Solar Panel Breaker

CYQK

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Sep 11, 2009
576
beneteau first 42 kenora
Designing my solar system and was wondering what you did for circuit protection
Should there be a breaker near as possible to the panels themselves or can a breaker be placed closer to the controller?
Want to place protection on the line in and also the line going out of the controller
Thks
 

Bob J.

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Apr 14, 2009
773
Sabre 28 NH
I just used an in-line fuse at the disconnect prior to connecting the panel input to the controller.
 
Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
Designing my solar system and was wondering what you did for circuit protection ...
I placed my controller at the Nav station. I have 2 x 40-watt panels, so have a DPoffDT switch for each panel just off the nav breaker panel. I can switch the panels from series to parallel. Also have a breaker between MPPT controller output and the main DC panel, bridging the feed from the OEM battery switches..
 
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Feb 6, 1998
11,667
Canadian Sailcraft 36T Casco Bay, ME
Designing my solar system and was wondering what you did for circuit protection
Should there be a breaker near as possible to the panels themselves or can a breaker be placed closer to the controller?
Want to place protection on the line in and also the line going out of the controller
Thks
Solar panels on boats are what are considered "current limited" meaning any sort of failure can't create more current that the wire can already handle (providing it was already sized correctly). Thus no fuse is really necessary, nor required under the ABYC standards, before the controller. On land based systems (much higher voltages) the NFPA/NEC require fusing before the controller. That said if you have a massive series array, with high voltage, a fuse before the controller is not an awful idea.

The batteries on the other hand are not current limited and can deliver thousands of amps into a dead short so any fuse for the PV system needs to be in the positive conductor within 7" of the "source of power" which is your battery bank.
 
Feb 16, 2012
198
Hunter 45 CC Alamitos Bay, Long Beach
We mounted 3 Kyrocia 135 w panels on a custom made aft arch. The wires from each panel were routed down, and into the boat (2005 Hunter 45 CC), and to a Breaker box with 3 separate breakers, located in the aft cabin. From there one set of wires were routed to the controller mounted in the main cabin near the battery's. The system has worked perfectly for the past 10 + years.
 

CYQK

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Sep 11, 2009
576
beneteau first 42 kenora
Wow
Thanks for some great replies
Have two 100 watt panels right now and plan to expand two more down the road
Have a 40 amp controller the person at the supply store says to put a 40amp breaker on the output conductor of the mppt
That sound right?
 
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
Wow
Thanks for some great replies
Have two 100 watt panels right now and plan to expand two more down the road
Have a 40 amp controller the person at the supply store says to put a 40amp breaker on the output conductor of the mppt
That sound right?
Depends on the wire size, circuit breakers protect the wire, not the device. Check an ampacity table.
 
Jul 1, 2010
962
Catalina 350 Lake Huron
Have a 40 amp controller the person at the supply store says to put a 40amp breaker on the output conductor of the mppt
That sound right?
Read Maine Sail's response above. An inline fuse at the battery is what is needed. (sufficient in size to protect the wiring between the battery and controller). If you put the fuse at the controller, any short in the wiring on the battery side would not be protected.
 
Feb 6, 1998
11,667
Canadian Sailcraft 36T Casco Bay, ME
We mounted 3 Kyrocia 135 w panels on a custom made aft arch. The wires from each panel were routed down, and into the boat (2005 Hunter 45 CC), and to a Breaker box with 3 separate breakers, located in the aft cabin. From there one set of wires were routed to the controller mounted in the main cabin near the battery's. The system has worked perfectly for the past 10 + years.
I hope they installed over current protection near the battery bank, not just where the PV cables enter the boat. I have seen a couple of controllers short out inside the box (both Chinese no-name) and luckily they tripped the battery side over current protection. Without the battery side OCP they both would have likely been full blown boat fires.
 

CYQK

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Sep 11, 2009
576
beneteau first 42 kenora
was asking about the output side of the controller
are the fuses at my buss good enough or do i need to install a fuse at the controller for the conductor headed to the buss?
 
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
was asking about the output side of the controller
are the fuses at my buss good enough or do i need to install a fuse at the controller for the conductor headed to the buss?
Yes. So long as the fuses are sized to protect the smallest wire in a circuit. If the wires leading from the panel to controller are 16 gauge, then fuse for 16 gauge wire.
 
Jul 1, 2010
962
Catalina 350 Lake Huron
was asking about the output side of the controller
are the fuses at my buss good enough or do i need to install a fuse at the controller for the conductor headed to the buss?
I may be wrong but I think you're still looking at this backwards. The fuse is to protect the wire from battery current if the controller or wiring shorted to ground, ie, the power would be coming from the battery and shorting to ground...the opposite of what happens when your controller was charging the battery. So the fuse in question has to be located at the battery (within 7"of, as Maine Sail stated) to protect the wire from burning up.

Concerning a fuse or breaker at the controller...you would likely have chosen a wire size for the run from the controller to the battery that was large enough to handle any amount of current the controller could provide. You would have also done a calculation to use a wire size that would minimize voltage drop between the controller and battery. This wire would not need to be fused at the controller because the controller could never put out enough current to burn it up. The battery easily could, though.
 
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Bob J.

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Apr 14, 2009
773
Sabre 28 NH
Both switches up, series, both down parallel, either one in center, panel not online.
Thank you very much Ron. Greatly appreciate it!!
I have 2-24 volt panels in series so I can charge either the 48 volt propulsion bank or the 12 volt housebank. This wiring configuration would allow me to parallel the panels for the house bank & get more amperage out of them. Nice!
 

CYQK

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Sep 11, 2009
576
beneteau first 42 kenora
Thks for the explain
Yes i was looking backwards
Was interested in a controller problem but that would cause the amps from the battery to go there so i get it now fuse at battery