What would happen if two inverters feed the circuit breaker box?

softdownsoftdown Solar Expert Posts: 3,137 ✭✭✭✭
My 48 volt solar array is working very well. So far, it rarely needs help from the generator. The problem with the diesel generator? It doesn't like to start when it is very cold. That is also when it is most likely to be needed. The fumes also work their way around a little bit.

The giant 24 volt forklift battery seems to be a good one. What would happen if the circuit breaker box was fed by two different inverters? In my case, a 48 volt inverter and a 24 volt inverter. Of course both of them are putting out ~120 volts.

My guess is that the circuit breaker box may simply use both sources of power? In essence, doubling the size of the battery array? Or....disaster awaits the eager "explorer"?

FWIW: the 48 volt inverter is part of an Outback MATE system. The 24 volt inverter is a pure sine wave Cotek that costs much less money.   And...I am broke and in debt...before someone tells tell to simply cough up a few thousand dollars.
First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries

Comments

  • Dave AngeliniDave Angelini Solar Expert Posts: 5,183 ✭✭✭✭✭
    Right up there with letting a bear get into your home.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • softdownsoftdown Solar Expert Posts: 3,137 ✭✭✭✭
    Thanks for the input....I'll try to avoid that. Have another couple options:
    1) Feed one side, with the lower demand, of the circuit breaker box with the 24 volt inverter.
    2) Feed the freezer with the 24 volt inverter. This may be the soundest idea.
    3) Set up a switch. Use the 24 volt array for a day or two when the main 48 volt array needs more time to recuperate.


    Dave Angelini said:
    Right up there with letting a bear get into your home.

    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • stillchillinstillchillin Registered Users Posts: 45 ✭✭✭
    add a second breaker panel and split the loads how you please. The neutral also carries current, you do not want to share that between two uncompatable inverters, I'm sure someone in the forum can tell you exactly why but I would say no.
    18- 235 W Kyocera panel, 12- 4-KS-25PS Rolls 1350 Ah, Magnum MS4448PAE, ME RC50, ME AGS, Outback FM 80, Generac 8KW LP generator, 6.5 Honda Portable generator
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    softdown said:
    Thanks for the input....I'll try to avoid that. Have another couple options:
    1) Feed one side, with the lower demand, of the circuit breaker box with the 24 volt inverter.
    2) Feed the freezer with the 24 volt inverter. This may be the soundest idea.
    3) Set up a switch. Use the 24 volt array for a day or two when the main 48 volt array needs more time to recuperate
    Do not run both inverters into the same circuit breaker box unless you use a transfer switch so that only one inverter at a time is connected to the breaker box.  I am presuming that the bond between neutral and ground is in the breaker box.

    By the way, what are you using for a battery in the 24 volt system?  How do you charge the 24 volt battery?

    How difficult will it be to separate the loads into two breaker boxes so that you can run two systems simultaneously?

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • softdownsoftdown Solar Expert Posts: 3,137 ✭✭✭✭
    Have a 1652 pound forklift battery for the 24 volt system. Seller thought it was 48 volt. Got it for scrap value since it showed 22.2 volts. He also paid scrap value so nobody got hurt.

    I charge it with a couple extra 190 watt panels. I'm not an electrician so I'll just run a wire to the freezer and hope it handles the chest freezer. For now anyway.

    I bought so many panels that I don't know what to do with all of them. My solar guy said he could easily sell them but that has not materialized. I may just sell them on Craigslist. Went to California and bought 48 used panels a few months ago.


    vtmaps said:
    softdown said:
    Thanks for the input....I'll try to avoid that. Have another couple options:
    1) Feed one side, with the lower demand, of the circuit breaker box with the 24 volt inverter.
    2) Feed the freezer with the 24 volt inverter. This may be the soundest idea.
    3) Set up a switch. Use the 24 volt array for a day or two when the main 48 volt array needs more time to recuperate
    Do not run both inverters into the same circuit breaker box unless you use a transfer switch so that only one inverter at a time is connected to the breaker box.  I am presuming that the bond between neutral and ground is in the breaker box.

    By the way, what are you using for a battery in the 24 volt system?  How do you charge the 24 volt battery?

    How difficult will it be to separate the loads into two breaker boxes so that you can run two systems simultaneously?

    --vtMaps

    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • mike95490mike95490 Solar Expert Posts: 8,762 ✭✭✭✭✭
    > Or....disaster awaits the eager "explorer"?

