Pump speed for solar heating

[brimorga]

Does the Hayward OmniLogic automatically calculate the pump speed required to run solar pool heating? I could swear that a few days ago the minimum speed was 2550, but now it is running at a minimum speed of 2760. It might not seem like a big deal, but the extra RPM's use almost 50% more electricity and I don't really notice any improvement on the results.

Could it be possible that is calculates this on it's own and any reason for the sudden change? Nothing has changed on my setup and everything is just a few months old.

 

[ajw22]

Does the Hayward OmniLogic automatically calculate the pump speed required to run solar pool heating?

No.

I could swear that a few days ago the minimum speed was 2550, but now it is running at a minimum speed of 2760. It might not seem like a big deal, but the extra RPM's use almost 50% more electricity and I don't really notice any improvement on the results.

Gremlins.

Could it be possible that is calculates this on it's own and any reason for the sudden change?

No.

Nothing has changed on my setup and everything is just a few months old.

Put it back where you want it.

 

[Dirk]

I determined the optimum flow rate for my solar panels by consulting the panel manufacturer's documentation and then doing the math. Turned out to be 40GPM (8 panels x 5GPM each = 40GPM). I installed a FlowVis flow meter into my pool plumbing (about $150). Then it was a very simple matter of adjusting my VS pump to get the flow meter to read 40GPM. I check the flow rate a few times a season, as filter resistance can change over time (as the filter gets dirty). I can then just tweak the VS pump speed to accommodate. My VS pump usually runs at around 2200 RPM to get 40GPM through the panels. I am confident that my panels produce the best heat-to-cost ratio possible. I could run the pump at a lower speed to save some money. Or I could run it higher to get a little more heat. But my MO finds the sweet spot for the most cost-effective heating.

Because there are so many variables (pool size, number and type of panels, height of panels, pipe size, number of elbows, etc, etc), there is no way an automation system could figure all that out. Nor could a pool guy or solar panel manufacturer (or forum member) tell you a generic RPM number that would work best for your particular system. Each system will have its own best setting.

There are a few other ways to determine the proper RPM, as complicated as measuring pipe runs and elevations and pump head numbers, etc, etc; or as simple as putting your hand in front of a return while the solar heater is engaged and estimating flow rate based on "how warm the water feels." IMO, there is no more reliable, accurate or changing-conditions-adaptable way than how I did it.

If it hasn't already, my FlowVis will pay for itself. I also use it to optimize the flow rate for my SWG and for my pool cleaner. It also helps me monitor my filter's condition. I feel it was a $150 well spent. If you already have the right type of check valve somewhere in your plumbing, you can replace its guts with the guts of a FlowVis, and spend a little less. FlowVis sells their meters both ways: with and without the housing.

What your automation controller can do is determine when to call for solar heating. A properly installed system will have a temperature sensor on your roof (or wherever your panels are located), and a second sensor measuring pool water temperature. The controller calculates when to turn your solar heater on and off, based on your desired temperature setting, the temperature of your pool and the available heat in your panels. But that's all it can do. It can't calculate the flow rate, only the on/off cycle(s). You have to provide the flow rate (RPMs). What the FlowVis adds to the equation is optimizing your heater's efficiency, so that the pool heats up to your desired temperature in as little time as possible, using the least amount of electricity possible to get there. That's where the savings come from...

 

[brimorga]

No.



Gremlins.



No.



Put it back where you want it.

So it's not gremlins AJW22, I figured out the mystery! Apparently I have solar heater setup twice with different configs. Would there be any reason for this or should I just delete the extra? I'm guessing the pool company guy setup a placeholder and the solar heater folks didn't realize that and setup another one. The only good reason I can think of is to use one setting for the spa and another for the pool, where the spa solar runs a little slower so the water comes out hotter.

