One Line Drawing, I believe I am missing something from NEC under total RMS AMPS

Hey guys, small problem I am having with a client. Client owns a 8 circuit 2ooamp main, and i have to fit both the chargstation, and solar onto a single dual pole.
Is there a reason why I can't find a quadplex 20/100 dual pole (2)? It would make life a whole lot easier.

Check my one line I believe I am within code according to AMP RMS, as long as its a dedicated sub panel.

Please Advise

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Comments

  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: One Line Drawing, I believe I am missing something from NEC under total RMS AMPS
    Hey guys, small problem I am having with a client. Client owns a 8 circuit 2ooamp main, and i have to fit both the chargstation, and solar onto a single dual pole.
    Is there a reason why I can't find a quadplex 20/100 dual pole (2)? It would make life a whole lot easier.

    Check my one line I believe I am within code according to AMP RMS, as long as its a dedicated sub panel.

    Please Advise
    You will not find a quadplex with 100A components either because they will not fit into that space or because pulling the combination of 20A and 100A from the same bus stab may not be acceptable. (In your case the two currents will never add up, but the hypothetical quadplex breaker cannot be listed and sold under that assumption.)

    Your 40A total of breakers going into the 125A MLO sub-panel will OK because the feed breaker is considered to be the 100A breaker in the main and a 125A bus gives you a 120% factor of 150A.
    Your 40A is just fine given that 50A allowance.

    At the main panel, your 40A of backfeed will probably also be OK even if you have only a 200A bus in the main. Fortunately you do not have to count the whole 100A feeder breaker as backfeed!
    SMA SB 3000, old BP panels.
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    Re: One Line Drawing, I believe I am missing something from NEC under total RMS AMPS
    inetdog wrote: »
    You will not find a quadplex with 100A components either because they will not fit into that space or because pulling the combination of 20A and 100A from the same bus stab may not be acceptable. (In your case the two currents will never add up, but the hypothetical quadplex breaker cannot be listed and sold under that assumption.)

    Your 40A total of breakers going into the 125A MLO sub-panel will OK because the feed breaker is considered to be the 100A breaker in the main and a 125A bus gives you a 120% factor of 150A.
    Your 40A is just fine given that 50A allowance.

    At the main panel, your 40A of backfeed will probably also be OK even if you have only a 200A bus in the main. Fortunately you do not have to count the whole 100A feeder breaker as backfeed!

    ive been reading that this NEC rule is only applicable if the distance between sub panel and main panel
    is under 15'. Would you happen to have clarification on this since it's rule change between NEC 2014 and NEC2011.
    I appreciate your help, very knowledgable.
    im just wondering due to the conflictions between local jurisdictions if I should just indicate in the one line that it is a dedicated solar combiner, not solar combiner/charge station sub panel. Then when inspectors are gone just add the home run for charge station.
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: One Line Drawing, I believe I am missing something from NEC under total RMS AMPS
    ive been reading that this NEC rule is only applicable if the distance between sub panel and main panel
    is under 15'. Would you happen to have clarification on this since it's rule change between NEC 2014 and NEC2011.
    I appreciate your help, very knowledgable.
    im just wondering due to the conflictions between local jurisdictions if I should just indicate in the one line that it is a dedicated solar combiner, not solar combiner/charge station sub panel. Then when inspectors are gone just add the home run for charge station.
    Which NEC rule are you talking about, since the whole discussion ranges over 10 or more sections?
    I am not aware of any 15 foot provision, except maybe a tap rule that would allow you to use a smaller gauge wire between sub and main than you would need for the 100A breaker.
    (Note that under 2011 and earlier the 120% rule would also be applied to the feeder from main to sub. That means that you would have to use wire which is sized for at least 120A to cover the 140A requirement of applying the 120% rule to the feeder.
    Some inspectors will definitely choose to apply the 120% rule to the feeder wires even is the sub is just a combiner and contains no loads. So I am not sure what good hiding the charger circuit would do for you at inspection.

    I did not check the size and ampacity of the 100A feeder, so you may indeed have a problem there if you have not allowed for 100A of load.
    The tap rules would only allow you to use smaller than 100A rated wire if the sub-panel contained a main breaker which limited the current to what the wire was rated for.

