11.8Kw Ground mount and 3-SPF Growatt 5000 ES, Grid pairing and backup Generator. But will it work?

[Jim Lee]

I finally got it drawn up. Here is the PV ground mount the way I plan to set it up 2@6s2p and 1@3s2p. The only way I can think to get AC to the GW "AC in" is to add 2 new panels. One to be a new main 200A panel and the other to be a solar production panel only and change my original main house panel with almost all the house circuits in it to a Sub Panel with a generator Interlock kit to prevent Grid and PV power in the same box at the same time. It would also allow me to switch back to grid only easily if needed. This seems to be the only way that I can use solar 1st then batteries 2nd then have the grid pair AC with the Inverter AC if the PV or battery can't handle the load. If the grid goes down, I would use PV then Battery then the natural gas generator as a last resort. Please look at my drawings and let me know if anything is done wrong. I do realize I don't show sharing or paralleling the inverters and the wiring is basically what is connected to what and doesn't show L1, L2 or N connections. N and grounds are bonded in the Transfer switch per my electrician, the 1st box after the meter. Please comment positive or negative. I'm ready to purchase all this, but need to know if it will work. "Signature Solar DIY" just said they are just a parts dealer(Noting the DIY in their name) and I need to DIY. I was hoping for a little more considering this is an $18,000.00 purchase from them. I would appreciate any help anyone could give.

 

[Prefersdirt]

Honestly, for $18K I would contact Engineer 775 and pay the consultation fee. I have mentally been setting up something similar as a brain exercise (never gonna happen in my current location). Others may be better for consultation.

 

[stienman]

So far as I can tell, it'll work. Note that the three inverters also have parallel cables that go between them, which you haven't included in your diagram.

I'd suggest you have your welder and hot water on the solar as well, but I'm sure you understand your needs better than I.

The only thing that needs to be understood and perhaps mitigated is that the two autotranformers only handle 5kW each, and you're generating up to 15kW of power. While exceptionally unlikely, failure in one could lead to a cascade failure in the other if the imbalance is over 5kW, which will result in damaging nearly every 120v device at the same time. Adding a third one would provide some peace of mind. Temperature monitoring which forces the inverters to shutdown might also resolve that - the autotransfromers have temperature sensors in them, but they aren't connected to anything.

It's the same direction I'm leaning towards, though, and I really like the panel that handles those transformers and the inverters together before going to the next panel. Right now I have the autotransformer right on my main panel, but my inverter supplies split phase so it's only meant to help the imbalance in my home.

 

[Jim Lee]

Thanks for the quick replies. I left out the GW paralleling and the power sharing wire connections because David Poz has a great you-tube showing how easy it is and I didn't want to clutter the diagram. The welder and Hot water are for future use and not used at all. When I built the house I put them in for future possibilities. My hot water is preheated with my Geothermal HVAC then ran through an on demand hot water heater. I'm being told that only one Split phase transformer is needed for 3 or up to 6 Growatts. I put 2 in for redundant protection in case one trips a breaker or fails for any reason it should still balance the line with one operating. There is a thread on how to protect these, but I can't make heads or tails of what they are saying the fix is. I'm still looking for that fix. 2 or 3 transformers may be the only answer I get. If I get more comments on my entire system maybe I'll feel comfortable enough to start the build. Well, I already started the Ground mount, but at 69 years old everything moves at a snails pace. Thanks again

 

[Jim Lee]

Honestly, for $18K I would contact Engineer 775 and pay the consultation fee. I have mentally been setting up something similar as a brain exercise (never gonna happen in my current location). Others may be better for consultation.

Never heard of engineer 775. Who or what is that and how do I contact them.

 

[Struc]

I'm collecting parts for a near identical system (I'm only doing 2xGrowatt to start), right down to the NG generator (mine is 15kw). All looks good and is very close to the design in my head, but I have more subpanels I need to feed due to the way my property was set up when I bought it.

