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Changing out a pair of older Fronius IG3000's...

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  • Changing out a pair of older Fronius IG3000's...

    Hi all.. I'm new here, but back in late '07 we had a 6kw system installed here in sunny CA by a contractor. Long story short, we've had nothing but issues with these Fronius inverters which are now out of warranty. we had a number of them replaced under the warranty as one of the two would pretty much fail annually.

    Our system has two strings of Sharp panels -- I don't recall the exact configuration anymore nor the exact Sharp panels -- they looked like lightweight concrete roof tiles in shape. Anyway, I vaguely recall there being perhaps 108 of those panels.

    So, one inverter is still functioning, but the other is dead. They almost always seem to crap out in the same manner -- the logic that senses grid voltage croaks and then the inverter shuts off and that's the end of it. What I'm looking into and what I ultimately need your input on is whether I can swap these two inverters for a pair of Sunny Boy 3.0-US (240v) models to pretty much match what the IG3000s specs are (more or less) -- if I'm reading its spec sheet properly. Is this a good plan or ??? This is SCE (So-Cal Edison) territory here and they've had issues with line power quality from time to time -- most recently a few years ago a local transformer was putting out 175V instead of 110.. It fried a bunch of stuff in the house.

    My questions are as follows :

    1) Are the Sunny Boy's pretty good as I'm under the impression that they are?
    2) Will power quality issues nuke them as well as they did with the Fronius's or are they better able to handle power quality issues? This is not an issue 99% of the time but occasionally pops up.
    3) Ive done house wiring before and know about AC and DC power and whatnot -- is this something I should leave to a solar contractor or can I do the swap using common sense (ensuring I don't electrocute myself obviously, taping wires so they don't short during the swap, etc)..?
    4) Are there any reputable and reasonably priced places to get the offending Sunny Boy inverters if they are in deed a good match?

    I think that's about all I've got for the moment.. Thanks so much!!

  • #2
    What sort of surge protection device are you using to prevent surges coming in through the line? I had the same issue with similar size Fronius. Most SPDs do not clamp at a low enough voltage to protect sensitive electronics. Midnight Solar's SPDs clamp at lower voltage. I now have one on my imcoming panel as well as out at my arrays.

    Why not go with a single 6 KW inverter with two MPPT inputs?. If you want to take risk there is dealer on Ebay selling Delta 6 KW inverters for less than $600 bucks, They are branded as Solar City. If you dont need remote data monitoring you cant beat the price. They have some sort of guarantee. For the price you can buy a spare.
    Last edited by peakbagger; 04-30-2020, 07:29 PM.

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    • #3
      You can definitely do this, but keep in mind that this is high-power electric circuits. Bad connections can be really dangerous. Find the exact specifications and follow them. For example, if they recommend stripping 5/8" of wire and torqueing the screw to 110 inch-pounds, do exactly that. If you have to change things, use the right wire, the right connectors, the right cable glands, whatever you need. Most electric supply stores can advise you. This is not the time to "wing it". Work with the breaker off and test the circuit to be sure it is dead before touching it.

      Sorry, I know this is common sense.
      7kW Roof PV, APsystems QS1 micros, Nissan Leaf EV

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      • #4
        Thanks guys! Let’s see.. I’m fine with moving to a single 6KW inverter if it will handle both strings with dual MPPT inputs as you suggest @peakbagger. @bob-n, I may opt to just cover my rear and have a local Solar place that’s worked the warranty issues before handle the swap IF I fully spec the changes to be made.

        Peakbagger — you asked about surge protection on any of this equipment and the answer is there is NONE. It seems like a good time to get a whole house surge protector installed as this seems to be more of an issue in the area for some reason. Regarding the Midnight Solar SPDs, what exactly do they do and where do they fit into the solar setup? I’m not sure I understand their role with preventing issues. Are these protecting the backend solar equipment from being cooked by inherently problematic line voltages in a grid-tie system or from transient spikes within the solar equipment itself? I’m assuming its more from the grid-tie side of the world but perhaps I’m wrong. I did do some poking around on the net regarding these things and I suppose lightning could be an issue but this property is in Southern CA and the likelihood of that happening there is SUPER remote IMHO.

        Anyway, I’m not in any hurry to try and figure these things until I understand the proper upgrade path to take.

