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Here's the setup I've had for 20+ years: Indoor 16 X 32 17.5k Gal pool with 1 HP single speed pump, sand filter and auto brominator. There are 10 solar thermal panels on roof of pool enclosure with a circulator and closed glycol loop to a heat exchanger for pool and a 110 gal solar/electric domestic tank. The pump has to run on sunny days in order to sink the heat from solar - it's way too much for the domestic tank. On cloudy days it may not run at all unless make up heat is needed from boiler (via a second heat exchanger). My question - now that I've added a PV array and want to lower elec usage - would a variable or multi speed pump offer any savings in this application or would I just end up running at high speed all the times it would have to run? The existing pump is a Hayward Super II and draws around 1500 Watts and is controlled by an X10 timer and telephone dialer remote control. Any similar experience or feedback appreciated.
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I've found of couple of motor replacement options that would save re-plumbing the pump:
1. Century/AO White B975T Two Speed 1 HP Full Rate Motor with Timer
2. Century/AO White CT1102 Single Speed Energy Efficient 1 HP Full Rate Motor
I'm just not sure how much I could run the first one at low speed since it's only 1/6 HP. -
yeah - thanks - saw those. Look similar to Pentairs and Ecopumps. Cost about 2-3X more than motor alone. There would still be the question if there would be enough running hours at lower speeds to get any reasonable payback.Comment
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Here's another player in the motor replacement game: US Motors. They offer 2 speed and variable speed direct replacements and an online calculator to estimate savings <http://www.usmotors.com/Energy-Efficiency/Pool-Calculator.aspx>. Has anyone gone this route and confirmed the promised savings? The variable speed model is less $ than the equivalent AO Smith/Century - about $400 at hydropool.com for the 1.5 HP VS.Comment
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I'm in the same boat
I just put seven evac tube collectors on the roof of a similarly sized indoor pool. I'm looking at closed loop with excess heat shunted to pool. But I don't want to run a 3/4 hp pool pump all the time.
Do you have a flooded suction on your pump? Could you put a small circulating pump where it would stay primed? If so, a check valve and a bit of piping would let you use a small pump to run through your pool heat exchanger. I was advised that a Hartell (sp?) magnetic drive pump could run directly off one panel, and would pump enough when the thermal panels are working to do the job. I haven't got farther than that, but I'm sure someone here has.Comment
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SunnyBoy 3000 US, 18 BP Solar 175B panels.Comment
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Pool pump stays primed so starts right away. My collectors are AET flat panel series AE 4X8 and depending on time of year at full sun can boost the pool water (outlet vs inlet) 2 or 3 deg F. That's with 170 def F at collectors and 1 hp filter pump running. With pump off in these conditions the domestic tank will boil over in a couple of hours. Those Hartells look like fractional hp condensate pumps - are you looking at moving pool water with those or a separate glycol loop? I've always had the option of setting a high limit shutdown in the differential controller for the circulator but that ends up leaving heat on the roof. Fortunately over the years the downtime on the pool pump has been minimal and during those times have just drained the glycol and shut everything down. Last time was during a liner replacement.Comment
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Understood INET.
I thought I might have time this morning to try out ac circulator pump, as I'm running pool water through the panels until I get a storage tank for dhw and heat exchangers. By 10:00 AM I was getting steam out of the discharge. I have a 3/4 hp Pentair pump, but I'd like to go variable speed on the pool pump, and power direct off of pv panels, as I don't have grid tied system yet. Let me know what you find out about changing your motor. My pump has 2" in and out, but is running a 1750 rpm motor, so my options are not as varied as yours. I am looking at Schneider Altivar Solar vfds which are made to run direct off of panels. I would need to replace my motor with a three-phase one, but that might still be the best way for me to go. I think these drives are just hitting the US, but I'm hoping to hear from someone who has one.Comment
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solar pumping and heating
jff6791, I am interested in what you decided to do with your pool and panels. I am still in the middle of my install of a system much like yours, though I don't yet have any PV. I really like the idea of the solar hot water/pool heating running completely off solar. I am now looking at installing a flexible impeller pump like a Jabsco Water Puppy in parallel with my pool pump. My pool is indoors and does not require a lot of filtration. I could run this pump and the circulator pump for the glycol loop off of a few panels. I am worried that otherwise if there is a grid outage, I would boil off my glycol pretty quickly, as the stagnation temp for my panels is 500 deg F. I figure that even if this little pump does 5-6 gpm it would put enough water through the pool/glycol heat exchanger to keep glycol temps safe. I'm still looking at replacing my older pool pump with a variable speed unit that would let me optimize flow through the heat exchanger and filter.Comment
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I ended up going with the energy efficient 1HP option but haven't swapped it in yet..probably do it next time the seal goes on the pump. Since my hours of pool pump operation are not driven by filtering requirements (indoor pool) I need full flow through both heat exchangers for maximum efficiency. That is extracting maximum solar when available and using lowest boiler hours when make up heat required. As far as dealing with pump outages during peak solar periods the backup plan is just drain glycol from system which I've had to do on at least one occasion.Comment
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