Thanks Dirk! It seems like a flow meter would be super helpful. I don't think the guys who set this up had any kind of flow meter, they probably just use some rule of thumb, but they aren't the ones paying my power bill!! I'm going to try 2300 and see if I get better results. 650watts is a LOT better than 1250!

As opposed to feeling the pipe, can I just look at the cell temp on the SWG since it is inline after the heaters? I did some more reading and it sounds like I can look for bubbles in the pool to determine if the solar heating is set high enough or not.

Maybe I need a flow meter in my future, although there is not much room to fit it anywhere, guess I need to do further research on that to get an optimal setup.

 

[Dirk]

So it's not gremlins AJW22, I figured out the mystery! Apparently I have solar heater setup twice with different configs. Would there be any reason for this or should I just delete the extra?

No. Delete the extra.

Thanks Dirk! It seems like a flow meter would be super helpful. I don't think the guys who set this up had any kind of flow meter, they probably just use some rule of thumb,

That's exactly what they did.

but they aren't the ones paying my power bill!! I'm going to try 2300 and see if I get better results. 650watts is a LOT better than 1250!

As opposed to feeling the pipe, can I just look at the cell temp on the SWG since it is inline after the heaters?

Probably not. The sensors in an SWG are usually pretty lame. Your automation controller should be able to provide what its water temp sensor is reading. Just a matter of finding the right screen. Not sure what you mean by "feeling the pipe." That's not going to provide you anything useful.

I did some more reading and it sounds like I can look for bubbles in the pool to determine if the solar heating is set high enough or not.

Never heard that one. Not sure what bubbles mean, in terms of heat efficiency. As I said, I don't know of any better way to determine solar heater optimization than what I described. There may be one, I just don't know of it...

Maybe I need a flow meter in my future, although there is not much room to fit it anywhere, guess I need to do further research on that to get an optimal setup.

Do you have an existing check valve in your setup? If it's made by Jandy, the FlowVis can replace it. A FlowVis flow meter is also a check valve, so it can replace an existing check valve to pull double duty. As I mentioned, you might be able to just replace the guts: eight screws, no gluing or cutting...

 

[BMerrill]

Have the same pump with 2" plumbing, cartridge filter; no solar.
Have the FlowVis flow meter.
I'm guessing you are flowing around 75 gpm.
For comparison with my system
At:
1000 rpm, flow rate 35gpm using 92 watts
1250 rpm flow 44gpm using 148 watts
1500 rpm flow 50gpm using 230 watts
1600 rpm flow 55 gpm using 275 watts
1750 rpm flow 60 pgm using 350 watts
2000 rpm flow 65gpm using 494 watts
2250 rpm flow 75 gpm using 932 watts.
2750 rpm flow 92 gpm using 1230 watts

 

[ajw22]

The solar heater folks WAS the gremlin.

 

[riny]

Because there are so many variables (pool size, number and type of panels, height of panels, pipe size, number of elbows, etc, etc), there is no way an automation system could figure all that out.

I do the same thing as you, which is tune my pump speed until my FlowVis reads what I want it to read. This is a tangent but I think I remember seeing that Pentair has a pump which you can program with a flow rate, so you can set your pump for 40 gpm for example and it will automatically adjust its speed to maintain that rate using an internal flow sensor. I've always wondered how well it actually works though?

 

[brimorga]

Probably not. The sensors in an SWG are usually pretty lame. Your automation controller should be able to provide what its water temp sensor is reading. Just a matter of finding the right screen. Not sure what you mean by "feeling the pipe." That's not going to provide you anything useful.

It's basically a proxy to feel the return pipe from the solar heating and feel how warm it is, but you're right, I tried it and it's worthless. At least for running solar in Feb on a east facing roof with 75% coverage, I'm learning quick that it doesn't really do much, even though is 76 air temp with 61 degree pool water. I will say, the temp of the SWG at least kind of works, but like you said, not really that well. Right now at 2415 RPM it says the chlorinator cell temp is 64.5. I'm going to try and find some more time to play around with it and see how much it matters by adjusting pump speed. It primarily matters to me cause I might be able to get the spa warmer from the solar panels before turning on gas and I can give up a ton of efficiency to do that, whereas it probably makes sense to run as close to peak efficiency as possible to heat the pool.