        By the way, these SPDs, would they handle brown-out situations and other crappy line voltage issues or just the spikes? — I’m assuming just the spikes. I want to ensure that any crappy line voltage issues will be handled at the connection point to the grid and eliminate ANY issues with things in the house being cooked. When the local SCE owned transformer started spitting out 175VAC it really took out a bunch of things — I think I replaced 3-4 transformers that got cooked (furnace, door bell, camera system transformer) and other electronic items too.. If I can I’d like to prevent that from happening again.

        I’m sure I’ll have other questions but that’s all I’ve got for now!

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        • #5
          Midnight Solar has a few videos on their SPDs on their website.. The Surge Protection Devices do what they are named. If there is a voltage surge in the system, the SPD "clamps" the excess voltage and sends it directly to ground. Surges on incoming lines are weird, they seek the path of least resistance to ground and sometimes that ia circuitous route.Long ago my mom worked nights and slept during the day. One day there was strike somewhere in the neighborhood. We had a big old GE console stereo system, The strike decided to go through the stereo, it melted the solder on the circuit board to bypass the power switch and play the stereo at full blast, Needless to say my mom gets woken up with a stereo playing full volume and it could not be shut off. She eventually dared unplug it but needless to say she was not a happy camper.

          The MIdnight solar units use Metal Oxide Varistors (MOVs) to do their thing. They also have a few LEDs incorporated to show you that the SPD is installed correctly and is running. .

          So 95% of the stuff in the house is okay and only one or two circuits have problems. Not sure why an inverter seems to be the lightning rod but it is frequently. I think its because we go to a lot of trouble grounding it. Lightning strikes can create surges and nothing will stop the primary surge reliably but there can be reflected surges where a SPD should help. Years ago the standard was a Delta brand SPD but they were mostly designed to keep the house from burning down. Yes they may stop 1000 volts but at that point stuff is cooked. The Midnight Solars are designed to clamp the excess voltage a lot closer to the actual normal voltage so there is good chance gear on the other side of SPD might survive.In my case the utility's high voltage line on top of the pole was unsupported when the top of the pole snapped. There were high winds and the guess is the high voltage line momentarily made contact with the 240 volt line coming into the house. The only damage was the Fronius which they promptly swapped with a rebuilt one. I had a smaller inverter next to it and it was fine.

          Conversely there can be electrical surges coming in from the PVs. This is usually a deflected lightning strike, the SPD hopefully clamps the excess current to a nice big #4 conductor going direct to the house ground rather than heading through the SPD and the higher resistance house wiring. There also can be surges generated in the house but most just install a SPD in the main panel and then one at the panels. I have three arrays and one of them is a pole mount located away from the house with less protective tree canopy near by. I have a local ground rod and a #4 running in the trench from the ground rod at the pole to my main ground rod to try to direct any indirect strikes to ground but I also have the PV wires headed to the house underground. I have a SPD at the pole mounted disconnect. My roof array has a #4 going outside my house to my main ground rod but it also has junction box with a SPD before the wires head inside. My third array is a wall mount (kind of weird). I dont have a SPD on that one as the bottom of the frame is connected to a #4 going to my ground rod. The PV wires actually are mounted at the top of the panels before they run in an outside conduit to my basement. BTW I design and install my own systems, some of the money I save goes towards things like SPDs.

          No they will not deal with brown outs or add voltage back to the house. All they do is cut off the peaks up the rated capacity of the internal components they are made with. Fuses normally are the line of defense for brown outs,If a device is using power and the voltage drops, the current goes up. As long as the equipment can handle the higher current it should not cook. The fuse or circuit breaker in the unit will theory trip once the safe current is exceeded.

          If you really want to clean up your incoming power than you are getting into a UPS type unit that normally bypasses the UPS unless the power is out of spec and then the UPS takes over. If you are old school a Motor Generator set used to be the ultimate device for isolating a circuit. The rotating inertia of the equipment smooths out voltage surges and sags.

          Talk to any ham or radio station engineer about all the things they have to try and do to keep the equipment running at the base of radio tower in a thunderstorm. They usually have lots of war stories about arcs jumping around the room blowing things up..
          Last edited by peakbagger; 05-02-2020, 04:08 PM.

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          • #6
            Thanks @peakbagger! That was quite a read! Sounds like at a minimum we need to get an SPD plugged in as part of this Fronius switch-out.. If we’re going to move to a 6KW single inverter, downsizing from two Fronius, we ought to have plenty of wall space to accommodate the box the SPD will be mounted in unless it can be attached to an existing cut-off box which may be the case. Thanks so much!

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            • #7
              TThe SPD usually can be screwed into spare knockout on the inverter of on the main panel.

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