Connecting 12v Prosine 2.0 to breaker box / sub panel

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Hairfarm
Hairfarm Solar Expert Posts: 225 ✭✭✭
in Off Grid Solar & Battery Systems #1
Greetings,

I found a little bit of info on this but I still have some questions.

My Xantrex 12v Prosine will be connected to a breaker box (like this one: http://www.homedepot.com/p/Square-D-by-Schneider-Electric-Homeline-125-Amp-12-Space-24-Circuit-Indoor-Main-Lugs-Load-Center-with-Cover-Value-Pack-HOM1224L125VP/202529821#.UUzoqBmJhS0)

My inverter is 120vac, so what is the best way to connect it to both phases / buss bars in a 240vac breaker box? My cabin will have 6 circuits in it. My Prosine came with the wired GFCI option too. But my generator won't be grounded so I'm going to bond the neutral to ground in the breaker box (according to the tech from Schneider this is the correct way if I'm not using grounded shore power).

Here're some images I found on the internet (one on this forum) that match what I have in mind.

Attachment not found.Attachment not found.Attachment not found.



Question: Is this the preferred way to wire an inverter to a two-phase breaker box ? Is there a better way, like a single phase (120vac) breaker box? Does that even exist?

Documentation: http://www.xantrex.com/documents/Inverter-Chargers/PROsine-2/PROsine_2.0_User%27s_Manual%28445-0089-01-01_rev-C%29.pdf


thanks again for taking the time encourage my folly!;)

Hairfarm
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #2
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel
    Hairfarm wrote: »
    Question: Is this the preferred way to wire an inverter to a two-phase breaker box ? Is there a better way, like a single phase (120vac) breaker box? Does that even exist?

    Documentation: http://www.xantrex.com/documents/Inverter-Chargers/PROsine-2/PROsine_2.0_User%27s_Manual%28445-0089-01-01_rev-C%29.pdf

    What you propose will work just fine as long as you do not go above 1/2 of the current rating of the panel or the neutral busbar is oversized by default. The neutral bus is not expected to carry twice the phase current, which is what will happen with phase wires that are in phase instead of opposite.

    You cannot use any 240 volt loads, of course, but that should not be a problem.

    Or you can use just half of the breaker slots in the panel, the ones that are all connected to the same bus, and not wire up the second phase wire jumper.
    SMA SB 3000, old BP panels.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel

    This issue actually comes up more often than you think.

    The answer is: there isn't any problem because a 2kW inverter can only put out about the equivalent of one 15 Amp circuit. So if you connect the two hot lugs with a jumper wire there is no danger of overloading anything other than the inverter itself.

    If someone goes and rewires it later for a larger inverter, they'd better have sense enough to change the jumper out.

    BTW, you can not put a neutral-ground bond after a GFCI or else it will trip all the time (ground wire creates current path around the neutral of the GFCI). There should already be a N-G bond in the inverter before the GFCI circuit.
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  • Hairfarm
    Hairfarm Solar Expert Posts: 225 ✭✭✭
    #4
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel

    Thanks for your help Cariboocoot. What is the best way to wire a 30 Amp two-pole circuit breaker as a main breaker / cutoff switch in the breaker box?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel
    Hairfarm wrote: »
    Thanks for your help Cariboocoot. What is the best way to wire a 30 Amp two-pole circuit breaker as a main breaker / cutoff switch in the breaker box?

    Why bother? Pretty expensive overkill of an AC off switch.
    Remember if every branch circuit is on a breaker you can shut them all off individually, the inverter can then be shut down. There's really no need for a main breaker at all. A basic sub panel (6 breaker for example) will not have a provision for a main breaker. This is in fact what I use for AC distribution. Very much like this one: http://www.homedepot.ca/product/100-amp-qo-sub-panel-loadcentre-with-4-spaces-8-circuits-maximum/901454
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  • Hairfarm
    Hairfarm Solar Expert Posts: 225 ✭✭✭
    #6
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel
    Cariboocoot wrote: »
    Why bother? Pretty expensive overkill of an AC off switch.
    Remember if every branch circuit is on a breaker you can shut them all off individually, the inverter can then be shut down. There's really no need for a main breaker at all. A basic sub panel (6 breaker for example) will not have a provision for a main breaker. This is in fact what I use for AC distribution. Very much like this one: http://www.homedepot.ca/product/100-amp-qo-sub-panel-loadcentre-with-4-spaces-8-circuits-maximum/901454

    Where do you connect the hot wire from your inverter? Do you use a jumper too. I can't seem to locate any images of the INSIDE of the panel you provided.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel
    Hairfarm wrote: »
    Where do you connect the hot wire from your inverter? Do you use a jumper too. I can't seem to locate any images of the INSIDE of the panel you provided.

