Instalation/devolpment help

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  • Caveman
    Caveman Solar Expert Posts: 83 ✭✭✭✭
    #32
    Re: Instalation/devolpment help

    Okay here's what I bought, and I scratched my head for awhile reading the instructions of how to wire it.
    http://www.solar-electric.com/miso30amp240.html

    Basically both breakers can't be on at the same time, so one breaker interrupts/completes the solar power, and the other one interrupts/completes the generator power. Ill try a drawing.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #33
    Re: Instalation/devolpment help

    Oh yes: the external mechanical interlock - which can be defeated by removing the cover just as you did for your photos. :roll: That's why I don't like them. But they can work.

    The wiring is fairly straight forward, though. This does explain why there are two sets of wires coming from the transfer switch instead of one. The output of the two breakers could be joined in the transfer box, btw.

    Okay so back to the basic N-G bond problem. Because you have the bond at the generator already, if there is another one on the other side of the gen's GFCI circuit you essential create the problem the GFCI is designed to protect against: an alternate path for current beside the neutral wire.

    This is where the RV type transfer switch comes in handy: it is essentially a three pole, double-throw switch. One pole controls "Hot", switching between inverter and generator. The second does the same for the "Neutral" line. Ordinarily this would be enough, but for the grounding issue.

    Enter the third pole. In "inverter" position it connects the AC load ground line to the inverter's neutral, creating the N-G bond. In the "generator" position it connects the AC load ground to the generator ground (the N-G bond is within the gen itself). The AC load ground line is connected to the Earth grounding rod.

    RV's tend to need this sort of switch because they connect to shore power, which already has an N-G bond and Earth grounding rod. Sometimes they also have MSW inverters which can not have an N-G bond on their output. This type of switch allows flexibility in placing the bond and Earth grounding connections depending on which power source is used.
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  • Caveman
    Caveman Solar Expert Posts: 83 ✭✭✭✭
    #34
    Re: Instalation/devolpment help

    Ok here goes nuthin'....

    Attachment not found.

    The yellow romex in the pictures are outgoing circuits to the cabin outlets (this whole setup is inside the cabin).
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  • Caveman
    Caveman Solar Expert Posts: 83 ✭✭✭✭
    #35
    Re: Instalation/devolpment help

    Ok, thanks for the explanation. While I don't fully understand yet, I think I get the idea that if I had used an RV type of transfer switch I wouldn't be having a ground wire issue at all...

    Just did a brief search for "RV transfer switch" and couldn't find one. Have a particular model you could show me?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #36
    Re: Instalation/devolpment help

    Right.
    As I said the output for the loads could be combined in the transfer switch box for simplification, but it works either way.

    I don't think you have any problem with Hot or Neutral, just that grounding issue.
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #37
    Re: Instalation/devolpment help

    You can use the other half of your transfer switch breakers to switch neural.

    When your generator is on, you'll be using neutral from the generator. It is to be interrupted by the "generator" breaker. Wire it so that it goes from the generator to the breaker, and from the breaker to the AC box.

    When solar is on, you'll be using neutral bonded to the ground. It is to be interrupted by "solar" breaker. Keep the wire coming from the solar connected to the bus bar in the transfer switch. Connect short wire from this bus bar to the solar breaker, then from the breaker to the AC Box. Put a jumper wire between the bus and the ground screw.

    You also need to remove the ground bond from the AC box.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #38
    Re: Instalation/devolpment help
    NorthGuy wrote: »
    You can use the other half of your transfer switch breakers to switch neural.

    When your generator is on, you'll be using neutral from the generator. It is to be interrupted by the "generator" breaker. Wire it so that it goes from the generator to the breaker, and from the breaker to the AC box.

    When solar is on, you'll be using neutral bonded to the ground. It is to be interrupted by "solar" breaker. Keep the wire coming from the solar connected to the bus bar in the transfer switch. Connect short wire from this bus bar to the solar breaker, then from the breaker to the AC Box. Put a jumper wire between the bus and the ground screw.

    You also need to remove the ground bond from the AC box.

    Major caution here for others (but not for you with 120 volt only) : If your system includes 240 volt and 120 volt loads, interrupting the neutral with the same breaker (not just two or three with handle ties) may be OK, but may also allow for a brief 240 volt surge onto 120 volt equipment if the neutral breaks before the hot on disconnect or makes after the hot on connect. You never want to be able to have the neutral disconnected and L1 and L2 connected at the same time.
    SMA SB 3000, old BP panels.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,622 admin
    #39
    Re: Instalation/devolpment help

    One big caution about neutrals, grounds, and AC Inverters...

