Possible to use Sol Ark Gen terminals with a 3 Phase Generator ? Sol Ark techs said NO !

[res242]

Hi all, I have a bit of a mystery here that I have not been able to get a full answer yet. I spoke with two Sol Ark techs and I got two conflicting answers.

Here's a description of the problem and a breakdown of how I have the system configured. I know there is lots of knowledge in this community and some of you will have valuable input.

SYSTEM DETAILS
Residential
Grid = 3 Phase

2 × Sol Ark 15KW
Connected parallel as three phase unbalanced

Inverter Mode = 3 Phase 208v

Utility Grid is 3 phase and connected to the Grid terminals on both Sol Ark inverters
AB BC

PV and Batteries charge fully during the day and system works well... but during the night the batteries drain.

The issue is that I am searching for a way to connect a Generac 20kw 3PH generator to the Gen terminals of both inverters (unbalanced) and so the sol ark will two wire start and charge batteries during the night.

BTW I do not Grid charge because my country is stupid expensive rates for electricity.

Sol Ark documentation does not specify specs of what the Gen terminals will accept nor limitations of the Gen terminals.
Neither do the sol ark wire diagrams show a generator being used in a Parallel three phase unbalanced situation.

 

[timselectric]

I don't see any reason why it wouldn't be fine.
But I'm not familiar with the requirements for the generator input.
Someone would have to explain in detail why it wouldn't work.
As I can't see any reason why it wouldn't.

 

[DIYrich]

I'm guessing with Split Phase, it doesn't matter which line goes to which connection. The inverter can synch.

With 3 phase, I'm guessing there is a "direction" or order. Get it wrong (A-C-B, and not A-B-C), and ...

As always, the easy solution is to use a Chargeverter to directly charge the battery.

 

[res242]

Hey thanks. I do like the Chargeverter idea. I just have not yet figured out how to wire it in from the 3 PH Gen to the parallel sol arks.

Last option may be to use the Grid terminals as Gen input.

 

[timselectric]

Hey thanks. I do like the Chargeverter idea. I just have not yet figured out how to wire it in from the 3 PH Gen to the parallel sol arks.

It would connect to one of the phases, and directly to the battery bank.
Or you can connect 3 chargeverters (one to each phase) for the most efficiency.

 

[Carlos_Sol-Ark]

I don't see any reason why it wouldn't be fine.
But I'm not familiar with the requirements for the generator input.
Someone would have to explain in detail why it wouldn't work.
As I can't see any reason why it wouldn't.

The generator terminals on the Sol-Ark cannot differentiate between 120/240 split-phase and 120/208 3-phase connections. Our grid terminals have more hardware and sensors behind them, allowing us to connect and sync up to many different utility types.

For the Sol-Ark to connect to a generator we have to be disconnected from the Grid and then be able to sync up to the generator. Because the gen terminals are not equipped to read 3 phase input, the inverter can't sync up correctly. This is what prevents the GEN terminals from being used with 3 phase power sources. The best thing for you to do may be to install a double pole double throw switch with the output being the Sol-Ark grid terminals and the two inputs being the Grid or Generator that can be flipped at night to charge the batteries up. You could also get an automated 48V battery charger that can accept 3 phase and start your generator.

 

[timselectric]

View attachment 212699

The generator terminals on the Sol-Ark cannot differentiate between 120/240 split-phase and 120/208 3-phase connections. Our grid terminals have more hardware and sensors behind them, allowing us to connect and sync up to many different utility types.

For the Sol-Ark to connect to a generator we have to be disconnected from the Grid and then be able to sync up to the generator. Because the gen terminals are not equipped to read 3 phase input, the inverter can't sync up correctly. This is what prevents the GEN terminals from being used with 3 phase power sources. The best thing for you to do may be to install a double pole double throw switch with the output being the Sol-Ark grid terminals and the two inputs being the Grid or Generator that can be flipped at night to charge the batteries up. You could also get an automated 48V battery charger that can accept 3 phase and start your generator.

