Sol-Ark 12k AC Coupling Side Load (into sub panel) vs into Gen breaker

[629658]

Currently I running a 10kw 200ah Fortress battery. Would it be possible to add more similar batteries (I.e., 30 kw server rack) in parallel with the Fortress? Seems like this would work but not sure how to split the charging run from the Solark Perhaps a distribution block.

Try these

 

[Carlos_Sol-Ark]

Hello all! Hopefully, I can clear up some information about AC coupling as there are a lot of options and use cases. Just to be clear the Sol-Ark 12K and 15K can support AC couple directly to the GEN breaker or use LOAD side AC coupling. That being said, if possible we recommend using the GEN breaker to accept your loads for a few reasons, which I will outline below. Please also note that AC-coupled solar must be initially turned off during an outage and can only be re-activated to charge your batteries in off-grid situations. For that reason, we recommend at least some DC-coupled solar if you’re expecting any kind of long-term off-grid scenarios.

We are also not able to limit the incoming power to match your loads. We will either accept all of the AC coupled to power or none of it. In the event of an outage, we will use frequency shifting to raise the frequency of the inverter from 60Hz to 62 Hz which will signal the microinverters to disconnect preventing them from damaging us, the batteries, or the loads.



GEN BREAKER AC COUPLING:

The GEN breaker can be used as an AC input to accept generator power or your AC-coupled solar. If programmed to accept AC-coupled solar we will always keep the internal GEN relay connected and connect your micro OR string inverters to the utility harmonics allowing it to sell. You can still connect a generator to the GRID breaker either directly or through a transfer switch that can connect either the utility or the generator to the GRID breaker. When the inverter calls via two-wire start for the generator to start and connect through the GRID breaker, the inverter will automatically open the GEN relay ensuring the generator and AC coupled solar is never on at the same time. Please note this will not happen if you manually start the generator! If you want to manually start the generator please make sure AC coupled solar is turned off or it is at night and there will be now back feeding issues.



LOAD SIDE AC COUPLING:
This configuration is not able to connect a generator to the gen breaker because by default the inverter will never utilize the GEN breaker. This is because although we can frequency shift to turn AC-coupled solar off, when the generator is on we have to match the generator’s harmonics to connect. Therefore, we can’t frequency shift and be connected to a generator at the same time. We have no way to isolate ethe generator and AC-coupled solar to protect us or the generator from incoming solar power. You can still connect a generator through the grid breaker, but you should only charge at night or when you have manually turned the AC coupled solar off.



Please note that if you do have a generator connected to the grid breaker directly or through a transfer switch you will need to select the “Gen Connect to Grid Input” option on the inverter to let it know to look for generator harmonics versus utility harmonics. This will dictate if we can or can not sell power through the grid breaker.

 

[Carlos_Sol-Ark]

I currently have a grid tied 12k with a 32 kw of panels (south facing roof) into the two MPPT's and 25 kwh of LFP batteries. I want to add some additional panels (east and west roof) using micro inverters.

The current 12k manual shows (I think) two ways of doing this. The first (pg 9) is a 'side load' running the panels directly to sub/critical loads panel. the 2nd (pg 10) shows the micro inverted panels going into the generator breaker.

Other than not being able to us a generator if you use the gen input, are there any advantages/disadvantages of either way?

Please see above post.

 

[Benzimidazolone]

Hello all! Hopefully, I can clear up some information about AC coupling as there are a lot of options and use cases. Just to be clear the Sol-Ark 12K and 15K can support AC couple directly to the GEN breaker or use LOAD side AC coupling. That being said, if possible we recommend using the GEN breaker to accept your loads for a few reasons, which I will outline below. Please also note that AC-coupled solar must be initially turned off during an outage and can only be re-activated to charge your batteries in off-grid situations. For that reason, we recommend at least some DC-coupled solar if you’re expecting any kind of long-term off-grid scenarios.

We are also not able to limit the incoming power to match your loads. We will either accept all of the AC coupled to power or none of it. In the event of an outage, we will use frequency shifting to raise the frequency of the inverter from 60Hz to 62 Hz which will signal the microinverters to disconnect preventing them from damaging us, the batteries, or the loads.



