Inverter A.C. wiring

colderthancolderthan Registered Users Posts: 20
I'm going to add a 2nd inverter to my system. In the A.C. breaker box, can I wire the new inverter to one side on the hot side and the old to the other and then combine the nuturals? Or does it need its own breaker box?

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Inverter A.C. wiring

    What inverter?
    Many are "stackable" and can be added together either doubling the 120 amperage capacity or giving 240 voltage, providing the inverters are identical.

    Otherwise neutrals would be connected together, but it's probably not a good idea to have dissimilar inverters' power available in the same box.

    That is not expressed well, so wait for the better replies from the experts here! :D
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Inverter A.C. wiring

    Off grid,,, or grid tied?

    If you are off grid, AND the inverters have grounded neutrals, then you should be able to energize one bus from one inverter, and the other from another similar inverter. Inverters with floating neutrals might pose a problem however,,, and I will leave that to others.

    Remember if you do this, only those circuits on any given buss will be energized by each inverter, so that you might, depending on your loads, have a pretty unbalanced load. You may want to reconfigure your breakers so that the loads are spread somewhat equally between the inverters.

    Tony
  • colderthancolderthan Registered Users Posts: 20
    Re: Inverter A.C. wiring

    Thanks for your replies. I'm off grid currently using a 2400 w. msw. thats been doing a good job for the last 15 years. I'm adding an 1100 w. sine wave that will be used just on a few dedicated curcuits(radio,computer,ect) and continue to use the msw for the heavy lifting on the rest of the house. My first plan was to add a small breaker box and move 2 or 3 curcuits but I have plenty of room in the existing box. The two neutrals are going to be joined eventual anyway wear they bond to ground.
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Inverter A.C. wiring

    As I said before,, I don't see any reason why you shouldn't be able to energize each buss in a split phase panel from a different inverter, and essentially tie the neutrals together on the same neutral buss bar. It would seem silly to add a second box just for that reason.

    Something niggles at me mixing msw with sw, but I wouldn't think it would be a problem,,, but I would certainly trust those with more smarts than I on that subject.

    Tony
  • colderthancolderthan Registered Users Posts: 20
    Re: Inverter A.C. wiring

    Yeah, kinda "niggles" at me to. thought I better ask.
  • PhilSPhilS Solar Expert Posts: 370 ✭✭✭
    Re: Inverter A.C. wiring

    I have my home wired much as you are proposing. The neutrals are tied together between the "big" inverter and the "small" inverter, and both circuits enter the house through one breaker box. For at least 20 years the "big" inverter was an old Heart Interface 2000 MSW. I added a true sine wave Prosine 1.0 maybe 8 or 10 years ago to power most of the lights, computer and all of the 'entertainment' circuits (L&E).

    A year ago I replaced the "big" inverter with a true sine wave Magnum 2500. There was never any interference with the modified and true sine wave inverters sharing the neutral, so changing to the better inverter made no difference.

    OK, now I'll don my flame-resistant suit and continue.

    As far as your question of "in one breaker box or two", all of my circuits pass through the one main box. I have no doubt that you could split the two busses and wire it that way. Since my L&E circuits are powered by a 1000 watt inverter, I chose to simply connect the hot leads from those circuits directly to the hot lead from the small inverter (inside the breaker box but not through the busses). Those circuits do NOT use the individual breakers in the box, they are only protected by the single 20A breaker for the inverter output.

    To code? Not likely. Unsafe? Not really. Advantages? Not having a 10 amp inverter feeding small loads through 6 additional 20 amp breakers. Disadvantages? I can't isolate breaker-by-breaker my L&E circuits since it's just one multi-string circuit. Hasn't been a problem.

    I am NOT recommending you wire you home in any particular manner. I AM confirming your suspicions that connecting the neutral of a MSW and SW inverter makes no difference (in my home). If you are subject to any kind of inspection, powering your home with two dissimilar inverters would probably make you fail, since anything out of the ordinary is unacceptable anyway.

    Ok, flame suit back off so Icarus, BB, niel and crewzer can fire away ;)

    Phil
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Inverter A.C. wiring

    Phil,

    Nothing requiring a fire suit on my end! As long as you have each L&E wire large enough for the 20 amps (#12) then there really is no problem.

    On the other hand, I probably would have wired each circuit through individual breakers in the panel just to keep it clean and simple. In fact that is the way that my house is wired,,, the out put to the inverter is wired to the buss bar of the small panel, feeding the circuits through the breakers. Seems a bit over the top since the inverter is only 300 watts!