    Most MSW (Modified Square Wave) inverters do not like either AC power lead + Battery Bank ground referenced. It creates "short circuit" for the internal MSW inverter circuitry). For MSW inverters that may connect to ground referenced neutrals, they need a two (or three) pole transfer switch that will "lift" the neutral bond for safe operation.

    Most TSW (True Sine Wave) inverters have an Isolated AC output and can have the "neutral" bonded to the common green wire/safety ground with the battery bank.

    In your system, it looks like the AC neutral is not grounded in this AC panel (not sure).

    -Bill

    If you have a "typical" MSW inverter and are only switching one AC pole, it is possible you are getting a "ground referenced" neutral through the AC inverter.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Caveman
    Caveman Solar Expert Posts: 83 ✭✭✭✭
    #40
    Re: Instalation/devolpment help

    Okay I'm getting lost... it sounds like one way or another I need to remove the N-G bond. Would getting an RV type of transfer switch mean that I could do this and keep the generator unmodified? If that is what it comes to I would rather use a different transfer switch than modify the generator. I'm getting the impression that there is more than one way to skin this cat, and due to my ignorance I can't decide quite what to do....

    Sorry to be such so dependent on y'all s advice, but for some reason the particulars of setting this up are kicking my butt, part of my problem is that I don't know what to ask....
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #41
    Re: Instalation/devolpment help
    Caveman wrote: »
    Okay I'm getting lost... it sounds like one way or another I need to remove the N-G bond. Would getting an RV type of transfer switch mean that I could do this and keep the generator unmodified? If that is what it comes to I would rather use a different transfer switch than modify the generator. I'm getting the impression that there is more than one way to skin this cat, and due to my ignorance I can't decide quite what to do.

    No. You can do that by re-wiring your transfer switch without modifying the generator. Read my post #37 in this thread where I tried to explain how to do that wire-by-wire.

    I know that I sometimnes bad at expaining things ...
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #42
    Re: Instalation/devolpment help

    What NorthGuy said.

    You're not using 1/2 of the two breakers functioning as a transfer switch. You can use those other sides to switch the ground configuration:

    In generator position connect generator's ground wire to system ground (connected to Earth ground). This is a single pole connection between the generator's grounding wire and the system ground which is connected to Earth ground (but not neutral).

    In inverter position connect system neutral to system ground. This is a single pole connection between system ground (connected to Earth ground) and neutral.
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  • Caveman
    Caveman Solar Expert Posts: 83 ✭✭✭✭
    #43
    Re: Instalation/devolpment help

    Thanks for your help,

    Right now I have power coming from generator to "generator breaker", then off to the AC box.
    I also have a PV wire (no power to it yet, just a dead wire) going to "solar breaker" then off to the AC box.

    At no time do they touch until they both plug into the same lugs at the AC box (respective breakers at transfer switch prevent any backfeed).

    Your saying I can fix this problem by connecting a jumper from the neutral buss to the breaker. This doesn't make any sense to me, won't the neutral bus have power now? Furthermore, by then connecting neutral to ground, won't all three have power?
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  • Caveman
    Caveman Solar Expert Posts: 83 ✭✭✭✭
    #44
    Re: Instalation/devolpment help

    Unless I'm misunderstanding (very likely), it sounds like I would have to disconnect/reconnect the neutral every time I switched between gen & solar....
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #45
    Re: Instalation/devolpment help
    Caveman wrote: »
    Unless I'm misunderstanding (very likely), it sounds like I would have to disconnect/reconnect the neutral every time I switched between gen & solar....

    No, it will happen automatically: your breakers used for making the transfer are double pole but presently you are only using one side of each because you are only switching the 'hot' leads. Use the second pole of the breakers to make the grounding changes.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #46
    Re: Instalation/devolpment help

    Perhaps this crude drawing will help (shown in inverter connected position).
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  • Caveman
    Caveman Solar Expert Posts: 83 ✭✭✭✭
    #47
    Re: Instalation/devolpment help

    Ohhhhhhhhhhhhh!!! I get it,! That's what those other lugs are for haha. thanks for bearing with me.

    So i don't connect generator neutral to buss, but rather connect it to the breaker and then to the AC box, bypassing the neutral buss in the Transfer switch.

    But I DO connect neutral coming from solar to neutral buss, and then through the breaker and on to the neutral buss of the AC box.

    The only thing I earth-ground is the transfer switch.
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #48
    Re: Instalation/devolpment help
    Cariboocoot wrote: »
    Perhaps this crude drawing will help (shown in inverter connected position).

    I meant it a little bit differently, but that would be the same effect. In the drawing the red lines show white (neutral) wires. If you re-wire like that, you can connect the green generator wire to the ground.

    Both drawings assume that your inverter does require neutral to ground bond.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #49
    Re: Instalation/devolpment help
    Caveman wrote: »
    Ohhhhhhhhhhhhh!!! I get it,! That's what those other lugs are for haha. thanks for bearing with me.

