diy solar

diy solar

Minor Backfeed Issue with Utility

Chris30559 said:
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..?
Click to expand...

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.
 
Last edited:
Chris30559 said:
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..?
Click to expand...
What loads do you have on grid? It is possible the minor grid export was caused by having a large inductive load shutting off. It may be a case of false attribution.
 
k490 said:
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.
Click to expand...
It is hybrid yes. Although it's supposed to only have grid interaction with the ac1 grid input. And not the ac2 gen input which is what I use when I do use it. But like I mentioned this was completely disconnected via contactor at the time. Which is why I suspect the induction theory.
 
Mattb4 said:
What loads do you have on grid? It is possible the minor grid export was caused by having a large inductive load shutting off. It may be a case of false attribution.
Click to expand...
At that point not much. I took most of those heavy loads off gird. The whole point right. AC, well, fridge, washing machine, etc nothing left on grid except for some lights, range, microwave and air compressor, just didn't want to squeeze my inverter. Anyway None where in use at the time.

Now that I recall I did however have a large 3000w ac transformer, one of those step up 110v to 240v Heavy 30lb beast. I was experimenting with around that time frame. Although I don't think it was on the same day they mentioned , but I could be wrong. It was not loaded at all, I was just switching it on and off measuring the inrush current for a project, maybe 5 or 6 times within a few minutes. This was using the grid power. If I recall the inrush was quite high. And the no load consumption is on the order of 80watts. Maybe the collapsing magnetic field in the transformer produced enough to back feed?? And like I mentioned nothing else was really on at the time so my grid loads couldn't absorb it, thus went to grid??
 
It's a bit surprising that people are getting caught for single digit watt backfeed. Is it so difficult to maintain a minimum grid load to prevent single digit watt backfeed?
 
Chris30559 said:
It is hybrid yes. Although it's supposed to only have grid interaction with the ac1 grid input. And not the ac2 gen input which is what I use when I do use it. But like I mentioned this was completely disconnected via contactor at the time. Which is why I suspect the induction theory.
Click to expand...
I went back and read that I edited my original post about the manual switch you have. I think the hybrids just a power circuit between the input and output. Possible induction how it happened. UL listed reliance control generator transfer switch going could induce voltage on the line side all the wires in there are shared expect for the hot wires. Utility views any inverter that is plug into a grid as "Grid Connected" which is stupid because they sell portable systems that can charge from the grid. Even an RV with a shore power. They see hardwired connection to an inverter it's "Grid tied" in their minds.
 
Chris30559 said:
At that point not much. I took most of those heavy loads off gird. The whole point right. AC, well, fridge, washing machine, etc nothing left on grid except for some lights, range, microwave and air compressor, just didn't want to squeeze my inverter. Anyway None where in use at the time.

Now that I recall I did however have a large 3000w ac transformer, one of those step up 110v to 240v Heavy 30lb beast. I was experimenting with around that time frame. Although I don't think it was on the same day they mentioned , but I could be wrong. It was not loaded at all, I was just switching it on and off measuring the inrush current for a project, maybe 5 or 6 times within a few minutes. This was using the grid power. If I recall the inrush was quite high. And the no load consumption is on the order of 80watts. Maybe the collapsing magnetic field in the transformer produced enough to back feed?? And like I mentioned nothing else was really on at the time so my grid loads couldn't absorb it, thus went to grid??
Click to expand...
That rather sounds like the cause. But just guessing on my part. The fact you may have had no other loads on at the time would help contribute to the situation.
 
The problem is the only way you know is when you get a call from the utility I'm assuming rather not get calls from them. Maybe it happens lot more then we know lot of people have portable battery stations any of those could back feed somehow.
 
k490 said:
The problem is the only way you know is when you get a call from the utility I'm assuming rather not get calls from them. Maybe it happens lot more then we know lot of people have portable battery stations any of those could back feed somehow.
Click to expand...
Yea same here. I personally made so many fail safes and design decisions to ensure that back feed would be impossible. And then of course they come knocking on my door. It would be very unfortunate if it was that transformer theory I mentioned. And had absolutely nothing to do with my solar. But now the cat is out of the bag so to say and as far as they know it was the solar, Hopefully they leave me alone going forward. The worst thing about the whole ordeal was not actually know how something got back fed. Can't fix a problem that I can't find. So I had to disconnect every single thing that even comes withing a foot of grid power to be sure. No more backup power for my off grid loads I guess. Hopefully the sun holds up 😆
 
It adds up. I'm set to not sell with my Sol-Ark 15k, but so far this month the little spikes have added up to .2kWh.
 
Tulex said:
It adds up. I'm set to not sell with my Sol-Ark 15k, but so far this month the little spikes have added up to .2kWh.
Click to expand...
He has an air gapped manual switch on the grid connection to the inverter it was shut off when they said it was back feeding. The only thing could have done it was through the neutral, or inductance between wires that were close together. I have wondered about this is have an inverter sharing a ground and neutral running at a different phase how would they see that maybe if the N&G bond was not good in the panel. Neutral doesn't pass through the meter it's bypassed. Kind of leaves inductance between wires that are close together the reason.
 
k490 said:
He has an air gapped manual switch on the grid connection to the inverter it was shut off when they said it was back feeding. The only thing could have done it was through the neutral, or inductance between wires that were close together. I have wondered about this is have an inverter sharing a ground and neutral running at a different phase how would they see that maybe if the N&G bond was not good in the panel. Neutral doesn't pass through the meter it's bypassed. Kind of leaves inductance between wires that are close together the reason.
Click to expand...
Oh, I understand his situation. But unless they are wrong/meter is false reporting, something is doing it. Just saying that even the smallest amount adds up over time.
 
Tulex said:
Oh, I understand his situation. But unless they are wrong/meter is false reporting, something is doing it. Just saying that even the smallest amount adds up over time.
Click to expand...
He mentioned was playing with a large transformer that week also.
 
Brucey said:
He mentioned was playing with a large transformer that week also.
Click to expand...
Yea the transformer has me the most suspicious. More so than the inductance on the lines in the grid panel. The transformer testing is something I did for the first time since I got it and while house was using basically zero power no less.. Otherwise nothing had changed in my house grid/off grid setup for weeks. And hadn't turned on the grid backup power contactor for 2 weeks prior to the claimed incident day. Which would be the only time I was even technically connected to the grid. That's why I was so perplexed, obviously they looked at me like I was lying or hiding something haha. But I was truthful with the way everything was connected just like on here. And of course all these theory's of actual possible causes come up after they leave.
 
I think meter looks at L1 to L2 voltage and separate L1 & L2 current.
A 240V inductive load would have power cycling in and out, but always net consumption over a cycle.

Wonder if a transformer that also touched N, trying to rebalance, could skew voltages so even though net power was consumed, meter ASSumed same voltage L1-N and L2-N so miscalculated??
 
Hedges said:
I think meter looks at L1 to L2 voltage and separate L1 & L2 current.
A 240V inductive load would have power cycling in and out, but always net consumption over a cycle.

Wonder if a transformer that also touched N, trying to rebalance, could skew voltages so even though net power was consumed, meter ASSumed same voltage L1-N and L2-N so miscalculated??
Click to expand...
Wonder about 110V inductive loads like window AC units would do this?
 
Most loads would register as loads, with net consumption.

I'm just thinking of how power drawn from one 120V leg and backfed into the other 120V leg could look like net backfeed. It would involve drawing current at higher voltage, feeding back at lower, which seems unlikely first glance.

Unless the meter registers a backfeed that only lasts part of each phase. Reactive loads do that.
 
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