Using two inverters - wiring help

RybrenRybren Solar Expert Posts: 348
I know that a few of our members have two inverters connected to their system - a small one for every day loads and a larger one for the occasional bigger loads. I assume that both are permanently installed and that the operator has a set of switches that they can use to swap between the inverters.

I would like to be able to do the same and am looking for ideas on how to best accomplish the task.

Thanks, Jerry

Comments

  • BB.BB. Super Moderators, Administrators Posts: 29,514 admin
    You can use a relay or get an automatic transfer switch:

    Transfer Switches and Generator Auto Start Accessories
    http://www.solar-electric.com/installation-parts-and-equipment/electrical-devices-transfer-switches-noise-filters/autrswandgea/pomaxpmautrs.html

    Or--Leave your "small loads" wired to the small inverter and setup an separate AC branch circuit that is only powered up when large loads need to be supported.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    Ive contemplated this, and basically the plan was to wire the workshop,the water pump, and a couple of specific outlets in the house (for the vacuum prmarily) to the big inverter, and the balance to the smaller one. It means rejigging some of your loads. But its relatively easy to buy lower wattage appliances, sub 1kW, eg kettle, toaster, hairdryer, iron, all can be had for around the 1kW mark. The stecca is an 1100W unit, with 10W tare. A victron inverter with similar specs is also available. I dont know what it is, but find myself not trusting transfer swithces. Still, I suppose people have used them for decades... Anyway, ended up wiring up the VFX to everything, with its 20W tare its bearable.

    Note though, for the above, almost all of our 24/7 electronics are on our DC system. This means that i can turn the VFX off when not in use. Others might benefit from the morningstar 300W unit for such things, but its tare is around 6W i think. I keep on nagging midnite about their upcoming inverters tare. Hopefully if others do the same, they will have something ground breaking to show for it.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • RybrenRybren Solar Expert Posts: 348
    Hmmm. Thanks for the suggestions guys.

    I guess that I was thinking more in terms of using something like a battery switch between the EPanel output and the inverters to swap the power input between them.
  • westbranchwestbranch Solar Expert Posts: 5,142 ✭✭✭✭
    I had the electrician wire up two Distribution ('fuse') boxes in preparation of getting a second smaller inverter. Both are powered by one inverter at this time
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • SkiDoo55SkiDoo55 Solar Expert Posts: 414 ✭✭✭
    I
    Rybren wrote: »
    Hmmm. Thanks for the suggestions guys.


    I guess that I was thinking more in terms of using something like a battery switch between the EPanel output and the inverters to swap the power input between them.
    I don't think the inverter will like seeing voltage from another source on the non operating inverter. I would put transfer switch/relay on the outputs then to loads or keep loads totally separated.
    GT3.8 w/4600W Trina 230W, TX5000 w/5000W ET-250W, XW4024 w/1500W ET-250W, 4 L16, 5500W Gen. (never had to use) Yet!!
  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    Wont like, no it wont like it one little bit. A transfer swtich, ie one that definatively ensures the two inverters are never connected is the only kind of switch you should contemplate there.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • lkruperlkruper Solar Expert Posts: 115 ✭✭
    westbranch wrote: »
    I had the electrician wire up two Distribution ('fuse') boxes in preparation of getting a second smaller inverter. Both are powered by one inverter at this time

    How much power do you save when running the smaller inverter instead of the larger one with small loads?
  • westbranchwestbranch Solar Expert Posts: 5,142 ✭✭✭✭
    my 1500W inverter uses ~18W in no load mode and 3.6 W in standby mode, I have been looking at a Victron 800W inverter and it uses 5.0W in no load and 2W in standby. So if I were to use that one, it would save ~ 13W/hr. If I go up to the 2500W model ( to power fridge and vacuum at same time) I would save an additional 18W per hr... so the longer the large one is in standby and the small one carries the light loads (internet, lights, chargers) the more saved per hr..

    Winter is the critical time...
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • RybrenRybren Solar Expert Posts: 348
    Transfer switch it is, I guess. Thanks.
  • SkiDoo55SkiDoo55 Solar Expert Posts: 414 ✭✭✭
    I'm
    zoneblue wrote: »
    Wont like, no it wont like it one little bit. A transfer swtich, ie one that definatively ensures the two inverters are never connected is the only kind of switch you should contemplate there.
    Trying be nice my real statement would be going to let the smoke out of one of them if not both!
    GT3.8 w/4600W Trina 230W, TX5000 w/5000W ET-250W, XW4024 w/1500W ET-250W, 4 L16, 5500W Gen. (never had to use) Yet!!
  • lkruperlkruper Solar Expert Posts: 115 ✭✭
    westbranch wrote: »
    my 1500W inverter uses ~18W in no load mode and 3.6 W in standby mode, I have been looking at a Victron 800W inverter and it uses 5.0W in no load and 2W in standby. So if I were to use that one, it would save ~ 13W/hr. If I go up to the 2500W model ( to power fridge and vacuum at same time) I would save an additional 18W per hr... so the longer the large one is in standby and the small one carries the light loads (internet, lights, chargers) the more saved per hr..

    Winter is the critical time...

    Do you change the angle of your panels seasonaly?
  • westbranchwestbranch Solar Expert Posts: 5,142 ✭✭✭✭
    lkruper wrote: »
    Do you change the angle of your panels seasonaly?

    Yes...
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • RybrenRybren Solar Expert Posts: 348
    Just to be clear. My intention was not to have the outputs of both inverters connected to the epanel at the same time. I was looking for a way to to have the DC inputs permanently wired and be able to switch between the two. Only one inveter would be live and connected to the panel at any particular time, On reflection, however, I see where my post could have been confusing.
  • westbranchwestbranch Solar Expert Posts: 5,142 ✭✭✭✭
    A marine battery selector switch....#1 - \OFF\... #2, without a 1&2 position should work for you... on the positive /power line..
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • RybrenRybren Solar Expert Posts: 348
    That's what I was thinking all along, thanks. However, after reviewing the specs of my two inverters - the PST 1500-24 and Meanwell 400-124, there is only a 3W difference in tare loads, so it hardly seems worth the effort, especially since the camp gets used rather infrequently.
Sign In or Register to comment.