Size to use for solar array disconnect?
- Thread starter calias
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WorldwideDave
Solar Enthusiast
This is a series string of 6 panels at over 10A each? 60 won't cut it I don't think. Not an expert, but that seems logical. If you are doing 2 parallel strings of 3 each then, maybe.
I have 15A inline on the ends of my strings, which then go into a MC4 Y cable/combiner/parallel cable, then into a 30A DC fuse for overcurrent protection. Not sure if I'm doing it right, but better to have some than none.
Brucey
Velcro Man
In a series string the voltage will increase, the current will remain the same. Assuming a single string and not parallel he should be ok with a 16A imo style disconnect. More headroom dor future parallel strings with a 32A unit.
WorldwideDave
Solar Enthusiast
I wish there was a way to graphically represent that with series strings. I struggle to get my head around this.
For example, if you have 12V, 100 W panel putting out 10A, you have 100W (on paper).
If you connect 4 of them in series, you have 48V and 10 A, how many watts are you putting out, 400W, or still 100W?
And if in parallel, if you connect 4 of them, you are still at 12V, with each putting out 10A for a total of 40A, but putting out just 330W, or 400W, or ?
I get stuck with this often.
SilverbackMP
Solar Addict
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- Apr 4, 2022
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Aren’t disconnects from solar arrays rated in volts? I seem to remember having to source all weather disconnects rated for 600v (Schneider or Square D for the win).
Fuzes and breakers are rated in amps.
I could be wrong here or they may have both ratings.
Fuzes and breakers are rated in amps.
I could be wrong here or they may have both ratings.
They are rated for both, just like you do not want a fuse to fail to extinguish a high current arc even after it's fried.
This is pretty solid for wiring in series if you only have six panels at 50v open. You can sometimes find them cheaper on eBay.
signaturesolar.com
This is pretty solid for wiring in series if you only have six panels at 50v open. You can sometimes find them cheaper on eBay.
IMO DC Disconnect Rooftop Isolator Switch | 4 Pole | 2 String
The IMO DC Disconnect Rooftop Isolator Switch ensures safe disconnection of rooftop solar systems, offering reliable operation and compliance with industry standards for enhanced system safety.
signaturesolar.com
ShaneC
Solar Enthusiast
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- Nov 3, 2022
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Watts = Voltage x Current
12v panel @ 10A = 120W
4x12v in series = 48v x 10A = 480W
4x12v in parallel = 12v x 40A = 480W
Size your breaker to current but also ensure your voltage doesn't exceed it's rating. Unlikely unless you have very high voltage strings.
WorldwideDave
Solar Enthusiast
Thank you so much.
I think that it's great that we talk about PV Isolators, and DC Breakers, and Inline fuses for parallel strings - see will's earlier videos - but there isn't a comprehensive guide on this.
Example: Today I learned that even if you have a DC breaker attached to your PV input, that if the series strings are then grouped in parallel (6s2p), you should inline fuse the series strings before connecting to the MC4 branch ("Y" or "Parallel") connector, before going into your DC breaker. Of course I've heard this all in different places as drawings on whiteboards, but an actual video walkthrough explaining someone's set up is rare to see, especially here, on the smaller/medium sized builds. Super big build? No problem, but not relatable. Super small build, like Will's early RV videos when he's wrapping up fuses he's bolted on batteries with electrical tape together, are in abundance.
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