What is the maximum possible grid feedback from the EG4 18Kpv?

[skoshorek]

I bought a EG4 18Kpv and 30kWh of LifePower4 batteries to add to an existing 8kW solar array and grid-tied inverter. The existing grid-tied system can feedback 32A max through a 40A feedback breaker. This stays within the 120% rule for the 200A busbars in that breaker panel. My preference is to only use the batteries as backup, for grid down emergencies, and not use them for grid feedback or to power loads when the grid is available.

I will be AC-coupling the existing solar system through the GEN terminals, so I need to calculate the total max feedback to the grid from the EG4 inverter. I will not be adding any additional PV to the EG4's DC input terminals at this time. Will the 32A from the AC-coupled system still be available for feedback to the grid?

I understand that the maximum continuous output from the EG4 18Kpv is 12000W/50A, so if I were to add 12000W or more of solar panels to the MPPT connections in the future, that 50A could be fed back to the grid. True? Assuming that I had 12000W of additional solar panels attached, would the EG4 inverter add its max output (50A) to the AC-coupled input (32A) to afford 82A of solar feedback to the grid? The Signature Solar techie told me that the EG4 18Kpv would limit the feedback to a maximum of 50A, although she seemed a little iffy about it. That doesn't seem logical to me since the AC-coupled input doesn't put any load on the new inverter.

Without adding additional solar, the batteries could easily max out the EG4 18Kpv's AC output. Can any battery power ever get fed back to the grid? I didn't notice anything in the manual that suggests that it could. Signature Solar says that battery power will never be fed back to the grid.

I want to avoid having to de-rate my main breaker for the 120% rule. If I only have to do my calculations with the AC-coupled 32A, then I stay with the 40A feedback breaker and my 200A main breaker. If I have to add potential 50A feedback from the batteries, or 50A from potential future solar panel additions, to the 32A from AC-coupling, I will have to de-rate my main breaker to 125A. I noticed a setting for limiting the AC feedback to the grid in the manual. Will using this setting to limit my feedback be acceptable to local inspectors, or will they always require me to use the theoretical max output from the EG4 inverter (for my physical configuration) to determine the 120% rule?

I am assuming, for now, that I only have to use the 32A AC-coupling input as my max grid feedback current for this installation. I will be doing my permit application in several days, and would appreciate any feedback you might have on these questions.

If anyone is going to suggest using feeder taps, I met today with the local inspectors to discuss how I could take that approach, and it appears to be more complicated than I want to take on at this time. My existing utility hookup does not lend itself to feeder taps without major modifications and new electrical boxes.

 

[Hedges]

I think you're correct that the EG would be capable of backfeeding in excess of 32A.
Maybe so long as you leave the 40A breaker there, just tell EG to behave itself, and the breaker provides protection if it doesn't.

Installed taht way, I would put a critical loads panel after the EG4. And, an interlocked "generator" breaker in main panel so it can be backfed during power outages.

With the 18kPV, as with SolArk, it might be desirable to install inverter between meter and main panel, providing whole house backup. And, have a bypass switch in case inverter goes down.

Doing so does require splitting meter & main breaker from main panel.
It may be possible to install a 200A sub-panel, transfer all branch circuits to it, put a 200A tap off existing main panel to feed inverter. What brand/model panel do you have?

 

[skoshorek]

I think you're correct that the EG would be capable of backfeeding in excess of 32A.
Maybe so long as you leave the 40A breaker there, just tell EG to behave itself, and the breaker provides protection if it doesn't.

Installed taht way, I would put a critical loads panel after the EG4. And, an interlocked "generator" breaker in main panel so it can be backfed during power outages.

With the 18kPV, as with SolArk, it might be desirable to install inverter between meter and main panel, providing whole house backup. And, have a bypass switch in case inverter goes down.

Doing so does require splitting meter & main breaker from main panel.
It may be possible to install a 200A sub-panel, transfer all branch circuits to it, put a 200A tap off existing main panel to feed inverter. What brand/model panel do you have?

I have just found that the EG4 18Kpv can backfeed a maximum of 33.6kW AC power to the grid (using feeder taps). Up to 21.6kW (90A) of AC-coupled power plus 12kW (50A) of inverter output if 12kW or more of solar panels are connected to MPPT channels. This is in section 3.8, page 28, of the manual. There's no mention of backfeeding battery power, so I'm sure that's not an issue. So, for my system, I will only have 32A of AC-coupled input to feedback to the grid.

