k490
Solar Enthusiast
Wow. This just happened to me, Although my case is slightly different and wondering what everyone's opinion is. Just got a visit from Poco saying I backfed. My first response was impossible....I have a 3pole contactor that is manually activated to connect grid to my ac input of my xantrex xw6048 inverter. This contactor which switches L1,L2, and N was not active it is also normally open state. So couldn't have accidentally closed with loss of power . The Poco couldn't tell me how much or for how long I apparently backfed. But the day range they gave me the contactor was never engaged.
Ive been racking my brain trying to figure out how they could have recorded a back feed. This is what I've come up with.
1. My actual grid consumption was so low, near zero that they just assumed I back fed after they noticed my solar panels. I've brought this up and they assure me that isn't the case.
2. This is far fetched to me but I do believe possible. Some of my off grid load wires actually pass through my original grid connected panel, they were extended and routed to my off grid panel next to it. Nothing electrically connected except the ground wire. However I did notice several of the N wires ran parallel with one of the Lines from the grid. Probably about 12inches worth. And further one was actually wrapped 1 turn worth around it. I wonder if my grid tie loads were so low at a point, Maybe zero, That current was induced through the wires from my off grid loads that recorded as a back feed.
After seeing how little it appears to take for them to register it, I'm guess it's in the single digit watts like you. I'm starting to think scenario 2 has merit.
Also The day in question I did notice a power surge/dip on my on grid panel loads. (Lights dimmed for maybe 1-2seconds. ) I'm almost wondering if that had anything to do with the meter reading backwards also in combination with scenario 2. Again the only physical connection to the grid I had was through a contactor that was off.
Needless to say I was perplexed when they told me. Hopefully my outcome is similar to yours. So far they have just told me to disconnect and all will be ok, but not knowing how it detected backfed to begin with doesn't help me fix the problem.
In any case I've removed all wires that traveled through the grid panel, and removed the contactor. So I have ZERO physical connection what so ever except the ground, And also no wires running parallel anywhere near each other. If I get another call it would have to be scenero 1 at that point. Right..?
xantrex xw6048 isn't that a hybrid inverter? Likely the power just coming from that. You should be able to see the inverter voltage spike up with an oscilloscope, or maybe a DVM that records max voltage. Watch what is causing the voltage to go higher then the grid voltage.
You said the grid input was open by air gapped switch likely it's the neutral wires that has me thinking if I share the neutral they detect it somehow. I have a reliance control generator transfer switch it only switches the hot lead not the neutral. I suppose wires close together are causing some kind of spike on the grid. The AMI meter must be very sensitive.
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