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Combining low wattage Victron Phoenix with Growatt 12K inverter

CubesAreShapes

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Aug 27, 2022
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Hello,

I am wondering if anyone else has done this already or has some feedback about this idea.

As you all know, Growatts use a lot of power compared to other inverters (see https://diysolarforum.com/threads/idle-no-load-consumption-specs-vs-your-personal-observation.31747/). I have a Growatt SPF 12000T DVM-US MPV and it consumes ~.8A from each of my four 48V batteries in idle - ~153W at best. This is about 76AH @ 48V for a day of idle - which is a massive 19% of my battery capacity - whether or not I'm even using any electricity. The power save mode does not work for me because 1) Does not play well with my energy efficient fridge that requires intermittent power 2) I am concerned about my electronics with the pulsing - I see one of my bulbs get brighter every 3 seconds 3) My regular energy usage seems to be low enough for it to turn off (don't know what that is exactly, maybe 100-150W, but I can be on the PC with my Starlink satellite running and it starts turning off and on - at times I have resorted to turning on an LED light just to keep it from cycling). I have this giant inverter because I have a standard 240V split-phase range and heat pump. I've realized with these cloudy Canadian winters that I cannot rely on the heat pump in the winter (going to be using wood/propane for winter heat), so I'm mostly running this inverter just to turn my stove on whenever I want. 95% of the time I am using ~200W or less (Starlink satellite, some LED bulbs, monitor, laptop).

The plan:
Buy a Victron Energy Phoenix 1200VA 48-Volt 120V AC Pure Sine Wave Inverter which uses 10W idle, and a 2 way switch to choose between the inverters. That way, I simply switch it to the Growatt inverter before cooking (bonus is some arduino controlled thing or an out of the box AC switch that has wireless capabilities as the switch would be about 200ft away in my shed but I digress) or in the summer when I have ample energy I could leave it on and run the heat pump for AC. Best of both worlds. Fortunately, even when the Growatt inverter is off, it'll come on and charge up my batteries if the PV input is sending some power, but that means I don't want the switch between the inverters and the batteries (like originally planned - almost even bought the Bluesea DC 2 way switch), rather after the inverters and before the AC breaker panel seems like the best place.

However, I'm not exactly sure the best route to accomplish this. Currently the Growatt is wired into a breaker box as the mains supply, and goes through a 60A breaker straight to my house panel. With the Phoenix inverter, should I also just have it coming right into the mains (I suppose it would be connected with the Growatt output wires before the box and one set of wires going into the box in this case)? My plan is also to just send the 120V single phase down both conductors (that way I don't have to make sure all my 120V breakers in the house are on the same leg). I'm not sure how my 240V split phase appliances would react to this if I did indeed turn them on (could it damage them?). Also very curious what would happen if I had BOTH inverters on at the same time - would the "phase" of each leg remain perfectly in sync with the added power from the Pheonix? My suspicion is no, turning to a MAYBE if it distributed equal power to each leg which is very unlikely. Maybe the Growatt would supply all the power and the Pheonix wouldn't detect a load? This seems very circumstantial though. If Growatt power saver mode worked better then maybe this could be a better option (Growatt could just kick on automatically when I start using the stove or need more power! That would be incredible). Is there a smarter way to do this that I'm not thinking of. Can anyone think of any unintended consequences of having both inverters wired up like this? Things I should be careful of?

Hopefully this ultimately saves me a lot of idle energy - even right now I'm using about 150W so the Growatt is doubling my usage. Don't want to talk about it's usage compared to when I go to bed in a few hours (turning it off at night isn't really an option as I run a 120V fridge).

Thanks for reading!
 
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Why not just put the light loads you want ran by the victron on their own sub panel?
 
you can run 2 inverters on 1 batt bank. Its done all the time. Use a quality 48v DC switch like those Blue Sea switches.
The Chinese all in 1 inverters are nice price but you pay in other ways.....will get better in the future..
 
Why not just put the light loads you want ran by the victron on their own sub panel?
This would probably involve a lot of complicated rewiring. I have a 200ft 6/3 cable running from the shed to a standard split phase box in my house which powers everything in the house. Not even sure how I'd begin splitting the loads, and the load would basically be "everything 120V" anyways. All my lights, electronics, etc. The only thing the Growatt will really be powering is the range and heat pump, and my higher 120V usage (maybe power tools and heavy kitchen appliances like a high powered blender).
you can run 2 inverters on 1 batt bank. Its done all the time. Use a quality 48v DC switch like those Blue Sea switches.
The Chinese all in 1 inverters are nice price but you pay in other ways.....will get better in the future..
Yes, I know this is possible. I cannot use the DC switch though because the Growatt AIO would not charge the batteries while I'm using the Phoenix in that case. I think I'd have to use an AC switch on their outputs to control which one is powering the panel.