Thanks
That explains it very well.
And makes perfect sense.

 

[timselectric]

Last option may be to use the Grid terminals as Gen input.

This appears to be the only option for connecting a 3-phase generator directly to the Sol-Arks.
But I still would prefer the Chargeverter/s.

 

[timselectric]

I actually just purchased my 3rd Chargeverter for this purpose.

 

[DIYrich]

OK. Generator on grid input. Since you prefer to charge from generator vs grid, do you ever use Grid power? If not, then disconnect from grid, and just have generator connected.

If you are off-grid, do you need 3 phase power? Or is everything divided across the 3? Maybe just run 2 of the 3 phases. Maybe put everything on one phase. Don't know if the SA can be single phase.

 

[Cmiller]

The generator terminals on the Sol-Ark cannot differentiate between 120/240 split-phase and 120/208 3-phase connections. Our grid terminals have more hardware and sensors behind them, allowing us to connect and sync up to many different utility types.

For the Sol-Ark to connect to a generator we have to be disconnected from the Grid and then be able to sync up to the generator. Because the gen terminals are not equipped to read 3 phase input, the inverter can't sync up correctly. This is what prevents the GEN terminals from being used with 3 phase power sources. The best thing for you to do may be to install a double pole double throw switch with the output being the Sol-Ark grid terminals and the two inputs being the Grid or Generator that can be flipped at night to charge the batteries up. You could also get an automated 48V battery charger that can accept 3 phase and start your generator.

@Carlos_Sol-Ark just curious on this whole gen input issue. (I call it an issue for various reasons.) I have looked at the circuit board in a 12K and it looked to me like there is only a CT sensor for one leg of the gen input. Am I correct on that? The reason I ask is because that would make a whole lot of sense to me then on why gen terminals won't accept 3 phase and also why gen shave is no longer supported.

Any comments or thoughts on my theory/observation?

For context on my interest in this:

• We installed a 15K, telling the customer that we can use it on 2 legs of his 3 phase and still auto start his backup gen feeding into gen terminals. (This job is off-grid with (2) 3 phase gens for working hours. These are "big" and "bigger"with a transfer switch between them, then there is a small 15kW gen for backup after hours.) Well, ends up the customer had to buy an additional charger, since gen terminals don't support 2 phases of 3 phase input.
• We have many (off-grid) installs with Kohler 14kW gen auto started and feeding into Grid terminals, then we have an additional 30A twistlock gen cord feeding into Gen terminals. This gives a backup charging option for if the Kohler ever fails. (When off-grid here in Ohio, you depend on generator to get you through the winter months, and you put a bit of hours on your gen!) Not being able to use gen shave makes it a real pain, as our only limiting factor is charge amps. When loads go up, you end up overloading the gen.

 

[Carlos_Sol-Ark]

@Carlos_Sol-Ark just curious on this whole gen input issue. (I call it an issue for various reasons.) I have looked at the circuit board in a 12K and it looked to me like there is only a CT sensor for one leg of the gen input. Am I correct on that? The reason I ask is because that would make a whole lot of sense to me then on why gen terminals won't accept 3 phase and also why gen shave is no longer supported.

Any comments or thoughts on my theory/observation?

For context on my interest in this:

• We installed a 15K, telling the customer that we can use it on 2 legs of his 3 phase and still auto start his backup gen feeding into gen terminals. (This job is off-grid with (2) 3 phase gens for working hours. These are "big" and "bigger"with a transfer switch between them, then there is a small 15kW gen for backup after hours.) Well, ends up the customer had to buy an additional charger, since gen terminals don't support 2 phases of 3 phase input.
• We have many (off-grid) installs with Kohler 14kW gen auto started and feeding into Grid terminals, then we have an additional 30A twistlock gen cord feeding into Gen terminals. This gives a backup charging option for if the Kohler ever fails. (When off-grid here in Ohio, you depend on generator to get you through the winter months, and you put a bit of hours on your gen!) Not being able to use gen shave makes it a real pain, as our only limiting factor is charge amps. When loads go up, you end up overloading the gen.

