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Old 13-04-2016, 10:33   #1
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Breaker advice

I need a bit of advice, or even a nudge in the proper direction, on breakers. Putting the solar system in, and the breaker is the latest snag in this never ending journey. I have three panels, that I intend to wire in series, feeding into a Rogue 3048 MPPT. From the MPPT, this will feed into the household 12v AGM bank. Specs for the panels below.

Open Circuit Voltage: 26.5 volts
Short Circuit Current: 5.85 amperes
Max Power: 22.10v @ 5.42 amps

The issue I come to is the Blue Sky breakers seem to top out at 65v. I need something higher, simply due to the series wiring. Keep in mind, until 18 months ago, electrical might as well been black magic. While I've come far since then, in comparison to many here I'm a rookie.

Can anyone point me to a breaker that would work?
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Old 13-04-2016, 10:50   #2
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Re: Breaker advice

Maybe an AC 120V breaker?
If that is un-acceptable, how about a fuse?
Sorry, best answer I have
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Old 13-04-2016, 10:53   #3
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Re: Breaker advice

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Originally Posted by a64pilot View Post
Maybe an AC 120V breaker?
If that is un-acceptable, how about a fuse?
Sorry, best answer I have
I came up with one from Midnite Solar, but don't have a clue if it is the direction I should go.

MidNite Solar Inc. Renewable Energy System Electrical Components and E-Panels

I should have added that the breaker will be wired in between the panels and MPPT, so I can shut down power to the MPPT if needed.
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Old 13-04-2016, 12:18   #4
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Re: Breaker advice

Looks like a blue seas 7353 is rated 20A, to 80Vdc. Paneltronics are really low, like 40v.
https://www.bluesea.com/products/735...le_Pole_20_Amp

I know you asked about the panel->controller, but you most definitely need a breaker (or fuse) between the battery and the controller. This should be sized to the wire running to the controller (i.e. 30A for 10G wire).

From the panels to the controller, you're quite unlikely to catch anything on fire even if it shorts. The panels could all be outputting Isc - but that's OK because your wire from the panels should be sized to handle Isc X 3. (yes, I know every drawing ever made has a fuse here, but I'm at a loss to see how it would ever blow - there's never going to be enough power to blow it)

Having a disconnect is very good though, as ~60v at ~15A can indeed zap you quite well. If you don't find a suitable breaker you could use a fuse that you could pull to effect a disconnect.
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Old 13-04-2016, 12:40   #5
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Re: Breaker advice

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Originally Posted by jeepbluetj View Post
Looks like a blue seas 7353 is rated 20A, to 80Vdc. Paneltronics are really low, like 40v.
https://www.bluesea.com/products/735...le_Pole_20_Amp

I know you asked about the panel->controller, but you most definitely need a breaker (or fuse) between the battery and the controller. This should be sized to the wire running to the controller (i.e. 30A for 10G wire).

From the panels to the controller, you're quite unlikely to catch anything on fire even if it shorts. The panels could all be outputting Isc - but that's OK because your wire from the panels should be sized to handle Isc X 3. (yes, I know every drawing ever made has a fuse here, but I'm at a loss to see how it would ever blow - there's never going to be enough power to blow it)

Having a disconnect is very good though, as ~60v at ~15A can indeed zap you quite well. If you don't find a suitable breaker you could use a fuse that you could pull to effect a disconnect.
Thanks for the reply! Just got off the phone with Northern Arizona Wind & Sun. They set us up with two Midnite Solar breakers for each side of the run, from and to the MPPT. Problem solved!
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Old 13-04-2016, 15:57   #6
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Re: Breaker advice

You will absolutely need a breaker/ fuse in the circuit between the controller and the battery bank. 12+ volts will be fine and it should be as close to the battery terminal as possible. Blue Sea makes a nice small double pole battery switch which I would put in between the panels and the controller (switch both + and -). Check the voltage rating though. Assuming the wiring will be based on voltage drop vice current expected, there is nothing in the panels or the controller that should cause a overheated wiring problem. The aw sh** condition is a short circuit in that controller and or wiring feeding a couple of thousand amps from the house bank back into the fault. Thus locate the fuse close to the battery offers the most protection.
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Old 13-04-2016, 19:11   #7
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Re: Breaker advice

The OP is already settled, but there is really no need to put a breaker on the panel side. The panels themselves are current limited, and so will never trip a breaker. A switch in this location is fine for disconnecting the panels from the controller if you have reason to do so. It still must be DC rated and for the proper voltage.

DC switch/breaker voltage ratings are all about arc length. The higher the voltage the longer an arc the DC can maintain.
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Old 14-04-2016, 17:13   #8
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Re: Breaker advice

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Blue Sea makes a nice small double pole battery switch which I would put in between the panels and the controller (switch both + and -). Check the voltage rating though.
Looking for the same thing. on blue sea site, can't find this. searching double pole leads to nothing, but maybe i am not looking for the right type of switch. I am only finding rotary battery 1/2/both/off switches.

Could I trouble you for a link or pic? Thanks.

Also, any reason not to use just a regular wall switch. Assuming these will rust?
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Old 14-04-2016, 17:29   #9
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Re: Breaker advice

I used a 15 amp standard wall switch in an outdoor plastic box, mounted next to the TS-MPPT 60.

The output is fused at 80 amps.

I have 3, 225 watt, 36 volt panels, wired in series.

