Minor Backfeed Issue with Utility

[WaterWiz]

I have two LV6548v2 inverters, 25K solar, 50Kwh battery with utility power input only to make up the power difference. None of the inverter output connects to the utility. I only use utility for supplemental.

Issue: I charge my Tesla at 11:45 am. My Solar batteries are usually 100%, solar is not enough to 100% charge Tesla. Usually, 80% is solar, and 20% is offset by utility. Got tired of doing battery dance so I charge solar-utility-battery

The utility company sees a 1-watt back feed ripple when I start charging my car. They know I have solar and are wanting me to fix the issue or turn off the solar

The Tesla charger is downstream of the inverter.

This is where I am at.

Going to install a Grid Only EV Charger.
Going to completely disconnect the utility input.

Concern

Can a battery charger, EV charger, etc cause this ripple? I am afraid no matter what I do the minute I ripple the system (instantaneous high demand) the utility will go we warned you not to do this again we are pulling the meter.

Is the LV6548 the issue? It's only supposed to go one way input

Need help?

 

[hwy17]

Very interesting report of a utility noticing insignificant backfeed. You have a smart meter of course? Does it show any backfeed indicator or power flow on it's display or did you only find out when the utility contacted you?

Also cool that they are just saying fix it, and not informing the building department or something.

Do you supply your entire house from your inverters, or just a critical loads panel?

The only 100% guaranteed way to avoid all backfeeding is to go to a double conversion system, with a grid charger that is separate from the inverter. Otherwise inverters cannot help backfeeding for a split second when a large load shuts off.

It sounds like maybe your utility is only concerned with the continuous backfeed though, and maybe they won't notice the momentary events. Non solar systems also have certain kinds of slight momentary backfeeds. If this was the case, then maybe somehow you could set the inverters to always draw some amount, 500 watts or something, from utility. But I don't know if that's an option on those inverters.

 

[DougfromdaUP]

My utility is ok seeing a small occasional backfeed, they just wanted to make sure my equipment is UL1741 compliant. It's almost impossible to prevent.

 

[WaterWiz]

I am at the we know you have solar. We see the back feed. Make it go away stage. I am awaiting a call from the "supervisor" for me to explain the situation. I.e. the post to cover as many questions as possible.

I have a new AMI power meter which is real-time for the utility. I was able to determine the exact time of the spike and it coincides with my Tesla charging cycle. They noticed the solar when they set the meter. Saw the spikes and defaulted to your connected to the grid. Technically yes but it's a UL1741 connection...

I'm in Florida, we can do our electrical work as owners, it's off-grid I don't think the utility cares so much about what is on my property. I feel the concern is what potential exists of you hurting our lineman. I 100% agree I want absolutely no chance of backfeeding.

I have a critical loads panel isolated from the house. I intend to go with the whole house solar/battery. However, I need to get past these spikes. I will need to use the utility as supplemental when low solar, prefer not to use gas/generator when I have 400amps for quick battery top-off.

These back feed spikes do not show on my Emporia or Solar Assistant logs.
They are not even a watt and momentary. Their system is flagging this and I am on notice, so they care.

Double Conversion System? - My assumption is the MPPT is causing the spike. Therefore, I cannot directly connect the MPPT to Utility cause we know it spikes. Would an EG4 Chargeverter connected directly to batteries possibly work? I have the original LV6548v1 that I could repurpose as a 500w battery charger. I think a low 10 amp max draw on the charger would keep the batteries with sufficient charge.

But as I write this I could simply limit the current the inverters get from the utility to say a max of 10 amps (current is 60 amps)??

I would use solar EV chargers on sunny days or long weekends. Have utility EV chargers for quick charge. If I must use utility with inverter keep it slow and low...

​

 

[Tulex]

Is there a setting for minimal grid draw? With the Sol-Ark, you can set any amount you want, they recommend 20 watts, but I sometimes see it still go a few watts negative. Fairly sure that if I set it to 30, it would stay positive. I'm not concerned because I'm not on a smart meter.