    Yes: it has a neutral bus bar and two lugs for L1 and L2. I just hooked the inverter neutral to neutral and hot to L1 then jumpered that to L2. On mine that's where the N-G bond is as well (OB VFX3524 inverter).
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #8
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel
    Cariboocoot wrote: »
    I just hooked the inverter neutral to neutral and hot to L1 then jumpered that to L2.

    Apparently, to do that you would need to connect 2 wires to the same lug. I need to connect 2 wires to the same lug too. How did you do that?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel
    NorthGuy wrote: »
    Apparently, to do that you would need to connect 2 wires to the same lug. I need to connect 2 wires to the same lug too. How did you do that?

    :confused: Uh, put the two wires (twisted together) in the lug and tightened the screw.
    We're not talking about 4 AWG here as the inverter's output is only 30 Amps. It is wired with 10 AWG (I do not run it anyplace near its maximum either).
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  • Hairfarm
    Hairfarm Solar Expert Posts: 225 ✭✭✭
    #10
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel

    I should also mention that the cabin is already wired with Romex 14/3. Any problems there?
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #11
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel
    Cariboocoot wrote: »
    :confused: Uh, put the two wires (twisted together) in the lug and tightened the screw.
    We're not talking about 4 AWG here as the inverter's output is only 30 Amps. It is wired with 10 AWG (I do not run it anyplace near its maximum either).
    Regardless of the size, the lug may not have been rated/listed for terminating two wires. Fortunately you did not have an inspector to make a fuss about it.
    The other way is to use a splice to split the one wire into two, one for each lug.
    SMA SB 3000, old BP panels.
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  • Hairfarm
    Hairfarm Solar Expert Posts: 225 ✭✭✭
    #12
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel
    On mine that's where the N-G bond is as well (OB VFX3524 inverter).
    Do you mean that the bond is made in your inverter? Or were you referring to your breaker box?
    Regardless of the size, the lug may not have been rated/listed for terminating two wires. Fortunately you did not have an inspector to make a fuss about it.
    The other way is to use a splice to split the one wire into two, one for each lug.
    Like this? http://i01.i.aliimg.com/wsphoto/v0/640463137_1/500-scotch-locks-quick-splice-electrical-font-b-terminals-b-font-assortment-font-b-Wire-b.jpg_250x250.jpg
    Apparently, to do that you would need to connect 2 wires to the same lug. I need to connect 2 wires to the same lug too. How did you do that?

    He said he wired his box the same way that these following images show, with a jumper.... more or less. Please correct me if I'm wrong Cariboocoot.
    Attachment not found.Attachment not found.Attachment not found.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #13
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel
    inetdog wrote: »
    Regardless of the size, the lug may not have been rated/listed for terminating two wires. Fortunately you did not have an inspector to make a fuss about it.
    The other way is to use a splice to split the one wire into two, one for each lug.

    Well, there's the inspector known as me.
    There is nothing wrong with the process as described, 'rating' or not.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #14
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel
    Cariboocoot wrote: »
    Well, there's the inspector known as me.
    There is nothing wrong with the process as described, 'rating' or not.

    Try that on the Mike Holt forum and see who agrees with you. :-)
    SMA SB 3000, old BP panels.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #15
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel
    Hairfarm wrote: »
    Do you mean that the bond is made in your inverter? Or were you referring to your breaker box?

    N-G bond in the breaker box.
    He said he wired his box the same way that these following images show, with a jumper.... more or less. Please correct me if I'm wrong Cariboocoot.
    Attachment not found.

