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Pool Pump Off Grid Solar Installation

Jagjeet2011

New Member
Joined
Jul 4, 2022
Messages
4
Hi All,

I have a decent size pool (23k Gallon) that uses 3/4 HP pool pump motor. I run it daily for 6 hours. I was planning to run it on Solar to save some $s. I live in the Bay Area, California. I do not plan to change my AC motor to a DC pool pump as cost adds up quickly.

I have a few questions and will appreciate if you share your experience.

Q1- I searched and found that 3/4 HP (110 volt ac) motor needs 850watts, but a surge power of 2600 watts. Wattage Link
Battery Size Calculation -
Watts Required = 900 watts (round up from 850)
Amps Require = 900 / 12v battery = 75amp
Total AmpH with 50% usage = 75 * 6 * 2 = 900AH

- Is above calculation correct? I know I tried to simply it, and I can go bit higher to accommodate some losses
- if yes, it seems battery installation is costly. Though, is there a chance I can reduce the battery requirement as I will be running the pump while sun is shining.

Q2- And above question led me think - Do I really need a battery, what if I simply put a 1.5kW system and get it going while sun is shining, we get decent sun hours and I can try to use AC on cloudy days. Any thoughts?


Q2.1 -- Another question I have is - based on my experience, how do we handle the inverter that automatically shuts off if there is no enough electricity and starts when there is enough, irrespective of serial or parallel solar panels. So I want to pump kick off when there is sun and enough power, and switch off when sun sets or not enough power. I tested a few inverter, they have shut off when there is low voltage but they don't get start automatically after that point, have to reset manually.

Thanks All
 
I'm surprised OP never got an answer on this.
I have a 25K gl pool, the pump is about the same, but runs on 240V - two legs. Not sure why, perhaps it is that start up surge - it's on 15A breakers.

I don't have an answer on exactly how to do it, but a couple of things come to mind...

1. There may be a soft-start appliance that would reduce that startup surge. That would simplify addressing capacity.
2. The cost of a PV array to power it might take a LOT of years to break even verses cost for grid power.

900W X 6 hours daily is 4.5kW. I pay 47cents/kWh here with SCE, so that's $2.12/day, or $63 a month. I did a quick search for costs in SF and came up with 32cents. That would calc to $1.44/day.

Now I might run my pump that long during summer, but just an hour or two over winter. My calc is about $500 a year to run my pool pump. Chlorine and chemicals costs nearly that much. I just did some work and drained it halfway, cost $85 for the water to refill it. And this doesn't include cost for LNG to heat it, which we sometimes do for a month or two pre and post season, plus any spa time.

You could spend a couple of grand putting a system together. Could be worth it for the long run, make sure you're not planning a move.
 
I wouldn't expect a single phase induction motor to start or run effectively with a batteryless PV system (unless excessively oversized)
3-phase could work. At least for my 2HP size, 3-phase motor was drop-in replacement (I use it with VFD).


If your electric utility offers net metering (without changing terms such that it is a bad deal), grid-tie PV is the way to go.
If not, consider zero export grid tie PV, which probably requires informing the utility and getting their approval.

I would also consider guerilla solar - connect a grid-tie PV system behind the switch controlling pump, size it so it never exceeds consumption of pump, put in PV array consisting of one string oriented SE and one SW to flatten production curve.



Chemical cost - significantly reduced with a bubble cover. But mine (silver/blue) disintegrated in a couple years. Maybe a different one would be more sunlight resistant.
 
I did read your intention to not change pumps.

Not recommending, as I have not used this product... I have been using a WBS 750w 48v solar direct submersible well pump for 3 years without issue; my brother has been using a submersible and a surface pump for about a year.

This unit offers wide range DC and 120/240v AC with auto switching. Soft start means limited surge and reduced solar panel requirement.


I think you should at least look at this type equipment, even if not this company, or you reject the idea.

WBS has become pretty active on youtube...


 
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Now that I think about it, I have a 2hp pump, much like Hedges. A Pentair fixed output one I replaced about ten years ago. Newer variable speed pumps are supposedly a lot more efficient. They're also a lot more expensive.

We used those bubble covers for a few years early on - been in this house since 1993. Not only do they disintegrate sending all that plastic everywhere, they are a GIANT PITA to put on and take off every time you want to use the pool. Could be a good solution over winter but that's not where our energy costs lie. We gave up a long time ago.

It got a lot of use while the kids were home, but they're all grown and gone now...it mostly just sits there looking nice. LOL. A lot of our neighbors are filling in their pools - which costs about eight grand to do right. I've seriously considered it. About half the homes have a pool.

A few houses down, they thought they would fill theirs in the cheap way - had yards of dirt dumped in their driveway, and their kid and a buddy or two wheelbarrowed the dirt back to the backyard pool to fill it in. The next winter it flooded their house. Evidently you have to jackhammer the bottom out to drain or they overflow. A complete removal runs about ten grand. There is always a home or two that will put a new pool in - they're really expensive these days.

Somebody turned me on to a solar ionizer that puts copper into the water and kills bacteria and algae. This has cut our chlorine costs by more than half. Nothing short of fantastic, and they're about $100.

images
 
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BTW, net-metering is out in CA with that new nem rule.
We just met with a solar contractor, they're doing all non grid tie type systems with a battery storage 'power wall'. Trying to decide if we're moving and when - retirement is looming.
He said they don't call it a battery, they call it 'energy storage'. "Battery" scares the prospects. LOL
 
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