Inverter's AC OUT to Generator Inlet Box?

TommyBoy
TommyBoy Registered Users Posts: 9
Hello again. As I eagerly wait for my NAWS gear to show up, I've got a question I am curious about.

I have a 30A generator outlet box outside my garage, L14-30. If I get a 2000w pure sine wave inverter with AC wiring interface, could I connect a generator cord from the Inverter's AC out to the generator inlet box to feed the main panel to run 120 stuff in the house?

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Inverter's AC OUT to Generator Inlet Box?

    In theory--yes...

    In practice--you have to know what you are doing and beware of some of the issues or you could start a fire.

    Basically, the issue is your inverter is probably a 120 VAC sine wave inverter. And the L-14 30 plug is a 120/240 VAC plug.

    Typically, what is done is that Line A and Line B are tied to the 120 VAC "Hot" output of the 120 VAC inverter and the Neutral of the plug is tied to the Inverter Neutral.

    Now, 120 VAC appliances will work fine, but 240 VAC appliances will not work at all (they will see 0 volts between Line A and Line B).

    The danger is how the Neutral wires are run in your home... Normally with a Center Tapped 120/240 VAC split phase transformer, if you load the Line A and Line B with 120 VAC loads to neutral--the Neutral wire (return) carries no current.

    However, with the Line A and Line B tied together, when you have two 120 VAC loaded Line A and Line B circuits, the return current on the Neutral (white wire) is 2x the LineA/B currents (sum of A+B current)...

    So, in a home, if you have the typically Black/Red/White wiring (shared neutral), it is possible, if you have a large 120 VAC inverter, like 2,000 watts--It is possible that you could get ~17 amps (worst case) in your neutral lead (and more if >2,000 VAC inverter) and you wire it to power LineA+B with the inverter "Hot" Lead...

    Will it happen--not likely (running two hair dryers on two circuits that happen to share a common neutral)... But the possibility is there.

    If you get a 120/240 VAC split phase inverter setup, limit yourself to ~1,500 watt inverter, or only power 1/2 your AC loads in your house (only Line A loads, for example)--you can do it safely.

    Hope that makes sense.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • TommyBoy
    TommyBoy Registered Users Posts: 9
    Re: Inverter's AC OUT to Generator Inlet Box?
    BB. wrote: »
    In theory--yes...

    In practice--you have to know what you are doing and beware of some of the issues or you could start a fire.

    Basically, the issue is your inverter is probably a 120 VAC sine wave inverter. And the L-14 30 plug is a 120/240 VAC plug.

    Typically, what is done is that Line A and Line B are tied to the 120 VAC "Hot" output of the 120 VAC inverter and the Neutral of the plug is tied to the Inverter Neutral.

    Now, 120 VAC appliances will work fine, but 240 VAC appliances will not work at all (they will see 0 volts between Line A and Line B).

    The danger is how the Neutral wires are run in your home... Normally with a Center Tapped 120/240 VAC split phase transformer, if you load the Line A and Line B with 120 VAC loads to neutral--the Neutral wire (return) carries no current.

    However, with the Line A and Line B tied together, when you have two 120 VAC loaded Line A and Line B circuits, the return current on the Neutral (white wire) is 2x the LineA/B currents (sum of A+B current)...

    So, in a home, if you have the typically Black/Red/White wiring (shared neutral), it is possible, if you have a large 120 VAC inverter, like 2,000 watts--It is possible that you could get ~17 amps (worst case) in your neutral lead (and more if >2,000 VAC inverter) and you wire it to power LineA+B with the inverter "Hot" Lead...

    Will it happen--not likely (running two hair dryers on two circuits that happen to share a common neutral)... But the possibility is there.

    If you get a 120/240 VAC split phase inverter setup, limit yourself to ~1,500 watt inverter, or only power 1/2 your AC loads in your house (only Line A loads, for example)--you can do it safely.

    Hope that makes sense.

    -Bill

    Thanks Bill, I appreciate your beautifully precise reply. Even wood-noggin tommyboy can understand that. That makes complete sense.