    Phil, I was un aware that you are off grid.
  • PhilSPhilS Solar Expert Posts: 370 ✭✭✭
    Re: Inverter A.C. wiring
    icarus wrote: »
    Phil, I was un aware that you are off grid.

    Then you haven't been looking very carefully at signatures... :roll:

    Things warming in your area?

    Phil
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Inverter A.C. wiring

    I noticed your signature after I posted that comment. I'm sure I've seen it before,,, but it must be an age thing!

    We had a wonderful week last week,, major melt off, with temps in the +50f range, and then bingo, back to -10 for a few nights. Just came through a pretty significant ice storm. Don't expect the ice to leave for another 6 weeks though.

    T
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Inverter A.C. wiring

    I think Phil has hit the nail on the head: we all agree that technically it will work, but an inspector is likely to find a problem with it because it wouldn't be 'legal'. Besides; inspectors like to find problems! :p

    I once had a problem with a MSW inverter causing a 'buzz' in a breaker, but never could figure out why. Some kind of interference between it and the UPS it was feeding. There may be a similar interference problem with two different inverters sharing 1 common line, maybe not. There's so many different inverters out there ... and some are from China! :p

    So the issues are: code violation, which is certain and; potential wave-form interference which is not.

    And in future someone may try to tap the two poles to get 240 and be very disappointed. :roll:
  • PhilSPhilS Solar Expert Posts: 370 ✭✭✭
    Re: Inverter A.C. wiring
    And in future someone may try to tap the two poles to get 240 and be very disappointed. :roll:

    Well Marc,

    THAT'S a problem I hadn't thought of. In my system, that 'someone' would find only 120V (the SAME 120V) on both legs. Splitting the two bus bars, that 'someone' would find two different 120V sources from the two inverters.

    Tapping in for 240V on mine would send 120V to the appliance and trip the breaker on the inverter. With split busses, no telling what would happen if two different inverters were tied together and sent to one 240V load. Well, we know the load wouldn't operate properly, but would it affect the inverters? That's a situation I wouldn't choose to try.

    One possible problem with my method would be if that dang 'someone' flipped off the main breakers at the box assuming all power to the house would then be off. The L&E circuit would still be energized. I DID affix some stickers above the breakers that warn of the inverters and flipping breakers MAY not remove all power, but I could actually do more for "warnings".

    Dang, Icarus... March came in like a lion so you may be about done with winter. S'posed to be 80 here today, which means the skeeters are gonna be out and about this weekend.

    Phil
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Inverter A.C. wiring

    If you are worried about disconnects,

    Why couldn't you wire one inverter to one leg of a main 240 breaker, the other to the other leg of the breaker, thus energizing the buss's through the breaker. That main would serve as a disconnect for the entire system. Each branch circuit would then be protected with individual breakers sized for the wire size of the circuit. (None bigger than the total output of the inverter(s)).

    As long as you don't have any double pole breakers,, there would be no chance if energizing the wrong buss/breaker assy in error. At least if someone tried to tie the two legs together to try to get 240vac they would have to really try, as opposed to an accident.

    Phil,

    As for our weather,, we had a big Blizzard,,, 40cm of snow followed by brutal cold(-30) the second week of March, followed by the warm spell, followed by the ice storm,, (1' of ice on everything,, trees down everywhere!) followed by normal for the next week or so. Freezing or a bit above during the day,,,-10-20C over night. Great solar weather however.

    T
  • colderthancolderthan Registered Users Posts: 20
    Re: Inverter A.C. wiring

    I'm in a remote part of interior Alaska, no building codes here. I doubt if both inverters will spend much time on together so interference (hopefuly) won't be much of a problem. When the old msw inverter does die, I'll do what Phil did and replace it with a larger sw.
    Thanks guys!
    Paul
  • BrockBrock Solar Expert Posts: 633 ✭✭✭✭
    Re: Inverter A.C. wiring

    Technically you want the incoming power to the panel come in through a main 240 breaker even if it is from two different inverters. If you were working in the panel you would just flip off the "main" and you’re safe. If they are wired backwards in through a breaker and the main is off and you happen to hit the other side of the bus it would be hot.

