Advise needed on AC well pump to run on solar! 5kw Growatt

[jonoslade]

Hey friends, I am trying to help my parents get their well pump setup on solar. They had been running it on a generator that just blew up so the house backup is currently being used down at the pump house. I am trying to see if we can move towards solar instead of buying another generator. They are fully off grid and have a separate 48v system for the house but it is 150yards away. The pump only needs to run occasionally so we can maximize peak sun hours and only turn on the system when it is sunny (they live in the High Desert of Southern CA so that's pretty much every day). They pump to holding tanks then gravity feed into the house/property.

The pump is a 1.5 HP Franklin.

What we currently have to use for the system:
30 used 175w 44voc panels
6 8v 245amp hr used deep cycle batteries that used to run the 48v house system before I upgraded them to Lithium.

My questions:
Would the 5kw Growatt (spec below) work for this system?
Could I avoid wiring up the batteries and just run the system on solar?
What am I overlooking? I certainly don't want to blowup the well pump with an undersized system but budget is a factor.

 

[snoobler]

What is the surge current of the 1.5hp Franklin pump. It is typically about 5X the run current and likely close to 7500W at a guess, and it lasts for several seconds.

High frequency inverters like this one have a very misleading surge rating. It's only good for about 20 milliseconds, so you can't count on it.

Additionally, this particular inverter likely consumes about 75W+ continuous, loads or not. That's 1.8kWh/day in just being powered on. In this application, you could possibly enable the power saving mode since you only need to power the one device when it has need, but again, the surge probably eliminates this unit.

If you find the surge is less than 5kW, go for it.

Pretty sure this unit needs batteries.

 

[Wibla]

I would look into one of their VFD's with soft-start to reduce that starting current.

 

[jonoslade]

What is the surge current of the 1.5hp Franklin pump. It is typically about 5X the run current and likely close to 7500W at a guess, and it lasts for several seconds.

High frequency inverters like this one have a very misleading surge rating. It's only good for about 20 milliseconds, so you can't count on it.

Additionally, this particular inverter likely consumes about 75W+ continuous, loads or not. That's 1.8kWh/day in just being powered on. In this application, you could possibly enable the power saving mode since you only need to power the one device when it has need, but again, the surge probably eliminates this unit.

If you find the surge is less than 5kW, go for it.

Pretty sure this unit needs batteries.

Thank for the reply, I have been trying to track down the surge rating without much luck. I think I saw a table on this forum in the past but haven't been able to track it down. Should I just take 5x the Maximum Load Watts that are 2080 based on the table below?

 

[jonoslade]

I would look into one of their VFD's with soft-start to reduce that starting current.

Thanks for the reply, correct me if I am wrong but this seems like a pretty expensive option. What would the advantage be other than reducing the starting current and allowing me to buy a slightly cheaper inverter? If I have the panels and batteries wouldn't it be cheaper to just invest in a large enough inverter?

 

[snoobler]

Thank for the reply, I have been trying to track down the surge rating without much luck. I think I saw a table on this forum in the past but haven't been able to track it down. Should I just take 5x the Maximum Load Watts that are 2080 based on the table below? View attachment 54821

LRA = locked rotor amps = surge = 51.4A * 230V = 11.8kW