EG4 18kPV whole house back-up with no sell back wiring assistance

[ResonateSunshine]

We are preparing to install EG4 18kPV to be mostly off-grid but using the grid bypass as back-up for now. We do not have any permits or inspections needed here in the country nor do we have a sell back agreement. I have attached image of wiring diagram from EG4 with some details from our system and questions I have. The main service breaker is on a pole near the garage shop ~100' from the house. There are loads for the shop in this panel but the breaker shuts off service to the house.

1. The EG4 notes say no load before feeder tap but there is no room to tap at the pole and would require long cable run. Can the tap still be done at the house service breaker?

2. For the same reason as above, can the CTs be located before the feeder tap in the house?

3. The diagram says 200 A breaker for the feeder but that the inverter can backfeed 50 A, should this be reduced to 150 A or lower? (Jesse Muller installed 70 A breaker after feeder tap

)

4. Wire Sizes need to correspond to breaker sizes. If 200 A grid-pass through, but EG4 load is only 50 A, should wires and breaker be full 200 A? Different than Muller install

5. Instead of manual transfer switch, plan to install interlock as EG4 apparently approved in Muller video, and main breaker off unless need to work on inverter.

6. Instead of just a PV isolater, considering retrofitting PV combiner box with a breaker for each PV string (details in diagram). The max ISC is calculated at 17.2 A and string max VOC at 586 V. Any issues with using 600 V 32 A breaker and 10 awg PV cable and labeling this box as PV disconnect 2 of 2?

7. EG4 will be installed inside. By installing RSD outside next to PV and labeling PV Disconnect 1 of 2, is there any need for 200 A non-fused disconnect?

8. Is the 6A 110V/3 A 240V stop switch sufficient for the RSD?

Thank you in advance!

 

[Daddy Tanuki]

You want guaranteed no sell back with grid backup? Buy some chargverters and use them to charge your batteries. Guaranteed 100% separation absolutely no possibility of sell back do not even hook the inverters to the grid… only the chargverters.

 

[ResonateSunshine]

You want guaranteed no sell back with grid backup? Buy some chargverters and use them to charge your batteries. Guaranteed 100% separation absolutely no possibility of sell back do not even hook the inverters to the grid… only the chargverters.

Thank you but this would defeat the purpose of the grid pass-through and time of use optimization on the 18kPV.

 

[Daddy Tanuki]

Thank you but this would defeat the purpose of the grid pass-through and time of use optimization on the 18kPV.

Yes it would but which is better a grid sell back plan where you are constaNyla on your toes and worried or a simple Battery system where it works with no worries?

 

[UberTenere]

You want guaranteed no sell back with grid backup? Buy some chargverters and use them to charge your batteries. Guaranteed 100% separation absolutely no possibility of sell back do not even hook the inverters to the grid… only the chargverters.

Totally agree, I use 2 transfer switches and a changeover switch to optimize my load and keep the power from touching the grid. Yes I'd love to utilize the grid pass through and turn off feedback but my Power company will NOT allow any connection to the inverter because it CAN back feed. The rule sucks but luckily there is a workaround.

 

[ResonateSunshine]

Totally agree, I use 2 transfer switches and a changeover switch to optimize my load and keep the power from touching the grid. Yes I'd love to utilize the grid pass through and turn off feedback but my Power company will NOT allow any connection to the inverter because it CAN back feed. The rule sucks but luckily there is a workaround.

Thank you! I'm trying to understand this all. Why 2 transfer switches? If using an interlock keeping the main grid breaker off, leaving only the feeder tap breaker on, and the inverter set to zero export, how would it backfeed?

 

[Citlalatonac]

Tanuki is 100% correct. The only way to not backfeed is to decouple using an AC-DC transformer, which leaves you needing to be able to power your entire home on just inverters.

Linesman have the 3rd most dangerous job in the US. Unpermitted backfeeding is just another safety hazard they have to deal with. If you have a digital power meter, and most do, your utility can and will detect backfeed in just about real-time. It's very likely you will be shutdown as soon as they notice, because that's not a risk they want to take.

You either need to have an interconnection agreement, or a fully decoupled system

 

[jeff.lankford]

Tanuki is 100% correct. The only way to not backfeed is to decouple using an AC-DC transformer, which leaves you needing to be able to power your entire home on just inverters.

Linesman have the 3rd most dangerous job in the US. Unpermitted backfeeding is just another safety hazard they have to deal with. If you have a digital power meter, and most do, your utility can and will detect backfeed in just about real-time. It's very likely you will be shutdown as soon as they notice, because that's not a risk they want to take.

You either need to have an interconnection agreement, or a fully decoupled system

That's a different issue than occasional brief backfeeding due to a sudden change in loads. As I understand it, the 18Kpv disconnects its output from the grid port whenever it detects a grid outage. I don't think it could pass UL testing without this...

 

[ResonateSunshine]

Tanuki is 100% correct. The only way to not backfeed is to decouple using an AC-DC transformer, which leaves you needing to be able to power your entire home on just inverters.

