Starting up a new SW4024… Strange outputs

rpvietzke
rpvietzke Registered Users Posts: 48 ✭✭
in Off Grid Solar & Battery Systems #1
All,

I am activating a new system and am getting some very strange results. I -think- it may be an out-of-box failure of the inverter, but figured I might let smarter minds consider this…

This is a Schneider SW4024, purchased new, coupled to a MPPT-60 charger and 12 T105RE (3 groups of 4) batteries. The batteries have been in place for about a month and I've been monitoring them remotely by a combox and all seems fine. I finally got around to finishing the AC wiring and put the inverter in "enable" mode for the first time, with -no- load. It is set to "always on" and is not waiting to sense a certain load, etc.

The inverter comes on and does not fault on the front panel or the combox. However, when I put a volt-meter on the output I am reading 164volts AC on one side to neutral and 64 volts AC to neutral on the other. This is completely bizarre. I did put a small inductive motor load (a cut off saw) on to see if it needed a load to stabilize and it made no difference.

The combox noted that both the SW4024 and the MPPT charger logged errors that amount to saying there was a "voltage collapse". I've checked all the lugs and they all seem tight, so I don't think that is it, nor do I think a loose connection could cause the strange voltage readings.

Time Action Device ID Code Description
2014/09/26 18:55:13 Cleared CSW4024 502935 F47 DC Under Voltage OK
2014/09/26 18:55:12 Cleared MPPT60 1212486 F71 DC Over-current shutdown OK
2014/09/26 18:55:04 Set MPPT60 1212486 F71 DC Over-current shutdown
2014/09/26 18:54:11 Set CSW4024 502935 F47 DC Under Voltage

I am not a total newbie here (I have another system with an older inverter) and think I've done everything right, although maybe there is something about this inverter that I'm missing.

Brilliant ideas?

Rob
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Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: Starting up a new SW4024… Strange outputs

    Sounds like a floating neutral (neutral you are measuring from is not connected correctly to the inverter output's true neutral/transformer center tap).

    These inverters (I think) have an internal transfer switch... The neutral bonding may not be setup correctly or you are on the "wrong side" of the transfer switch.

    My first guess.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • rpvietzke
    rpvietzke Registered Users Posts: 48 ✭✭
    #3
    Re: Starting up a new SW4024… Strange outputs
    BB. wrote: »
    Sounds like a floating neutral (neutral you are measuring from is not connected correctly to the inverter output's true neutral/transformer center tap).

    These inverters (I think) have an internal transfer switch... The neutral bonding may not be setup correctly or you are on the "wrong side" of the transfer switch.

    My first guess.

    -Bill

    Thanks Bill. I rechecked the config and manuals and can't find a way to change this. There are no settings that I can see for how Neutral references ground. There are just lugs for L1, L2, N and G. G&N are tied together at the main panel the inverter feeds and there is a solid #6 to a 10' ground rod nearby. I don't have a grid feed (or Generator attached), so there are no neutrals or grounds elsewhere at this time.

    Still poking around, but still thinking something may be wrong with the unit itself.

    Rob
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #4
    Re: Starting up a new SW4024… Strange outputs

    Have you tried placing a cheap filament lamp from Lx to neutral, then measured the voltage?

    If the voltage goes to zero volts, probably a bad neutral connection. If the voltage stays wrong, probably a bad inverter.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Dapdan
    Dapdan Solar Expert Posts: 330 ✭✭
    #5
    Re: Starting up a new SW4024… Strange outputs

    Rob,

    Sounds like you need to make contact with customer service. I have had one of those inverters running for exactly one year with no issues like the one you have described. I recently sold it and buying another one. If you are having in problems with customer service let me know and I will put you with direct contact with a warm body at schneider.

    Good luck.
    Cheers...
    Damani
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  • rpvietzke
    rpvietzke Registered Users Posts: 48 ✭✭
    #6
    Re: Starting up a new SW4024… Strange outputs

    Answering my own question here… I said I wasn't a total newbie, but I did make a total newbie mistake.

    When I went back and put the meter on the CSW4024 outputs itself, voltage to neutral was fine. It was only at the panel that the weird voltages appeared.
    What does that mean? While the lug was tight, the connection must not have been. So, I must have been measuring output voltage against a earth ground in a way that the inverter's neutral was never tied to earth ground.

    Having pulled the neutral out and reseating it and tightening those lugs, it has been running fine for a week now.

    Rob
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  • DMJ72
    DMJ72 Solar Expert Posts: 131 ✭✭
    #7
    Re: Starting up a new SW4024… Strange outputs
    rpvietzke wrote: »
    Answering my own question here… I said I wasn't a total newbie, but I did make a total newbie mistake.

    When I went back and put the meter on the CSW4024 outputs itself, voltage to neutral was fine. It was only at the panel that the weird voltages appeared.
    What does that mean? While the lug was tight, the connection must not have been. So, I must have been measuring output voltage against a earth ground in a way that the inverter's neutral was never tied to earth ground.

    Having pulled the neutral out and reseating it and tightening those lugs, it has been running fine for a week now.

    Rob

    Good to hear you got it sorted out Rob!
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