240v AC Relay

Discussion in 'Off Grid Living' started by BenP, Aug 20, 2018.


  1. BenP

    BenP Monkey++ Site Supporter+

    I wanted to make my off-grid air conditioning only come on when the batteries were completely charged and kick off when they started to get low and this little relay I found is just the ticket. The relay is controlled by 12v and I wired it into the auxiliary output of my charge controller which you can program to put out a 12v signal under certain conditions. I made this whole panel switch on and off depending on the condition of the batteries, these will be my luxury appliances.
    IMG_20180819_204441.
    IMG_20180819_122452.
     
    Last edited: Aug 20, 2018
  2. Asia-Off-Grid

    Asia-Off-Grid RIP 11-8-2018

    Cool beans, @BenP.
    I've used charge controllers and 12vdc relays switching 230vac contacts, for single devices before. But, never to control an entire panel. Great idea, man.

    How large is your system?
     
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  3. Altoidfishfins

    Altoidfishfins Monkey+++ Site Supporter+

    Good idea. I would use a Solid State relay, control my well pump with one (based on water level in the tank, not a solar controller output). No contacts to pit, burn or stick over time. They take only 10 or 20 mA to activate the "coil".
     
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  4. BenP

    BenP Monkey++ Site Supporter+

    It is a small 24v system, I have about 2600w worth of 12v panels that I wire in series to get 24v.

    Schneider Electric Conext XW MPPT 60 Amp Charge Controller (x2)
    Schneider Electric Conext SW 4024 3,400 Watts, 24VDC Inverter 120/240 VAC
    Schneider Electric Conext XW+/SW System Control Panel (SCP)
    LiFePO4 Prismatic Batteries 300Ah

    I also have a 2000w wind mill that never does anything, we get a lot of wind in the winter and I'm hoping it will pay dividends then, if not I will take it down. I think some vines have grown over it at the moment. :)
     
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  5. BenP

    BenP Monkey++ Site Supporter+

    What relay do you use? If there is something more reliable than this one I would like to have it, at least for a spare.
     
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  6. Altoidfishfins

    Altoidfishfins Monkey+++ Site Supporter+

    How much current does your Air Conditioner draw and at what voltage? We already know that you're controlling the coil with 12 volts, so we can probably find one with a "coil" that will operate from 3 to 24 or 3 to 32 volts DC. Since you're controlling AC, you'll probably need a Triac type. My well pump runs on about 150 volts DC from the solar array when it's under load (has a built in MPPT controller) so the SSR is a FET type.
     
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  7. 3M-TA3

    3M-TA3 Cold Wet Monkey Site Supporter++

  8. Altoidfishfins

    Altoidfishfins Monkey+++ Site Supporter+

  9. BenP

    BenP Monkey++ Site Supporter+

    The air conditioner and water heater are both on that panel and they will draw 15 amps combined worse case but the panel is fed by a 30 amp circuit so it would probably be good to have at least a 30 amp relay. Air conditioner is 120v AC, Water heater is 240v AC.
     
    Last edited: Aug 20, 2018
  10. ghrit

    ghrit Bad company Administrator Founding Member

    Is that starting draw, and is it possible for them both to kick on at the same time?
     
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  11. Tempstar

    Tempstar Old and crochety Site Supporter+

    Those solid states are also great for rapid switching. You see them on a lot of cooking equipment to control the temps by rapidly switching on and off to keep elements at the right temperature. They will last almost forever in a cooler environment.
     
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  12. Altoidfishfins

    Altoidfishfins Monkey+++ Site Supporter+

    There are SSRs that can handle more current. Crydom, Omron, as well as Automation Direct manufacture them. They probably should be attached to a heatsink.
     
  13. BenP

    BenP Monkey++ Site Supporter+

    They always both kick on at the same time but their behavior is somewhat unpredictable. The air conditioner does not have a big starting load, usually 300w or so when the outdoor unit kicks on then the draw will cycle up and down between ~300-1000w. The water heater will draw about 500w at startup if it is in heat pump mode then level off around 300w. If the water is really cold it will use the resistance elements for 500w then switch to the heat pump later when the water gets to 75-90 degrees depending on the temperature setting.
     
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