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Old 04-12-2016, 20:00   #1
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Solar disconnect switch?

Hi,
I'm installing two 100w solar panels on my boat, each with its own Genasun controller. I once fried such a controller with a quick short circuit in the system, and this time I'm planning on installing an on/off switch between each controller and the batteries so that I can take the solar offline if I am doing any electrical work.

If you set up a switch like this, what did you do? I'm mounting the controllers on a board under a seat and don't want to cut any holes, but surface mounted toggle switches seem hard to come by (except for those old style knife switches). I could use a battery on/off switch but they are too big and expensive for the purpose. I could also just run the wires to a bus bar and disconnect the controllers that way.

Any suggestions?
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Old 04-12-2016, 20:08   #2
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Re: Solar disconnect switch?

Blue Sea makes some small battery switches in single and double pole versions for less than$30. You will need a fuse/ circuit breaker at the battery bank connection so it can serve as the service disconnect means. I also suggest a double pole switch on the solar collector feed to the controller (beats a tarp if you need to work on the system).
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Old 04-12-2016, 20:36   #3
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Re: Solar disconnect switch?

You're talking about more switches than I had in mind. Why would I need a fuse/breaker at the battery bank connection? The controller is meant to be unfused, if I understand correctly, hence the vulnerability to a short.

Also, I have MC4 connectors on the panels themselves. Are you saying I would install another switch between each panel and its controller?

I hadn't noticed the Blue Sea "mini" series, thanks for pointing me to that.
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Old 04-12-2016, 20:49   #4
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Re: Solar disconnect switch?

Perhaps the breaker is there in case the controller shorts out completely? If that's the case, I could use an in-line breaker and that would also function as a switch.
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Old 04-12-2016, 20:51   #5
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Re: Solar disconnect switch?

Some controllers cannot be switched off completely unless the connection to the panels is opened...my 60A Mastervolt chargers comes to mind...
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Old 04-12-2016, 20:58   #6
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Re: Solar disconnect switch?

All systems I am aware of require the solar to be disconnected from the controller FIRST. What you suggest could indeed fry the controller, just what you are trying to avoid.
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Old 04-12-2016, 22:14   #7
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Re: Solar disconnect switch?

Why not just cover the panels with a thick towel to turn them off?
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Old 04-12-2016, 23:38   #8
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Re: Solar disconnect switch?

Quote:
Originally Posted by Stu Jackson View Post
All systems I am aware of require the solar to be disconnected from the controller FIRST. What you suggest could indeed fry the controller, just what you are trying to avoid.
My Genasun GV-10 controllers do not require that the solar panel be disconnected first, or last. In fact, when installing they recommend connecting the panels first, and then the battery -- this is to avoid shorting the panel connections when the battery is connected. This will cause damage. Otherwise it doesn't matter in which order you connect panels and battery.

I'm using surface-mounted breakers for the panel disconnects. A switch would probably be just as good. I do have a breaker between the controllers and the battery.
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Old 04-12-2016, 23:51   #9
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Re: Solar disconnect switch?

The correct way to do it is double pole DC circuit breakers between each Panel and the controller and then a DC circuit breaker between the controller and the battery. All sized according to your current expected.


My system bigger but still the same idea panels connected to more than 1 controller connected to battery.

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Old 04-12-2016, 23:54   #10
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Re: Solar disconnect switch?

Quote:
Originally Posted by Stu Jackson View Post
All systems I am aware of require the solar to be disconnected from the controller FIRST. What you suggest could indeed fry the controller, just what you are trying to avoid.

Second this, every system I've been involved with has the PV disconnect switch between the controller and the panels. You will also want to have the lines from the panels to the controller fused. to keep the component cost down you could use a couple of breakers as your isolating switches.

If you don't isolate your controller, how will you make it safe for you to work on.....
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Old 05-12-2016, 01:34   #11
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Re: Solar disconnect switch?

If you have MC4 connectors on the panels, just disconnect those. Don't put breakers on the PV side, just another thing to go wrong. Use a surface mount breaker for the CC output.
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Old 05-12-2016, 01:37   #12
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Re: Solar disconnect switch?

You don't need fusing or breakers on the PV side, solar panels can be shorted all day without issue. The exception is if you combine more than two strings, unless the cabling is rated for the short circuit current.
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Old 05-12-2016, 03:34   #13
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Re: Solar disconnect switch?

Quote:
Originally Posted by Stu Jackson View Post
All systems I am aware of require the solar to be disconnected from the controller FIRST. What you suggest could indeed fry the controller, just what you are trying to avoid.
That's the way I do it.
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Old 05-12-2016, 05:11   #14
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Re: Solar disconnect switch?

MC4 connectors were not designed to function as load break switches. Unplugging in the dark would probably work.

No overload protection required on the panel feed, short circuit current not a lot greater than operating current.

Anytime you make an electrical connection to a battery bank it needs to be fused (or circuit breaker) as close to the battery as practical. A short in this wiring/ device can result in thousands of amps feeding from the battery bank back into the short.
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Old 05-12-2016, 05:37   #15
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Re: Solar disconnect switch?

The Genasun manual indeed says to connect to the panels first and battery second. It sounds like I will just need breakers instead of switches (for reasons that are now clear to me) but otherwise I can stick with my original plan. I agree with mason and others that I shouldn't need any switch or fuse between controller and panel.

Frankly, what do you mean by "unplugging in the dark would work"? If I need to remove the panels, I would just reverse the order and flip the breakers first then disconnect the MC4s second, yes? This is the opposite of what Stu said is normal but the manual is pretty clear.
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