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SolarEdge Technologies SE500A-US (240) and 27KW On demand WaterHeater

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    SolarEdge Technologies SE500A-US (240) and 27KW On demand WaterHeater

    I have 6.16Kw DC Solar electric system installed on a SE SE5000A-US (240). Everything works normally until... The home owner turns on the hot water and as its elements turn on (3) 37.5 amp 240 volt draws the amperage slowly rises from about 17 amps 240 volts at roughly solar noon (peak production) to 22 amps which causes the inverter to throw error code 13 and reset.

    9, 13
    N/A
    AC Current Surge
    The internal hardware that measures AC current has measured substantially high output currents. This may occur because of changes in the AC voltage or a switching load near the site.
    If the fault persists:
    o
    Check the AC connection to the inverter
    o
    Check with the grid operator if a large surge source or irregular load exists near the site.

    I know this draw is a ridiculously huge draw. 112 amps when all three elements are on. I told solar Edge and they told me that the inverter is running properly until a pre existing condition occurs. And that is it. They have nothing more for me. I asked if a larger inverter wouldn't rise high enough and they told me it might just take longer to reach the error code. They also said that is an absolute first for them. They have never had a case of it before. Any one have any similar cases or more importantly any solutions.

    #2
    The error message does not seem particularly useful in this case.
    One explanation might be the voltage drop caused by the heater load, all the way from the subpanel (if used) back to the utility transformer.
    If the voltage drop were, for example 5 volts AND the on-demand heater had to cycle off and on to maintain temperature regulation, the inverter could see an apparent sudden POCO voltage shift of 5 volts.
    That might cause the programmed voltage output of the inverter to try to deliver more current to the GT interface than is sustainable while the internal regulator circuitry was adapting to the voltage drop.
    Try looking at the voltage at the inverter terminals with a slow sweep scope or a programmable power data recorder.
    The solution may be as simple as larger wiring.

    Comment


      #3
      Already have #8 Thhn running about 75'. The voltage does drop from 249 before the heater kicks on to about 238 before the inverter shuts off.

      edit: SMA calc says 1% voltage drop or 2.5 volts

      Comment


        #4
        Originally posted by gporter85 View Post
        Already have #8 Thhn running about 75'. The voltage does drop from 249 before the heater kicks on to about 238 before the inverter shuts off.

        edit: SMA calc says 1% voltage drop or 2.5 volts
        The voltage drop in that length of wire (doubled?) may only be 1%, but the measured voltage drop is more like 5%.
        Under most circumstances not a problem, but you may want see if it can be improved wherever the drop exists.

        Comment


          #5
          Originally posted by GoldDigger View Post
          The voltage drop in that length of wire (doubled?) may only be 1%, but the measured voltage drop is more like 5%.
          Under most circumstances not a problem, but you may want see if it can be improved wherever the drop exists.
          I measured the voltage change at the main panel i didn't measure it at the inverter.

          Comment


            #6
            Originally posted by gporter85 View Post
            I measured the voltage change at the main panel i didn't measure it at the inverter.
            I believe i found and fixed the problem. The water heater was set up to run on (3) 40 amp 2 pole breakers. I pulled them out to check them and realized that only 2 strands of one of the 8 thhn wires were actually landed on one of the terminals. It was on the primary heating element. So i took it out and landed it properly. Next I turned the water heater on and tried to cause the error and the inverter kept running. I don't know if by the primary heating element having only 2 strands of the wire landed would cause the secondary heating element to run earlier. Maybe that was causing the voltage to leak or whatever you want to call it? A reputable local electrical company did all the work to install the new circuits and main service panel for the water heater a few years ago. And it had been running with only the two strands in the breaker since they installed it. My question is would that cause the ac current surge at the inverter. Time will tell for me.

            Comment

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