GEN BREAKER AC COUPLING:

The GEN breaker can be used as an AC input to accept generator power or your AC-coupled solar. If programmed to accept AC-coupled solar we will always keep the internal GEN relay connected and connect your micro OR string inverters to the utility harmonics allowing it to sell. You can still connect a generator to the GRID breaker either directly or through a transfer switch that can connect either the utility or the generator to the GRID breaker. When the inverter calls via two-wire start for the generator to start and connect through the GRID breaker, the inverter will automatically open the GEN relay ensuring the generator and AC coupled solar is never on at the same time. Please note this will not happen if you manually start the generator! If you want to manually start the generator please make sure AC coupled solar is turned off or it is at night and there will be now back feeding issues.



LOAD SIDE AC COUPLING:
This configuration is not able to connect a generator to the gen breaker because by default the inverter will never utilize the GEN breaker. This is because although we can frequency shift to turn AC-coupled solar off, when the generator is on we have to match the generator’s harmonics to connect. Therefore, we can’t frequency shift and be connected to a generator at the same time. We have no way to isolate ethe generator and AC-coupled solar to protect us or the generator from incoming solar power. You can still connect a generator through the grid breaker, but you should only charge at night or when you have manually turned the AC coupled solar off.



Please note that if you do have a generator connected to the grid breaker directly or through a transfer switch you will need to select the “Gen Connect to Grid Input” option on the inverter to let it know to look for generator harmonics versus utility harmonics. This will dictate if we can or can not sell power through the grid breaker.

Thanks for your detailed response. If my utility will not accept power going back to the grid, then it sounds like I cannot do AC coupling (because once the batteries are full and if there is no load, the power will flow back to the grid). Is that accurate?

 

[jrcromer]

Currently I running a 10kw 200ah Fortress battery. Would it be possible to add more similar batteries (I.e., 30 kw server rack) in parallel with the Fortress? Seems like this would work but not sure how to split the charging run from the Solark Perhaps a distribution block.

JJHDTV, I am curious about your battery age.

The reason being if it is one of the new LFP10 MAX, you may simply want to consider another LFP10 MAX.
If it is an older LFP10, you may care less about the warranty and be more focused on the DIY aspect of expanding your battery bank.

Fortress technical support (https://support.fortresspower.com) can you help figure out a path forward while maintaining your warranty (although they might find also a sizing issue depending on your inverter size).

But if you decide you would rather experiment, be sure to put 80A or 100A fuses (preferably fast acting but at the very least, something) on the LFP10 MAX to protect against battery-battery backfeeding and be very careful to balance the battery banks to the same SoC when commissioning. There's still more to the story when paralleling multiple battery banks, but these are the most important bits.

Another way to expand capacity is also add an additional inverter and run separate banks on a cascading wiring layout.
This can be a very smart solution especially if you also need additional inverter capacity.

 

[jrcromer]

Thanks for your detailed response. If my utility will not accept power going back to the grid, then it sounds like I cannot do AC coupling (because once the batteries are full and if there is no load, the power will flow back to the grid). Is that accurate?

You can still do AC coupling but the potential power generation will be lost.
In general, I find that DC coupling is a bit more reliable than AC coupling.

I'd really only advise AC coupling if the installer is committed to micro-inverters or as a retrofit, given how awesome hybrid inverters like the Sol-Ark have become over the past couple years.

As far as that stranded energy goes, the best ROI you can have is to put an electric tank water heater on a time, such that it only heats during the day. YMMV.

 

[Carlos_Sol-Ark]

Thanks for your detailed response. If my utility will not accept power going back to the grid, then it sounds like I cannot do AC coupling (because once the batteries are full and if there is no load, the power will flow back to the grid). Is that accurate?

That is correct, we do not recommend having AC-coupled solar if you cannot sell to the utility, we will have no way to limit the incoming power to ensure it doesn't get sold. In your case, DC PV would be ideal.

