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  • 1.  SW 4024 Drops GridTie on Weekdays, but Not Weekends

    Posted 10-11-2021 09:27 AM
    Hello ASES Community:

    We have a Xantrex/Trace SW4024 with a Gridtie Interface module that's been running reliably for 20+ years.  Recently we upgraded some panels (after discovering some of the AstroPower ones had failed), and to increase production to cover a heat pump water heater.  We also upgraded the Charge Controller, which allows us to monitor daily harvesting.  We have a small (450Ah) battery backup to a mission critical circuit panel; our PG&E / SF Bay Area grid rarely drops but nice to have power on any occasion it does.  

    With the new setup and being home more through the pandemic I've noticed a curious pattern, that with comparable weather we often produce more on weekends than weekdays; the inverter will drop offline around the middle of the day, sometimes repeatedly, but again only on some weekdays, and never on the weekend.  

    Curiouser and curiouser. 

    Has anyone ever witnessed a similar phenomenon?  Or do any of you brilliant people have a theory to the cause, or a recommended next step towards solving this?  I'm guessing the grid is to blame, but have never noticed the AC input vary from 120V more than a few volts, and the Hz is steady as well.  I'm tempted to think something on our end is awry, but the pattern suggest otherwise. 

    Thanks in advance for any insight anyone has to offer, 


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  • 2.  RE: SW 4024 Drops GridTie on Weekdays, but Not Weekends

    Posted 10-12-2021 09:26 AM
    Did you measure the grid voltage and frequency at the times the inverter shut down during the weekdays and compare to other times, like on the weekends when the issue does not occur?
    You can use a Multimeter but may want to invest in a logging meter like from Egauge so you can collect granular measurements over time and do the comparison/analysis.
    What I would check:
    1. Grid going out of frequency specs
    2. Voltage rise at inverter during peak production times exceeding specs
    3. Voltage sag at inverter during peak grid load times


    Ken Nadsady
    AviSun Renewable Energy
    Hudson OH

  • 3.  RE: SW 4024 Drops GridTie on Weekdays, but Not Weekends

    Posted 10-12-2021 10:12 AM
    Edited by Mike Curran 10-12-2021 10:13 AM
    If your grid AC quality is somehow degrading on weekdays (over or under voltage, or frequency) due to different load patterns on weekdays vs. weekends, that could be the cause. Your inverter grid interface module will disconnect if that's the case.  Perhaps this was happening all along and your new monitoring capability has revealed it to you?

    Edit:  Sorry, posted this before seeing the previous reply.

    Mike Curran
    Retired from (dare I say it?) Fossil Plant Mgt.

  • 4.  RE: SW 4024 Drops GridTie on Weekdays, but Not Weekends

    Posted 10-14-2021 09:02 AM
    Intermittents....gotta love them. Also check your peak allowed battery bank voltages since you added production. If that is going over, it will probably shut down. Also what is your max sell watts on that inverter? Can you new capacity exceed your potential grid output if bank is full? How big in KW is your array at this point?
    Just some thoughts... allot of "good stuff" from others....

    william fitch