Is this Doable?

[BrianLee]

Hi,

I currently have a Sol-Ark 12K inverter (Grid-tied) installed with 10KW of solar panels. I have another set of panels on hand (4.5KW) that I would like to utilize. They are not compatible with the panels feeding the Sol-Ark, so I had the idea of adding a cheap Growatt inverter.
The Sol-Ark DOES backfeed to the grid, but the Growatt will not be backfeeding into the grid and its output will only be used to power a 240 volts miner.
I wasn't sure if there would be an issue with the main Sol-Ark inverter. I know I could add a second Sol-Ark inverter, but I really don't want to spend another $7K just to use the 4.5KW array.

Thanks

 

[sunshine_eggo]

Without researching that specific Growatt, assuming you're pulling 240V from the Sol-Ark to the Growatt AC input, then I don't see any problems. If you're on 120/240V split phase, and only using the Growatt as single phase 240/60Hz, watch out for your grounds. I don't believe you can just bond to the 120/240V split phase ground.

If you ever add batteries, make sure you understand the AC charger on the Growatt. Most models do not follow a bulk/absorption/float profile, but follow an "On when battery drops to X" and "off when battery raises to Y." X & Y are different values from those used by the MPPT charger.

 

[BrianLee]

Thank you for the reply.

 

[sunshine_eggo]

Checked the manual. Looks like mode SUB mode will cut it. Solar while it can and then utility when solar can't.

Not sure of the miner load, anything the array is pulling above that will be wasted.

Do you need 230VAC?

Spitballing - Is it possible to use a hybrid model that can back feed to your Sol-Ark grid so any surplus solar from the 4500W array can also power other house loads?

4.8kW Bundle-2 x LV2424 Hybrid 2400W ,24Vdc120V/240V Solar Inverter Split Phase bundle, 2 x 80A Mppts – Watts247 Wholesale

watts247.com

Costs more, but would provide 120/240VAC split phase (eliminate ground concern), handle your 4.5kW array and backfeed to your house to provide house loads. Could the sol-ark then send surplus back to the grid?

 

[BrianLee]

OK, so maybe I'll back up a little with what my plan is. Originally, I had my Sol-Ark hooked up to the 4.5Kw array and ran that setup for August and September. I had planned to double the array after I finished out testing my install (it was a DIY project). Well, it turned out the panels were sold out and I couldn't find more. About the same time I found some new panels that a guy was selling locally for a very good price and decided to replace everything with the new panels--which are working out very well.

So, I now have the original 4.5Kw worth of panels sitting doing nothing and thought why not use them for the miner.

The miner does run on 240VAC and pulls about 3100 watts of power. The 4.5Kw panels were peak generating around 3400-3500 watts on a good day, so it would not really be wasting that much generated surplus. Plus I'll probably have a couple of fans running for air exchange.

I haven't purchased the Growatt, I'm still considering options. I'll definitely check out the MPP Solar inverters you recommended (because they are split phase compatible). I don't want to backfeed to the grid with whatever inverter I eventually go with. Maybe I got this wrong, I'm not an electrical engineer, but I thought the inverter used frequency shifting to backfeed into the grid. If you had two different inverters backfeeding into the grid wouldn't there be an issue with one fighting the other with frequency shifting?

Currently, I have the Sol-Ark set to backfeed into the grid, and actually, during the day my household electric use is so very low the majority of the generated electricity from my Sol-Ark goes into the grid.

 

[Roqm]

OK, so maybe I'll back up a little with what my plan is. Originally, I had my Sol-Ark hooked up to the 4.5Kw array and ran that setup for August and September. I had planned to double the array after I finished out testing my install (it was a DIY project). Well, it turned out the panels were sold out and I couldn't find more. About the same time I found some new panels that a guy was selling locally for a very good price and decided to replace everything with the new panels--which are working out very well.

So, I now have the original 4.5Kw worth of panels sitting doing nothing and thought why not use them for the miner.