 

[jjhdtv]

Hello all! Hopefully, I can clear up some information about AC coupling as there are a lot of options and use cases. Just to be clear the Sol-Ark 12K and 15K can support AC couple directly to the GEN breaker or use LOAD side AC coupling. That being said, if possible we recommend using the GEN breaker to accept your loads for a few reasons, which I will outline below. Please also note that AC-coupled solar must be initially turned off during an outage and can only be re-activated to charge your batteries in off-grid situations. For that reason, we recommend at least some DC-coupled solar if you’re expecting any kind of long-term off-grid scenarios.

We are also not able to limit the incoming power to match your loads. We will either accept all of the AC coupled to power or none of it. In the event of an outage, we will use frequency shifting to raise the frequency of the inverter from 60Hz to 62 Hz which will signal the microinverters to disconnect preventing them from damaging us, the batteries, or the loads.



GEN BREAKER AC COUPLING:

The GEN breaker can be used as an AC input to accept generator power or your AC-coupled solar. If programmed to accept AC-coupled solar we will always keep the internal GEN relay connected and connect your micro OR string inverters to the utility harmonics allowing it to sell. You can still connect a generator to the GRID breaker either directly or through a transfer switch that can connect either the utility or the generator to the GRID breaker. When the inverter calls via two-wire start for the generator to start and connect through the GRID breaker, the inverter will automatically open the GEN relay ensuring the generator and AC coupled solar is never on at the same time. Please note this will not happen if you manually start the generator! If you want to manually start the generator please make sure AC coupled solar is turned off or it is at night and there will be now back feeding issues.



LOAD SIDE AC COUPLING:
This configuration is not able to connect a generator to the gen breaker because by default the inverter will never utilize the GEN breaker. This is because although we can frequency shift to turn AC-coupled solar off, when the generator is on we have to match the generator’s harmonics to connect. Therefore, we can’t frequency shift and be connected to a generator at the same time. We have no way to isolate ethe generator and AC-coupled solar to protect us or the generator from incoming solar power. You can still connect a generator through the grid breaker, but you should only charge at night or when you have manually turned the AC coupled solar off.



Please note that if you do have a generator connected to the grid breaker directly or through a transfer switch you will need to select the “Gen Connect to Grid Input” option on the inverter to let it know to look for generator harmonics versus utility harmonics. This will dictate if we can or can not sell power through the grid breaker.

Thanks for the above, definitely helps understanding the Solark software logic. Just a few more questions:

When the inverter calls via two-wire start for the generator to start and connect through the GRID breaker, the inverter will automatically open the GEN relay ensuring the generator and AC coupled solar is never on at the same time. Please note this will not happen if you manually start the generator! If you want to manually start the generator please make sure AC coupled solar is turned off or it is at night and there will be now back feeding issues.

I think I got it. I suppose if I did not have auto start generator, one could hook a 12 volt source up to the gen start pins on the Solark. When the software called for a Gen Start the relay would close and the Solark would then detect a generator running and open the (GEN/AC Couple relay), thus disconnecting the AC Couple. Just a thought for a work-around.
I'm not sure I understand the "back feeding issues". If my generator is connected with a transfer switch shared with the Grid Input what concern of backfeeding would there be?

Please also note that AC-coupled solar must be initially turned off during an outage and can only be re-activated to charge your batteries in off-grid situations. For that reason, we recommend at least some DC-coupled solar if you’re expecting any kind of long-term off-grid scenarios.

We are also not able to limit the incoming power to match your loads. We will either accept all of the AC coupled to power or none of it. In the event of an outage, we will use frequency shifting to raise the frequency of the inverter from 60Hz to 62 Hz which will signal the microinverters to disconnect preventing them from damaging us, the batteries, or the loads.

The above statement still has me confused about the Solark software logic. If I'm utilizing AC coupling and the grid goes down, the Solark will open the GEN/AC Couple relay thus shutting off the AC coupling input (correct ?). In this scenario, the Solark would still be powering loads, and if needed, charging batteries with DC solar (correct ?). When will the Solark allow the use of the AC coupling solar to be used to assist with charging batteries (while the Grid is out)?

Not sure if I should ask this question, but what would the Solark do if the software was set for generator input on the GEN breaker, but one connected AC input (240 split phase) from micros or string inverter? Thanks.