My only bit of advice would be to go 6s1p on that last string of panels. Apparently the Growatt inverter will handle more amps, but will only use 18A, so might as well boost up the voltage instead.

Guessing you'll be running 10awg PV or THWN cable from the panels to the inverters?

Engineer775 is a guy on YouTube that builds solar systems for a living.

 

[Zwy]

Why the SPF 5000ES? Why use something that requires an auto transformer? Signature Solar always pushes these, but I have to wonder why. Three SPF5000 ES with 2 autotransformers is $3500. Many split phase units in pairs are cheaper.

PV input is limited to 18A per unit according to Sig Solar website under Specs and Manual. https://shop.signaturesolar.us/products/5kw-48w-240vac-80a-off-grid-inverter-by-growatt

Your PV amps are too high. You have a few options. You could go up to 8S with 3 strings and one 6S string and still be under 450V. The problem is the SPF5000 ES only has one PV input. You would need to add additional SCC's.

 

[Prefersdirt]

Never heard of engineer 775. Who or what is that and how do I contact them.

He is on youtube under that name. Practicalpreppers dot com.

 

[Struc]

Another thought... It appears you are powering the transformers on the 2nd Subpanel (Growatt combiner). You're going to need a way to disconnect the transformers when you swap to grid power in the 1st subpanel, or power the transformers in the 1st subpanel so they work with grid power as well. I'm planning on a transfer switch that switches L1, L2 and N instead of the interlock you show.

 

[robby]

I finally got it drawn up. Here is the PV ground mount the way I plan to set it up 2@6s2p and 1@3s2p. The only way I can think to get AC to the GW "AC in" is to add 2 new panels. One to be a new main 200A panel and the other to be a solar production panel only and change my original main house panel with almost all the house circuits in it to a Sub Panel with a generator Interlock kit to prevent Grid and PV power in the same box at the same time. It would also allow me to switch back to grid only easily if needed. This seems to be the only way that I can use solar 1st then batteries 2nd then have the grid pair AC with the Inverter AC if the PV or battery can't handle the load. If the grid goes down, I would use PV then Battery then the natural gas generator as a last resort. Please look at my drawings and let me know if anything is done wrong. I do realize I don't show sharing or paralleling the inverters and the wiring is basically what is connected to what and doesn't show L1, L2 or N connections. N and grounds are bonded in the Transfer switch per my electrician, the 1st box after the meter. Please comment positive or negative. I'm ready to purchase all this, but need to know if it will work. "Signature Solar DIY" just said they are just a parts dealer(Noting the DIY in their name) and I need to DIY. I was hoping for a little more considering this is an $18,000.00 purchase from them. I would appreciate any help anyone could give.

Your going to need an electrician and I can assure you that once he sees a single phase 240V system being hooked up through a transformer he is going to tell you NO! The power company is also going to have to be alerted before he can do the work and the plans are going to have to be approved. Save yourself a lot of headache and get a properly certified split phase inverter. It's the only thing that you can install without an issue and it's also the only thing that your home owners insurance will allow for fire coverage on your house.

 

[Jim Lee]

Your going to need an electrician and I can assure you that once he sees a single phase 240V system being hooked up through a transformer he is going to tell you NO! The power company is also going to have to be alerted before he can do the work and the plans are going to have to be approved. Save yourself a lot of headache and get a properly certified split phase inverter. It's the only thing that you can install without an issue and it's also the only thing that your home owners insurance will allow for fire coverage on your house.