My electrical system has a combination breaker panel outside that includes the meter, a main breaker of 200A, and a small number of breaker connections on 200A busbars. The bottom lugs on the busbars are connected to another breaker panel inside my garage, by 2/0 cables, which contains most of my load breakers. These are both Eaton boxes. I proposed connecting the EG4's grid1 and grid2 terminals directly to the bottom lugs on my main utility breaker panel (outdoors) to the chief plans examiner at our city permit dept. and he said it would still have to meet the 120% rule for that panel's 200A bus. At that time I thought I might have 82A feedback, including battery feedback of 50A, but now it looks like I'll only have 32A. With 82A feedback I would have had to derate my main breaker to 125A. With 32A I can maintain my full 200A service when the grid is up. I intend to move all but my EMP Shield breaker from the outside panel to the inside breaker panel. Since I have all major natural gas appliances, I should be able to handle whole house backup with the 82A combined from batteries and AC-coupled solar. Even 50A from batteries alone will keep me in A/C for a couple of days of bad solar, if I minimize other loads.

Today I met with two of the city's inspectors to discuss whether I could re-purpose my main breaker panel (outside) as a junction box to house three Polaris taps. My proposal was to leave the meter and main breaker where they are, and either disconnect or remove the busbars so no additional breakers could be installed. The taps would be attached to the bottom terminals on the main breaker. They were very close to saying this would be acceptable, but any such modification to the combination panel would de-list it, and they want all UL Listed equipment. Otherwise, I would have to move the meter to its own box, have a main 200A breaker in another box, and house the three taps in another enclosure. The utility would also have to shut off power for some time. Now that I can maintain my 200A service with a 40A feedback breaker there's no big reason to want to use feeder taps. If I ever add extra solar panels, that may again push me toward the feeder tap design. I was intending to use all 3/0 cable for 200A current, but I was surprised when they said I could use 2/0 for all my 200A cables (without me even asking). Cool. That makes for better conduit fill calculations.

I was going to include a manual transfer switch as shown in the manual, for potential EG4 inverter servicing, but now I'm thinking that it would be easy to re-wire for utility power in that situation, and I can save some extra work now and about $700 for equipment and wiring.

 

[DIYrich]

It can feed back battery power. You can set it to not feedback from battery.

 

[Hedges]

My electrical system has a combination breaker panel outside that includes the meter, a main breaker of 200A, and a small number of breaker connections on 200A busbars. The bottom lugs on the busbars are connected to another breaker panel inside my garage, by 2/0 cables, which contains most of my load breakers. These are both Eaton boxes.

I think that if only grid and bottom lugs are used, all branch circuit breakers are removed, then 120% rule does not apply. But maybe not all jurisdictions.

Adding storage to my Enphase system

Looks like you have a good plan to help the thermostat sense the actual cooling requirements! When I lived in upstate NY back in the 1970's, I put an incandescent lamp near the thermostat to reduce the heater operation cycles below what the old "mercury tube" thermostat could sense. Heating...

diysolarforum.com

Adding storage to my Enphase system

Looks like you have a good plan to help the thermostat sense the actual cooling requirements! When I lived in upstate NY back in the 1970's, I put an incandescent lamp near the thermostat to reduce the heater operation cycles below what the old "mercury tube" thermostat could sense. Heating...

diysolarforum.com

 

[skoshorek]

I think that if only grid and bottom lugs are used, all branch circuit breakers are removed, then 120% rule does not apply. But maybe not all jurisdictions.

Adding storage to my Enphase system

Looks like you have a good plan to help the thermostat sense the actual cooling requirements! When I lived in upstate NY back in the 1970's, I put an incandescent lamp near the thermostat to reduce the heater operation cycles below what the old "mercury tube" thermostat could sense. Heating...

diysolarforum.com

Adding storage to my Enphase system

Looks like you have a good plan to help the thermostat sense the actual cooling requirements! When I lived in upstate NY back in the 1970's, I put an incandescent lamp near the thermostat to reduce the heater operation cycles below what the old "mercury tube" thermostat could sense. Heating...

diysolarforum.com

It turns out that you are correct. In my area of Florida, the inspectors allowed me to use the bottom lugs on my main exterior breaker panel, without any feedback breaker, as the feed directly to the GRID terminals on the EG4 18Kpv (and therefore also the connection for any export to grid). I moved the only load on the exterior panel, a mini-split heat pump, to the interior sub-panel. I left my EMP Shield, and the BRSURGE that was installed by the builder, on the busbars. At this time my only feedback to the utility is 32A from the existing AC-coupled solar system. I have no other solar attached directly to the EG4 18Kpv MPPTs, and have the batteries set for no export to grid. My utility required me to add another AC disconnect between the main meter/breaker panel and EG4 18Kpv, even though the AC-coupled solar system has its own 60A AC disconnect. This is required to allow cutoff to any possible feedback from the EG4 18Kpv, and because of the 200A pass-thru capability, this disconnect is rated for the full 200A. It's BIG! The utility also had me remove all labels from the 60A AC disconnect box and label the 200A disconnect as the main solar system disconnect.

 

[Hedges]

Can you post a photo of that?

 

[skoshorek]

Here are some photos. Note that I had to use "Polaris" multi-port connectors in the main breaker box to get those 2/0 cables to make a sharp 90 degree turn.