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  • Microinverter questions to replace an orphan inverter

    My original solar array is 660 Watts. It goes back to 2007 when a great deal on panel was $6.60 a watt. The Inverter is a Advanced Energy 1000 Watt inverter that went on line in 2007. The panels are 48 volt 165 watt panels. Advanced Energy inverters were not particularly long lasting and they went bankrupt long ago. So I now have an installed 660 watt array with no inverter. When I wired the array, I figured in for obsolescence and ran the output of each panel to a terminal strip in my basement next to the inverter with #8 cable. This means I have some flexibility on how to rewire the panels.

    My thought is the least cost approach are a couple of microinverters. Enphase has a 320 watt version that will accept 48 volt input so that solution would be to rewire the panels two in parallel, This obviously is a small set up so I would want to install the least amount of other components and the least amount of hassle. I do not need online monitoring and would prefer to DIY it. I currently aggregate my three arrays and manually report the total so no need for remote reporting.

    So what is the bare minimum least cost microinverter solution?

  • #2
    If you are talking about the Enphase IQ-7 320 Watt micro inverter at $159, then your are looking at $318 plus freight and sales tax. Alternatively you could pick up 5 used M215 for $20 to $30 each. That way you would have a spare and save at least $168. That would be the bare minimum least cost solution.
    Last edited by Ampster; 11-27-2019, 01:40 AM.
    9 kW solar, 42kWh LFP storage. EV owner since 2012

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    • #3
      Thanks for the quick reply. One follow up question is do I need any sort of gateway box for them to work or can I just connect the trunk cable directly to a breaker with either device?. I considered skipping the trunk cable but expect the UL listing would not cover it. Since its getting cold out in Northern NH, I will probably just install them down at the terminal box in my basement for now but in the spring I will consider putting them directly on the back of the panels so I am covered for rapid shutdown within 1' of the panel. I really do not want the cost and hassle of an Envoy box or equivalent if I can avoid it.

      I didn't realize there were folks selling used microinverters but it makes sense given how many are out there.

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      • #4
        They should work without a gateway. You won't get any monitoring.
        Yes' the trunk cable needs to connected to a breaker. I recently sold some M215s on Ebay.
        9 kW solar, 42kWh LFP storage. EV owner since 2012

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        • #5
          To close this one out. With the holidays it took me several weeks to get the bits and pieces together. I finally got everything together and got two of the four panels up and running. I got a deal on a 5 port trunk cable from one seller on Ebay and a couple of used M215s from a different vendor. For now everything is installed in my basement on the wall. As mentioned the outputs of each individual panel are run terminal switch in a terminal box in my basement. For now the inverters are mounted hanging off unistrut in my former inverter location. I made up some jumpers with MC4s that run from the Enphase connectors to the terminal box. I will pick up 2 more M215s and should have the last two panels lit up soon.

          The only loss was my primitive metering, my old inverter was 120VAC. I had a totalizing wattmeter (looks like a Hobbs meter) on it since the panels went on line in 2002. The 215s are 240 VAC and the watt meter is only set up for 120VAC. I also had an analog ammeter that is 0 to 5 amps. Full sun amps out of all four panels when new would be 2.75 amps, with only two on line I am looking at 1.4 Amps full sun. Today was hazy sun so the meter was not moving much.

          The microinverters may stay in the basement, if the 215s are as speculated being "cooked' under the panels in a typical roof mount installation, the new location in cool basement is going to be definitely far cooler. These panels are adjustable wall mounts with far better cooling as they are mounted at an angle from the house so there is plenty of ventilation if I decide to move them out to the panels. The only reason I see to move them is so they meet RSD requirements.

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          • #6
            If you want to add low-cost power monitoring, you can get a very inexpensive device from people on ebay or elsewhere, like this:
            https://www.ebay.com/itm/192406580810
            This one doesn't have wifi or connectivity, but might be good enough for a bare-bones monitor.
            7kW Roof PV, APsystems QS1 micros, Nissan Leaf EV

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            • #7
              Thanks, would be a good option but will probably stick with the existing meter. I have a revenue meter that aggregates my three arrays for SRECS.

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              • #8
                Your Wattmeter might work on one leg of the 240 output of the microinverters since the output is balanced. If there is a way to multiply the output times two or if it will take 240 power.
                9 kW solar, 42kWh LFP storage. EV owner since 2012

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                • #9
                  Interesting approach, it got "burned" into me years ago that "thou shalt not run current in a neutral on a 240 volt circuit" Then again the recording wattmeter was rated a 2 watts peak so its not whole lot of current.
                  Last edited by peakbagger; 01-18-2020, 09:18 PM. Reason: left out on a 240 volt circuit

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                  • #10
                    Originally posted by peakbagger View Post
                    Interesting approach, it got "burned" into me years ago that "thou shalt not run current in a neutral" Then again the recording wattmeter was rated a 2 watts pek so its not whole lot of current.
                    Well I guess it depends on what that statement applied to. The reality of a 240 volt electrical panel in the USA is that current does flow on the neutral on 120 volt circuits. I have heard that some 240 volt appliances won't run unless there is a neutral because some of the low current control circuits run off the 120 volts between one leg and the neutral. Other 240 volt hard wired devices like my water heater don't even have a neutral. Not an issue in the rest of the world that runs off 240 volts.
                    9 kW solar, 42kWh LFP storage. EV owner since 2012

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                    • #11
                      You are right. Got my ground and neutral mixed up. In older 240 volt appliances they would only have two hots and a ground. The appliances would get 120 volts by hooking to the ground. Newer appliances have 2 hots, a neutral and a ground so any 120 connects to one hot and the neutral. I have neutral nearby so I can get my 120 V power meter working again. The recording wattmeter has a CT so I can just loop the wire through the CT so it goes through twice to double the output so the 120 wattmeter reads the right wattage.

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                      • #12
                        There you go. I forgot about that trick.
                        9 kW solar, 42kWh LFP storage. EV owner since 2012

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                        • #13
                          I got my remaining two microinverters. The original two looked like brand new, they have a removable sticker on each that I presume is for warranty purposes?. The third showed up in similar condition. the fourth was decidedly in far more "shop worn" condition minus the sticker. They all work and my analog meter output lines up roughly with my expected output. Getting the KW totalizer meter running is going to wait a few days.

                          Granted its a small array but its my most reliable one for winter as the snow slides or melts off the quickest due to it being hung off a south wall of the house and adjustable for angle. Despite my pole mount also being adjustable for the same winter angle (30 degrees), it looses its snow cover slower. I attribute it to sun bouncing off the snow in front of the house warming up the façade of the house and creating a small microclimate that is warmer than the surrounding air. Its interesting that during cloudy periods it takes roughly the same time for the wall mount and pole mount to melt off.

                          The weather was cloud for most of the duration of the panels being down plus it was winter with less than 8 hours of daylight , so not much impact on my annual production. The days are getting longer and the weather pattern in my area is looking like a bit more sun so its good to see these ticking away. I am surprised that they do not get very warm even at full sun.

                          Last edited by peakbagger; 01-27-2020, 10:00 AM.

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