Yeah, thats part of the hardware differences between the GRID and the GEN terminals I mentioned above. These hardware differences mean a 3-phase generator can only be input on GRID terminals though we try to clarify this limitation in the manual. The best setup for integrating a 3-phase generator is having a transfer switch with the two inputs being the generator and the grid, and the output of the transfer switch leading to the Sol-Ark Grid terminals.
From there, the Sol-Ark can control the two-wire start when the batteries get low, or you can have the generator start when the grid goes out via the transfer switch two-wire start. Although this means only the grid or the Gen can be connected to the Sol-Ark at any one time, it wouldn't affect functionality because the Sol-Ark would only ever connect to a generator on the Gen terminals if the grid was down. - The inverter can and will only connect to one external AC source at any given moment.

 

[Hedges]

Yeah, thats part of the hardware differences between the GRID and the GEN terminals I mentioned above. These hardware differences mean a 3-phase generator can only be input on GRID terminals though we try to clarify this limitation in the manual. The best setup for integrating a 3-phase generator is having a transfer switch with the two inputs being the generator and the grid, and the output of the transfer switch leading to the Sol-Ark Grid terminals.

Can SolArk, whether configured for split-phase or 3-phase, accept single phase 120V at Gen terminals?
It would then be expected to continue making the other phase(s).

This would support use of 1 leg of single, split, or 3-phase generator regardless of inverter configuration.

 

[Cmiller]

Can SolArk, whether configured for split-phase or 3-phase, accept single phase 120V at Gen terminals?
It would then be expected to continue making the other phase(s).

This would support use of 1 leg of single, split, or 3-phase generator regardless of inverter configuration.

No, Sol-Arks don't connect to 120V only.

 

[Cmiller]

Yeah, thats part of the hardware differences between the GRID and the GEN terminals I mentioned above. These hardware differences mean a 3-phase generator can only be input on GRID terminals though we try to clarify this limitation in the manual. The best setup for integrating a 3-phase generator is having a transfer switch with the two inputs being the generator and the grid, and the output of the transfer switch leading to the Sol-Ark Grid terminals.
From there, the Sol-Ark can control the two-wire start when the batteries get low, or you can have the generator start when the grid goes out via the transfer switch two-wire start. Although this means only the grid or the Gen can be connected to the Sol-Ark at any one time, it wouldn't affect functionality because the Sol-Ark would only ever connect to a generator on the Gen terminals if the grid was down. - The inverter can and will only connect to one external AC source at any given moment.

Yes, I have heard that before from the Sol-Ark techs. Let me explain why using an ATS on grid terminals is not a viable solution....

Let's say there is an ATS on grid side that picks grid or gen, now grid goes down. SA runs on battery until the low batteries get to the gen start point. Gen starts, ATS switches to gen, SA starts charging. Now grid comes back on......

Here is where things start getting..... shall we say.... not practical.

For one, an ATS will do a fast transfer back to grid, which may be fast enough to cause out of phase transition to the SA from gen to grid. This could end catastrophically. For the next issue, even if the SA can "catch" the transfer in the ATS and disconnect it's own relay fast enough to avoid toasting it, the next issue is that the gen will continue to run until the SA is satisfied with it's gen run...... that could be 10 minutes, or it could be 5 hours. No customer would be pleased to have their gen run another 5 hours after the grid comes back on. That could empty a propane tank or a diesel tank. Or it could cost the customer money that he is trying to save by having the system in the first place.

So, how soon will Sol-Ark update the hardware to improve the gen terminal's functionality??

Is there any chance of that happening @Carlos_Sol-Ark ?

I know I'm sort of putting you on a spot here, but in the off-grid world the non-functionality of the gen terminal is a huge issue! And unfortunately it is also an issue in the grid-tie world, even though most people don't think about it.

