Inverter and 2 way switches.. and possible issues..??

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  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    Re: Inverter and 2 way switches.. and possible issues..??

    Well it would be 40 amps max on the neutral.. I was just saying 50 for each HOT leg..

    Thank you though.. makes sense.

    The other comments got me all twisted in a knot..
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Inverter and 2 way switches.. and possible issues..??
    ywhic wrote: »
    Well it would be 40 amps max on the neutral.. I was just saying 50 for each HOT leg..
    Which is a lot less than 100 per HOT leg, so no problems at all anywhere in the plan.
    SMA SB 3000, old BP panels.
  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    Re: Inverter and 2 way switches.. and possible issues..??

    Will the neutrals riding from 2 separate inverters be an issue (if I went that way with 2 inverters)??

    I mean the neutral will be feeding all the outlets in the house since they are all wired to the 1 terminal strip in the load center..

    Granted each circuit will have a 15 amp breaker on them..

    Does the neutral carry a live 'backfeed' per se on 110VAC???
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Inverter and 2 way switches.. and possible issues..??
    ywhic wrote: »
    Will the neutrals riding from 2 separate inverters be an issue

    Depends on the inverters. If they're pure sine with a transformer isolating the output from the internal electronics, it should be no problem. If however they're the usual MSW type with "floating" neutral that must not be bonded to ground, it will likely cause then go blow up, or at least make big smoke and die.
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Inverter and 2 way switches.. and possible issues..??
    ywhic wrote: »
    Will the neutrals riding from 2 separate inverters be an issue (if I went that way with 2 inverters)??

    I mean the neutral will be feeding all the outlets in the house since they are all wired to the 1 terminal strip in the load center..

    Granted each circuit will have a 15 amp breaker on them..

    Does the neutral carry a 'backfeed' per se???

    Since this is an isolated rather than a grid tie system, there is no issue of "backfeed" exactly. But as long as the hot lead from the one inverter is interrupted, there will be no interaction from the other inverter. This assumes that the two inverters are both happy to work with one side of the AC output grounded. (Otherwise connecting just the two neutrals together could cause a problem, and you would have to run a separate neutral for each.

    There is a problem with working on the wiring, though:
    If you have one outlet or lamp or appliance which is wired to inverter 1, and you decide to safely work on it by turning off inverter 1, you will have to realize that there may still be current flowing in the neutral wire from something powered by inverter 2. That means that if, as part of your work, you disconnect the neutral, one of the two wires may be at 120 volts AC!

    It is safest for anyone working on the wiring that you run a separate neutral for each circuit, regardless of which inverter it is powered by. That way opening just one breaker will make it safe to work on both hot and neutral for that circuit.
    SMA SB 3000, old BP panels.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Inverter and 2 way switches.. and possible issues..??
    inetdog wrote: »
    There is a problem with working on the wiring, though:
    If you have one outlet or lamp or appliance which is wired to inverter 1, and you decide to safely work on it by turning off inverter 1, you will have to realize that there may still be current flowing in the neutral wire from something powered by inverter 2. That means that if, as part of your work, you disconnect the neutral, one of the two wires may be at 120 volts AC!

    Well, no. Not exactly. He's talking about sharing only the neutral bus bar between inverters; each circuit would still have its own hot & neutral lines. Since this should only be done with sine wave inverters just like Wayne said, the neutral should also be bonded to ground and thus tied to the Earth grounding rod. Thus there is no current potential between any neutral line and ground. But you do have to be sure you killed the power to whatever line you are working on.
    It is safest for anyone working on the wiring that you run a separate neutral for each circuit, regardless of which inverter it is powered by. That way opening just one breaker will make it safe to work on both hot and neutral for that circuit.

    Totally. Shared neutrals are a bad idea in any type of wiring.
  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    Re: Inverter and 2 way switches.. and possible issues..??

    So its OK to do with Sine Wave Inverters.. but also use the ground neutral bonding screw in the panel to tie the neutral to the ground just in case and to be safe..