    Yup; that's pretty much it.
    Been working since 2008 too.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    #16
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel
    Cariboocoot wrote: »
    BTW, you can not put a neutral-ground bond after a GFCI or else it will trip all the time (ground wire creates current path around the neutral of the GFCI). There should already be a N-G bond in the inverter before the GFCI circuit.

    I thought this could be repeated. I'm about to deal with this myself, having just recieved my first prosine that has a GFCI rather than a hard wire setup. So you need to disable the nuetraql ground bond in the panel. FWIW I've always had my nuetral ground bond in my outside electrical box with my inverter and Power center and now E-Panel. I would think this is common for Off grid use, but I'm just one of many.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #17
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel
    inetdog wrote: »
    Try that on the Mike Holt forum and see who agrees with you. :-)

    I couldn't care less.
    As I always say, everyone is free to disagree with me; it's not my money you're spending.
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #18
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel
    Cariboocoot wrote: »
    :confused: Uh, put the two wires (twisted together) in the lug and tightened the screw.
    We're not talking about 4 AWG here as the inverter's output is only 30 Amps. It is wired with 10 AWG (I do not run it anyplace near its maximum either).

    Yes, that is easy to do with #10. Mine are #6 and #8 :cry:
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #19
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel
    NorthGuy wrote: »
    Yes, that is easy to do with #10. Mine are #6 and #8 :cry:

    Problem there. You're going to have to 'bug' it I think; making a 'Y' to feed the two lugs. Keeping it insulated from everything then becomes an issue. I don't trust electrical tape.

    Might as well say right now that is not to code either. :roll:
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  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    #20
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel

    I'm not an electrician, as I recall you can use good old wirenuts up to 15 amps, at 2000 watts your just above that. You could put in a power distribution block or just a split lug, on a screw down connector. though I don't know if these are UL rated for AC.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #21
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel
    Cariboocoot wrote: »
    Might as well say right now that is not to code either. :roll:

    Definitely. Seems like a common task. I can't believe there's no clean solution to that.
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #22
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel

    I usually write my own Code.....lol

    I like Split Bolts with heat shrink over them, if you have to make a " Y ".
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #23
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel
    Hairfarm wrote: »
    I should also mention that the cabin is already wired with Romex 14/3. Any problems there?

    If you have an inverter with > 15 amps @ 120 VAC output--Yes, there can be a problem.

    A 14/3 (black+red+white+ground) is intended for use with 120/240 VAC split phase power. In that situation, the current in the white wire is the difference between the current in the Black - Red current (i.e., if black is 10 amps, and red is 6 amps, there will be 4 amps flowing through the white/neutral wire).

    If you have a 120 VAC only output--The black+red wires are now the same phase, and the current through the white wire is the sum of "black+red" = white (really "black+black" since the two bus bars are jumped together).

    That means if you have 15 amps on the "black" circuit and 15 amps on the "red" circuit, the white will be carrying 30 amps--Obviously, not a good thing for 14 awg wiring.

    The "fix" is to either run 14/2 (black+dedicated white/neutral) from each breaker to the load(s), or to connect the black+red to the same 15 amp breaker in the panel (black+red paired with the white in the same ROMEX cable)--That way, the 14 awg white wire cannot "see" too much current.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #24
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel

    Will a 12v Prosine 2.0 put out 30 Amps @ 120 V ??, I never saw one that would. @ 12 V I doubt that you could ever get enough Battery current to ever support it for very long. I do see BB point.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #25
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel
    BB. wrote: »
    That means if you have 15 amps on the "black" circuit and 15 amps on the "red" circuit, the white will be carrying 30 amps--Obviously, not a good thing for 14 awg wiring.

    No, this is not possible because the red and black are the same feed from the inverter. If you try to draw 30 Amps the inverter will shut down before you could possibly overload the neutral because it simply can not supply the 30 Amps of current. We are not talking about tapping in to an existing service panel and wiring here either.

    Needless to say the reality here is that the two legs are being used as an extension of one. There won't be any split 240 lines balancing against each other with the possibility of sending same phase current at 2X max through the neutral. Each branch would have its own neutral just as it would with a longer bus of 15 Amp circuits.

    Where you get into trouble with jumpering legs is when you go to higher Wattage inverters. Then the wires don't fit the lugs and you have to 'Y' the feed and maybe you do run two parallel blacks and can feed 2X current down one neutral et cetera.

