Anyone run a solar pool pump?

[ladman]

Taking a look at this unit, reviews are OK. With my 20k pool, with filter, and salt water system, this pump claims 136GPM, and I was thinking of installing this in series with my existing variable speed pump for those overcast days. Any thoughts? I easily have room for 8x250w panels.

Amazon.com: PWS Solar Powered Swimming Pool Pump, 72VDC, 1.6HP, 62ft, 136GPM, Solar Water Pump with MPPT Controller, Suitable for Salt Water, JP31-19/1200: Home Improvement

Amazon.com: PWS Solar Powered Swimming Pool Pump, 72VDC, 1.6HP, 62ft, 136GPM, Solar Water Pump with MPPT Controller, Suitable for Salt Water, JP31-19/1200: Home Improvement

www.amazon.com

 

[ajw22]

I think connecting two pumps in series with only one running at a time will choke the flow on both of them.

@mas985 thoughts?

 

[Andrew_D]

I don't think you'd plumb them in series.

Instead, consider plumbing in parallel with check valves at the inlet and outlet of each pump. Then either pump could run.

Andrew

 

[mas985]

With pumps in series, both pumps should be on to prevent cavitation and flow issues.

If you want to be able to use either pump without the other running, they need to be plumbed parallel.

However the solar pump isn't likely to pay for itself within its lifetime given the run cost of a regular VS pump is so low.

 

[Dirk]

However the solar pump isn't likely to pay for itself within its lifetime given the run cost of a regular VS pump is so low.

Don't forget the cost of the panels when you're doing that math! I think you might be much better off putting that money into a whole-house PV solar system.

Yes, I paid $12K for mine, but I haven't given a dime to the power company in over two years. Another two or so and the system will pay for itself... And then I'll be running my entire house and pool for free.

While the tax credit just got extended recently, it's still progressively getting less and less each year. And PG&E is going to keep hiking their rates, that's a given. Now's the time.

 

[ladman]

Thanks for the replies everyone. Parallel with check valves sounds like the right path. Not sure what/if regarding the long term payoff. Figure 300 watts @ 8hrs a day for the VS pump, and then the salt water generator (unknown, 40-100watts?), but it will be a nice little project to keep me busy.

 

[mas985]

The VS pumps should be using much less than 300 watts. What is the RPM setting?

But even at 300 watts, that is 72 kwh per month and at $0.30/kwh, if that is the tier you are in, that is about $20/month. Assuming pumps + panels are $2k, it would take 100 months to break even. Maybe even longer if you optimize the VS pump RPM and run time (e.g. shorten run time in winter, run at 1000 RPM). Point is that the payback could be longer than the pump life.

 

[jseyfert3]

I think that most people in the reviews (I skimmed the top ones) are thinking this is such a great deal cause they don’t currently have power sipping VS pumps but instead have power hogging single speed pumps. Since you have a VS pump already, and the space and money to buy 2 kW of solar panels, I’d suggest you skip this and get 2 kW of panels and a grid-tied inverter instead. Now you have say 1800 watts of power after conversion loss offsetting your electric bill on sunny days, while your current VS pump takes 300 W or less. That leaves 1500 watts or so to run OTHER things in your house besides your pump, lowering your electric bill much more than this solar pump would.

And on top of that there’d be zero re-plumbing to do.

 

[Dirk]

Yep. Even if you don't go full on PV solar, and spend less initial outlay using Jseyfert's suggestion, probably less than what you'd spend on your original idea by the way, you will get a much better ROI. Mark has already shown you there is little or no return on the solar pump, and quite possibly a net loss. And that's if the pump runs the entire 8+ years time without needing any repair or replacement. And consider, with two pumps, you'll double the repair expense probability...

I checked, and it seems that in your area you rarely get freezing temps at night. But you should plan for it anyway. Most pumps have a freeze protection setting. You might be able to schedule your two pumps to never run at the same time, but freeze protection overrides all schedules. The VS pump will go into low RPM freeze protection whenever it needs to. A pump's freeze protection is not really intended to protect the pipes, that's a nice by-product. It's designed to protect the pump and its electronics. Which means thinking you can just shut down the breaker to one or the other pump on a cold night won't solve the problem, because they both have to run when it's cold out. And how are you going to plumb for that? On the off chance your solar pump doesn't have freeze protection, that still doesn't solve the problem, because then you'll need to shut it down and drain the water out of it (and I'm not sure even that would actually protect the electronics). And of course, if you remember to do all that, you'll only remember to when it's 11:00 at night and already freezing cold out! (Murphy's Law, Chapter 8, Section 17b)

As Mark implied, your search-for-savings hobby could be redirected to optimizing your pump runtime and RPM, and that requires no investment at all. That will give you the savings you're after...