 

[629658]

Thanks for the above, definitely helps understanding the Solark software logic. Just a few more questions:


I think I got it. I suppose if I did not have auto start generator, one could hook a 12 volt source up to the gen start pins on the Solark. When the software called for a Gen Start the relay would close and the Solark would then detect a generator running and open the (GEN/AC Couple relay), thus disconnecting the AC Couple. Just a thought for a work-around.
I'm not sure I understand the "back feeding issues". If my generator is connected with a transfer switch shared with the Grid Input what concern of backfeeding would there be?

Please also note that AC-coupled solar must be initially turned off during an outage and can only be re-activated to charge your batteries in off-grid situations. For that reason, we recommend at least some DC-coupled solar if you’re expecting any kind of long-term off-grid scenarios.

We are also not able to limit the incoming power to match your loads. We will either accept all of the AC coupled to power or none of it. In the event of an outage, we will use frequency shifting to raise the frequency of the inverter from 60Hz to 62 Hz which will signal the microinverters to disconnect preventing them from damaging us, the batteries, or the loads.

The above statement still has me confused about the Solark software logic. If I'm utilizing AC coupling and the grid goes down, the Solark will open the GEN/AC Couple relay thus shutting off the AC coupling input (correct ?). In this scenario, the Solark would still be powering loads, and if needed, charging batteries with DC solar (correct ?). When will the Solark allow the use of the AC coupling solar to be used to assist with charging batteries (while the Grid is out)?

Not sure if I should ask this question, but what would the Solark do if the software was set for generator input on the GEN breaker, but one connected AC input (240 split phase) from micros or string inverter? Thanks.

The Sol Ark get its generator frequency info from the CT’s not the 2 wire start. The 2 wire is simply open or closed there is no voltage on the start pins

 

[jjhdtv]

The Sol Ark get its generator frequency info from the CT’s not the 2 wire start. The 2 wire is simply open or closed there is no voltage on the start pins

Hmm Good to know. I guess I was trying to figure the differences Carlos was explaining between autostart Gen and manual start Gen. That is auto start opened the internal Gen breaker and manual start did not. Hence creating a possible back feed when AC coupled when auto start was not used.

 

[629658]

Hmm Good to know. I guess I was trying to figure the differences Carlos was explaining between autostart Gen and manual start Gen. That is auto start opened the internal Gen breaker and manual start did not. Hence creating a possible back feed when AC coupled when auto start was not used.

Opens the gen relay if AC coupled. Closes the gen relay if not AC coupled. Can also function as a smart load panel feed.

 

[629658]

In regards to when will it utilize the AC coupled power, if the batteries are not 100% it will us the AC coupled power to charge the batteries. The most frequent problem we see reported with AC coupling only occurs in an off grid situation and 100% AC coupling. Once the batteries are fully charged the AC coupled power has no where to go and it cannot be throttled back quick enough to be responsive to the house loads. If grid tied and grid connected you will have zero issues. The absolute best is a combination of both AC and DC coupling.

 

[Carlos_Sol-Ark]

Thanks for the above, definitely helps understanding the Solark software logic. Just a few more questions:


I think I got it. I suppose if I did not have auto start generator, one could hook a 12 volt source up to the gen start pins on the Solark. When the software called for a Gen Start the relay would close and the Solark would then detect a generator running and open the (GEN/AC Couple relay), thus disconnecting the AC Couple. Just a thought for a work-around.
I'm not sure I understand the "back feeding issues". If my generator is connected with a transfer switch shared with the Grid Input what concern of backfeeding would there be?

Please also note that AC-coupled solar must be initially turned off during an outage and can only be re-activated to charge your batteries in off-grid situations. For that reason, we recommend at least some DC-coupled solar if you’re expecting any kind of long-term off-grid scenarios.

We are also not able to limit the incoming power to match your loads. We will either accept all of the AC coupled to power or none of it. In the event of an outage, we will use frequency shifting to raise the frequency of the inverter from 60Hz to 62 Hz which will signal the microinverters to disconnect preventing them from damaging us, the batteries, or the loads.

