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Fusing solar panels?
#1
Do I need to fuse my solar panels? If so wich fuse would you use?
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#2
Depends where you are in the world as to what standards applies. In Australia, yes you do.
The manufacturers spec sheet for your panels will say the fuse size per string.
The correct type has to be used for PV, called gPV basically high DC voltage rated, fast blow types.
Usually 38mm x 10mm size.
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Running off solar, DIY & electronics fan :-)
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#3
Since the OP is in Germany, that kinda narrows it down to his location Wink
I agree with Repacket. It depends on the building codes in your area. But most likely, you do need to fuse your panels.

You also should have at least 1 cutoff switch that is easily accessible outside of your building. This is for first responders or if you need to shut it down asap.
I believe some even install a separate cutoff for each series connection run for added safety.

I know you are asking about fuses, but I figure that cuffoff panels would be soon to follow as well Wink
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#4
How could such a cutoff panel look like? Any pictures or links?

Would an automatic circuit breaker do the job. Both in one?
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#5
Either a standard breaker panel box rated for DC loads, or a manual pull handle style used on A/C units.

You can use a breaker that "looks" similar to what is in a standard breaker box, however it MUST be rated for DC loads. These breakers are usually a little more expensive and a bit beefier as they have to handle directional current instead of alternating current.

For a good explanation, please watch bigclivedotcom's video on the subject:

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#6
I can only find very expensive ones of these. Any cheaper models available? Or any other possibilities to fuse and disconnect the solar panels?
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#7
You could get something like this:
https://www.homedepot.com/p/GE-30-Amp-12.../100576894
30 Amp 120/240-Volt 240-Watt Fused AC Disconnect
$11USD

They have heavy copper lugs and can handle high arcs during disconnect. They are nice because you can pull the disconnect, turn it upside-down and re-insert it as there's a built in holder, close the box so it doesn't accidentally get turned on.

Here's the exact same model that Clive was showing:
https://www.amazon.co.uk/Circuit-Breaker...B017Q6DL2Y
it's only about $11USD as well
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#8
The disconnect type switches are cheaper than breakers, but you still need the PV rated fuse.
These are popular here:
http://www.zjbenyswitch.com/DC-Isolator-...-1818.html
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#9
I have a combiner/disconnect at the PV array on outside of house per city code. It happens to be circuit breakers because the Midnight Solar combiner box with 'all-off-handle' encourages them. But electrically I don't see why an actual 'fuse' (overload/short) function of the circuit breaker would be needed as panels can be shorted and not hurt anything.

I also have a circuit breakers on the combined PV array strings just before the Charge Controller. Not sure if this is required by code or not. This serves as PV array cutoffs inside the house conveniently located next to the Charge Controllers. For this combined circuit (of several strings of panels) I'm pretty sure a circuit breaker is recommended to protect the wire and/or Charge Controller - but not sure what that would be. There are already lightning (surge) arresters at the outside combiner boxes to take of lightning - so what else could cause a 'surge' beyond the rated capacity of the wire / system might be the question.

Interesting topic - maybe the simple on/off (which is convenient and for safety working on system) is so often provided by circuit breaks that fusing (overload) is combined because no makes simple on/off switches that snap into combiner boxes.
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#10
(05-28-2019, 02:21 AM)OffGridInTheCity Wrote: But electrically I don't see why an actual 'fuse' (overload/short) function of the circuit breaker would be needed as panels can be shorted and not hurt anything.

A single panel shorted won't do anything, but a string of panels shorted will create a blinding flash. Depending on how many panels you have, shorting the wires could easily become as powerful than a welder, or more so. Not to mention all that current flowing as well. I'd hate to be in between those wires.

What is the voltage that your solar panel string operates at?

(05-28-2019, 02:21 AM)OffGridInTheCity Wrote: I also have a circuit breakers on the combined PV array strings just before the Charge Controller. Not sure if this is required by code or not. This serves as PV array cutoffs inside the house conveniently located next to the Charge Controllers. For this combined circuit (of several strings of panels) I'm pretty sure a circuit breaker is recommended to protect the wire and/or Charge Controller - but not sure what that would be. There are already lightning (surge) arresters at the outside combiner boxes to take of lightning - so what else could cause a 'surge' beyond the rated capacity of the wire / system might be the question.

Interesting topic - maybe the simple on/off (which is convenient and for safety working on system) is so often provided by circuit breaks that fusing (overload) is combined because no makes simple on/off switches that snap into combiner boxes.

A circuit breaker in a combiner box would basically be replacing the fuse. I think what Redpacket was alluding to was having the fuse as a failsafe. Just in case the circuit breaker didn't, well, break as expected. When dealing with high voltages, more points of controlled failure is desired. You never know when one will fail and the other saves your, or others, lives.

But, with that said, most homes only have 3 breakers. Mains at the pole, mains in the house panel, and one for each circuit. So having 2 breakers already may be good, but a 3rd wouldn't hurt Wink
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