Another note. Having only single leg monitoring on gen terminals not only renders it a "NON-gen functional" with 3 phase. It is also a "NON-gen functional" now on single phase. Very seldom will an auto start backup gen be big enough to handle both charging loads AND downstream inverter loads at the same time!

 

[DIYrich]

Subject to Carlos' response, my thoughts are:

Let's say there is an ATS on grid side that picks grid or gen, now grid goes down. SA runs on battery until the low batteries get to the gen start point. Gen starts, ATS switches to gen, SA starts charging. Now grid comes back on......

Here is where things start getting..... shall we say.... not practical.

For one, an ATS will do a fast transfer back to grid, which may be fast enough to cause out of phase transition to the SA from gen to grid.

The ATS has to be Break-Before Make (otherwise the Gen is connected to Grid and you have even worse problems). I'm guessing that the "break" time is at least 4ms (1/250th of a second). At which point, the Sol-Ark would have disconnected from the Grid Input.

I'm betting that: When Gen is disconnected, the SA goes into UPS mode. It then waits for the grid to stabilize (few minutes). During that time, it slowly syncs its inverter to the Grid so you have a clean transition back to the Grid. This is what happens when it starts the generator. It has to sync to the generator before connecting.

This could end catastrophically. For the next issue, even if the SA can "catch" the transfer in the ATS and disconnect it's own relay fast enough to avoid toasting it, the next issue is that the gen will continue to run until the SA is satisfied with it's gen run...... that could be 10 minutes, or it could be 5 hours. No customer would be pleased to have their gen run another 5 hours after the grid comes back on. That could empty a propane tank or a diesel tank. Or it could cost the customer money that he is trying to save by having the system in the first place.

I'm guessing that once the SA has disconnected from the Grid Input, it should know that it is no longer connected to the Generator (Gen on Grid check box), and turn off the generator.

Another note. Having only single leg monitoring on gen terminals not only renders it a "NON-gen functional" with 3 phase. It is also a "NON-gen functional" now on single phase. Very seldom will an auto start backup gen be big enough to handle both charging loads AND downstream inverter loads at the same time!

Most of the "generator requirements" for inverters state: "Generator must be capable of providing enough power to supply load AND charge batteries". The few inverters that can supplement the generator do not have that limitation.

 

[mapsofilti]

If you want a transformer, you could use 208:240 V split phase or a Scott-T transformer to better balance the load.

Many three phase generators are reconfigurable to split phase, if there are enough poles/winding taps to do so on yours.

 

[Cmiller]

I'm betting that: When Gen is disconnected, the SA goes into UPS mode. It then waits for the grid to stabilize (few minutes). During that time, it slowly syncs its inverter to the Grid so you have a clean transition back to the Grid. This is what happens when it starts the generator. It has to sync to the generator before connecting.

Yes, it "should" do this. I agree. But nobody knows 100% for sure until it's tested.

I'm guessing that once the SA has disconnected from the Grid Input, it should know that it is no longer connected to the Generator (Gen on Grid check box), and turn off the generator.

And how would the Sol-Ark know that it's not just seeing gen power yet?

There is really no way for it to tell the difference between gen and grid if it's a good stable gen.

And from personal experience in pretty positive this is not what happens. In fact Sol-Ark tech support told me in this case the gen would indeed keep running...

Most of the "generator requirements" for inverters state: "Generator must be capable of providing enough power to supply load AND charge batteries". The few inverters that can supplement the generator do not have that limitation.

The inverter doesn't need to supplement gen. It only needs to dynamically adjust charge rate. Gen needs to be at least big enough to feed loads. I do realize that is better to have a gen that can handle both! But most people don't want to buy a 24kW or bigger gen for backup for their "backup for grid" system!

Also, having an input amps or breaker size setting that dynamically controls charge amps has been available for 15+ years on inverters like Magnum, Schneider, Outback, etc.! Personally I have been using this option for the last 12+ years on literally hundreds of systems.... so there's that.

