SW4048 Grid Question

BillFBillF Solar Expert Posts: 48 ✭✭
I have two SW4048 in a 240vac configuration that we use in an off grid scenerio while using the grid for back up. Some time ago a surge (most likely lightning) cause one of the inverters to stop sensing the grid. The green light does not blink and it will not switch to grid under the low battery switchover. The other unit is fine. They both continue to work quite reliably. We use solar and wind to keep the batteries charged when possible.
Is there an internal fuse or some other compnent that I can check and replace/repair? Were would I need to look?



  • Solar GuppySolar Guppy Solar Expert Posts: 1,987 ✭✭✭
    Re: SW4048 Grid Question

    There is nothing user serviceable in the SW4048's. You likely lost a input current sensing transformer. The cost to repair an SW is more than half the cost to buy a new XW inverter and I'm not even sure if there are places that do repairs any more on the SW line
  • RCinFLARCinFLA Solar Expert Posts: 1,453 ✭✭✭✭
    Re: SW4048 Grid Question

    Sounds like the same thing happened to mine.

    There are three small 120v to about 13.8v voltage sense transformers on the power connection / relay board. These take the 120vac voltage sense measurements on ACout, AC1, and AC2 and send the stepped down voltage to the controller board.

    The one for AC1 is labelled T4 on PCB.

    Mine got zapped from a lightning strike on the AC mains in the neighborhood.

    The primary (120vac) windings are hair fine wire. The ends wrap around the bobbin post that solders into the PCB. On mine the wire melted for about 0.025 inch at the post end. There was still about 0.070 inch of the wire coming out of the transformer winding still visible. I was able to solder a wire around the solder post and tack the the little strip of the primary winding with solder. That was about six years ago and still working.

    If you can not repair the transformer you might try a Xantrex authorized repair shop. Final option would be to use a 120v to 12.6 vac transformer. It will be about right output since it is unloaded. You might be a little off on AC1 voltage calibration.

    You could also steal the AC2 transformer, T8, if you can live without generator input.

    If you don't want to mess with it at all you can put the grid wiring to AC2 inputs and live with that. (do to both units in the series stacking)

    I attached schematic of relay board I made when I had it apart.
  • boBboB Solar Expert Posts: 1,007 ✭✭✭✭
    Re: SW4048 Grid Question

    Very nice job on that control board schematic !! :D
    Yes, "hair wire" was always a problem with those sense transformers.

    Nothing serviceable ? Yes, typically.... But it really depends on who and/or how technical one is.

  • BillFBillF Solar Expert Posts: 48 ✭✭
    Re: SW4048 Grid Question

    Thanks RCinFLA for the info. The schematic is very nice. In just a quick look from the outside of the case I was able to find T4. Nothing obvious to see from that vantage point. Now the big question can I pull the cover off the inverter while it is still on the wall without causing major problems? I'll have to take the system down nonetheless but don't relish the job off taking the whole inverter off the wall/dc disconnect etc.

    I do have an old SW2512 which took a hit through the wind turbine some years ago and stopped working. If the transformers are the same I may be able to use the 2512s to replace the 4048 unit if it did not get damaged.
  • RCinFLARCinFLA Solar Expert Posts: 1,453 ✭✭✭✭
    Re: SW4048 Grid Question

    Yes the cover can come off while still on wall. Might have a little trouble getting to screw heads depending on size of bolt heads used for wall attachment. I had a couple that were a little difficult since my wall mount bolts where 5/8" with 9/16" bolt heads.

    If you substitue, the transformer needs to produce exactly same output voltage (around 13.8vac at 120vac mains) as it is used to match the inverter output to AC1 voltage before engaging AC1 relay. I am sure there is a calibration adjustment on control board but better not to mess with them unless you have a service manual to know what exactly to tweek.

    Make sure you have cut AC power and battery supply.
  • BillFBillF Solar Expert Posts: 48 ✭✭
    Re: SW4048 Grid Question

    That's good news although a couple of the screw for the cover will be a bear. And ditto on the complete shut down. Thanks for the advise and info.
  • RCinFLARCinFLA Solar Expert Posts: 1,453 ✭✭✭✭
    Re: SW4048 Grid Question

    Little trick I used since I have five big bolts on top and five on bottom of mounting.

    On ones that have interference to cover screws, back that single bolt out enough to clear head of cover screw. Tighten back down after extracting that cover screw. Repeat as needed.
  • BillFBillF Solar Expert Posts: 48 ✭✭
    Re: SW4048 Grid Question

    Hello all,

    I wanted to resurrect this thread to deal with another problem that developed related to this one. I have recently converted the system to grid intertie with a Fronius IG3000 and am using the stacked SW4048s as a whole house UPS. However when I moved the utility input from AC1 to AC2 as was suggested, I started getting a chattering type noise from both inverters. The inverters are in SLT mode and have no problem switching to off grid inverting when needed at which time the noise stops. The noise gets much louder when a timed battery charge is activated in SLT mode then the noise diminishes when the charging is done. Any ideas?
  • Constantine FallerConstantine Faller Registered Users Posts: 11 ✭✭
    Re: SW4048 Grid Question

    BillF, do you still have that 2512. I have a cooling fan(s)on a SW2512MC that will not stop running. Given that the fans are variable speed, I am guessing the temp control is ss and not just mechanical, but I have not been inside the unit yet. Also, I do not know if control of the fans may incorporate a relay that may be stuck.

    And RCinFLA, very nice schematic.
  • VicVic Solar Expert Posts: 3,145 ✭✭✭✭
    Re: SW4048 Grid Question

    Hi Constantine,

    As has been alluded to earlier, would seem that the temp sensor that controls the fans is probably on the FET Board ... quite probably mounted on the Heat Sink. If the fans have speed steps (like my SW+ inverters), then the sensor almost has to be something like a Thermistor or even a diode junction. It is possible that there are several sensors, like one on/near the power transformer/s, etc.

    Of course it is quite possible that some of the control electronics are defective. Also connectors/cables might be a first place to start.

    Just too many guesses, have no knowledge or experience with the 2512. Good Luck, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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