The above statement still has me confused about the Solark software logic. If I'm utilizing AC coupling and the grid goes down, the Solark will open the GEN/AC Couple relay thus shutting off the AC coupling input (correct ?). In this scenario, the Solark would still be powering loads, and if needed, charging batteries with DC solar (correct ?). When will the Solark allow the use of the AC coupling solar to be used to assist with charging batteries (while the Grid is out)?

Not sure if I should ask this question, but what would the Solark do if the software was set for generator input on the GEN breaker, but one connected AC input (240 split phase) from micros or string inverter? Thanks.

It may help to clarify that there are two ways the sol-ark will shut off AC coupling and they happen for two different reasons.

First is during a grid outage event: When the utility goes down, the inverter goes from matching your grid's frequency to maintaining and forming our own. Typically we output 60Hz, but if you are programmed for AC coupling we will frequency shift to 62Hz which is high enough that most micro or string inverters will disconnect themselves. In this scenario we don't have to open the gen relay, we leave it connected and your AC coupled inverters will disconnect themselves. In the event that your batteries get low enough to start accepting large amounts of charge, we will lower the out frequency back to 60Hz. This will essentially call your AC coupled inverters to reconnect and send in solar power that will charge your batteries and help cover loads. We have to wait for your batteries to need a significant charge to give us a place to put solar that is produced in excess of your loads. EX: AC coupled solar is bringing in 5KW, if your loads are only 1KW, we need to be able to send that 4KW somewhere otherwise it would damage us or your loads, so we send it to the batteries. (Can't do that if they are full). Hopefully, this also explains why we have to turn it off in the first place. If we kept AC solar connected during an outage and your batteries are full, if the solar panels ever produce more than the loads there is a large chance that excess power will damage a component on the inverter. The power has to go somewhere.

The second is opening the GEN relay. Again this is only done when the inverter autostarts and calls for your generator to come on (Generator is connected to the GRID breaker, we can't do this with load-side AC coupling). Now in order to connect to your generator we will have to match its harmonics, including its frequency. The GEN frequency is normally around 60Hz meaning your AC coupled inverters will want to stay on and send us power. The back feeding I was mentioning earlier was not about back feeding your utility but back feeding your generator! Remember that the AC side has a shared bus bar so for example if you are producing 5Kw of solar and only have 1Kw of loads, by default the extra 4 KW will want to be fed back to your generator which can damage it or the inverter. Since we can not frequency shift and stay connected to your generator at the same time, the solution is to open up the GEN relay. Then we can connect to your generator, charge the batteries and not worry about AC coupled solar having any negative effects. Once charging is complete we turn the generator off with the two wire start feature and reconnect the GEN relay. Although since your batteries will likely be full after charging from the generator we will be outputting 62Hz keeping AC coupled disabled until we need to charge again.

If you manually start the generator the inverter will NOT open the GEN relay, so be sure to either only do this at night, or disconnect your AC Coupled solar manually if you wish to manually start your generator.

In these scenarios, the preferred order is to use AC Coupled solar to charge your batteries intermittently when off the grid and only use the generator if solar is still not producing enough to keep the batteries charged. This process can be complicated by several different use cases and programming with TOU. As always if you are planning for any sort of long term outage we do not recommend an entirely AC Coupled system and do recommend having at least some DC connect panels that we can directly control. If you have a more specific scenario I highly recommend giving us a call or sending an email to support@sol-ark.com

 

[jjhdtv]

Thanks again. The explanation helps. I did not see a menu option to Autostart the Generator, so assumed if the Gen Charge was selected (in Batt Setup) the autostart relay would automatically close when the start charging parameters were hit (regardless if connected to an autostart gen or not). Still trying to figure out how the Solark knows the difference between manual start and autostart generator.

Appreciate the Solark education related to AC coupling. I would also like the logic behind generator power management (without AC coupling, just DC Solar) when the generator is going through the GEN breaker on the Solark.

