Trying to keep up w/ Chem Geek

[ShelleyAnn]

I've been reading Chem Geek's thread on pump efficiency. I see his lips moving, but can't understand what he's saying being only a mortal.

I installed and AG 15 x 30 last spring. I was unsure the size of pump/filter after reading the posts here that pumps are too large so I called the manufacturer (Waterford) to confirm what size I needed. I told them I was to receive a 1.5hp pump and a 21" high rate sand filter and their response was that those two units were designed to work together. Okay, good enough for me. Heck I even called the manufacturer and they said that was what works...right?

After being on this fabulous web site for a year now, I'm getting that ole feeling again that I am way overboard on the pump. I don't understand head, curve or any of the other terms regarding pumps, but I've just received a new 4 x 20 solar panel and planned to add it to my 2 4 x 10s I used last year. I plan to go from flexable hose to a more permanent pvc rig and even make a rack to angle them toward the sun. Am I going to cause a shift in the quantum flux and cause havoc for the world and all it's inhabitants with this pump? What I really mean is am I going to blow the lid off of all my stuff?

Shelley

[CarlD]

Chem_Geek loves to get technical and has been a WONDERFUL contributer to all our knowledge. Sometimes we have to filter it down to practical usage rules for the non-tech pool owner. But, even when I can't follow it, I value his input enormously. When I can, I sometimes even can add an intelligent comment!

But that's OK. As posters we have some limits on what we can say, but analysis of the chemistry and physics of pools is pretty open. The REALLY high-level stuff goes into the China Shop.

The SIMPLEST solution I can offer to your solar panel question is really simple--just have an adjustable valve to control the water flow to the solar panels and valve it down so the pump doesn't over-stress them and cause them to fail. That's ALL you need to do.

[Poconos]

I think Carl just left out the solar panel bypass line. You really don't want to restrict the total flow so the easiest way is to add valves so you can divert only part of the total flow to the solar panels. That's what I do. I basically split the filter output 3 ways. Straight to the returns and one each to the two solar collectors with ball valves in each line. The solar collectors just dump into the deep end from a couple of hoses under the diving board but you could just as well plumb them back into the return line.
Al

[CarlD]

Of course, Al is right. I was simply saying that the pipe to the panels you restrict with the valve. I didn't mean the flow to the returns--you do NOT want to mess with that!

[ShelleyAnn]

So that post was not the really high level stuff huh? I guess I'm glad I can swim!

Last year I had ALL the water going thru the 3x9s tandem. Was I just lucky they didn't leak? It did seem like a LOT of pressure going thru, but this was the way the pool guy set them up. They worked like a charm in the noon time sun.

Don't tell me...is this Waterford pump going to last 25 years with proper maintenance? I'm already wanting a different refrigerator with our 10-year old one is working just fine. I don't want to push the husband over the edge asking for a new pump too.

[CarlD]

So that post was not the really high level stuff huh? I guess I'm glad I can swim!

Last year I had ALL the water going thru the 3x9s tandem. Was I just lucky they didn't leak? It did seem like a LOT of pressure going thru, but this was the way the pool guy set them up. They worked like a charm in the noon time sun.

Most pool guys have no idea how to set up solar panels.

The EASIEST way is to have a Y in the return line. One branch of the Y goes to the return(s) with nothing in between. The other goes to the solar and you can have 1 valve or 2 or 18, depending on your setup. I have 3 valves. The first is just an on/off cuttoff for all the solar panels, then there's ANOTHER Y off of that one that each has a valve for each set of panels (I have 2 sets of solar panels).

Can't get you a picture of it right now, though.

[ShelleyAnn]

Thanks everyone for all your input.

Carl, I will wait for the ice to melt in your neck of the woods so you can send me that pic! We are up to our eyeballs in snow here so it's not like I'm being held up or anything.

From what I gleened from the Hot Sun Industries web site, my panels were upside down all last year, meaning the pipe leaving the panel was at the bottom, not the top so air could have been trapped in the upper corner. Live and learn. In another 100 years, I'll have EVERYTHING figured out.

[CarlD]

Ok,
I've attached a pic of my return setup. To the left of the red ball-valve handle, you'll see a Tee--the part going up is the return to the pool, the part going right to the ball valve is for the solar panels. To the right of that you'll see another tee and on each leg is a sluice valve, with the blue knobs.

Each sluice valve is for a solar panel group (my solar panels are 2'x4' and I have about 32 of them). I can open each group just a crack, depending on whether my pump is on low speed or full speed. At full speed I open each group 1 and 1/4 turn. At low speed I open them all the way.

Each group of solar panels has its own return at the far end of the pool.

Very, very simple. Hope this helps!

[ShelleyAnn]

Yep, very simple, but beautiful.

You've got about 256sf of panels. I will have about 134sf for my 15 x 30 AG. I remember reading somewhere here that it's quantity of water thru the panels that gives the most hot water. I sure did that last year with forcing all 1.5hp thru 2 panels that measure 3 x 9 each!

I do see some flexible pipe in the right side of the pic. Is that connected any way or is that just some hose for vaccuming? I currently have everything connected with white flexable hose, but would like to go to pvc. How much $$ do you have invested in the materials (pipes and knobs) would you guess?

[chem geek]

ShellyAnn,

It is not true that simply increasing the rate of flow through the solar panels increases the amount of heating to your pool. There is a point of diminishing returns. Though every manufacturer's solar panel is different, take a look at this link which is a common solar panel from FAFCO and look at the graph that says "EFFICIENCY vs. FLOW". You will notice that you get to 80% efficiency at a rate through the panel of 4 GPM, but that the efficiency increase is slowing way down. The maximum flow rate recommended for this panel is 8 GPM, but the efficiency won't be very much higher (it won't be more than 90%).

When water flows faster through your panel, it spends less time in the panel so gets heated up less. So while you push more water through the panel at higher flow rates, it gets heated up less and the net result is roughly the same amount of temperature rise in your pool. You should generally stay near the recommended flow rate for your panel and not exceed its maximum rate.

I don't know enough about your system to know if you need a 1.5 HP pump, but that seems extraordinarily high. I have exceptionally long runs for my solar setup (due to many roof segments and hips) and am already over-pumped at 1.0 HP and could easily use 0.75 HP. It is true that sand and DE filters have higher pressure (at the same flow rate) compared to cartridge filters, but even so the pump seems over-specified. Your pool builder is recommending a 21" high rate sand filter and yet your pool is an above-ground 15x30 which is not a very large pool (it's not small, but it's not so big as to require "high-rate" and a large pump for fast turnover). This just doesn't seem right to me.

At any rate, you most certainly want to have a bypass for your solar panels so that only some of the water goes through them since there is no way you can run high rates like 50 GPM through just 3 panels (for 17 GPM each) unless your panels are of a design very different than the FAFCO one in the link above. The setups that Al and Carl described in previous posts sound good where you can split the output of your pump to go partly through the solar panels and the rest into your pool. My only concern is that your PB is designing a high flow-rate system, including a filter designed for such flow rates, without good reason (except more expense for a larger pump and high-flow rate filter). Even if your pool were 4 feet deep throughout, that would be about 13,500 gallons so to get one turnover in even 4 hours (so two in 8 hours) would be 56 GPM, but it sounds like your PB is designing your system for even higher flow rates. Maybe when he is quoting 1.5 HP he is talking about an "up-rated" pump so that this is roughly equivalent to a 1.0 HP "full-rated" pump. That would make more sense.

Richard