Never heard that one. Not sure what bubbles mean, in terms of heat efficiency. As I said, I don't know of any better way to determine solar heater optimization than what I described. There may be one, I just don't know of it...

I've read that the solar panels do have a peak efficiency level, but if it is not at peak, it only suffers 1% efficiency loss. Doesn't make complete sense to me, because flow matters, but whatever.
In terms of bubbles, I had read that when you turn on the pump, it runs the pump at 100% to prime the system and eliminate the air bubbles and create a vacuum flow up and down the roof. Then you can lower the flow to the point where it will be ok as long as you maintain the vacuum effect and if you see air bubbles coming from the returns, that means your flow isn't high enough to maintain a vacuum and push the water through. It basically helps you establish a minimum pump speed, but it doesn't optimize for efficiency like you are doing.

 

[brimorga]

No. Do you have an existing check valve in your setup? If it's made by Jandy, the FlowVis can replace it. A FlowVis flow meter is also a check valve, so it can replace an existing check valve to pull double duty. As I mentioned, you might be able to just replace the guts: eight screws, no gluing or cutting...

I do have a Jandy check valve, 2 of them!

Would it be better to replace the one in front coming out of the filter or the one in the back after the heaters prior to the SWG?

Looks like I have 2" Jandy check valves, 7236, I'm assuming I want this flowvis, FJV-R, and it's not worth it to get the digital one?

FlowVis Pool Flowmeter for 2 or 2.5 Inch Retrofit for Jandy 2-Way Valve - H2flow - FVJ-R

The FVJ-R FlowVis Flowmeter for 2 or 2-1/2 inch retrofit for Jandy 2-way valves has a higher average accuracy than any other flowmeter out there.FlowVis is the most advanced, affordable, and reliable precision flow meter designed specifically for pools, spas, fountains, and water features...

www.poolweb.com

 

[riny]

The laws of physics will tell you that it doesn't matter... but it looks like the back one is cut off by the heater bypass. The front one is never bypassed, and is probably easier to see anyway.

Personally, I don't see any reason to spend the extra money (and it's a lot) for the digital one.

 

[brimorga]

The laws of physics will tell you that it doesn't matter... but it looks like the back one is cut off by the heater bypass. The front one is never bypassed, and is probably easier to see anyway.

Personally, I don't see any reason to spend the extra money (and it's a lot) for the digital one.

Thanks! Would it make any sense to get 2, so I can see if the heater is a bottleneck?

 

[mknauss]

Thanks! Would it make any sense to get 2, so I can see if the heater is a bottleneck?

the flow is the same throughout the system.

 

[Dirk]

Yes, Marty is on it. Might have been who taught that to me. While the speed of the water might vary based on what it is passing through at any given point (a pipe compared to, say, a filter, or a valve body), the flow (the volume of water) is exactly the same from one end of your system to the other.* Riny is on it, too. You only need one Vis, put it where it is always "in the loop" and/or where it is easiest to read. There is a knack to reading a FlowVis, you have to align your line of sight just so, so you have to have good access to the lens, directly in front of it, to get a good reading.

I didn't know they had a digital one. While it might be cool to get flow rate readings remotely, they really don't change all that much. You should be checking your pad once a day anyway (for leaks and pressures and flow, etc). If anything, a digital solution will just make you lazier about paying attention to your pool, instead of your screens. Not to mention: digital = one more thing to poop out.

Regarding your "bottleneck" experiment: you can still perform that, if you care to. Put the Vis in one of the check valve bodies, observe it for a period of time. Then physically move it to the other check valve body, lather, rinse, repeat. You don't need two Vis to do that. And since they're both going to be reading exactly the same anyway, you'd only be kicking yourself that you bought two!