    I am not saying to not bring the power backwards in through a breaker, but I wouldn't. If you’re not there and someone needed to work on something they will assume shutting of the main will shut off all the power and it would be safe to work in the box. If you do it that way make sure you very obviously label things.
    3kw solar PV, 8 L16's, xw 5548, Honda eu2000i, iota DLS-54-13, Leaf EV, 4 ton horizontal geothermal, grid tied - Green Bay, WI
  • PhilSPhilS Solar Expert Posts: 370 ✭✭✭
    Re: Inverter A.C. wiring
    colderthan wrote: »
    I'm in a remote part of interior Alaska, no building codes here. I doubt if both inverters will spend much time on together so interference (hopefuly) won't be much of a problem. When the old msw inverter does die, I'll do what Phil did and replace it with a larger sw.
    Thanks guys!
    Paul

    Well, Paul, at least you don't have inspectors to deal with!

    My old Heart Interface never died... it had devolved to powering only our water pressure pump and the pump did not like MSW. Our 56-step Xantrex had been powering the house loads, so I moved it to power the water pump and the pump has been happy since.

    I bought the Magnum so that I could have a GOOD inverter to power a new fridge and that has worked out very well. I'd been on propane refrigerators for decades but the price of propane dictated I phase it out.

    So I still have this Heart Interface 2000W "ultra-efficient" inverter sitting in the garage and no idea what to do with it. The thing is too heavy to ship anywhere. It's 20 years old (and MSW) so not something I'd want to sell to anyone starting down this power road. I offered it (free) to a friend with a houseboat but warned that microwave ovens (about the only thing he'd need it for) didn't work as well on the MSW. He doesn't seem eager but it's not houseboat season yet either.

    So what could I do with this inverter? Any suggestions? I could mount it in one of our trail machines or tractor so I could run an electric tool far out in the woods. But.... I've not yet needed an electric power tool for any of the work I do in the forest (but it's only been 30 years... maybe I just haven't discovered the need yet?)


    Brock,

    If your post was referring to my box, there's nothing wired 'backward' through any breakers. I just have one separate feed into the box from the inverter that ties to those circuits for L&E and doesn't use any breakers in that box.

    Since I have a ground pedestal (w 2 main breakers) feeding the house box (with another 2 main breakers), I COULD (should?) separate those pedestal breakers so one is for each inverter.

    My inverters are in a building about 50' from the house with underground wiring feeding the pedestal which then feed the main box. (We live in a mobilehome and that's the way it has to be done by code.)

    Phil
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Inverter A.C. wiring

    I'm assuming that one would be wiring this is a small sub-main type panel. In a panel with a main breaker of course you would wire the panel energizing the buss through the main breaker.

    In a sub-type panel, with lugs to energize the buss' directly, I'm suggesting that you could energize the buss by wiring the breakers "backwards",, hot to the lugs on the breaker, through the breaker to the buss bars.

    I suspect that them more I write,, the less clear it is.

    To answer the Colder Than's original question,,,I don't see a problem wiring two inverters to two different buss's in the panel,,, either from the main, or to the buss's directly,,, regardless of the waveform of the inverters. As long as 120vac is all that is desired as an output.

    Tony
  • colderthancolderthan Registered Users Posts: 20
    Re: Inverter A.C. wiring

    Phil, if I could figure out what to do with an old msw inverter I would have a shiny new magnum like you have, but it's been taking care of me for so long I just can't bring my self to pull the life support plug on it......oh well.
    Take care.
    Paul
  • PhilSPhilS Solar Expert Posts: 370 ✭✭✭
    Re: Inverter A.C. wiring
    colderthan wrote: »
    Phil, if I could figure out what to do with an old msw inverter I would have a shiny new magnum like you have, but it's been taking care of me for so long I just can't bring my self to pull the life support plug on it......oh well.
    Take care.
    Paul

    Hey Paul... swing by here next time you are out and about (VERY out and about, of course) with a cold six-pack and I'll give you a spare!! :p

    I just hope my Magnum lasts as long as that Heart Interface! Although I'm sure the engineers of the Heart are enjoying retirement by now, the lineage of that company is linked to Magnum, isn't it? I certainly couldn't ask for a better service life than the Heart has given me.

    Phil
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Inverter A.C. wiring

    If you were to tap both poles there's a high probability (almost dead certainty) that the power would be out of phase. Since the neutrals would be tied, a load across the poles would probably be like a dead short for both inverters.

    I don't want to try it either! :p

    If you have both in the same box, some type of 'kill all' is a must; you don't want to work around some charged lines. Running the two 'hot' lines back through a 240 breaker that ties to both busses may work, but not all breakers like to function backwards. Should be okay for a disconnect though.

    But there's always that bug-a-bear "what happens when the next guy comes along?"
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Inverter A.C. wiring

    Marc,

    You said it right, (don't know where my brain was,,) you would only use the main breaker as a disconnect.

    T
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