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12-02-2014, 11:35
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#16
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Nearly an old salt
Join Date: Jun 2009
Location: Lefkas Marina ,Greece
Boat: Bavaria 36
Posts: 22,801
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Re: Switch for solar panel circuit
Quote:
Originally Posted by Dsanduril
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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+1
Dave
__________________
Interested in smart boat technology, networking and all things tech
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12-02-2014, 11:58
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#17
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Registered User
Join Date: Apr 2006
Posts: 4,413
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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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12-02-2014, 12:01
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#18
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Nearly an old salt
Join Date: Jun 2009
Location: Lefkas Marina ,Greece
Boat: Bavaria 36
Posts: 22,801
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Re: Switch for solar panel circuit
Quote:
Originally Posted by Sandero
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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Why would it be " confused"
Dave
__________________
Interested in smart boat technology, networking and all things tech
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12-02-2014, 12:12
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#19
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Marine Service Provider
Join Date: Jan 2007
Location: Maine
Boat: CS-36T - Cupecoy
Posts: 3,197
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Re: Switch for solar panel circuit
Quote:
Originally Posted by skipmac
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?
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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...
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12-02-2014, 12:35
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#20
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Registered User
Join Date: Jan 2010
Location: Portland, Oregon, USA
Boat: 31' Cape George Cutter
Posts: 3,274
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Re: Switch for solar panel circuit
Quote:
Originally Posted by goboatingnow
Why would it be " confused"
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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.
Greg
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12-02-2014, 13:33
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#21
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Senior Cruiser
Join Date: Oct 2007
Location: 29° 49.16’ N 82° 25.82’ W
Boat: Pearson 422
Posts: 16,306
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Re: Switch for solar panel circuit
Quote:
Originally Posted by Maine Sail
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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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.
__________________
The water is always bluer on the other side of the ocean.
Sometimes it's necessary to state the obvious for the benefit of the oblivious.
Rust is the poor man's Loctite.
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12-02-2014, 14:02
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#22
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Registered User
Join Date: May 2011
Posts: 48
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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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12-02-2014, 14:09
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#23
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Registered User
Join Date: May 2011
Location: Portland, OR, USA
Boat: Hallberg Rassy 35'
Posts: 1,200
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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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12-02-2014, 14:20
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#24
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Senior Cruiser
Join Date: Oct 2007
Location: 29° 49.16’ N 82° 25.82’ W
Boat: Pearson 422
Posts: 16,306
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Re: Switch for solar panel circuit
Quote:
Originally Posted by seadrift
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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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?
__________________
The water is always bluer on the other side of the ocean.
Sometimes it's necessary to state the obvious for the benefit of the oblivious.
Rust is the poor man's Loctite.
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12-02-2014, 16:02
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#26
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Registered User
Join Date: Feb 2014
Location: NC
Boat: Prout 34
Posts: 51
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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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12-02-2014, 16:23
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#27
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Registered User
Join Date: Aug 2011
Location: Petersburg, AK
Boat: Outremer 50S
Posts: 4,229
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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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13-02-2014, 04:45
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#28
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Marine Service Provider
Join Date: Jan 2007
Location: Maine
Boat: CS-36T - Cupecoy
Posts: 3,197
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Re: Switch for solar panel circuit
Quote:
Originally Posted by Dsanduril
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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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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13-02-2014, 05:22
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#29
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Senior Cruiser
Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 49,242
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Re: Switch for solar panel circuit
Greetings and welcome aboard the CF, hurricanehole.
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"
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15-02-2014, 10:44
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#30
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Registered User
Join Date: Feb 2014
Location: NC
Boat: Prout 34
Posts: 51
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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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