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  • #16
    The danger is that it would be possible for a fault to occur in which the busbar would get overloaded, handling all 200 A from the service feed plus whatever the PV breakers could supply.

    NEC requires the PV breakers to be installed at the opposite end of the bus (if the sum of the supply breaker and PV breakers exceeds the busbar rating)... in that configuration, you can see that there is no way for the bus to ever see more than the current for which it is rated.

    https://dept-wp.nmsu.edu/swtdi/files...n-feb_2013.pdf

    http://www.jadelearning.com/thejunct...erconnections/



    CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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    • #17
      Originally posted by sensij View Post
      I just pulled the trigger last week on buying an EGauge at work, to support measurements of three phase power consumption.... thanks in part to some of the feedback given by other forum members. I'll have feedback soon to share with those interested, but the interface looks slick.

      The meter itself is base 1% accuracy for about $500, with 12 CT capability. For $30 more, the 1% accuracy is verified with a calibration certificate, and for another $50 on top of that, calibration to 0.5% will be certified.

      They offer Magnelab split core CT's starting at $35, but state that the published system accuracy only applies when using revenue-grade CT's, costing at least $50 ea direct from the mfg, or $65 through EGauge for the C0.6 rating. All these CT's are 0.333 mV full scale.

      On my home system, I went with EKM metering, which offers a three channel ANSI meter with 12.20 Class 0.5 accuracy, $220 base or $275 with a cert. It requires CT's with 26.6 mA full scale output, and claims that the split and solid cores models they sell are 0.1% accuracy class. The split cores start at $40, the solids at $15... I bought the solid cores and didn't pay for the meter cert, and although I haven't put it on the service feed to verify accuracy directly against the Poco meter, I can say that the gross consumption calculations (net consumption from Poco meter - PV generation from EKM meter) come out very consistent throughout the day, leading me to believe that the accuracy is as stated. The CT's don't appear to be re-branded, although the meter itself is made in China (at one point with exclusive distribution through EKM in the USA), and it wouldn't be surprising if the CT's are as well.

      The CT's used with Curb appear to be the Magnelabs in one of the pictures on their site. They say in the copy that they have seen 99.5% accuracy on their systems, but it is hard to trust without rigorous testing, For $400, there is almost no way they can be making money on this... but they did close over $1M in a seed round last year following the successful Indiegogo campaign, so that probably covers the unit losses and then some. It looks like their business plan is going to veer more towards services than hardware, so selling these early systems at cost or less just to get them out there could make sense.

      On a completely different note, it is really unusual to see the PV breakers located right next to the supply breaker. In the picture the supply breaker is 200 A, so if the busbar is only 200 A as well, it is not NEC compliant.
      I have used the split core Accu-CT before and they seem to be very accurate current transformers. Of course their price at $65 is almost double the cost of the Magnelab split core CT's that eGauge sells.

      I guess it comes down to what accuracy is important for the job and how much you are willing to spend on quality equipment. IMO eGauge falls into the quality equipment category but the jury is still out concerning the "Curb" product.

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      • #18
        Originally posted by sensij View Post
        The danger is that it would be possible for a fault to occur in which the busbar would get overloaded, handling all 200 A from the service feed plus whatever the PV breakers could supply.

        NEC requires the PV breakers to be installed at the opposite end of the bus (if the sum of the supply breaker and PV breakers exceeds the busbar rating)... in that configuration, you can see that there is no way for the bus to ever see more than the current for which it is rated.

        https://dept-wp.nmsu.edu/swtdi/files...n-feb_2013.pdf

        http://www.jadelearning.com/thejunct...erconnections/


        I shared all this with my electrician and he was very receptive and impressed with how well the PDF explained the concept.

        He might be in town this weekend, so he'll move the PV breakers all the way up for me.

        I've had so many strange things happening around data, reporting, actual impact on production when micros are maxing out while demand is high, that I really hope the placement was the culprit.

        I'll be back to report once the fix and more data are in. Amazing stuff.
        10 x LG300 ACe, 24 x M250 (9.84 kW DC)

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        • #19
          Sensij - how's this? Moved two PV breakers all the way to the top, consolidated two Ethernet data feeds into one powerline switch, installed the whole house surge protector with a double 20A breaker on the left, and put in a spare one for my upcoming third solar string (it will get moved to the top once in place.)
          10 x LG300 ACe, 24 x M250 (9.84 kW DC)

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