Linesman have the 3rd most dangerous job in the US. Unpermitted backfeeding is just another safety hazard they have to deal with. If you have a digital power meter, and most do, your utility can and will detect backfeed in just about real-time. It's very likely you will be shutdown as soon as they notice, because that's not a risk they want to take.

You either need to have an interconnection agreement, or a fully decoupled system

I understand the need to not backfeed, but thought that keeping the main breaker off through interlock and the zero export function of the 18kPV with the CTs installed will prevent backfeeding.

 

[Citlalatonac]

.

 

[Citlalatonac]

I understand the need to not backfeed, but thought that keeping the main breaker off through interlock and the zero export function of the 18kPV with the CTs installed will prevent backfeeding.

We aren't really talking about a significant backfeed, but a noticeable one. EG4/Luxpower makes good equipment, but it's not magical.


For the same reason a switch over on grid loss can take 20ms, your inverter might be putting out 5kw to run a heater for 20ms after the heater switches off, since there's nothing in your home using the power there's only one place for it to go, back to the grid, causing a small, momentary backfeed.

 

[ResonateSunshine]

We aren't really talking about a significant backfeed, but a noticeable one. EG4/Luxpower makes good equipment, but it's not magical.


For the same reason a switch over on grid loss can take 20ms, your inverter might be putting out 5kw to run a heater for 20ms after the heater switches off, since there's nothing in your home using the power there's only one place for it to go, back to the grid, causing a small, momentary backfeed.

Thank you for that explanation! With the main grid breaker off, where would that power go? How could it back feed in this scenario? During power outages, the current setup for most homes in the area is to run a generator with breaker in the service panel, turning off unnecessary breakers and the main. If power can backfeed with the main breaker off, wouldn't this be a major concern for linesmen?

 

[Citlalatonac]

Thank you for that explanation! With the main grid breaker off, where would that power go? How could it back feed in this scenario? During power outages, the current setup for most homes in the area is to run a generator with breaker in the service panel, turning off unnecessary breakers and the main. If power can backfeed with the main breaker off, wouldn't this be a major concern for linesmen?

It goes through the feeder tap. Your house is still on the grid when running through the feeder tap. Your main breaker is more of a bypass, it lets you run your house still with your inverter broken, disconnected, or otherwise no in the loop.

Without something like Maxwell's demon there's no way to make a power line one way. What is in the way is your UL 1741 rated anti-islanding equipment in your inverter. Which physically disconnects your system on grid down, saving the linesmen. They gently work in <20ms, and most pocos require something like 50-100ms response, so that's perfectly fine.

The problem is if you don't have an interconnection agreement, your PoCo doesn't know about any of this. They don't know if you're an idiot with a tractor PTO, some lamp cord, and a dream or if you have properly installed UL rated safety equipment. So, they take the less risky route and assume you're a moron trying to blow up their power lines.

 

[ricardocello]

I understand the need to not backfeed, but thought that keeping the main breaker off through interlock

If the EG4 inverter is physically disconnected from the grid, there can be no back feed.

and the zero export function of the 18kPV with the CTs installed will prevent backfeeding.

The zero-export function (with CTs) is a misnomer. It isn’t zero.
It does the best it can, but power still feeds back for a second or two when big loads switch off.

Some PoCos will detect this using your smart utility meter and threaten to shut off your power unless you correct it,
or sign an interconnect agreement.
Some PoCos don’t care at all.
Some people have ancient utility meters that cannot detect the backfeed.

None of this has anything to do with protecting linemen,
The 18kpv always disconnects its input relay from the grid if it goes down, like almost all inverters sold today.

 

[Citlalatonac]

In an ideal world you would email them a copy of the UL certificate and they would text back in 5 mins saying "let'er rip."

In the real world: Some like Tenere above just outright ban it all and be done with it. Others, like mine, will require additional equipment, like meters and shutoffs. Some will charge fees, one-time or ongoing, or force you into disadvantageous power plans. And that sucks, but that's life.

 

[UberTenere]

Thank you! I'm trying to understand this all. Why 2 transfer switches? If using an interlock keeping the main grid breaker off, leaving only the feeder tap breaker on, and the inverter set to zero export, how would it backfeed?

lol, I have a wife and 3 kids, and they will use power hogs on dark days and not think about it. Basically this allows me to use the grid for power hogs and my solar for everything else. My logic is the batteries are for night time and energy hogs are for sunny times when the batteries had their fill. 2 Transfers switches allow me to balance loads over different seasons. I have a 50A for my AC units which are not being used in the winter. Then my normal 30A transfer switch for "base" loads in the house basically everything but the dryer and oven. I have all circuits powered on the 30A in the winter but there is spare power during/after the batteries recover from the night and it annoys me that my panels aren't working, so I added a change over switch for the dryer that uses the 30A circuit so The dryer gets run from 10:00-about 12-1:00 when there is "extra" power. Ultimately I like the ability to optimize my circuits with multiple transfer switches so I can turn stuff on or off based on the time of year and weather. Grid assist would be ideal but I didn't want to play in the power companies sandbox. aka my power company needs an interconnect agreement, overbearing rules, and only Wholesale pricing for feedback, it just wasn't worth it, when I can optimize myself $500 in transfer switches.

