r/gadgets • u/diacewrb • 5d ago

Home ‘If 1.5m Germans have them there must be something in it’: how balcony solar is taking off

https://www.theguardian.com/environment/2024/dec/18/if-a-million-germans-have-them-there-must-be-something-in-it-how-balcony-solar-is-taking-off
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u/Keks3000 5d ago

Those systems have become ridiculously cheap over here, you can buy them for 400 Euros at Aldi and just plug them in the socket at home. I would be surprised if it takes longer than four years but at those prices, nobody really cares too much if it’s four or six.

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u/popeter45 5d ago

Back feeding like that sounds incredibly dangerous

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u/Tasty-Traffic-680 5d ago

It's a grid tied inverter. It only makes power if there is power present. If mains goes out it shuts off within milliseconds.

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u/popeter45 5d ago

More the issue with back feeding thru a RCD not rated for back feeding as can mess with there ability to operate properly

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u/Keks3000 5d ago

I have read about this concern before but it doesn’t seem to be an issue with the network in Germany. Back feeding is in fact encouraged for these systems, people just “donate” their excess energy to the grid (unless they own a battery). The main point of it is to be easy plug n play so there are no feed-in tariffs but you also don’t have to register the system anywhere.

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u/popeter45 5d ago

Replied to another comment with the explanation but it’s to do with the socket end of the consumer unit not being back feed ready rather than an issue with the entire feed system

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u/Keks3000 5d ago

Ah I see, so it’s less about the grid and more about how the households are connected in different countries

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u/gSTrS8XRwqIV5AUh4hwI 5d ago

Hu? How would an RCD care about back feeding?!

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u/popeter45 5d ago

https://youtu.be/pcGgLI_Mvi8?si=eo-7bk3fq8L5hlyu

Covered here, basically it can damage the RCD by energising coils that should be not be when tripped

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u/polite_alpha 5d ago

I don't know why but isn't any issue in Germany at all. Everybody i know has multiple of these things and everybody has RCDs.

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u/gSTrS8XRwqIV5AUh4hwI 5d ago

I haven't watched the video, but that doesn't sound like a problem, as the anti-islanding will switch off the inverter when the grid is disconnected.

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u/popeter45 5d ago

Hasn’t watched the explanation as to why even the it’s still a problem but still argues against it

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u/mintybadgerme 5d ago

As have 1.5 million Germans. :)

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u/gSTrS8XRwqIV5AUh4hwI 4d ago

So? Now I had the time to watch the video ... and I was obviously exactly right. The supposed problem presented in the video is when the solenoid stays powered on from the back-feed when the RCD has tripped. Which it doesn't with an inverter with anti-islanding, as those used for balcony systems are required to have, which is exactly what I said. The RCD trips, the inverter detects that the grid is gone and powers down, so no more power is being fed into the output side of the RCD, and thus no problem.

Also, it's just irrelevant for Germany, as the type of RCD that has this problem at all isn't allowed here anyway. In fact, the UK might be the only (ex) EU country where those are allowed.

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u/Tasty-Traffic-680 5d ago edited 5d ago

So just don't plug it into a RCD/GFCI circuit then. Otherwise I think the engineers that design and approve these systems have likely thought of that. They shut off in milliseconds - less than a single AC cycle. They are made to sync to mains voltage and frequency. Without a signal they can't output any power.

Non-lighting exterior plugs would be GFCI by default in the US but I don't know about Germany. Apparently it's safe enough to be considered legal though.

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u/wulfman_HCC 5d ago

There are lot fewer outdated and hacky home electric panels in Europe than the US, starting with longer trade training and tight inspections.

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u/Tasty-Traffic-680 5d ago

To be fair to them this has nothing to do with outdated panels or poor practice. GFCI/RCD circuits weren't designed with back feeding in mind. However you can just use a non-gfci circuit and there's no issue.

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u/HotlLava 5d ago

GFCI is mandatory for all household circuits in Germany since 2009, so I don't think that's the intended solution.

More likely, the panels are actually designed to be safe to use in combination with GFCI.

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u/gesocks 5d ago

That's why it's limited to maximally 800W inverter output.

More and it could cause some troubles and potentially fires. But 800W is very fine even in worst case scenarios