up for quite a few years already. And typically, German regulations err on the side of caution.

But sure, with 110 V, you will have more problems with the extra current for the same power, so in the American grid there could be further precautions necessary.

You cannot rely on that limit though. People WILL plug in more than that. The whole system has to be kept inherently safe. All other concerns are solvable, but I don't see how you solve this, bar having a special balcony-solar-socket installed where an electrician has verified that it will be safe in all scenarios.

Why? It works in many countries without incident. What makes the US different?

Americans are, for the most part, fucking morons. We invented the infamous warning labels like DO NOT EAT THE TONER CARTRIDGE or DO NOT HOLD THE CHAINSAW BY THE BLADE or REMOVE CHILD BEFORE FOLDING STROLLER or PEANUTS: CONTAINS NUTS

We're also very litigious, as it isn't hard to convince a jury to award damages to a fellow moron.

Everybody in the world is a moron. Americans just recognize some places where we are morons and try to prevent stupid people (which includes me and you!) from doing some stupid things.

Not everything, Americans do get by with doing other moronic things that other countries do things to prevent. However other countries also do their own moronic things that Americans are much less likely to.

Italy has the "Do not store your cat under the seat" warning. They do NOT put it on Italian-market scooters and they definitely DO put them on US-market scooters.

https://members.modernvespa.net/brian_herwick_-_coolass/uplo...

It would in practice be (mostly) fine, just as it is elsewhere. But electrical safety principles in the US are typically "must be safe regardless of the dumbest possible use" so that "mostly" is a big obstacle.

I would contest it's without incident. The US is higher risk since it uses 120V => the currents are x2 higher and US electrical safety standards are an eclectic mess of: world leading and 3rd world.

Not picking on the US though. These panels in their current incarnation, are lowering the level of safety of electrical everywhere.

This is all just my opinion though. A lot of my background is in compliance. I've been frustrated by some obvious electrical safety advancements that are STILL not being implemented. I also have first hand experience with many many signed off electrical systems which were death traps. This all biases me heavily towards not compromising on electrical safety. But maybe I am overreacting.

I sincerely get your concern. Clearly explain on the box what NOT to do and be explicit about the risk. Use an icon of a house on fire. Done. Life is risk, and regulating and banning things based on the lowest common denominator of human judgement is a fool's errand. Should we ban vehicles as well since about 40k people die from vehicle related fatalities annually?

In my view it's more that: electrical safety has advanced to it's current "version" and allowing these panels is a regression in safety. There's already plenty of products/theoretical-products that are banned and/or tightly controlled for electrical safety sakes (suicide cable is the poster child).

To use your car analogy, we're not banning vehicles. We're disable one of the airbags when enabling fuel economy mode.

I'm still working through the UK rules, ( https://assets.publishing.service.gov.uk/media/6a60a03c47af6... ) but one of those is explicitly addressing that: no more than 1 such device is allowed per circuit. Also those are 3.5A each on our voltage.

> you can't wave this away with instructions

But apparently you can with legislation about instructions.

Edit: government safety investigation https://assets.publishing.service.gov.uk/media/6a32bfea0bea2...

Final edit: "61% of respondents support having one device per household circuit while 19% considered that only a single plug-in solar device should be permitted per premises citing alignment with 44 Engineering Recommendations G98 Issue 2 Amendment 1, impact on the network, old wiring in properties and the ability of consumers to correctly identify separate electrical circuits.

Government response: Having considered consultation responses and stakeholder feedback, the government's approach is to limit the deployment to one per power circuit, subject to corresponding changes to the G98. Some respondents suggested limiting the total capacity per dwelling to 800VA, but we think the evidence for doing this is weak considering most UK dwellings have a minimum of two power circuits"

-- i.e. they thought about it and the concerns got outvoted.

It's probably fine. There's a lot worse lurking in outdated UK installations. Then we get on to ring circuits, which the rest of the world disagrees with and also seem to be fine.

Wait, people in the UK actually follow those instructions?

In the US, even with a warning, you'd get regular home fires as people hooked one of these panels into every available outlet just because they can. I wish I were joking.

Thanks for those links I will check them out.

I hope it's at least "probably fine". I've seen some pretty shoddy electrical work in my lifetime (including new installs) and am now of the mind that the deep-defense-in-depth of electrical safety we have these days is to also "cope" with shitty electrician work.

Wouldn't all three being plugged in be likely to trip the breaker, because it's just AC and the breaker can't really tell whether energy is flowing "forwards" or "backwards"?

Seems like the worst case scenario is when you mix solar panels with load on the same circuit.

800W at 110v is about 7 amps. Suppose you have a 7 amp solar inverter plugged in as the first thing on that circuit. Further down the line, you have 22 amps worth of load. The circuit breaker sees 15 amps, but the wiring between the panel and the load is carrying 22 amps, which would ordinarily trip the breaker but it doesn't because the solar setup is masking it.

I'm not an electrician. Perhaps wiring code has enough safety margin that being 800 watts over on some circuit isn't actually a serious safety concern, but I could understand why this might not be allowed.

The EU is on 230v, so maybe it's a bit more practical over there because you can add twice the solar capacity for the same amount of additional current you'd have in the US, so they aren't eating into the safety margin quite as much. Though it seems they also use thinner wire gauge generally, so maybe the difference is moot.

Yup. Worst case scenario is indeed mixing generation and load on the same circuit. And you have to assume that some number of people will manage to do that and create a fire hazard. To connect it safely, you need to know the circuit layouts and the rating of the cables. This is not something solvable with a safety sticker and safety instructions. A huge amount of effort has gone into making domestic electrical installs as inherently safe as possible and these panels are a back door to that.

Don't get me wrong, I think they're a spectacular idea, especially for renters. But you'd need an electrician to check the circuit and maybe even have a special balcony-solar-plug to prevent people plugging in too many panels in the wrong locations.

Quick edit: Random idea. I guess if the panel could communicate with the RCBO it's connected to and that RCBO can dynamically alter it's trip current could also solve it. But again, that's an electrician call and new thing installed.

There is a YouTube video where a guy tested how many amps are required before a fire starts and it was like 70 iirc. 30 amps didn’t even get the wires hot. I’m not sure that’s true after several hours of continuous usage of multiple space heaters plus plug in solar, for example. It’s not a risk I would even entertain but I think the real risk is pretty low.

I’d also guess bad inverter hardware could cause lots of dirty/noisy AC power effects and damage other equipment on the system. This definitely doesn’t sound like a very safe approach without a lot of conditions being met and exactly like your example there are too many ways it can go wrong.

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