How slow should I run the pump? My theory.

[Davegvg]

Looks like I can go down to 200 watts or 1800RPM and still have skimming (no bobbing up and down from the skimmer) and keep the chlorinator happy and not "low flow" alert.

I'm thinking of running this going forward as the go forward filtration speed.

The solar tap seems to stay open about 6 hours a day at this stage so these slow periods will be broken up by about 6 hours of 750 watt (2800RPM) running to get better efficiency out of my panels.

(Or I could really juice it up to a full 1500 watts and really get the water warm quick, but Im trying to use the epump to actually save money vs use its performance for yet more hedonism..... hedonism is so much more fin though!)

A couple of times a week Ill throw the barracuda g4 in for a morning to clean it up.

Theory being 24x7 skimming will keep the Crud off the top better hence less Crud on the bottom.

Dave

 

[duraleigh]

I certainly don't disagree with your thinking. As long as your chemistry stays correct (FC mostly) and the cleaning is adequate, it looks like you've found a sweet spot.

For you newer members, each pool is unique......having it's own personality and requirements. Be cautious not to do so much calculating to hit an imiginary "perfect" pool that you disregard what works best for your pool and where your pool seems to be "happy".

My pool likes pH 7.8. I don't know why but it does. After fighting that for the first two years with acid, I now leave it alone and it almost seems to stabilise around that number. I've learned over the years to take some of my pool "advice" from the pool itself! :lol: :lol:

Somebody from the old PF said, "You will be at one with your pool, Grasshopper". (Apologies if you're too young to get the reference)

 

[JasonLion]

When running the solar panels you want enough water flow so the water coming out of the panels is only one or two degrees warmer than the pool. Running more slowly than that would fail to get all of the heat available from the panels.

If the solar panels are not in use, the only limitation is to make sure the skimmers are still getting most of the surface debris. Sometimes when running on very low speeds the skimmers won't actually catch all the floating leaves. One workaround, if this is an issue, is to bump the speed up for 10 minutes every couple of hours, which is usually enough to get most of the surface debris before it sinks.

 

[Davegvg]

Thanks guys, I hear where both of you are coming from.

Duraleigh - On the PH Im not sure if the "newer" setting of constant low flow will cause rise above the historic normal, or not, but the pool is not to acid hungry now, about a quart a week. It has seemed to "settle" as you say on staying at this level, and I havent been fighting it. I have a 40K cell for a 20K pool running at low output. I would think I should lower the output even more with a longer slower run time. Ill be testing a lot in the next few weeks.

Jason- definitely cooler panels are more efficient.... My "issue" if you could call it that is as such - I ran the whole system inc. solar for a full year on a 1HP pump and was happy with its performance. After the Epump install I put in a flow meter and found to get the panels "holistically" rated ideal flow of 48 GPM my system needs to pump at about 1.5 HP (1100watts approx+- 100 depending on cleaner combo) and when I give it that the systems performance is amazing, but it should be using that much energy. In the summer the system should really only run a few hours at this speed then settle back to the 200 watt setting fairly quickly.

I know the faster the water flows through the panels the better they work (thanks in small part to some excellent work done in this forum) - to a point, but whats the right balance of acceptable hydrodynamic performance vs energy efficiency?

750 watt -on solar tap speed running longer?
1100 watt -on solar tap speed running a shorter time?

there is also the matter of running a cleaner, it may be without it in the water 24x7 the 750 watt time will be needed for a clean bottom.

Maybe in the end its relatively inconsequential energy wise and more personal operation theory.

Anyway- its all good to even be able to "play" like this.....

"Uncle" Dave

 

[Beez]

My pool likes pH 7.8. I don't know why but it does. After fighting that for the first two years with acid, I now leave it alone and it almost seems to stabilise around that number.

Duraleigh, how are you so confident in that reading when it's so close to 8.0? Please understand, I'm not doubting you, it's just that I'm curious because I have no confidence in my own interpretation of the pH test between 7.8-8.0. Maybe it's because I've never seen a true 8.0 ... I really hate the color comparison tests!

 

[no-mas]

... how are you so confident in that reading when it's so close to 8.0? Please understand, I'm not doubting you, it's just that I'm curious because I have no confidence in my own interpretation of the pH test between 7.8-8.0. Maybe it's because I've never seen a true 8.0 ... I really hate the color comparison tests!