If the battery is not present (BMS failure or no battery installed) will the Solark allow the generator to power the loads (and itself) when the grid power is out?
If the battery is not below the Charge Start Voltage, will the generator power the Loads when the grid power is out? or wait until battery is depleted? Can I adjust so the Solark to keep the battery full and use generator to power the loads during an outage. Perhaps TOU settings. Might be nice to save battery power for sleeping hours so I don't need to tend to the generator.

Is the internal GEN breaker open when the Grid power is on and closes when grid is off?

Just trying to run through scenarios, make system improvements and prepare for the next power outage.

 

[RCinFLA]

My question is about what I can AC couple and what is the difference between what Sol Ark calls 'side loading' into the sub panel and AC coupling through the 'GEN' breakers.

Unless it is low power, no more than a couple of kW's, you want AC coupling to go through Gen input.

The HF inverter has limited surge capability. It relies on HV DC filter capacitor bank to make the mode switch over on battery to HV DC converter between supplying AC power and reversing to charge battery. This takes a few milliseconds to do the mode switching.

Injecting PV GT inverter into gen input relay gives the inverter the ability to 'pull the plug' on PV GT inverters that are AC coupled if inverter gets into trouble with over backfeed surge current. This can happen if a large house load is switched off when there is no grid to take the reverse power. Keep in mind, you never know when grid might go down so cannot count on grid to always be there to consume excess PV power. Freq shifting to reduce PV GT power output will not be able to react fast enough to prevent SolArk inverter damage. Back feed dump to batteries is limited by surge capability of inverter after switching to battery charging mode.

Whether it is internal SCC controllers or AC coupled PV GT inverters, the maximum current that can flow through pass-through relay is 50 amps, so is about 12kW's. You can generate more than 12kW of PV power if some of it is consumed by house loads. Just cannot push more than 50 amps back through pass-through relay.

 

[629658]

Thanks again. The explanation helps. I did not see a menu option to Autostart the Generator, so assumed if the Gen Charge was selected (in Batt Setup) the autostart relay would automatically close when the start charging parameters were hit (regardless if connected to an autostart gen or not). Still trying to figure out how the Solark knows the difference between manual start and autostart generator.

Appreciate the Solark education related to AC coupling. I would also like the logic behind generator power management (without AC coupling, just DC Solar) when the generator is going through the GEN breaker on the Solark.

If the battery is not present (BMS failure or no battery installed) will the Solark allow the generator to power the loads (and itself) when the grid power is out?
If the battery is not below the Charge Start Voltage, will the generator power the Loads when the grid power is out? or wait until battery is depleted? Can I adjust so the Solark to keep the battery full and use generator to power the loads during an outage. Perhaps TOU settings. Might be nice to save battery power for sleeping hours so I don't need to tend to the generator.

Is the internal GEN breaker open when the Grid power is on and closes when grid is off?

Just trying to run through scenarios, make system improvements and prepare for the next power

In a grid outage Sol Ark looks for PV then Batt when batts hit your gen start parameters gen will start power your loads and charge your batteries up to the amps you specify. Once batteries get to the parameters you input the gen stops and you go back on batteries. You could decide to run your generator to power your loads by setting gen charge to keep batteries at 100% in the TOU settings. Honesty, if you get your settings correct you shouldn’t need to even worry about staying up or even having to mess with it. The Sol Ark should cycle your gen automatically so you never run out of power be it PV, Grid or gen. We live rural so our gen is LP. Fuel is a real concern. Before Sol Ark if grid out gen fired and ran until grid restored. It could be manually switched off and on but in an extended grid outage I was 10 days max. Now with Sol Ark I’m looking at a 2.5 hr gen run once or twice a day. Now I’m looking at a 40-50 day fuel supply.

