Two inverters???

jarodbriscoejarodbriscoe Registered Users Posts: 3
I am setting up an off grid battery back up system and I want to run my AC 1hp well pump and a chest freezer and two refrigerators at a minimum. 

My pump is 240vac that requires 9.8 amps (call it 10a) at startup. So 2400w. 
My freezer and refrigerators will draw less than 1500w at 120vac combined. 

But I’ve found that without spending a small fortune I can’t get an inverter that will do both. So I was thinking about running two inverters. One for the well and one for the rest. 

I have a 48 volt battery bank that is set up in 2 strings of 4, using Eight 12v 200ah SLA batteries. 

I have 1200 watts worth of pv panels and a solid off grid solar charge controller. 

What am I about to do wrong? 

Comments

  • mike95490mike95490 Solar Expert Posts: 9,275 ✭✭✭✭✭
    edited July 2020 #2


    Your well pump.  Is going to need a 4kw inverter with a large surge rating.  It takes a $400 AC peak hold meter to read your starting current the inverter needs to supply, and if you have the option to only run the pump when you need to fill a tank, that makes things a lot more flexible.    My 1/2 hp pump, consumes 1kw, as measured by my inverter (that's Volt-Amps, since it's a motor, not simple watts)

    48A @ 230V starting = 11Kw surge capacity for your inverter.   That's why I run a 6kw inverter to manage my 1/2 hp pump, which has to run every day !







    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 ,

  • Dave AngeliniDave Angelini Solar Expert Posts: 5,912 ✭✭✭✭✭
    The other way to do this, and it may cost more than the XW inverter Mike is referring to is a new well pump with soft start. A Grundfo is what I tend to insist on when starting from scratch. This allows you to run the pump on a small genset, array direct with solar, or 240vac.

    The XW's that are currently on the market are 6.8KW continuous, 8.5KW for 30 minutes and 12KW for 60 seconds. Alot higher power for the short time it takes to start a well motor. At some point in this, the battery becomes a factor if it is too small. (below 400AH).
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • jarodbriscoejarodbriscoe Registered Users Posts: 3
    So I think I’ve got it. I have a 48vdc, 400ah battery bank and I’m gonna purchase a 240vac inverter that will run 6kw sustained and is advertised to have 18kw peak. That should certainly run the well pump. 
    I’m also gonna hook up a 3kw psw inverter for all my 120vac stuff. 
  • jarodbriscoejarodbriscoe Registered Users Posts: 3
  • mike95490mike95490 Solar Expert Posts: 9,275 ✭✭✭✭✭
    So, that 6kw  inverter, will it be on a manual switch? or sitting idle for 23 hours a day waiting for a pressure switch to activate the pump?
    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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