I guess my questions are:
1) How should I wire the AC outputs of the inverters for a nice clean, safe, setup? Since currently the Growatt output goes into the shed breaker box as the "mains" and out through a breaker, I imagine I'd also want the Pheonix to be wired into the "mains", somehow connected before the box so only one set of mains wires. Maybe there is a better way to do this?
2) What would happen if I had both inverters on at the same time delivering AC to the house - would that ruin the 240V split phase? My suspicion is yes unless the Phoenix distributed its power perfectly across both legs, which is very unlikely, but still an interesting theoretical thing to know.
3) How might my 240V appliances react if I'm sending single-phase 120V down both legs? I'd rather not have to make sure I physically disconnect them when switching between inverters, but that is my current accepted reality. I also don't really want to "test" this on my 2k range in case I damage it...but maybe. I'll be sure to report back to those interested if I do.
4) Any unintended consequences of wiring the inverters together like this that I might not be aware of?

I also thought this idea might be interesting to some members struggling with the idle draw of a larger inverter - and that maybe someone knew of someone already building a setup like this.
 
This would probably involve a lot of complicated rewiring. I have a 200ft 6/3 cable running from the shed to a standard split phase box in my house which powers everything in the house. Not even sure how I'd begin splitting the loads, and the load would basically be "everything 120V" anyways. All my lights, electronics, etc. The only thing the Growatt will really be powering is the range and heat pump, and my higher 120V usage (maybe power tools and heavy kitchen appliances like a high powered blender).

Yes, I know this is possible. I cannot use the DC switch though because the Growatt AIO would not charge the batteries while I'm using the Phoenix in that case. I think I'd have to use an AC switch on their outputs to control which one is powering the panel.

I guess my questions are:
1) How should I wire the AC outputs of the inverters for a nice clean, safe, setup? Since currently the Growatt output goes into the shed breaker box as the "mains" and out through a breaker, I imagine I'd also want the Pheonix to be wired into the "mains", somehow connected before the box so only one set of mains wires. Maybe there is a better way to do this?
2) What would happen if I had both inverters on at the same time delivering AC to the house - would that ruin the 240V split phase? My suspicion is yes unless the Phoenix distributed its power perfectly across both legs, which is very unlikely, but still an interesting theoretical thing to know.
3) How might my 240V appliances react if I'm sending single-phase 120V down both legs? I'd rather not have to make sure I physically disconnect them when switching between inverters, but that is my current accepted reality. I also don't really want to "test" this on my 2k range in case I damage it...but maybe. I'll be sure to report back to those interested if I do.
4) Any unintended consequences of wiring the inverters together like this that I might not be aware of?

I also thought this idea might be interesting to some members struggling with the idle draw of a larger inverter - and that maybe someone knew of someone already building a setup like this.
I am not an electrician, but I feel pretty confident you cant run two different phase inverters to the same panel at the same time. That's asking to be filed in the "Up in smoke" forum. ?

Your idea was briefly discussed by Will Prowse in a recent video he did for one of these high idle draw inverters. He gave 3 or 4 solutions, but didn't get into the details of wiring it.

Wiring a sub panel is very "easy." in theory....until you actually do it at someones house.
 
I am not an electrician, but I feel pretty confident you cant run two different phase inverters to the same panel at the same time. That's asking to be filed in the "Up in smoke" forum. ?

Your idea was briefly discussed by Will Prowse in a recent video he did for one of these high idle draw inverters. He gave 3 or 4 solutions, but didn't get into the details of wiring it.

Wiring a sub panel is very "easy." in theory....until you actually do it at someones house.
Yeah, I pretty much agree I'm asking for trouble by running them both at the same time. Though, it would be nice to just have the Growatt on in power saver mode (though issues with the pulsing still exist) to provide more power when the Pheonix can't supply it all, but I think I'm more theoretically interested in that idea - would the Phoenix, for example, stop detecting loads if they were supplied by the Growatt or vice versa? And how would that be chosen? Or would load be split between them arbitrarily and non-deterministic? Challenging my understanding of electricity here.