 

[OzSolar]

I am at the we know you have solar. We see the back feed. Make it go away stage. I am awaiting a call from the "supervisor" for me to explain the situation. I.e. the post to cover as many questions as possible.

Sounds like that even though you aren't exporting on purpose they still want you approved to interconnect. Doesn't matter to them if it's 1 w or 10kW.

 

[Danke]

What about adding an ATS and show them that? The ATS will shut the grid off/transfer if it doesn’t sense power from the utility, as in you cannot hurt the lineman that way with backfeed.

 

[Zwy]

Very interesting report of a utility noticing insignificant backfeed. You have a smart meter of course? Does it show any backfeed indicator or power flow on it's display or did you only find out when the utility contacted you?

Also cool that they are just saying fix it, and not informing the building department or something.

Do you supply your entire house from your inverters, or just a critical loads panel?

The only 100% guaranteed way to avoid all backfeeding is to go to a double conversion system, with a grid charger that is separate from the inverter. Otherwise inverters cannot help backfeeding for a split second when a large load shuts off.

It sounds like maybe your utility is only concerned with the continuous backfeed though, and maybe they won't notice the momentary events. Non solar systems also have certain kinds of slight momentary backfeeds. If this was the case, then maybe somehow you could set the inverters to always draw some amount, 500 watts or something, from utility. But I don't know if that's an option on those inverters.

In SBU mode with inverters running, these unit will always draw a slight amount of power, usually the self consumption amount. This allows quick engagement of bypass as it will synch to the grid.

Most of the time I run with utility AC input breaker off, this forces self consumption to come from battery and PV. When battery SOC gets low, I will switch grid input breaker on.

 

[Zwy]

I would disconnect AC input breaker to inverters. If they still claim they see these spikes, something else is causing it.

Use a Chargeverter to provide backup power so you have isolation from grid power to your system. @timselectric runs like this with it all automatic.

 

[Texas-Mark]

Very interesting report of a utility noticing insignificant backfeed.

My utility saw probably less than 10 watts on just one day for a few minutes and called me on it. So yes, the smart meters can see small amounts. Whether the utility will say or do anything depends on their policies.

 

[Zwy]

What I don't understand is how the Tesla charger can cause the ripple.

I'd use the Tesla charger on grid power, disconnect the AC input to the inverters and see if PoCo see the ripple. It might be the charger and PoCo is trying to blame the off grid inverters.

 

[hwy17]

see if PoCo see the ripple.

They probably aren't willing to sit with OP and give him that information live. They're saying "gtfo our wires and be sure about it".

 

[Zwy]

They probably aren't willing to sit with OP and give him that information live. They're saying "gtfo our wires and be sure about it".

I never said anything about asking them if they see the ripple and nothing about "live".

I'd do my own thing, never mention to PoCo the inverters have AC input disconnected with no possible connection to grid. Use the charger on grid power and wait to see if they ever notice. If they do notice, then the charger is at fault.

Most likely the charger draws more watts than the inverters can output when the charger is first turned on. Bypass is enabled in the inverters creating a spike as inverter internal transfer switch makes the switch.

 

[hwy17]

I'd do my own thing, never mention to PoCo the inverters have AC input disconnected with no possible connection to grid. Use the charger on grid power and wait to see if they ever notice. If they do notice, then the charger is at fault.

Yeah my system isn't in daily operation yet so I don't know how it will go yet, but I ended up building towards a double conversion design and I'm happy I did so. I think it's an underserved market for controlling a system like that. I'm putting the BMS in control of the grid charger.

 

[DougfromdaUP]

Is there a setting for minimal grid draw? With the Sol-Ark, you can set any amount you want, they recommend 20 watts, but I sometimes see it still go a few watts negative. Fairly sure that if I set it to 30, it would stay positive. I'm not concerned because I'm not on a smart meter.

I have a Sol-Ark too, and even set to 100 watts for the minimum draw it will occasionally send a momentary spike when the load changes. There's no way to stop it. I think @RCinFLA explained it in a post. Most smart meters can see that, and they notify the utility when it reaches a level that they can set.