 

[wheisenburg]

@Benzimidazolone
With 12.8kW of solar going through your MPPT in the SolArk and 25kWh of batteries you have a lot of flexibility to AC couple to the SolArk,
As far as I can tell you can AC couple more kWs if you use the Gen port. (I will try to find the specifice) I think the reason is that the gen port allows SolArk to open the port to shut down the AC coupled inverters in the situation when the grid drops and there is very little load. If you use subpanel connected to the load side of the SolArk, it has to use frequency Watts to control the AC coupled inverters and there is some latency so the SolArk algorithm needs some time to ramp down the GT inverters. This is pure speculation on my part based on previous experience with an Outback Skybox, much reading about AC coupling and my fairly recent experience with my new SolArk.
The pros and cons about using the Gen port or going through a subpanel are based on user preferences. I chose to go through the Gen port because I never intend to need a generator. One of the benefits may be that you get the internal shunts to measure your GT inverter(s) generation on your SolArk reporting. Other factors include how much capacity you want to couple and whether you want to use the Gen port for some other purpose. Remember this is only a factor when the grid is down and you want the SolArk to be the Grid Forming source to AC couple to GT inverter(s). When the grid is up the grid is a buffer and the SolArk can pass through as much as either of those ports will allow. As mentioned above, if you do use a subpanel, there is a NEC backfeed rule that must be followed. Hope that helps frame the issues for you. I love my SolArk.

I concur with this. They recommend the gen port as the preferred input because it can be shut off quickly. When the GT inverters are sending more power than the batteries can absorb, they will turn the gen port off.

Also be aware that you can not use a generator and Grid Tied PV simultaneously period. If you want to incorporate both into the system, you must use some type of lock out to make sure they are not both active at the same time. The reason is that if your total loads are less than your grid tied PV, the microinverters will attempt to push power into the generator. A double throw (manual transfer switch) or contactor (automatic transfer switch) will work.

 

[629658]

I concur with this. They recommend the gen port as the preferred input because it can be shut off quickly. When the GT inverters are sending more power than the batteries can absorb, they will turn the gen port off.

Also be aware that you can not use a generator and Grid Tied PV simultaneously period. If you want to incorporate both into the system, you must use some type of lock out to make sure they are not both active at the same time. The reason is that if your total loads are less than your grid tied PV, the microinverters will attempt to push power into the generator. A double throw (manual transfer switch) or contactor (automatic transfer switch) will work.

Sol Ark can do it and another reason the CT’s are necessary so it doesn’t grid sell to the generator.

 

[DIYrich]

Also be aware that you can not use a generator and Grid Tied PV simultaneously period. If you want to incorporate both into the system, you must use some type of lock out to make sure they are not both active at the same time. The reason is that if your total loads are less than your grid tied PV, the microinverters will attempt to push power into the generator. A double throw (manual transfer switch) or contactor (automatic transfer switch) will work.

The problem is with PV on the Grid Line or the Load Line. Sol-Ark can't frequency shift (to reduce power from PV) when the generator is running, so all it can do is disconnect PV connected to the Gen port. It can't disconnect PV on the Load Line or the Grid Line

 

[RCinFLA]

SolArk has to be user setup defined for GT inverter input to Gen port. It changes the function of how gen pass-through relay operates.

For normal generator connected mode, the relay remains open until inverter senses AC input and uses it to sync inverter to generator.

In GT inverter through Gen port, it defaults to closing Gen pass-through relay so GT inverter can sync to inverter. In GT through Gen port mode the inverter will make no attempt to sync to generator. If you connect generator when in GT inverter thru gen port mode it will likely just pop generator AC breaker due to AC phasing mismatch between generator and inverter.

You only can have one way or the other. If you want to remove GT inverter and connect generator to gen port you must first reprogram the setup mode on inverter back to generator input mode.

You also have to be careful when in GT inverter through Gen port mode as there will be live AC output on Gen port all the time. Any exposed generator input port junction box with exposed male prongs will have live AC voltage on them.

 

[wheisenburg]

Sol Ark can do it and another reason the CT’s are necessary so it doesn’t grid sell to the generator.

If you look at the installation manual, they will tell you that if you AC couple on the load side, you cannot use the generator input. See their wiring diagrams and it will say "Do not use". There is no "magic traffic cop" that directs the electrons in these inverters from one place to another. What you have is an AC bus just like in an electrical panel with relays that either connect or disconnect the various inputs and outputs. Most are designed to be mutually exclusive. For example if you have both a grid input and a gen input, the system will make sure that they are not both on at the same time. When either of these two inputs are active, the inverter is in "pass through mode" and the inverter is locked out. Although if the inverter has grid or gen support modes the inverter may add current to the AC bus to allow the system to handle surges or shave peaks, but it will follow the AC frequency of the source input.