* Technically, you can wind up with different flow rates within a single system, if within that system you have some sort of bypass path. If the flow is split somewhere into two paths, each path could have a different flow rate, and each of those would be different from elsewhere in the system. But right after the two paths merged back together, the rate of flow at that point would be identical to the rate of flow right before they split. Similarly, if you have a return manifold that splits your filtered water into two or more pipes, each of those pipes could have different flow rates, and each of those would have a lower flow rate than the main filter circuit. But for the purpose of your solar system, the flow rate in the pipes to the roof, or just before the filter, or between the filter and solar valve, or right after the heater, etc, all those flow rates will be the same.

They want $123 for just the guts? Yikes. Well, welcome to the supply chain, I guess... But that's the exact part I was referring to. And it looks like it'll go right into either of your Jandy housings.

If you're moving ahead with the Vis, then all the other discussions about bubbles and pipe temperatures, etc are moot.

I do want to point out BMerrill's post, where he was kind enough to build you a nice chart of flow rates. But he actually has reinforced a point I made earlier. You can't use his chart for anything but comparison, certainly not for setting up your system. I get 40 GPM at 2200 RPM. Apparently, that would only need about 1100 RPM in BMerrill's pool! That's a 100% difference (and that's just the RPM, cost would be even father "off the chart.") Plus, he doesn't have panels, which affects the flow rate drastically. That really illustrates why guessing and feeling and bubbles and "rule of thumb" or whatever are just not going to hold up to all the variables involved. If you really want to optimize flow through your panels, ya kinda need something that specifically measures flow, and measures that flow in your pool...

 

[brimorga]

Great input as always Dirk. Found one on Amazon for $96 and it'll be here Sunday!

BMerrill's post was great and much appreciated. I started to plot his values vs mine and found they were way different, but I also have 2.5" pipe running to the skimmers and returns (2" for equipment pad) and he has 2".

Once I get the Vis, I want to complete my table, including lower values, and share the flow rates vs RPM and Watts and then optimize mine, just like you said. It'll be much more valuable once I can add in the flow rates!

 

[Dirk]

If I may...

What might make both of your charts more helpful to others: is to (1) increment the RPMs with a consistent step value (like 50 RPM: 2200, 2250, 2300, etc), and (2) calculate the actual cost in your area per day (or month, or year) for each RPM. That would better illustrate that going up or down 50 RPM doesn't directly track, percentage-wise, with watts or flow or cost (you've already learned that the scales are exponential). It should also show how increasing or reducing X RPM at one end of the scale doesn't match doing so at the other, in other words: reducing RPM from 1500 to 1450 saves Y amount, vs the savings of reducing 2800 to 2750.

It might also help you better justify those 96 bones!

And maybe it'll help others figure out if fretting over RPMs is worth the trouble. To me, it is. But Bezos probably doesn't worry much about the RPMs on the pool pump in his new $500M yacht!

 

[brimorga]

If I may...

What might make both of your charts more helpful to others: is to (1) increment the RPMs with a consistent step value (like 50 RPM: 2200, 2250, 2300, etc), and (2) calculate the actual cost in your area per day (or month, or year) for each RPM.

If I could easily figure out how to do it, I totally would! The slider on the Hayward OmniLogic app doesn't seem to want to comply with exact values unfortunately.

My plan was to take as many data points as possible and then just plot a curve on a chart and share it, with the table secondary, but I can't seem to figure out the best data to plot on the X,Y axis and the best data to use for the chart itself.

 

[Dirk]

If I could easily figure out how to do it, I totally would! The slider on the Hayward OmniLogic app doesn't seem to want to comply with exact values unfortunately.

My plan was to take as many data points as possible and then just plot a curve on a chart and share it, with the table secondary, but I can't seem to figure out the best data to plot on the X,Y axis and the best data to use for the chart itself.

