wiring live switching from Solar/grid

lamplight
lamplight Solar Expert Posts: 368 ✭✭✭✭✭✭
in General Solar Power Topics #1
I guess what i want to do is probably the same thing people do for backup generators, but i dont need any auto-detecting of the battery voltage. i'd like something i could do with a live load (but only about 150w AC) . heres the situation:

I have a inverter supplied AC outlet 3 feet from a grid supplied AC outlet that i will manually unplug my UPS from (so things stay running) and put into the inverter when it's sunny. Id like to build a switch for this and am not sure whats the best approach. do they make anything prewired for this scenario? i think i could use a 3 way switch diagram to do this , but am seeking any advise on the best way to do this, and what kind of switches i should use. I do still have one of those inverter switches that i havent used yet but i dont think i need anything that beefy right?

so thanks!
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Comments

  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    #2
    Re: wiring live switching from Solar/grid

    Your need a double pole double throw switch. You must switch both the hot (black wire) and the neutral (white wire) at the same time. Also the switch must break before make or there will be sparks/smoke. A 3 way switch is only a single pole double throw switch.

    Here is a switch that will work:
    http://www.grainger.com/Grainger/items/2X468
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  • lamplight
    lamplight Solar Expert Posts: 368 ✭✭✭✭✭✭
    #3
    Re: wiring live switching from Solar/grid

    ok got it, that makes sense. i just did some looking and all i can find is household type units that are designed for a bunch of circuits.. do you have any source where i might check for smaller versions? best i can find is a furnace transfer switch for 15 amps thats about $100. i wonder if i can do better than that pricewise?? well, at least i know what im looking for now, thanks!
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  • lamplight
    lamplight Solar Expert Posts: 368 ✭✭✭✭✭✭
    #4
    Re: wiring live switching from Solar/grid

    actually, I did just find this:
    http://store.solar-electric.com/ioitauactrsw.html
    which i suppose would work if i made the grid outlet in question a switched outlet (ie, i could just shut it off to get this to kick onto the solar)

    thanks
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #5
    Re: wiring live switching from Solar/grid

    got a radio shack near you that still carries parts?
    http://www.radioshack.com/search/index.jsp?kwCatId=&kw=dpdt%20switch&origkw=dpdt%20switch&sr=1
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  • Brock
    Brock Solar Expert Posts: 639 ✭✭✭✭
    #6
    Re: wiring live switching from Solar/grid

    Matt I built one almost identical to that Iota transfer switch. I used a double pole double throw (DPDT) relay and wired it so the normally open side was fed by one plug and the other plug energized the relay and fed the other side of the relay, then took the middle to a regular 120vac wall outlet in the same box. So basically it was a 6x6 electrical box with 2 power cords coming out with a plug on it. It works great. I initially built it to plug one side in the grid and the other in the inverter so it would auto transfer when the grid (coil) side failed. Not as pretty as the iota, but all the parts cost maybe $15.
    3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
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  • lamplight
    lamplight Solar Expert Posts: 368 ✭✭✭✭✭✭
    #7
    Re: wiring live switching from Solar/grid

    excellent! thanks! gonna check the shack.. they have 10amp switches on that list that would be fine.. looks like im going to have to put something together either way, might as well go with the cheaper parts version if m going to have to build something.
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  • lamplight
    lamplight Solar Expert Posts: 368 ✭✭✭✭✭✭
    #8
    Re: wiring live switching from Solar/grid

    hey!! i built one with $10 in parts from radio shack: a recycled electrical socket from a dead UPS, and 2 existing computer power cords last night!! took me a few hours and was frustrating as i dont have the right tools / experience for this but it came out pretty nice, the functionality is very cool, much better than bending down to unplug and plug in manually.
    i used one of their project boxes, a 10a DPDT (on/off/on) toggle switch. it actually doesnt look bad either.. will post a pic later. thanks again guys!
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