Installed in 2012, no troubles since.
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Old 14-04-2016, 17:48   #10
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Re: Breaker advice

My observations regarding common sense, 'the rules', and what We have learned about lightening strikes is that you need to be able to isolate the panels from the MPPT and the MPPT from the battery. I am not keen on series panels unless you are not concerned about partial shading. In our system, each parallel panel has its own 2-pole breaker (total isolation). Likewise, the MPPT has an output 2-pole breaker to the batteries. Weather looks like bad pizza and its all off. If you are 3 X series then the panels are assumed to be one panel; one breaker. We used KIN rail breakers. THese are easy to find on Amazon. The voltage does not figure in this. Amps is Amps to size the breakers. Most of these are industrial - 600 volts - no problem. In the photo you see one per parallel panel 10 amp 2-pole breaker (3) and one 40 amp 2-pole output from the MPPT. Don't skimp on the wire gauge. Bigger is better.
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Old 14-04-2016, 17:56   #11
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Re: Breaker advice

Quote:
Originally Posted by Fog Bank View Post
I need a bit of advice, or even a nudge in the proper direction, on breakers. Putting the solar system in, and the breaker is the latest snag in this never ending journey. I have three panels, that I intend to wire in series, feeding into a Rogue 3048 MPPT. From the MPPT, this will feed into the household 12v AGM bank. Specs for the panels below.

Open Circuit Voltage: 26.5 volts
Short Circuit Current: 5.85 amperes
Max Power: 22.10v @ 5.42 amps

The issue I come to is the Blue Sky breakers seem to top out at 65v. I need something higher, simply due to the series wiring. Keep in mind, until 18 months ago, electrical might as well been black magic. While I've come far since then, in comparison to many here I'm a rookie.

Can anyone point me to a breaker that would work?
I think you are on the wrong track.

For the controller supply/panel output all you need is a fuse. If you connect the controller output to your main DC panel you need a 12V breaker sized to the smaller of the controller rating or the wire size you used. Other wise all you need is a fuse on the output.
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Old 14-04-2016, 18:07   #12
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Re: Breaker advice

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Originally Posted by Nicholson58 View Post
The voltage does not figure in this. Amps is Amps to size the breakers. Most of these are industrial - 600 volts - no problem.
Sorry, but that's just not true. Voltage is critical in sizing DC switches, breakers, and fuses. With AC power the voltage goes to zero 50 or 60 times every second, extinguishing arcs. With DC this doesn't happen, and the gap a DC arc can jump is directly correlated with the voltage/power flowing when it is opened. The higher the voltage the greater the arc length. So opening a DC breaker (switch, fuse) can just result in an arc across the contacts.

DC rated breakers include a magnet that is used to 'pull' the arc away from the contact gap, helping to extinguish the arc. This magnet is not found in AC-only rated breakers.

In high voltage DC system it is not unusual to use two, three, four or more sets of contacts in series in order to get the necessary gap length to extinguish the DC arc.

This didn't used to be much of a problem with 12V systems on boats, the arc length at 12V just isn't that great. But as we move to higher voltage solar panels, and put them in series, understanding the disconnect ratings is critical if you don't want to start a fire simply by opening your breaker/switch/fuse.
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Old 14-04-2016, 18:07   #13
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Re: Breaker advice

Here is the double pole BS battery switch. Noticed it is only rated for 32 VDC. I would not have a problem pushing that a little bit but your boat is your boat.

Breaking DC is a little more difficult than AC. Don't think wall switches carry a DC rating. Could throw a blanket over the panels if you needed to work on something.

https://www.bluesea.com/products/601...y_Switch_-_Red
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Old 14-04-2016, 18:43   #14
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Re: Breaker advice

Frankly, did see that after more searching. Thanks. Unlike the op, I have 2 panels in parallel, but mine are 39 V at V oc, 32 V at V mpp. So I don't think this switch will work. I just an on off switch, I don't care about a breaker for panel to controller. I have a blue sea breaker between battery and controller but since it is by a bulkhead with 4 feet of wire to the battery post, I am fusing the battery post as well.

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Old 14-04-2016, 19:04   #15
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Re: Breaker advice

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Originally Posted by Dsanduril View Post
Sorry, but that's just not true. Voltage is critical in sizing DC switches, breakers, and fuses. With AC power the voltage goes to zero 50 or 60 times every second, extinguishing arcs. With DC this doesn't happen, and the gap a DC arc can jump is directly correlated with the voltage/power flowing when it is opened. The higher the voltage the greater the arc length. So opening a DC breaker (switch, fuse) can just result in an arc across the contacts.

DC rated breakers include a magnet that is used to 'pull' the arc away from the contact gap, helping to extinguish the arc. This magnet is not found in AC-only rated breakers.

In high voltage DC system it is not unusual to use two, three, four or more sets of contacts in series in order to get the necessary gap length to extinguish the DC arc.

This didn't used to be much of a problem with 12V systems on boats, the arc length at 12V just isn't that great. But as we move to higher voltage solar panels, and put them in series, understanding the disconnect ratings is critical if you don't want to start a fire simply by opening your breaker/switch/fuse.
This may be true in high voltage DC but not at 12 to 50. Professional engineer with 43 years building custom machines. I have consulted with my 3 EE guys where we build testing machinery installed all around the planet. In this use, these Din Rail breakers will do nicely. BTW - they have a much larger gap than the tiny push button breakers in my DC panel. The open circuit rating is 600 volts - far greater than the DC breakers. Vendor's data also says AC or DC. I have also contacted our Allen Bradley/Siemens distributor. He confirms these are OK DC and Amps is amps.
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