The gen port on the Sol-Ark is literally a downgrade from the humble Magnum MS4024PAE.... shoot, even the Magnum 1512 has input amps setting that dynamically controls charge amps.

 

[Carlos_Sol-Ark]

For one, an ATS will do a fast transfer back to grid, which may be fast enough to cause out of phase transition to the SA from gen to grid. This could end catastrophically.

I'm going to dig up some more information on my end so can get a decent response for all the points you brought up, but I will say I have seen many installations work in that configuration with no issues, but its certainly woth looking into for you especially if it brings some peace of mind on your installs. I have to ask though, how fast is the transfer back to utility power on the transfer switch you are using? This single question will determine if this will be an issue or not. The Grid sample rates on the Sol-Ark are pretty quick.

The next issue is that the gen will continue to run until the SA is satisfied with it's gen run...... that could be 10 minutes, or it could be 5 hours.

Im pretty sure this is true of all configurations. If an AC charging cycle starts (GEN charge and GRID charge), it will run until the batteries reach full or the programmed cap ( in TOU). I will also double check on this for you too.

Very seldom will an auto start backup gen be big enough to handle both charging loads AND downstream inverter loads at the same time!

The inverter doesn't need to supplement gen. It only needs to dynamically adjust charge rate. Gen needs to be at least big enough to feed loads. I do realize that is better to have a gen that can handle both! But most people don't want to buy a 24kW or bigger gen for backup for their "backup for grid" system!

It really depends on how big the loads are and how fast you need the batteries to charge. Most people dont need a 24kW gen to cover loads and charge batteries at the same time in my experience. I typically saw 7-15kW generators being used in residential installs with great results. I also saw my fair share of 20-48kW gens too. If they have big loads and want to do a large load back up with double or triple redundancies you typically have to commit to sizing everything for the expected load (battery charging being considered a load for the generator).

 

[DIYrich]

Yes, it "should" do this. I agree. But nobody knows 100% for sure until it's tested.

Except that, in general, that is how they work. It shift its own production to synchronize with the grid (or generator), and then connect. I suppose a bad inverter can do a hard switchover. But one that is grid enabled has to be able to synch to the grid.

And how would the Sol-Ark know that it's not just seeing gen power yet?

There is really no way for it to tell the difference between gen and grid if it's a good stable gen.

Yes there is, or the settings wouldn't work. You don't tell by frequency, voltage, wave form, directly. There are dirty grids and ckean generators. Although grids tend to have very stable frequency, but a good generator can too.

The big "tell" is: the grid is "stif". Not much you can do to budge the grid. You are a gnat to the grid. If the inverter pushes on the grid, nothing happens. If the inverter pushes on a generator, it can budge the generator's output.

And from personal experience in pretty positive this is not what happens. In fact Sol-Ark tech support told me in this case the gen would indeed keep running...

Not hard to wire the SA's gen start line through the ATS gen start line. When the ATS switches back to grid, it opens the circuit.

The inverter doesn't need to supplement gen. It only needs to dynamically adjust charge rate. Gen needs to be at least big enough to feed loads. I do realize that is better to have a gen that can handle both! But most people don't want to buy a 24kW or bigger gen for backup for their "backup for grid" system!

If you want to charge batteries with the generator, it has to be able to supply more than load. Impossible to charge if there is no excess.

What better inverters can do: 5kw generator. Load goes above 5kw, and inverter supplements (6000xp can't). Load drops below 5kw, and inverter uses excess to charge batteries. What that allows you to do is run a 5kw generator for 6 hours to provide for your 30kwh daily use.

If the inverter can't supplement, then when load goes above 5kw, then inverter has to disconnect generator and run off battery. Now you don't know how long you have to run to recharge because you don't know how long you have been on generator. The only way you know for sure is to get a bigger (10 kw?) Generator.