The miner does run on 240VAC and pulls about 3100 watts of power. The 4.5Kw panels were peak generating around 3400-3500 watts on a good day, so it would not really be wasting that much generated surplus. Plus I'll probably have a couple of fans running for air exchange.

I haven't purchased the Growatt, I'm still considering options. I'll definitely check out the MPP Solar inverters you recommended (because they are split phase compatible). I don't want to backfeed to the grid with whatever inverter I eventually go with. Maybe I got this wrong, I'm not an electrical engineer, but I thought the inverter used frequency shifting to backfeed into the grid. If you had two different inverters backfeeding into the grid wouldn't there be an issue with one fighting the other with frequency shifting?

Currently, I have the Sol-Ark set to backfeed into the grid, and actually, during the day my household electric use is so very low the majority of the generated electricity from my Sol-Ark goes into the grid.

With the diagram you provided and using the growatt you wont backfeed the grid you also have the option of making a separate system thats isolated from the grid and your existing system...seperate load panel and a batteries miners will run from only solar and batteries.....do you have battery back up on the solark? As its not on your diagram.

 

[BrianLee]

I do have batteries on my Sol-Ark (I eliminated some items--batteries, critical loads panel, transfer switch, etc. to simplify the diagram). I don't want to create a separate system that is isolated from the grid because I want the second inverter to have grid pass through abilities when solar is not available--the item I wish to power runs 24/7 and trying to use batteries to create a system isolated from the grid would be very costly.

The more I research into the Growatt the more it looks like it's not the best fit for me. Not that I couldn't make it work, but if there are options available that are more compatible with my split phase system I would rather take that route.

On that note, I looked at the inverters sunshine-eggo recommended and they are not UL listed. My electric company was very, very adamant about UL listings, particularly UL 1741. So I definitely won't be backfeeding into the grid if I go with those. I'm not saying I won't consider using them, I just won't backfeed for sure.

 

[RCinFLA]

Do not AC output parallel two inverters not designed to work together in parallel, especially high freq inverters.

Just because you disable backfeed does not mean there can't be backfeed surge currents.

You will likely blow out one of the inverters, likely the Growatt.

 

[BrianLee]

Do not AC output parallel two inverters not designed to work together in parallel, especially high freq inverters.

Just because you disable backfeed does not mean there can't be backfeed surge currents.

You will likely blow out one of the inverters, likely the Growatt.

They aren't exactly in parallel, if anything I would say they are in series. Could you elaborate on what you mean about backfeed surges? Are you describing a surge caused by an inverter surging because of, for example, a partly cloudy day? Wouldn't the grid absorb the surge before pushing it to the Growatt?

Just asking because I honestly don't know the answers.

 

[RCinFLA]

You show no neutral connection (or batteries) and both inverters connecting to breaker box backbone through 240v breakers. I am presuming SolArk is pull or pushing to grid. Growatt is primarily only a pull from grid but will have some backfeed surge currents due to feedback control loop delay response time in controlling backfeed to grid.

The most significant risk is with SolArk pushing to grid when grid goes down in an open circuit situation. The presents of the Growatt may delay the SolArk recognition of grid going down if grid goes open circuit, like main breaker opening. This may put the Growatt at risk as SolArk slews it phasing for grid tie testing. This is similar to a generator input to Growatt with gen having poor freq stability which has a track record of blowing out Growatt inverters.

 

[BrianLee]

Thanks for the clarification.

 

[BrianLee]

Just an update on this post. So after consulting with a Sol-Ark technician, the solution is to use a grid-tied inverter for the additional 4.5kW worth of panels and AC couple it to the load center or the generator input on the Sol-Ark. According to the technician I can AC/DC couple up to 16kW as long as the majority (11-12kW) is DC. The Sol-Ark installation manual seemed to limit the amount to 14kW, but the technician said 16kW so take this with a grain of salt.