 

[chilly2]

1w is so tiny, I wonder if you could put another small always on load consuming at least a few watts between the meter and the ac in of your inverter. Any backfeed should then be consumed by it.

 

[RCinFLA]

I highly doubt the utility smart meter can detect a 1 watt ripple back feed, nor would they want to.

An AC motor with inductive power factor will return some ripple current to grid during a portion of the AC cycle. A pool pump or sprinkler pump will generate a lot more than 1 watt worth of ripple current back feed to grid if there is not other significant house loads to absorb it.

You have to have a sustained average power backfeed to trip a backfeed report. I don't know the exact level but likely at least 10-50 watts of sustained back feed power which allows for inaccuracy tolerance of the smart meter, particularly when power factor of loads is not the best.

 

[WaterWiz]

So just got off the phone with the Utility.

1. They updated their AMI system in January this year to deep dive on all meters. They are collecting serious data on usage, what type of usage, patterns, etc on everyone, big brother stuff. My inverter was flagged as an anomaly and so they investigated and discovered the solar.
2. Ten minutes were spent on why would I have solar without an interconnect agreement. I am the first DIY off-grid solar they have identified.
3. Explanation I have two EV vehicles. Energy costs .13Kw I get .6 at most from interconnect, not including equipment, agreements, and insurance 4. I was paying $100/mo in gas before I went EV now it's almost zero. Why would I interconnect? I don't have excess.
5. It is now elevated to engineering to decide.
6. I have now air-gapped the solar and utility. If it still spikes I need to deep dive into the Tesla
7. I will have a solar EV charger and a Utility EV charger. I generate enough power to run the solar on a battery alone with this method.

The big question is what legality/right do I have in having an EV Solar Charging Station? Does that need to have an interop agreement? If so why? I am now disconnected from the grid. Florida code specifically deals with interconnect but not solar off-grid. The rule wants people to use solar. What better way than EV charging?

25-6.065 Interconnection and Net Metering of Customer-Owned Renewable Generation.

(1) Application and Scope. The purpose of this rule is to promote the development of small customer-owned renewable generation, particularly solar and wind energy systems; diversify the types of fuel used to generate electricity in Florida; lessen Florida’s dependence on fossil fuels for the production of electricity; minimize the volatility of fuel costs; encourage investment in the state; improve environmental conditions; and, at the same time, minimize costs of power supply to investor-owned utilities and their customers. This rule applies to all investor-owned utilities, except as otherwise stated in subsection (10).

 

[OzSolar]

2. Ten minutes were spent on why would I have solar without an interconnect agreement. I am the first DIY off-grid solar they have identified.

As I suspected, they have zero tolerance for you paralleling with them without an interconnection agreement.

Fast forwarding to the end of the story: I strongly suspect that you are going to have be totally off-grid or get an interconnection agreement. There's almost zero chance of you getting them to accept your system without proving it's compliance with UL 1741 etc.

It used to be called Guerilla Solar. I was one of them in the 90's.

The Guerrilla Solar Movement – Mother Earth News

Solar advocates are starting a guerrilla solar movement to combat the notion that one should have to pay for energy.

www.motherearthnews.com

 

[1201]

As I suspected, they have zero tolerance for you paralleling with them without an interconnection agreement.

Fast forwarding to the end of the story: I strongly suspect that you are going to have be totally off-grid or get an interconnection agreement. There's almost zero chance of you getting them to accept your system without proving it's compliance with UL 1741 etc.

It used to be called Guerilla Solar. I was one of them in the 90's.

The Guerrilla Solar Movement – Mother Earth News

Solar advocates are starting a guerrilla solar movement to combat the notion that one should have to pay for energy.

www.motherearthnews.com

But he is not connected in parallel with the grid at all.

They made up some bs story because they probably felt he was not using enough power or knew about his solar.

Op should stand on the fact his system cannot feed the grid and is not in parallel and then make them prove they are seeing back feed