    OOPS. I also did not notice your "two pole" note on the feeder. Since most inverters require a neutral, if only for reference, you should be running three wires plus and EGC for the feeder (two hot, one neutral which may be reduced in size, and one EGC which might also be reduced in size.) The role of the EGC could be filled by metallic raceway properly bonded, but it will be hard to talk your way out of providing a neutral.

    #1 Al, if you can find it, will only be enough for 100A if you can justify using the 75C termination temperature at both ends and have no other issues.
    To meet the 120 rule if you get a stubborn inspector you would still have to go to 1/0 Al.
    For that short a run, why not just spend a little more for the 15 feet and use copper to make for a more manageable size wire?
    SMA SB 3000, old BP panels.
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    Re: One Line Drawing, I believe I am missing something from NEC under total RMS AMPS
    inetdog wrote: »
    Which NEC rule are you talking about, since the whole discussion ranges over 10 or more sections?
    I am not aware of any 15 foot provision, except maybe a tap rule that would allow you to use a smaller gauge wire between sub and main than you would need for the 100A breaker.
    (Note that under 2011 and earlier the 120% rule would also be applied to the feeder from main to sub. That means that you would have to use wire which is sized for at least 120A to cover the 140A requirement of applying the 120% rule to the feeder.
    Some inspectors will definitely choose to apply the 120% rule to the feeder wires even is the sub is just a combiner and contains no loads. So I am not sure what good hiding the charger circuit would do for you at inspection.

    I did not check the size and ampacity of the 100A feeder, so you may indeed have a problem there if you have not allowed for 100A of load.
    The tap rules would only allow you to use smaller than 100A rated wire if the sub-panel contained a main breaker which limited the current to what the wire was rated for.

    OOPS. I also did not notice your "two pole" note on the feeder. Since most inverters require a neutral, if only for reference, you should be running three wires plus and EGC for the feeder (two hot, one neutral which may be reduced in size, and one EGC which might also be reduced in size.) The role of the EGC could be filled by metallic raceway properly bonded, but it will be hard to talk your way out of providing a neutral.

    #1 Al, if you can find it, will only be enough for 100A if you can justify using the 75C termination temperature at both ends and have no other issues.
    To meet the 120 rule if you get a stubborn inspector you would still have to go to 1/0 Al.
    For that short a run, why not just spend a little more for the 15 feet and use copper to make for a more manageable size wire?

    Nevermind you were right about the 15' rule.

    Decided to go with 2AWG-3 THHN rated at 130amps.
    Load center rated at 125 RMS and conductor exceeds load center, I also only ran 3.5' from one stud bay to the next stud bay the main and sub are butted next to each other. Essentially the conductor is considered to be protected in raceway as one system main, is butted to the sub panel load center.

    RMS of the solar 16 RMS amps array 1, 2 RMS AMPS array 2, but is expandable for an additional 14 amps, for a total of 32 RMS AMPS
    Rapid 100 AMP charger 75 RMS AMPS

    Grand Total of 107AMPS

    107 X 1.25 (N.E.C rule)= 133.75 AMPS, however neither will ever see that as the solar will divert to the rapid charger before demanding load from the Service main, hypothetically the conductor will never see passed 100 amps on a 125 amp sub panel load center.


    The city Building department engineer made it clear that as long as I don't exceed 100 amp breaker protection to conductor, I would be fine as the rule for 120% pertains to the "total" capacity of the system bussing @ 200amp main service, since the main is what splits the load to numerous sub panels, not the other way around.
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    Re: One Line Drawing, I believe I am missing something from NEC under total RMS AMPS

    Update on the work according to the one line.

    After further inspection of the clients 200amp main service it was a good thing that we "restructured" the clothes dreyer to natural gas from electric. The 100amp sub panel "which basically powers the entire home" is under engineered. I think most of the problem was because of time of build the home was built in 1976 when the copper shortage hit. So the 100amp sub panel that powers everything in the home used a 2AWG-3 Aluminum conductor rated for 90AMPS, the conductor is old and the stamps non existent so I measured the insulation, and strand count.

    I cleaned up all the conductors with zip ties this is what I came up with.

    Still crossing my fingers the inspector is going to allow this set up to pass.

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