    You can only feed 2 inverters to a single panel, if they are a matched pair with a sync cable.  Otherwise, it will be "exciting".
    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 ,

  • SkipSkip Registered Users Posts: 16 ✭✭
    I have a similar question to this thread, I have 2 Cotek SK 1500 - 124 PSW Inverters, I have 2 sub panels, one in the garage and one in my bonus room, is it possible to connect 1 of the inverters to each of the 2 sub panels without any damage to the inverters, or anything else? as I have a 3500 watt grid tie stand alone system and would like to use the Coteks for for backup power during outages. I have an AC Disconnect switch to disconnect the power company from the main load center.
  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    If the sub panels are isolated. Which they tend not to be! And no relying on a breakers to isolate, is not enough you need a full transfer switch.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • SkipSkip Registered Users Posts: 16 ✭✭
    Thanks for the reply Zoneblue (nice website BTW), I am still wondering what it would take to make this work.
    I totally disconnect the juice from power company using my AC Disconnect switch on the main electric panel, and using the AC disconnect switch in the off position on my 220 vac PV Watts 3500 GT Inverter so the only possibility of any current running in the house would be power supplied by the Cotek PSW inverters wired into the sub panels, hooked to a battery bank and charged by my 1600 watt secondary set of solar panels. At this point will the inverters power up the 110vac portions on the house circuits without blowing the inverters, as they are NOT stackable?
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    You really need a transfer switch, even if you are using only 1 inverter.  It is extremely poor practice (and illegal) to power your house from either a generator or an inverter unless you have a transfer switch. 

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • SkipSkip Registered Users Posts: 16 ✭✭
    OK so lets say I add a Transfer switch would it matter if the transfer switch was automatic or manual? what will it take to get a answer to this question? using 2 inverters? I really don't want to spend more money on a transfer switch if my 2 inverter plan won't work. Yea I know that using a 3000 watt inverter would work but I don't have one on those yet.
  • WaterWheelWaterWheel Registered Users Posts: 337 ✭✭✭
    Skip said:what will it take to get a answer to this question? using 2 inverters
    Using 2 inverters on the same line that are not in sync with one another is a disaster even with the local utility totally disconnected.         I guess you could be unhooked from the grid and use one inverter tor L1 and the other inverter for L2 but their shared neutral would probably still make it an unusable setup.     And the shared earth ground would probably trip GFIs.

    In addition you could not use them to run 220v since they would be out of sync.

    There are more knowledgeable people than I here but no way would I be foolish enough to try it.

    Conext XW6848 with PDP, SCP, 80/600 controller, 60/150 controller and Conext battery monitor

    21 SW280 panels on Schletter ground mount

    48v Rolls 6CS 27P

  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    Skip said:
    OK so lets say I add a Transfer switch would it matter if the transfer switch was automatic or manual? what will it take to get a answer to this question? using 2 inverters? I really don't want to spend more money on a transfer switch if my 2 inverter plan won't work. Yea I know that using a 3000 watt inverter would work but I don't have one on those yet.
    Its important that you understand what people are trying to tell you, as what you are proposing is fraught with hazards.

    You can not / should not:
    - connect any separately derived system to the house without a UL listed transfer switch that categorically prevents the SDS and the grid (and your GTI) becoming connected.
    - connect the output side of 2 or more off grid inverters (or other SDSs) together unless those devices are specifically engineered to do so, (read stackable inverters).

    To achieve what you want, you will need several transfer switches (manual is ok), one for the grid, one for each sub panel that you want to power (possibly minus one), (to prevent the subpanels ever becoming connected accidentally.).

    There are of course easier ways, like using an hybrid inverter specifically designed for this application, or a single bigger off grid inverter and a single transfer switch.

    You should also ideally:
    - use quality off grid inverters, that are UL listed for hard-wire.
    - get an electrician involved






    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    In case the issue of two inverters and two subpanels isnt clear from the above, if you connect one inverter to one subpanel, and a second inverter to a second subpanel, and the subpanels arent safely isolated, you will likely destroy one or both of the inverters. This is because they will be out of phase, and fighting each other.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • SkipSkip Registered Users Posts: 16 ✭✭
    OK I would like to thank you zoneblue and foolami  for taking the time to answer this question, so if I get you both, I need a transfer switch and one large off grid inverter, to be safe and legal and I like that plan, so again Thank You both the this information.

  • brianbk1brianbk1 Registered Users Posts: 1
    I have a similar type question. My 5th wheel is designed to operate in 30 or 50 amp. For 50 amp I can plug in 1 50, or use a second plug on the RV to do a 30 and 20 connection. Would this work with 2 inverters?
  • EstragonEstragon Registered Users Posts: 4,478 ✭✭✭✭✭
    Why do you want to use 2 inverters?

    As I understand it the 50a plug is 120/240v split phase shore power source. If using two inverters in that setup I'd want them set up to duplicate that (stacked for phase sync). Don' t quite understand what you're trying to do though.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • bill von novakbill von novak Solar Expert Posts: 891 ✭✭✭✭
    brianbk1 said:
    I have a similar type question. My 5th wheel is designed to operate in 30 or 50 amp. For 50 amp I can plug in 1 50, or use a second plug on the RV to do a 30 and 20 connection. Would this work with 2 inverters?
    Short answer - no.  You cannot get one inverter to deliver 20 amps and a second to deliver 30 amps and have them, together, produce 50 amps.  If they are the same brand AND they support parallel operation you can do it - but from your question I have a feeling you are looking to do this on the cheap, and such parallelable inverters are not cheap (nor are they the best way to accomplish what you want to do.)
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