SW4024 Inverter issue with grid power?

JamesJames Solar Expert Posts: 248 ✭✭
Hello folks, I am having an issue with my old style SW4024.

I should first mention that it has been working flawlessly for a few years. Even though I have grid power, I have my system set up as off-grid system with dedicated 120 load circuits. No net metering or connection to the grid other than the following;

Here is the issue; Just out of curiosity, I ran a 120 grid line the AC in terminals. After adjusting the settings for the on-board charger, I turned on the grid AC line to the inverter. It performed correctly, first running a bulk charge, then going to float.

After that initial test, I shut down the AC grid power line to the inverter.
A few days later I ran the same test, powering up the AC line in.
This time, the inverter recognizes the grid power with the normal green flashing LED indicator, then connects and displays the bulk charge LED. After aprox. 60 seconds, the relay energizes and the inverter switches to bulk charge, but only stays there for about 30 seconds, then reverts back to the AC in flashing green LED, thus starting the cycle once again. This continues to do the same cycle as long as I keep the AC line in powered up.

I'm thinking that maybe there is an issue with the synchronization of grid AC to the inverter ac output.
Anyone have some idea of what is happening?

I can also note that I have tried this, with and without the PV panels connected to the battery bank system thru my outback MX60 unit. I makes no difference.


  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: SW4024 Inverter issue with grid power?

    Well the PV connection won't make a difference because the inverter doesn't "see" it.

    But this is an old SW and they are known to fail. One of the things that seems to fail first is the AC connections. Usually the transfer relay sticks and they won't even try to accept AC in. Or they won't disconnect from it.

    It sounds as though your 'waking up' the AC circuits after so many years dormant caused a component failure so now it won't qualify AC properly.

    So you can get it repaired possibly. You can replace it with a newer model. Or you can build a work-around transfer switch & battery charger if this function is now important to have.

    There really aren't a lot of easy D-I-Y fixes to inverter innards. Especially if you can't get the parts.
  • mike95490mike95490 Solar Expert Posts: 9,572 ✭✭✭✭✭
    Re: SW4024 Inverter issue with grid power?

    If you can pull the unit out, you can try to buff the relay contacts with a sheet of paper, to clean years of dust off them. If you can't get to the relays.......

    Not really a lot you can do with high voltage / high power electronics unless you have access to a lab.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

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  • VicVic Solar Expert Posts: 3,145 ✭✭✭✭
    Re: SW4024 Inverter issue with grid power?


    In addition to the other comments regarding the Relays, wonder just how you have the AC IN High and AC IN Low voltages set. Perhaps one of these settings is on the edge of what your Grid voltage happens to be on your subsequent test ... Perhaps that Grid connection might not be able to deliver the required current at the time of the second test (?).

    Also, you might try setting the AC In Amps to a very low value, and see if the SW can deliver a small amount of current.

    Also, the AC Grid source would need to supply all loads that are normally carried by the inverter, as you know.

    Have not played much at all with the venerable SWs, and do not have a manual here to see just what settings are available in SWs.

    FWIW, 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.
  • JamesJames Solar Expert Posts: 248 ✭✭
    Re: SW4024 Inverter issue with grid power?

    Hello and thanks to all the kind folks here with the suggestions. The fact the the unit recognized the AC in the first time around gives me some hope that it may in fact be dirty relay contacts. I'm not a electronics tech, but I do ok for an old guy.
    If I can get to the contacts, I'll clean them. The other suggestion about the AC high/low settings is also a good one. I don't mind saying that i never changed those settings, so they are factory defaults. I did set the AC line in current setting to 15 amps.

    The thought occurred to me that it may not go switch to bulk charging, because of load sharing??? I never considered the the live loads may be taxing the available current for the charger. Does that make sense?
    I will disconnect the loads on the inverter to see if the charger will power up the bulk charge.

    Finally, i should also mention that I'm not off grid and dependent on the inverter.
    Thankfully, I can test these ideas without disrupting normal living. Since I live alone, I can take my time looking into this. Last but not least, I count my blessing every day the old SW keeps producing power...like myself, it is past it's prime. :)
    I actually have another SW new in the box, as I never installed it. No need to with my small array size.

    So once again, thanks for the advise.
    I will post my findings.
  • JamesJames Solar Expert Posts: 248 ✭✭
    Re: SW4024 Inverter issue with grid power?

    Hello folks,
    A short progress report;

    I removed the dedicated loads from the SW4024 and powered up the AC line in.
    Problem remained. So as suggested by Vic, I set the AC in current setting lower (8 amps).
    (I had it set to 15 amps, which is the line current rating of that AC in feed circuit)

    The SW4024 properly switched to Bulk Charge setting.
    I then reconnected my dedicated load to the SW4024.
    It worked just fine powering the loads and the charger.

    I forgot to mention in my previous post that while the unit switches to bulk charge, I can see some arcing of a relay contacts.
    This was noticed while observing the unit left end ventilation slots in the front cover.

    Does anyone know if that is normal operation?

    My next step is to open up the unit and attempt to access the relays in order to clean the contacts as suggested.

    After that, I'm planning to run a dedicated grid powered 30 amp AC feed circuit to the SW4024 to see if the operation is correct and improves the available current to the charger section.
    Thanks again for your help.
    I will post results.
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