Ah, I was projecting. Pentair IntelliFlo pumps controlled by ScreenLogic can be dialed in to exact RPM numbers.

A chart would be very helpful for sure. You could plot RPM on the X axis, and then have multiple datasets on the Y: one for flow, another for watts, a third for cost, etc. Something like that would be very illustrative of how adjustments to RPM can affect things. Labeling more than one dataset type can be challenging. You can have multiple Y labels. Or you could always offer more than one chart: one per dataset type (RPM vs Flow, RPM vs cost, RPM vs watts, etc). Here's an example of a chart that depicts different types of data. The label colors match their associated chart lines:



For the chart style above, you'd have RPM along the bottom (X axis) and the other dataset labels as multiple Y axis. But you can swap the X and Y, the concept works either way. Excel probably has something built in that could handle multiple datasets with different labels.

 

[brimorga]

So I'm loving the flowvis. I can see how it's all a Crud shoot unless you have something like this. The difference in flow rate between running the pool, pool+spa, spa and then adding the solar heating on top are significant. It gives results I never would have expected. Using this to figure out normal pump cycles to do 1x water turn over wouldn't be possible without it or something similar given the wide variation of results.

I have 10 helicoil 12x4.5 panels for 500 sq ft of panels. The instructions recommend 5 gpm per panel minimum, 6-7 gpm to be optimal and up to 2x the minimum to run safely.

I can run 2415rpm to hit the minimum at 50gpm. When I run 2415 without the panels, that is 74gpm, a full 24gpm reduction. If I want to run at the upper end, 70gpm for the panels, that is the pump at full speed which is 3x the electricity of the minimum. At full speed without the heater I get 105+GPM! Running solar is a huge hit to GPM and it doesn't seem to make sense from an electric perspective to run it much higher than the minimum because small increases in RPM's yield so little GPM increase that it takes massive power to really make a difference.

Once we get into warmer temps, I'll probably run the pump for long hours with low RPM to get 1x turn over while using the least amount of watts. 1200rpm for ~13hrs looks about right.

 

[Newdude]

can see how it's all a Crud shoot unless you have something like this. The difference in flow rate between running the pool, pool+spa, spa and then adding the solar heating on top are significant. It gives results I never would have expected. Using this to figure out normal pump cycles to do 1x water turn over wouldn't be possible without it or something similar given the wide variation of results.

You just NAILED why the industry 'turnover' myth is *exactly* that.

One neighbor has a bunch of water features and a heater. One neighbor has a plain Jane pool. A 3rd neighbor had something in between and heavy trees that clog their small filter often. Yet all 3 need 3 turnovers a day, thay they have zero chanve of calculating without a flow meter. Now Multiply those variables across the land and how is anybody supposed to actually know when they hit their 3 turnovers.

Now, the truth is that each pool needs the skimming and filtering that it needs. Some need 2 hours, others 4 or 9. Heck, even the same pool will need wildly different schedules to clear the various crud levels throughout the season. Yet if they make everybody run for 16 (?) hours, they are RIGHT !!!!

If shooting for 1 or 2 or 3 turnovers makes you sleep better, then by ALL means do it for you. If you want to figure out what you truly need, try a runtime for a week. If the water is stupid clear? Try less next week. If the water isn't quite right, add some runtime. Reasses whenever necessary like in the early spring when you get overrun with pollen. I had to run 24/7 then to keep up with 80 Oaks. Shortly thereafter I barely needed to run at all for a couple of months if we weren't throwing a bunch of parties. Towards the end of the season I needed to ramp it up again.

I didn't care to ever care so I just ran 24/7 at low RPMs for peanuts. But I knew I was doing it for me and not some one size fits all reccomendation.

Also, absolutely LOVE the data if you are so kind to experiment and do the appropriate math. It will be a GREAT resource to point to for real world results as to why all 50 RPMs are not created equal, for flow or cost.