What Size Switch Do I Need

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Ako
Ako Registered Users Posts: 184 ✭✭
in Advanced Solar Electric Technical Forum #1
I need to insert a switch in

I need to install a switch in the line that comes from my Panels to Charge Controller as once in a while i need to adjust the settings on the Charge Controller or rotate or remove my Batteries for cleaning and each time the batteries are disconnect the panels have to be disconnected first which is a pain .

I have one of the Switches Attached but i have been told i cant use it because its not big enough , my input from panels are 24 volts with a Max of 45 amps .

I compared some basic toggle switches and its clear that the contacts and Cable connectors on them are far smaller although they are rated for 50 amps so i cant understand why the 660V 25 AMP is to small .

What is it that im not understanding .

2240 Watt Array  4 x 460 Watt Mono Panels + 2 x 200 Watt Panels
Victron Smart 150-70 MPPT Charge Controller
24 volt Battery Bank 4 x 6v 400 Amp/Hr Trojan L16 AGM
LiFePO4 Lithium 100 Amp/Hr Battery for Backup
Victron 1600w Multiplus Compact Inverter/Charger
DC to DC Charger ( Non Isolated )
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #2
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    You might want to look at 24+ volt rated DC circuit breakers (55-60 amp rated minimum would be nice--If you can find one--I like to over size circuit breakers by 1.25x for solar--You can have hours of maximum current and if too close to rating, the breaker/fuse may trip)):

    https://www.amazon.com/s?k=dc+circuit+breaker+50+amp
    https://www.amazon.com/s?k=dc+circuit+breaker+60+amp

    You hare two issues here... On is that running 45 amps through a 25 amp rated switch--You can overheat the contracts and the switch will fail.

    The second switch is only rated for 6-12 VDC... DC current will sustain an arc if over 12 VDC. So, this switch is not rated for 24 VDC and switching under load can cause it to arc internally and fail.

    Just to show you the difference between AC and DC current and how DC arcs "very nicely":
    https://www.youtube.com/watch?v=Zez2r1RPpWY
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    #3
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    If you have a protected area to mount a piece of DIN rail(<$5)..

    DIN Rail Slotted 15mm 55mm Height 1m Length Steel TH1555T Ferrules Direct

    ...or use a small DIN rail box (about $40)
    main product photo
    ...and use a DIN rail breaker;
    main product photo
    Link to 50 amp breaker;

    Midnite Solar MNEPV 150 Volts 50 Amps DC Circuit Breaker | Northern Arizona Wind & Sun (solar-electric.com)




    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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