I haven't seen that Will Prowse video! Taking a quick look before writing this yielded no result for me either. I'll look more after I post this, but do you perchance have a link?
 
Yeah, I pretty much agree I'm asking for trouble by running them both at the same time. Though, it would be nice to just have the Growatt on in power saver mode (though issues with the pulsing still exist) to provide more power when the Pheonix can't supply it all, but I think I'm more theoretically interested in that idea - would the Phoenix, for example, stop detecting loads if they were supplied by the Growatt or vice versa? And how would that be chosen? Or would load be split between them arbitrarily and non-deterministic? Challenging my understanding of electricity here.

I haven't seen that Will Prowse video! Taking a quick look before writing this yielded no result for me either. I'll look more after I post this, but do you perchance have a link?
I think it was in this video:

Will prowse EG46000EX
 
I think it was in this video:

Will prowse EG46000EX
Thank you so much, I will watch it right now.

One or both inverters will let the smoke out.
Usually the lower wattage unit loses the battle.
Nooo not the magic smoke! STAY INSIDE!

Now, I don't remember where I originally found this image, but had it saved in my images folder. Instead of combining the wires and having them come in as the mains, perhaps the second inverter can be on a double pole breaker and feed "backwards" into the house? I am not sure if this is the best idea though. Still unsure if its wise to send single phase 120V down both conductors but don't see a good way around that without creating major imbalance (putting all 120V loads on one leg in the house).
1670860753358.png
 
Thank you so much, I will watch it right now.


Nooo not the magic smoke! STAY INSIDE!

Now, I don't remember where I originally found this image, but had it saved in my images folder. Instead of combining the wires and having them come in as the mains, perhaps the second inverter can be on a double pole breaker and feed "backwards" into the house? I am not sure if this is the best idea though. Still unsure if its wise to send single phase 120V down both conductors but don't see a good way around that without creating major imbalance (putting all 120V loads on one leg in the house).
View attachment 124328
I'm not sure where you got this image but it doesn't make much sense to me. It doesn't matter if the breaker is on the right or the left side of an electrical panel. The inverter(s) breaker from this image could be above the load breakers on the left and it would operate exactly the same. What matters is which bus bar tab the breaker locks into. You can see in the photo that every other slot on the left side connects to a different tab (inverter #1 or inverter #2). and every other slot on the right side connects to a different tab. Double pole breakers connect to both tabs. Why not just run the inverter(s) into the main breaker on the bottom?

The main problem I see with this image is if you are truly using two different inverters (they are labeled inverter #1 and inverter #2), then they wont be phase aligned. When the sine wave of the AC on inverter #1 is at it's positive peak, what ensures that the other inverter will be at it's negative peak? They will each drift around. So if you have two seperate 120V inverters and you run them on different 120V circuits that's fine, but when you try to power a 240V appliance from two seperate 120V inverters the phases wont align and I'm not sure what would happen. Something between reduced power output and a fire.

This is the reason you cant just connect your phoenix 120V inverter to one phase of your Growwatt 120-N-120 split phase inverter. There's nothing to sync up the timing of the sine waves. Grid-tie inverters have a PLL(Phase Locked Loop) to detect the phase of the incoming grid power and align it's internal inverter with that. When the alignment is within limits, then it enables the power output of the inverter to feed the grid.
 
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As far as I know it's OK to run a single 120V inverter into both phases of a split phase wired 120V-N-120V panel. The 240V appliances wont work though. They are expecting two 120V legs 180 degrees out of phase so they add up to 240V but instead they will get two perfectly aligned 120V legs in phase which never have any voltage difference between them since they come from the same inverter and wont provide power to the 240V load.

Does the growwatt have a remote input to turn on the inverter? If so, you could use an automatic transfer switch in the shed. A switch inside the house sends a signal to turn on the growwatt inverter, the transfer switch detects that the growwatt voltage is on and switches to its "city power" input. If the switch is in the other position it turns the growwatt off and the transfer switch goes back to it's "generator" position which would be hooked to the victron.
 
Your growatt 12kw 240v split phase inverter has TWO hots. A 120v single phase inverter has ONE hot. That's THREE hots total. You can't just attach them on two bussbars. Your picture doesn't explain that to you.
 