I already checked and I DO NOT need a permit where I live and The Electric Company Has no Say in my Off grid System with no net meter needed. ( or wanted). I tried going the net meter grid tied route but the electric Company so politely said they would sell to me at 12 cent/ Kwh and buy my excess at 3 cents/ Kwh. They also reconcile every month, so no carry over and based on the number of panels used my base pay would go up from $0.00 to $70 or $80 per month. SOOO, I guess you know where the electric company can put any alerts, plans, approvals or permits they want. The Growatt is a plus because there are less headaches not more. A lot of people say stay away from growatt and the way they use a split phase transformer, but just say use something else without offering what else or showing how to do it. The growatt is clearly shown on you-tube exactly how to set it up and shown that it does work. If I had other options of different brands doing the same then I would consider other options. ALL other options that I have seen are extremely difficult to understand and don't show the whole picture. Maybe, That is why Signature Solar and Growatt are getting so much attention.

 

[Jim Lee]

Your going to need an electrician and I can assure you that once he sees a single phase 240V system being hooked up through a transformer he is going to tell you NO! The power company is also going to have to be alerted before he can do the work and the plans are going to have to be approved. Save yourself a lot of headache and get a properly certified split phase inverter. It's the only thing that you can install without an issue and it's also the only thing that your home owners insurance will allow for fire coverage on your house.

My electrician has already seen my plans and didn,t say "NO".

 

[stienman]

...once he sees a single phase 240V system being hooked up through a transformer he is going to tell you NO!

It's how the power company does it. Single phase in one side of the transformer, split phase at a lower voltage out the other side.

The only difference is that this being an autotransformer, both sides are one inductor, and we're not changing the voltage, just providing a center tap for neutral.

Quite frankly, the autotransformer is going to be the one of the most reliable parts of the overall design.

 

[robby]

I already checked and I DO NOT need a permit where I live and The Electric Company Has no Say in my Off grid System with no net meter needed. ( or wanted). I tried going the net meter grid tied route but the electric Company so politely said they would sell to me at 12 cent/ Kwh and buy my excess at 3 cents/ Kwh. They also reconcile every month, so no carry over and based on the number of panels used my base pay would go up from $0.00 to $70 or $80 per month. SOOO, I guess you know where the electric company can put any alerts, plans, approvals or permits they want. The Growatt is a plus because there are less headaches not more. A lot of people say stay away from growatt and the way they use a split phase transformer, but just say use something else without offering what else or showing how to do it. The growatt is clearly shown on you-tube exactly how to set it up and shown that it does work. If I had other options of different brands doing the same then I would consider other options. ALL other options that I have seen are extremely difficult to understand and don't show the whole picture. Maybe, That is why Signature Solar and Growatt are getting so much attention.

Since your not hooked up to the Grid and I assume you don't need any form of permits then sure some electricians will do the Job. Have you contacted your insurance company and told them the plan? That is why I stressed in another thread that it is the insurance company that will make you cry. I would also suggest that you get any kind of OK from them in writing.

As for UL complainant Hybrid Inverters inverters have you looked around?
You have Outback Sky box, Outback Radion, Sol-Ark and Schnieder. None of these systems are hard to setup and use.

 

[robby]

It's how the power company does it. Single phase in one side of the transformer, split phase at a lower voltage out the other side.

The only difference is that this being an autotransformer, both sides are one inductor, and we're not changing the voltage, just providing a center tap for neutral.

Quite frankly, the autotransformer is going to be the one of the most reliable parts of the overall design.

Yes I know that, but it has nothing to do with what is required on your end. Since he is totally off grid he can probably do what he wants so long as his Insurance company has no problem with it. Personally even if my electric bill went down to Zero I would stay grid tied. I have already experienced two weeks of fully overcast days with on and off rain. PV production was so low I doubt my fridge could have stayed on. Yes I have a generator but that brings with it other issues as well as even more expense for the power than the grid. At his price of 12 cent/KWh I would not even considered solar and batteries. The pay back period is going to be almost forever. I mean just the $18K of expenses on equipment will take over 8 year to payback if he uses as much as 50KWh per day. That's not even including the Installation and wiring expense which will add in probably another 4 years.

