question about switches and morningstar SSD

notsobright
notsobright Solar Expert Posts: 247 ✭✭
in Solar Beginners Corner #1
hi everyone, Im looking for 12 volt 30 amp toggle switches. they seem to be hard to find locally these days.

I have many toggle switches rated 30amp @250vac but Im assuming they wont be the same @12vdc.

how do I convert switch ratings from AC to DC? in other words if the switch is rated at 30amps/250vac, how many amps would it be if used for 12vdc?


I need to add switches to my morningstar sunsaver duo controller on the input side and output side because I have to turn it off and back on in order to connect my PC, it wont detect the controller unless it is powered on after the PC is on. I can pull the fusses but that gets old really quick.

I called morningstar's techs about it and they said "sometimes" thats the case but Ive tried with 3 PCs and 3 different OSs and none detect unless the controller is turned on after the PC on.

cant belive the SSD doesnt have a logging capability either but on thier website it says "coming soon" guess I'll have to wait.



it would be really nice if I could find one switch that could do this. (control three sperate circuts in one switch)


thanks
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Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: question about switches and morningstar SSD

    The short answer is: you don't. A switch that's not DC rated shouldn't be used for DC; it's more difficult to interrupt the current in a DC circuit. Without the right contacts, spring, and gap it can arc and burn up.

    Automotive/RV supply stores ought to be able to get switches rated for 12 VDC @ 30 A, although most of the shelf stock I've seen there lately has been strictly light-duty. You probably don't have SMS Electronics there, but that sort of specialty electrical supply would be another potential source.
    Another idea would be to use a light duty switch and a relay or relays rated @ 30 A. You could wire it to interrupt power when the relays are on (rather than off) so that there would be no draw during normal operating state. One switch could control the relays for all three circuits.
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  • RCinFLA
    RCinFLA Solar Expert Posts: 1,485 ✭✭✭✭
    #3
    Re: question about switches and morningstar SSD

    There is not a straight answer to AC to DC conversion of switches. You like to have a fast and strong contact switching. Don't want a switch that lighten the contact pressure gradually as it is opened. Good strong solid 'snap'.

    D.C. is harder on the contact when opening the switch under heavy current flow.

    You should be fine using the 250vac switches you have if they have a strong snap when toggled.

    If you can avoid switching at high current flow it is alway better whether AC or DC.

    Relay coils take power. A 30 amp contact relay coil can burn >2 watts of power.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: question about switches and morningstar SSD
    RCinFLA wrote: »
    Relay coils take power. A 30 amp contact relay coil can burn >2 watts of power.

    Which is why I suggested wiring them the other way 'round, so that they're energized when you want the circuits disconnected. They won't be drawing power all the time then. Screwy, but it'd work. :p
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #5
    Re: question about switches and morningstar SSD
    notsobright wrote: »
    hi everyone, Im looking for 12 volt 30 amp toggle switches. they seem to be hard to find locally these days.

    Radio Shack usually has a drawer full of 12v switches in various sizes (fuses too).

    My local Do It center also has a drawer full of 12v switches.

    Marine, RV or Off-Road supply should also have them.
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  • notsobright
    notsobright Solar Expert Posts: 247 ✭✭
    #6
    Re: question about switches and morningstar SSD

    had to settle for 25a switches which should be fine. 30a switches were not hard to find 10yrs ago.. now all anybody wants to sell it plastic disposable stuff. dont even get me started on radio shack...

    the local heavy equipment parts store had 50 amp ones but the toggle was twice as long.



    thats a neat Idea with the relay cariboocoot! I might incorporate it but thats also more wires and potential issues so I havnt decided.


    thanks for the help again guys!
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  • GreenerPower
    GreenerPower Solar Expert Posts: 264 ✭✭✭✭✭✭
    #7
    Re: question about switches and morningstar SSD

    If this is not too late - 30A, 12VDC rocker switch
    GP
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