    I do plan on running all wires from each outlet back to the load center panel and numbering them in case I have issues later on..

    I would always kill the circuit breakers and more than likely both inverters (if I go that route) before I touch the outlets and such..
  • erne
    erne Solar Expert Posts: 41
    Re: Inverter and 2 way switches.. and possible issues..??

    I am not a electrician and I do not do a/c wiring that is for licensed electricians. I live and do off-grid remote repair and some install, like on repeaters etc. I live in a very remote region where the rural electrification act never arrived.
    It sounds like the three way switches I am referring to were wired incorrectly and the mains box was jumped (according to the investigation) He is having trouble with the insurance company. I do not have all the answers and you guys have a lot of experience. I am not arguing with you about the safety. I believe it has been done safely, but caution should be observed and there is no room for mistakes. Here is a photo of what happens when one ignores the NEC.
    Attachment not found.
    fire.jpg 207.6K
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Inverter and 2 way switches.. and possible issues..??

    If 3 way switches are wired and used as intended, which is for controlling a light or any other applicable load supplied with power from a single fuse or circuit breaker, there will be no more problems than with a regular single pole switch. Anyone who manages to somehow and very wrongly wire a 3 way switch into the two legs of a panel is grossly incompetent and some might say deserve what they get for frigging around with things they know nothing about. But even then, I'd be far less worried about the power from any inverter causing problems, than I would be about the hundreds of amps @ 240 Volts coming in from the utility transformer out on the pole when it hits any switch so wrongly wired!
    Sorry for wording this so strongly, but this topic has been beaten to death. Lets put it to rest and move on.
  • British
    British Registered Users Posts: 3
    Re: Inverter and 2 way switches.. and possible issues..??

    I am afraid you have gotten a deal of bad advice, It may be that the reference to the 2 way switches was with the thought of transferring some of the circuits to your back up system in the event of a power failure, a inverter can not feed any circuit where there is a neutral ground bond unless your inverter is isolated. As respects any switched circuit weather it is for a fan or a light and weather it is a single pole switch, a three way or a four way (The neutral is never switched) the circuit is only fed from one power sorse. The number of switches that you have on that circuit does not matter. Also I saw a comment about how a three or four way switch was for 220 circuits (Wrong) They are both for 120, the only thing that the switches do is to re-rout the hot wire, that is why they are called travelers. If you would like a schematic of a three or four way set up just let me know. O, one more thing, on a three or four way set up the switches are daisy changed together with either 12/3 or 14/3 wire depending on the breaker size, The only wire that goes back to the breaker box is the feed wire, and that only needs to go back to the breaker box if you can not pick up a feed from a closer source. The feed wire only needs to be a 12/2 or 14/2, if you have a 15 amp breaker it can be 14/2, with a 20 amp breaker it would need to be on 12/2. again the wires from the switch box's do not need to all go back to the breaker box. You need to really talk to someone who is knowledgeable about this I feel you are making it much harder than it is.
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Inverter and 2 way switches.. and possible issues..??
    ywhic wrote: »
    Someone replied to my post on another subject.. hence the question is raised..

    They said you cannot have ANY 2-way switches on the inverter output 110-120V circuit as it may cause overload of the neutral and create a possible fire hazard.

    Anyone hear of this??

    I was planning on putting in a ceiling fan on the 110V AC side in my cabin and using a switch to turn it on/off from 2 different points in the cabin (front door and back room)..

    Obviously my 110V AC panel would have breakers and such and all wiring done correctly per normal codes..

    Is he/she referring to something else??


    All that I can think of would be the rather artificial and impractical situation in which a three-way (single-pole-double throw) or four-way (double-pole, double throw with internal crossover) is used to feed power to a load from two different breakers which are on different sides of a 240 volt feed. By moving the load from one bus to the other, you would be changing the balance of system, causing a neutral conductor current which is slightly higher than for a balanced load distribution. But even then the current would still be less than the rated current of the neutral!
    SMA SB 3000, old BP panels.