120/240

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ws9876
ws9876 Solar Expert Posts: 440 ✭✭✭
in Off Grid Solar & Battery Systems #1
If you want to run your inverter 120v output directly into your mains(disconnected from grid) and you disconnect all 240 loads..
you should have no problems with neutral overload, yes????
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #2
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    Re: 120/240
    ws9876 wrote: »
    If you want to run your inverter 120v output directly into your mains(disconnected from grid) and you disconnect all 240 loads..
    you should have no problems with neutral overload, yes????

    That depends - - - what size inverter, how many watts? If your inverter is 1800 watts MAX or less, no problem, assuming house is wired with standard #14 wire.
    Larger inverter and for example, there could be problems with split circuits supplied with 14/3 (two hots and one neutral) instead of two separate 14/2 cables.
    What size your inverter? What size your future inverter?
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #3
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    Re: 120/240
    waynefromnscanada wrote: »
    ...there could be problems with split circuits supplied with 14/3 (two hots and one neutral) instead of two separate 14/2 cables.
    The US technical term for these is MultiWire Branch Circuits (MWBC), and the neutral is sized the same as the two hot conductors under the assumption that the current in the neutral from both hots will cancel rather than adding. That will not be the case if you connect your single 120V inverter to both L1 and L2 inputs to your panel.
    If you connect only to L1 or only to L2 you will be able to safely power any of the half of your total circuits which are connected to that input bus. (Up to the limits of the inverter, of course.)
    Historically, they are also called Edison circuits, since he pioneered that system for power distribution as well as branch circuits.
    SMA SB 3000, old BP panels.
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  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    #4
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    Re: 120/240

    As inetdog said in the other thread, you can use a transformer to create proper split phase power. In this case, a 120 to 240 transformer with a center tap on the output side.

    Or check if you have any MWBCs and disable them.

    I am available for custom hardware/firmware development

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  • ws9876
    ws9876 Solar Expert Posts: 440 ✭✭✭
    #5
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    Re: 120/240

    Attachment not found.I have some of all of these MY circuits all appear to have 1 hot and 1 neutral. There is one double breaker for 2 small loads...maybe that is one of those...but I have only 1 and could easily replace that with a single... I will have extra slots after removing 240 loads...
    I dont need 240 at all..
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
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    Re: 120/240
    ws9876 wrote: »
    Attachment not found.I have some of all of these MY circuits all appear to have 1 hot and 1 neutral. There is one double breaker for 2 small loads...maybe that is one of those...but I have only 1 and could easily replace that with a single... I will have extra slots after removing 240 loads...
    I dont need 240 at all..

    Don't look at the breakers; look at the wires.
    If there are any cables coming from the box with three wires (usually black, red, and white) there could be a problem: black and red are L1 and L2 respectively and normally return only the current difference via neutral white. This is where you get into trouble with L1 and L2 being fed from one hot line: it will allow the possibility of 2X current on the white neutral.
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  • ws9876
    ws9876 Solar Expert Posts: 440 ✭✭✭
    #7
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    Re: 120/240

    say you had 2 outlets on 1 mbc on one buss..if you connect the inverter only to L1 then one of the outlets wont work. So you could pull one hot wire and move it 1 slot down on its own small breaker and it would now be on the L1. yes???
    as far as overloading the L1 neutral, that seems unlikely unless you have 2 really hot loads like 2 toaster ovens..
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #8
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    Re: 120/240

    Overloading neutral can occur if:
    1). the inverter is capable of putting out enough current and not faulting first;
    2). there are two hots fed by the output which share a neutral return wire.

    The combined load needs to exceed the neutral wire's capacity (14 AWG is good for 15 Amps continuous, 20 Amps intermittent).

    If you change the hot connections of such a wiring system so that both are fed by L1 at the box (instead of L1 and L2) this is no different as far as the shared neutral is concerned than connecting L1 and L2 at the box: you have two pieces of 'X' AWG wire on hot and one on the neutral so it still has the potential for being fed 2X current.
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  • ws9876
    ws9876 Solar Expert Posts: 440 ✭✭✭
    #9
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    Re: 120/240

    do you think a licensed electrician would put a gfc outlet in a kitchen on the same wire mbc as a regular outlet nearby??
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #10
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    Re: 120/240
    ws9876 wrote: »
    do you think a licensed electrician would put a gfc outlet in a kitchen on the same wire mbc as a regular outlet nearby??

    There's every possibility of it.
    The GFCI is only checking current on its hot against current on its neutral; other outlets attached to the same feed are unaffected (unless they are run from the GFCI outlet's "protected" terminals in which case it's the same as something plugged in to the outlet).
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #11
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    Re: 120/240
    ws9876 wrote: »
    do you think a licensed electrician would put a gfc outlet in a kitchen on the same wire mbc as a regular outlet nearby??

    That is pretty standard practice to have 2 circuits in a kitchen with all outlets GFI protected by placing the extra outlets on the load side of the GFI outlet. When they redid my kitchen they had to undo an outlet for the move of the fridge and place a GFI outlet in each box to allow the fridge to be not GFIC'd at the end of the run.
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