 

[Quattrohead]

my Power company will NOT allow any connection to the inverter because it CAN back feed.

Any grid interactive inverter could do this, but correct installation and programming will stop this.
The 18K PV is 100% capable of being set up like this, it will open the grid relays but is still able to monitor and sync to grid so that it can close the relays and use the grid if it is overloaded or the batteries are dangerously low. Other than that the grid connection is 100% open and there is absolutely no chance of it back feeding.
Again correct installation and programming is the key to getting this incredibly complex but highly capable piece of equipment working right in your situation.

 

[samlhop]

maybe im missing something but its my understanding that the eg418k made buy luxpower and ALSO SOLD UNDER THE MAKERS BRAND LUXPOWER 12K ARE THE SAME. i use my lux12K as hole home ups using the pass through with no feedback and it sends no mensurable power back to the grid. in other words when i look at the history there has been 0 sell-back. it switches to charge mod at midnight I have it set to charge between 00:02 and 03:00 and charges up the battery to 100% then the house runs off the battery in till SOC reaches %90 then we switch back to the grid. its been running like that for 4 months only problems have been a comm cable fail, and some learning problems for me. I i have a maines power fail grid fail the inv. auto switch to bat fast enough for all our electronics to keep working sub 20nans i think. when we run off batterys there is
no power at maines. lL1L2.

 

[Chuck E.]

maybe im missing something but its my understanding that the eg418k made buy luxpower and ALSO SOLD UNDER THE MAKERS BRAND LUXPOWER 12K ARE THE SAME. i use my lux12K as hole home ups using the pass through with no feedback and it sends no mensurable power back to the grid. in other words when i look at the history there has been 0 sell-back. it switches to charge mod at midnight I have it set to charge between 00:02 and 03:00 and charges up the battery to 100% then the house runs off the battery in till SOC reaches %90 then we switch back to the grid. its been running like that for 4 months only problems have been a comm cable fail, and some learning problems for me. I i have a maines power fail grid fail the inv. auto switch to bat fast enough for all our electronics to keep working sub 20nans i think. when we run off batterys there is
no power at maines. lL1L2.

I really like your answer! I would like to know if under a "stable" power situation where you are making more power than you are using do you know what the "GRID" wattage is? Maybe something like a small positive flow of like 100 watts flowing from the power company into your house?

I have a "zero grid feedback' string inverter that maintains approximately 200-300 watts POSITIVE power flow when I am making more power than I am using. Yes if an oven or clothes dryer is on and it suddenly turns off there is a whiplash of power toward the grid for a fraction of a second. Essentially I am interested if this EG 18K acts in a similar way in the zero grid feedback profile?

Thank You for any input you may have.

 

[rhorer]

This is an interesting and informative discussion. I'm wondering how it would apply to an 18Kpv going through a GridBoss. In other words, does going through a GridBoss negate any of the anti-backfeed protections that the 18Kpv has when used alone? Does the GridBoss's grid relay open when the grid input goes down? With the 18Kpv feeding out its grid port instead of load port, can it react quickly enough to changes in load to prevent backfeeding when the grid is up? And so on…

 

[EG4TechSolutionsTeam]

I understand the need to not backfeed, but thought that keeping the main breaker off through interlock and the zero export function of the 18kPV with the CTs installed will prevent backfeeding.

To ensure zero power is exported to the grid, you must enable Off-Grid Mode.

 

[samlhop]

I really like your answer! I would like to know if under a "stable" power situation where you are making more power than you are using do you know what the "GRID" wattage is? Maybe something like a small positive flow of like 100 watts flowing from the power company into your house?

I have a "zero grid feedback' string inverter that maintains approximately 200-300 watts POSITIVE power flow when I am making more power than I am using. Yes if an oven or clothes dryer is on and it suddenly turns off there is a whiplash of power toward the grid for a fraction of a second. Essentially I am interested if this EG 18K acts in a similar way in the zero grid feedback profile?

Thank You for any input you may have.

i do not have pv in place so i cant answer your question. all i can say is read the documentation for your equipment.
I can telll u that when my Lux 12K is running off batterys as it dose for about 3-4 hr a day after charging i that it shows 0 power to or from the grid.
I will say that i dont understand the 0 grid feedback issue under normal operating conditions. every time there are sun spots or a solar storm electricity is introduced to the grid and is only a problem in extreme conditions. are you worred about the 200-300Watts at what voltage ?.
It is my understanding that the BIG concern is a safety issue, feeding power into the grid when its down or not powered and may be being worked on could KILL THE LINE WORKERS. and that the Lux12K and EG4 18K are documented UL listed to be automatically isolating in event of grid power fails, something like sub 20ms. I supose i could put an AMP meter on L1 and L2 to check, or dq the mains I have a braker at my meeter that is in an isolatid area then with an OWM meeter check L1-2 to ground but I tend to believe the UL listing that.
If im compleatly missing the boat please someone fill me in
thanks sam