 

[Jim Lee]

Yes I know that, but it has nothing to do with what is required on your end. Since he is totally off grid he can probably do what he wants so long as his Insurance company has no problem with it. Personally even if my electric bill went down to Zero I would stay grid tied. I have already experienced two weeks of fully overcast days with on and off rain. PV production was so low I doubt my fridge could have stayed on. Yes I have a generator but that brings with it other issues as well as even more expense for the power than the grid. At his price of 12 cent/KWh I would not even considered solar and batteries. The pay back period is going to be almost forever. I mean just the $18K of expenses on equipment will take over 8 year to payback if he uses as much as 50KWh per day. That's not even including the Installation and wiring expense which will add in probably another 4 years.

I've talked to my insurance agent and he didn't have a problem adding it to my policy. He said if it is not already covered in outside structures, it would only add about $10 a month. I'll be getting more detail from him soon. Also, I am not totally off grid. I'll be using an off grid inverter that is grid tied but will not feed back to the grid, therefore no netmeter needed. I will have the benefit of using the grid if and when I need it, but PV 1st, battery 2nd, grid 3rd, even when the grid is down and generator 4th. After 26% tax credit and not figuring any price increases I figure my payback Including 32Kw of 48v Li Fe batteries will be less than 8 years. The $18k includes the batteries. Installation will be done by me. I'll do all the wiring except the wiring change from my transfer switch to my new main panel. about $200.

 

[Jim Lee]

Why the SPF 5000ES? Why use something that requires an auto transformer? Signature Solar always pushes these, but I have to wonder why. Three SPF5000 ES with 2 autotransformers is $3500. Many split phase units in pairs are cheaper.

PV input is limited to 18A per unit according to Sig Solar website under Specs and Manual. https://shop.signaturesolar.us/products/5kw-48w-240vac-80a-off-grid-inverter-by-growatt

Your PV amps are too high. You have a few options. You could go up to 8S with 3 strings and one 6S string and still be under 450V. The problem is the SPF5000 ES only has one PV input. You would need to add additional SCC's.

I am definitely no expert on this, but my understanding is using some of the split phase inverters, for instance a 5Kw inverter can only supply 2.5Kw to each leg which is fine if both phases are balanced, but if 1 phase spikes it can only spike to 2.5Kw. With the 5Kw GW and a split phase inverter one leg can spike to 5Kw with no problem. I'm sure there is more to it than that, but that is what I understand.

 

[Quattrohead]

Use 1 Growatt 12K that is properly designed and built for the USA split phase system from day 1. - https://shop.signaturesolar.us/products/12kw-48w-240vac-120a-off-grid-inverter-by-growatt
and add a second charge controller https://shop.signaturesolar.us/products/120a-mppt-250v-charge-controller-by-growatt

 

[Zwy]

I am definitely no expert on this, but my understanding is using some of the split phase inverters, for instance a 5Kw inverter can only supply 2.5Kw to each leg which is fine if both phases are balanced, but if 1 phase spikes it can only spike to 2.5Kw. With the 5Kw GW and a split phase inverter one leg can spike to 5Kw with no problem. I'm sure there is more to it than that, but that is what I understand.

I know Poz put up a video with a Sol Ark that ran a panel that wasn't very well balanced and made a big deal of it. Your panel should be fairly balanced if you set it up correctly.

I've read where many say a spare auto transformer is a good idea so I have to wonder just how reliable these are.

You do have a few choices, the GW 12Kw low frequency inverter is one, the surge rating on it is 36Kw. It's major downfall is charging capacity at 7Kw but an external SCC can be added. I went with the LV6548's, they haven't arrived yet so can't tell you either way how that will go. But my panel will be balanced fairly close.

 

[Struc]

I don't know why certain people feel the need to try and force the OP to switch their decision on what inverter to use.

HE DID NOT ASK THAT. He asked if his drawings, as drawn, would work. He didn't ask about an electrician or permits, or anything like that.

Read the post - answer or don't answer the question. Leave your opinions to somebody who asks for it.