When "on Grid", all the excess power will flow to the grid. When off grid with no generator running the inverter provides the AC clock frequency. All the excess power will flow to the battery. The inverter can change the frequency to curtail the PV output. If you run a generator that will take over as the AC clock all the excess power will flow either to the battery or the generator. Your GT inverters will run flat out and frequency shifting is not possible. Once the battery is full the PV inverters will attempt to back feed the generator.

Schneider has the same issue, but instead of just saying "Do not Use" in their wiring diagram they explain the issue and let you add a mutual exclusion contactor as a solution. When the generator is turned on, the gen ac energizes the contactor coil and it will disconnect the PV and connect the generator. You need a four pole contactor with a 240 volt coil with two NO and two NC contacts.

 

[629658]

If you look at the installation manual, they will tell you that if you AC couple on the load side, you cannot use the generator input. See their wiring diagrams and it will say "Do not use". There is no "magic traffic cop" that directs the electrons in these inverters from one place to another. What you have is an AC bus just like in an electrical panel with relays that either connect or disconnect the various inputs and outputs. Most are designed to be mutually exclusive. For example if you have both a grid input and a gen input, the system will make sure that they are not both on at the same time. When either of these two inputs are active, the inverter is in "pass through mode" and the inverter is locked out. Although if the inverter has grid or gen support modes the inverter may add current to the AC bus to allow the system to handle surges or shave peaks, but it will follow the AC frequency of the source input.

When "on Grid", all the excess power will flow to the grid. When off grid with no generator running the inverter provides the AC clock frequency. All the excess power will flow to the battery. The inverter can change the frequency to curtail the PV output. If you run a generator that will take over as the AC clock all the excess power will flow either to the battery or the generator. Your GT inverters will run flat out and frequency shifting is not possible. Once the battery is full the PV inverters will attempt to back feed the generator.

Schneider has the same issue, but instead of just saying "Do not Use" in their wiring diagram they explain the issue and let you add a mutual exclusion contactor as a solution. When the generator is turned on, the gen ac energizes the contactor coil and it will disconnect the PV and connect the generator. You need a four pole contactor with a 240 volt coil with two NO and two NC contacts.

Yes I am aware AC couple stuff should be brought in on the gen port. My generator is brought in on the grid input through a transfer switch so the CT’s 100% necessary so the inverter doesn’t try to grid sell to the generator.

 

[wheisenburg]

Yes I am aware AC couple stuff should be brought in on the gen port. My generator is brought in on the grid input through a transfer switch so the CT’s 100% necessary so the inverter doesn’t try to grid sell to the generator.

So with your generator running at 60 hz, your AC coupled PV will run flat out. That energy needs to go somewhere. Where do you think it will go once your batteries are full?

 

[629658]

So with your generator running at 60 hz, your AC coupled PV will run flat out. That energy needs to go somewhere. Where do you think it will go once your batteries are full?

I’m not AC coupled. I have 13.4 kW DC. I have the capability to bring in additional AC coupled panels on my gen port. So if my batteries are full it throttles back my MPPT’s to match the loads. When the gen fires up it takes the loads and charges the bank. Once full it stops the generator and back on PV/Battery. What is important is that it doesn’t try to grid sell my PV production to the generator (Grid out situation) which would be bad. That is why the CT’s are necessary.

 

[DIYrich]

So with your generator running at 60 hz, your AC coupled PV will run flat out. That energy needs to go somewhere. Where do you think it will go once your batteries are full?

The recommendation is to have DC PV > AC PV. Let's say you have 5kW of DC PV, and 4kW of AC PV. AC PV on Gen Input, and Generator on Grid Input.

Sol-Ark will throttle back generator to 0 amps.
Then it will start decreasing DC PV to 0 amps.
If load keeps dropping, it will disconnect 4kW of AC PV on Gen Port, and increase DC PV to 4kW to replace.
Now it can drop DC PV down to 0 amps if it has to.