I'm not sure where you got this image but it doesn't make much sense to me. It doesn't matter if the breaker is on the right or the left side of an electrical panel. The inverter(s) breaker from this image could be above the load breakers on the left and it would operate exactly the same. What matters is which bus bar tab the breaker locks into. You can see in the photo that every other slot on the left side connects to a different tab (inverter #1 or inverter #2). and every other slot on the right side connects to a different tab. Double pole breakers connect to both tabs. Why not just run the inverter(s) into the main breaker on the bottom?
To be clear, I know the left/right side doesn't matter. The idea I took from this is that the inverter is feeding power "backwards" through the breaker, something I hadn't thought of. Didn't realize that would work for one, and not 100% if that would be "up to code" now that I know it would work. Currently in my own panel, with only the Growatt wired, it does come into the mains. Adding the Phoenix though, maybe I could have it come in through a breaker, as opposed to wiring BOTH into the mains?

The main problem I see with this image is if you are truly using two different inverters (they are labeled inverter #1 and inverter #2), then they wont be phase aligned. When the sine wave of the AC on inverter #1 is at it's positive peak, what ensures that the other inverter will be at it's negative peak? They will each drift around. So if you have two seperate 120V inverters and you run them on different 120V circuits that's fine, but when you try to power a 240V appliance from two seperate 120V inverters the phases wont align and I'm not sure what would happen. Something between reduced power output and a fire.

This is the reason you cant just connect your phoenix 120V inverter to one phase of your Growwatt 120-N-120 split phase inverter. There's nothing to sync up the timing of the sine waves. Grid-tie inverters have a PLL(Phase Locked Loop) to detect the phase of the incoming grid power and align it's internal inverter with that. When the alignment is within limits, then it enables the power output of the inverter to feed the grid.
Yeah, I'm fully convinced that running both of these at the same time is a bad idea. I had already thought that...a little unfortunate it couldn't work as that would make an easier install, but that's reality.
As far as I know it's OK to run a single 120V inverter into both phases of a split phase wired 120V-N-120V panel. The 240V appliances wont work though. They are expecting two 120V legs 180 degrees out of phase so they add up to 240V but instead they will get two perfectly aligned 120V legs in phase which never have any voltage difference between them since they come from the same inverter and wont provide power to the 240V load.

Does the growwatt have a remote input to turn on the inverter? If so, you could use an automatic transfer switch in the shed. A switch inside the house sends a signal to turn on the growwatt inverter, the transfer switch detects that the growwatt voltage is on and switches to its "city power" input. If the switch is in the other position it turns the growwatt off and the transfer switch goes back to it's "generator" position which would be hooked to the victron.
That's what I'd love to do! Assuming only one inverter will ever be on at a time, I'll have to go out to the shed (200ft away) multiple times a day to toggle between them. Any setup that can have this done automatically, or even via a switch in my house would be incredible. Currently my best idea here is a networked arduino that can push the buttons, lol. The transfer switches are new to me, and so is remotely controlling the Growatt unit. Going to do a bit of research on this and get back to you. Thank you so much for your comments, you hit the nail on the button.

Your growatt 12kw 240v split phase inverter has TWO hots. A 120v single phase inverter has ONE hot. That's THREE hots total. You can't just attach them on two bussbars. Your picture doesn't explain that to you.
Right - currrently I have the Growatt wired into a subpanel that accepts both hots. For the phoenix, my plan is to just split the single hot into two and wire them into their own smaller breaker and "backfeed" or have them come in through the mains with the Growatt. And not run any 240V/split-phase appliances while the Growatt is off.
 
the inverter is feeding power "backwards" through the breaker, something I hadn't thought of.
This is done all the time for backup gas generators for normal grid tied systems. The thing you have to be concerned about is that you aren't getting power from two sources at the same time. And also that your generator isn't supplying power back to the grid which endangers line repair workers from the utility. So they sell "generator interlock kits" to physically prevent the main breaker and the generator backfeed breaker from being turned on at the same time. Are you fully off grid?

Capture.PNG
 
Its all the same thing it's just how you describe it. Two 120V sine waves 180 degrees out of phase add to form a single 240V sine wave. Since you have access to the two individual 120V sine waves it makes more sense to me to call them 180 degrees out of phase but I'm an analog engineer and maybe that's not the lingo that electricians use.
 
Why does an inverter need over current protection when wired into a panel? The inverter has built in overload protection right?
The breakers purpose is to protect the wiring.
You will have to increase the wiring to put it on a 100 amp breaker.
Which is entirely doable, if the inverter terminals can accept it.
 
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