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Old 12-02-2014, 11:35   #16
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Re: Switch for solar panel circuit

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Originally Posted by Dsanduril View Post
There really isn't a point to a breaker/fuse on the panel side, there is an absolute need at the battery end. A short from battery to ground/negative can lead to tremendous currents and requires a breaker with a high AIC.

Solar panels, on the other hand, are current limiting devices by nature. If a panel is rated at 8A it will put about 9A into a dead short. So what size breaker do you put in for that condition? 8.5A? There really is no breaker or fuse you can put in to protect against a panel to ground short because the current will not increase above Isc. If you size a breaker/fuse at even just 110% of normal current it will never open/trip.
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Old 12-02-2014, 11:58   #17
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Re: Switch for solar panel circuit

I added a switch allows me to take the panels out of the circuit when the engine is running and able to kick out more amps and the smart regulator not be confused by the voltage of the "trickle charge" of the solar panels.
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Old 12-02-2014, 12:01   #18
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Re: Switch for solar panel circuit

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I added a switch allows me to take the panels out of the circuit when the engine is running and able to kick out more amps and the smart regulator not be confused by the voltage of the "trickle charge" of the solar panels.
Why would it be " confused"

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Old 12-02-2014, 12:12   #19
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Re: Switch for solar panel circuit

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Hi Bill,

Glad you mentioned this point as it's something I've been thinking about as I finish the rewire of my boat. I plan to run alternator, solar and wind power outputs to a common bus and from there to a terminal fuse block on the battery. So that end of the hot wires will be protected but what about the other end?

For example, I have a 120 amp alternator and if the hot wire on that is shorted before it reaches the battery terminal fuse then that's a problem as well. But first, quick look at fuse options for that amperage I don't see any inline fuses that will work and installing a fuse block is not really the cleanest solution for my location. Maybe a terminal fuse on the stuc on the back of the alternator? Any other suggestions?
An alternator like a solar panel is a current limited device thus no requirement for a fuse at the alt or panel end. Battery end yes...
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Old 12-02-2014, 12:35   #20
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Re: Switch for solar panel circuit

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Originally Posted by goboatingnow View Post
Why would it be " confused"
When there are multiple smart controllers operating simultaneously they can interact in odd ways. With the solar panels charging and engine alternator running (using identical controllers as it happens) into a mostly charged battery, when the regulator opens the solar panels the alternator load increases and the engine reacts to the load. When the panels kick back in the engine runs a little easier. This on-off-on-off loading on the alternator can be very annoying to listen to. So I switch the panels off at that time.

For the size of panels considered here I am guessing that the maximum total current (for both panels at short circuit - Isc) is under 15A. Any switch that is rated at 15A and above will work nicely. You absolutely don't need battery switches and heavy duty circuit breakers to switch this load. You do need fusing at the battery for just about everything. The standards have gotten tighter for protecting wires at the batteries so you might review your situation there.

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Old 12-02-2014, 13:33   #21
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Re: Switch for solar panel circuit

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An alternator like a solar panel is a current limited device thus no requirement for a fuse at the alt or panel end. Battery end yes...
Oh yea. Doh! I knew that.

And since I will of course have the wire properly sized for the full output of the alternator, if it does short out then there will be no generation of smoke.
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Old 12-02-2014, 14:02   #22
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Re: Switch for solar panel circuit

A mildly circuitous but always informative thread. However, I still have not come across a light duty switch (say 15A) that will take 8 ga wire; can I thin the strands at a terminal??
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Old 12-02-2014, 14:09   #23
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Re: Switch for solar panel circuit

I have a water resistant plug through the deck between the panels and controller... so I just unplug the panels
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Old 12-02-2014, 14:20   #24
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Re: Switch for solar panel circuit

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Originally Posted by seadrift View Post
A mildly circuitous but always informative thread. However, I still have not come across a light duty switch (say 15A) that will take 8 ga wire; can I thin the strands at a terminal??
Can't you just use a circuit breaker (which is also a switch) with screws? Then crimp an eye fitting with the appropriate sized hole onto the 8 gauge wire?
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Old 12-02-2014, 15:39   #25
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Re: Switch for solar panel circuit

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Originally Posted by seadrift View Post
A mildly circuitous but always informative thread. However, I still have not come across a light duty switch (say 15A) that will take 8 ga wire; can I thin the strands at a terminal??
Switches with screw terminals are easy to find. Just one example:

Heavy Duty 20A 125V 15A 250V SPST 2 Terminal on Off Toggle Switch with Plate | eBay

Then use a sealed ring terminal for 8ga wire and #10 screw:

Heat Shrink Ring Terminal 8 AWG 10 Stud Ring Pink 5 | eBay

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Old 12-02-2014, 16:02   #26
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Re: Switch for solar panel circuit

Your question caught my attention as I just added a ~ GE 60 Amp 240-Volt 240-Watt Non-Fuse Non-Metallic AC Disconnect on either side of my solar controller. If you put this in the search on Home Depots page you'll find it. It's a plastic box with a bar that pulls out to cut the circuit, no fuses or breakers. Cost $14. One of my brothers who was an electrical engineer onboard a sub said these disconnects were needed. Admittedly I was a bit dubious.
For your consideration.
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Old 12-02-2014, 16:23   #27
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Re: Switch for solar panel circuit

Just a reminder to everyone, if the sun is out there is voltage on the panel leads. Once you open the disconnect that voltage will go up to Voc. If you are working on the panel side of any disconnect (including wiring said disconnect) either cover your panels or understand how to work on hot wiring.
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Old 13-02-2014, 04:45   #28
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Re: Switch for solar panel circuit

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Originally Posted by Dsanduril View Post
Just a reminder to everyone, if the sun is out there is voltage on the panel leads. Once you open the disconnect that voltage will go up to Voc. If you are working on the panel side of any disconnect (including wiring said disconnect) either cover your panels or understand how to work on hot wiring.

A couple of MC-4 connectors at the panel can suffice for the few times you may need to disconnect the panel side....
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Old 13-02-2014, 05:22   #29
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Re: Switch for solar panel circuit

Greetings and welcome aboard the CF, hurricanehole.
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Old 15-02-2014, 10:44   #30
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Re: Switch for solar panel circuit

Thanks for the welcome. While I've lived aboard for 7 years and worked as a contractor for twelve onboard cruise ships haven't done much cruising except to the Abacos. I enjoy the company on this site. Thanks for the work you do here also.
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