    Believe me, that Prosine will shut down before any other part of the wiring is overloaded.
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #26
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel

    What gets me is you figure the current and the wire capability and you do it by code and then you open the inverter and find it's all way under sized based on all the wire you'v hooked to it, their Rating Agency's apparently do not care that a #8 is hooked to a # 12 internally.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #27
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel
    BB. wrote: »
    If you have an inverter with > 15 amps @ 120 VAC output--Yes, there can be a problem.

    The first sentence--If he were to install a larger capacity inverter--Then the wiring is at risk.

    Even the Pro-Sine 2000 is large enough to be "iffy"...

    14 awg wire is rated for 15 amp circuit/breaker. With a 80% derating, that is 12 amps max continuous.

    12 amps * 120 VAC = 1,440 Watts

    So--Even in this configuration, feeding two 15 amp breakers with a 2kW ac inverter sharing a neutral return will load the 14 awg wire beyond the NEC ratings.

    But--the weird thing is that 14 awg wire is rated for 20-25 amps per NEC tables--However, for some unknown reason that I could never find, the NEC limits the rating to 15 amps maximum (they do this derating for 14/12/10 awg wiring). The fine print:
    The load current rating and the overcurrent protection for conductor types shall not exceed 15 amperes for 14 AWG, 20 amperes for 12 AWG, and 30 amperes for 10 AWG aluminum and copper-clad aluminum after any correction factors for ambient temperature and number of conductors have been applied.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #28
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel
    Blackcherry04 wrote: »
    What gets me is you figure the current and the wire capability and you do it by code and then you open the inverter and find it's all way under sized based on all the wire you'v hooked to it, their Rating Agency's apparently do not care that a #8 is hooked to a # 12 internally.

    That's everywhere. When I had to rewire Generac with ATS that struck me. All wires are undersized, too many wires per conduit, no fuses/breakers for ATS coils etc. How could it all pass?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #29
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel

    15 Amp continuous. Hence the wire's 20 Amp rating. Breaker will not trip at 15 Amps immediately.

    No chance the Prosine will produce enough power to trip the breaker, much less overload a piece of 14 gauge wire. There simply is no 30 Amp current source available.

    Further to that, it is my 30 Amp Outback that could cause trouble. But I'd have to be a moron and wire it up wrong (two hots feeding back on one neutral).

    So with the small inverters (<2kW) it is safe to jumper the two line feeds in a distribution box. As the inverter gets larger, then you can have trouble.

    As it is my VFX3524 will fault before any 15 Amp breaker trips (combined loads on all branch circuits adding to the current draw on any one that may be overloaded).

    I do not care what the NEC says about this; in reality it works. Unlike some of their requirements.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #30
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel

    In theory, NEC is a requirement for "generic" power systems. And is very conservative in is requirements (mostly--There are a few areas where it has been, or still is, a bit confused in what is safe or dangerous).

    "Listing" or "Registering" a system with UL/NRTL's is based on engineering design and validation (via the company and the NRTL) that the components used are "safe" for the particular application. So, you can use smaller gauge wiring as long as you don't exceed the insulation temperatures.

    In reality, at least for "systems" (i.e., larger computers, etc.), there are usually no explicit tests for overheated wiring (running system at maximum rated current in a 120F heat chamber) during NRTL testing.

    What is usually looked at more closely are the physical enclosure and such. Are the holes the "right size", is there a metal pan or screen (with smaller than X/Y diameter holes) that will not allow flaming material to fall to the floor, etc. Is there anyway a small kid can get fingers inside the system and get a shock or burn, etc....

    As long as the system "fails safely" (i.e., burning wire does not drip fire on the floor), that is all the NRTL really cares about.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #31
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    Re: Connecting 12v Prosine 2.0 to breaker box / sub panel

    I always use double throw breakers on all the Input Sources with lockout's if possible. It's not unusual the because the Main Panel and sub circuits are all integrated into one panel to overload something. With Shore Power x 2 and 2 generators ( 120 v & 240 v ) and 3 Inverters feeding the same panel it's a nightmare. With only 2000 W of input, well not a big deal.

    240 v runs down the middle and it has 4 x 100 amp breakers.

    Attachment not found.
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