    So i don't connect generator neutral to buss, but rather connect it to the breaker and then to the AC box, bypassing the neutral buss in the Transfer switch.

    But I DO connect neutral coming from solar to neutral buss, and then through the breaker and on to the neutral buss of the AC box.

    The only thing I earth-ground is the transfer switch.

    Not quite.

    The Generator neutral, inverter neutral, and load (AC wiring) neutral are connected and left together.

    With one pole of the breakers you switch the load hot between generator hot and inverter hot.

    With the other pole of the breakers you switch the generator ground to system ground (which includes all the AC load ground wiring and is connected to Earth ground) when in the "generator" position and tie the neutral to ground when in the "inverter" position.
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  • Caveman
    Caveman Solar Expert Posts: 83 ✭✭✭✭
    #50
    Re: Instalation/devolpment help

    So if I wire it like Northguy's modified picture, the only thing I earth-ground is the transfer switch.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #51
    Re: Instalation/devolpment help
    Caveman wrote: »
    So if I wire it like Northguy's modified picture, the only thing I earth-ground is the transfer switch.

    Not exactly.

    All the ground wires for the AC load distribution are connected to Earth ground. This is the system ground.

    What you are changing with the second poles on your breakers is what else is connected to that system ground. With the generator as active power source its ground wire is connected to this. That way the generator has Earth ground connection (and already has N-G bond built in). With the inverter as active power source the neutral is connected to this. That creates the N-G bond for the inverter, and prevents duplication of same when the generator is supplying power.

    I don't know if NorthGuy's drawing will work because I can't remember which of those wires is what.
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  • Caveman
    Caveman Solar Expert Posts: 83 ✭✭✭✭
    #52
    Re: Instalation/devolpment help

    Blue wrapped wire is generator in at top, out to AC panel at bottom.

    Orange Romex at bottom right is inverter in, out to AC panel at top right.
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #53
    Re: Instalation/devolpment help
    Caveman wrote: »
    So if I wire it like Northguy's modified picture, the only thing I earth-ground is the transfer switch.

    You would ground everything. It also should be a wire going into the earth usually connected to a ground rod.

    The transfer switch will only connect/disconnect the neutral wire to/from the ground, and it can only be a single place where neutral is connected to the ground. When the left breaker is on this single connection will be inside your generator, when the right breaker is on this single connection will be inside the transfer switch. If you have any other places where neutral is connected to the ground (check AC breaker box), you need to remove such connections. But the ground wire itself is spread everywhere, so that it is present in every receptacle or fixture.
    Cariboocoot wrote: »
    I don't know if NorthGuy's drawing will work because I can't remember which of those wires is what.

    On the top there's the generator on the left and the inverter on the right. On the bottom, both cables go to the AC box where they connect together. At least, that's what I thought it was when I drew the drawing.
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  • Caveman
    Caveman Solar Expert Posts: 83 ✭✭✭✭
    #54
    Re: Instalation/devolpment help
    NorthGuy wrote: »
    On the top there's the generator on the left and the inverter on the right. On the bottom, both cables go to the AC box where they connect together. At least, that's what I thought it was when I drew the drawing.

    Close, read my post, #52

    If I'm understanding correctly, the only thing that would change would be that I would add that jumper from the neutral to the bottom of the breaker instead of the top as you have it.

    AC panel is earth grounded with driven copper coated rod.
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #55
    Re: Instalation/devolpment help
    Caveman wrote: »
    Close, read my post, #52

    If I'm understanding correctly, the only thing that would change would be that I would add that jumper from the neutral to the bottom of the breaker instead of the top as you have it.

    AC panel is earth grounded with driven copper coated rod.

    I'm very sorry. A'm actually very good at confusing things :D

    That's a little bit confusing that breakers are wired in opposite direction.

    If that's the case, you need to change my diagram. I marked the cables to make sure I got it right this time.

    The jumper that I circled in blue is only needed if your inverter needs ground to neutral bond (must be in the docs). And if you remove it, then the green wire from the generator must go directly to the ground screw.
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  • Caveman
    Caveman Solar Expert Posts: 83 ✭✭✭✭
    #56
    Re: Instalation/devolpment help

    Please don't be sorry, not hard to confuse a confused man....

    No, actually you guys have been very helpful, thank you very much. I think I got it now. Yeah, the opposite breakers threw me for a loop at first.
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  • Caveman
    Caveman Solar Expert Posts: 83 ✭✭✭✭
    #57
    Re: Instalation/devolpment help

    Well here it is re-wired, and I'm very pleased to say it works great!

    Attachment not found.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #58
    Re: Instalation/devolpment help

    What? It works?!
    Hmm. Must have done something wrong. :p:D
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