Great question! I've often suspected that my pool wants to be at 7.8, but I can't trust my pH test at that level... Just too close to 8. I've often wished for a pH test that ranges from 7.4 - 8.2... or something higher than the swiming pool pH tests typically test at.

 

[Beez]

Great question! I've often suspected that my pool wants to be at 7.8, but I can't trust my pH test at that level... Just too close to 8. I've often wished for a pH test that ranges from 7.4 - 8.2... or something higher than the swiming pool pH tests typically test at.

This thread should probably be split off, but I think pretty much most pools want to be at a higher pH. However, like you, I just can't trust my reading at that level...

 

[duraleigh]

The Taylor K-1000 (inside the TF-100 as well) is the pH and OTO Chlorine combined test block. It has pH gradations up to 8.2.

That said, I think you get better and better at the pH test each time you do it. For the first year, my kids and I would do a consensus pH.........in other words, talk about our observations. Now, I can ask either of them to do the test and they will almost always have the same observation as I do.

Another point.....A pH of 8.0 will not corrode away your stainless ladder and deposit a 1/2 inch of scale in a week......it is just getting to the limit which you would not want to keep your pool long term. If your pH test only goes to 8.0 and it looks suspiciously close to that, your pool will not be harmed if you leave it there for a few days (usually....CH and ALk can alter that statement). If it is suspicious again in a few days, then lower it.

Sorta' like the 55mph speed limit.....60 causes few issues, 63 is borderline, and 75 may get you a fitting for the horizontally striped pajamas! Naturally, the forum always advocates 55mph.

 

[chem geek]

I know the faster the water flows through the panels the better they work (thanks in small part to some excellent work done in this forum) - to a point, but whats the right balance of acceptable hydrodynamic performance vs energy efficiency?

Though every solar system is a bit different, you can see from the Fafco SunSaver specifications that the efficiency does drop at lower flow rates, but not that much until you get to much lower flow rates. At 4 GPM per panel, it's around 80% efficient (assuming little wind and an ambient air temperature close to the water temperature in the panel). At 3 GPM, this drops to around 76-77% while at 2 GPM it's 70%. The energy consumption for the pump, on the other had, drops dramatically since the energy consumption varies closer to the square of the GPM. You also need to factor in the longer run time needed to heat the same volume of water (i.e. you need to run the pump twice as long at 2 GPM than at 4 GPM). So having 2 GPM will reduce efficiency by 12.5% but energy consumption by 50%. So you could run the pump a little longer to make up for the efficiency loss, assuming you've still got sufficient sunlight hours (i.e. that the turnover rate is fast enough).

In our own pool, we need the water to be warm and want to avoid gas heat so we pay the price for a 4 GPM per panel flow rate, but if we didn't keep our pool quite so warm then we could lower the flow rate and save a lot of money. During the peak summer months near July, I could probably turn down the flow rate somewhat since the solar cuts off earlier (usually 4 hours or less instead of 6 hours at other times of the year).

 

[Davegvg]

The added electrical cost of running the pump faster seems paltry next to the cost of running the gas heater,or at least until I go way beyond the baseline that is.Even above baseline its still cheaper. I think what its going to come down to is that Ill continuously vary the speeds of all the options i.e play with it forever.

Towards the beginning and end of each season Ill simply run the pump faster to get more heat out of the panels I have, and in the peak season Ill slow it back down to the 1 HP or less as the hotter temps overall demand less high speed pumping to attain and sustain a given temperature (85-87 ideal for everyone) - yeah yeah Im spoiled, but also like women in the pool vs sausage parties)

The next "step" is to automate the switchover time from pool heating to spa heating so that I can have a "free" (well relatively low cost anyway) spa each nite after work. Given I only have about 5-6 hours of full strength sun each day in the peak season Im left dividing that between the 85 I like the pool at and the 101 I like the spa at.

One upside to this fast water movement during the day is that I dont feel so alarmed about really slowing things waaay down off solar hours.

Working this way Im pretty sure ill need all the output I can get from the solar especially at the edges of my season.

If only the Jandy had Tempurature based switching then Id be all set- but it doesn't so Im back to using time based switching and running the pump faster than I'd like- for the sheer pleasure of enjoying warm and hot water.

I posted a quick vid of my setup in November.
http://www.youtube.com/watch?v=kYN92oAcPgc

Thanks Guys!

"uncle" Dave