PV power disconnect

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jumandda
jumandda Registered Users Posts: 1 ✭
in Solar Beginners Corner #1

I have an small experimental/ emergency backup solar system.

2-  REC 325W (24v) panels
1-  Victron 100/50 MPPT
2-  6V 210AH batteries

panels are 24V, wired in series at 48 volts

with the higher voltage (in full sun almost 80 volts) I don't disconnect under load (cover panels with blankets if needed).

What is a decent way to disconnect when there is load?


Choices:
battery disconnect switch.  are my volts too high?
standard 120V light switch.

Low-voltage Miniature DC Circuit Breaker, Din Rail Mount?

if so, single pole or dual pole?
with my 48 (80) volt, 650W system, best amperage value?

my thoughts so far:

2P 250V Low-voltage DC Miniature Circuit Breaker For Solar Panels Grid System Din Rail Mount 16A


I already have an inline blade fuse on the exposed positive lead, I never have exposed wires without some protection.


Thanks all,

Jim
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
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    I ran my power into a breaker box, and used 150VDC rated breakers to control things




    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • MichaelK
    MichaelK Registered Users Posts: 234 ✭✭✭
    #3
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    The standard 120V light switch would be a VERY bad choice.  It's designed for AC, which arcs much less readily than DC does.  What can happen is that went opening the circuit, the DC current can arc across the small gap, welding the metal together.  DC rated breakers separate the metal connections much further apart, reducing the danger of arcing.
    System 1) 15 Renogy 300w + 4 250W Astronergy panels,  Midnight 200 CC, 8 Trojan L16 bat., Schneider XW6848 NA inverter, AC-Delco 6000w gen.
    System 2) 8 YingLi 250W panels, Midnight 200CC, three 8V Rolls batteries, Schneider Conext 4024 inverter (workshop)
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    edited February 2020 #4
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    You will need a DC rated breaker,  which will provide protection for the cables,   and is rated  to act as a switch at its rated current.   One like this:
    https://www.solar-electric.com/midnite-solar-mnepv-15-amps-circuit-breaker.html

    This is about the smallest USEABLE box for the DIN Rail breakers:
    https://www.solar-electric.com/misobigbabox.html

    The above is s DIN Rail mount.  There is another MidNite breaker series,  is a Panel Mount.  These are MNEDC series.    Here:
    https://www.solar-electric.com/search/?q=mnedc++15

    Here is a small box for MNEDC breakers:
    https://www.solar-electric.com/mnedc-quad.html

    The breaker that you linked to,   is NOT rated for use in DC circuits.

    There are some other details,   Be certain to have a DC breaker (or perhaps a suitable fuse)  on the connection from the Charge Controller and the battery.

    FWIW,   Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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