Should I change my current pump for a solar heater?

[haz]

I have some questions related to pumps for a solar heating system. Thanks for any help in advance.

I just installed a pool, and they installed two pumps:
pool: Jandy Zodiac FloPro FHPM 2.0-2 dual speed: HP 2.0 & 0.25
spa: Jandy Zodiac Stealth Pro Series, SHPF3.0 HP 3.0.

The pumps’ manuals, which include the flow rates based on the dynamic head are:
http://www.zodiacpoolsystems.com/~/medi ... /SA/SA6220
http://www.zodiacpoolsystems.com/~/medi ... H/H0573800

The spa 3.0 HP pump also runs a water feature in the pool with an overflow edge into a trough, which also functions as the skimmer. It turns on automatically 30 minutes per day.

The main pump is set up to only use the SWG when in 0.25 HP low-speed mode, although the installer said that it can be changed to run the SWG in high-speed mode too.

Currently I don’t use the high-speed 2.0 HP mode of the pool pump. It is supposedly for using a cleaner, but I use a robotic plug-in cleaner - those seem to be much better and more energy efficient than the ones that run off the pool pump anyway.
I was looking to install a Heliocol solar heater. The installer suggested nine 4 x 12.5’ HC 50 panels (450 ft2 total), with 2" pipes.
My pool/spa surface area: 290 ft2. Southwest exposure in South Florida, with reduced direct solar heat from a screen enclosure with extra sun blocking on some sides.
My roof is 22' above the pool level. The roof looks like it has a 30 degree slope. So assuming the bottom of the panels start 2' from the edge of the roof (I don't know where they actually will install them), the bottom of the panels will be 23' above the pool level, and the top of the panels will be 29.25' above the pool level.

According to the solar installer, 0.75 hp is needed for a 2-story home. So with my current pump, I might have to run the pump at high speed 2.0 hp constantly in order to get the water up there, as low speed is 0.25 hp. According to the pool installer, and he could be wrong, there is no way to tell the Aqualink control to use high-speed if the temperature drops below the solar heaters settings and to use low-speed otherwise. JasonLion wrong on a different post:

With solar and a variable speed pump it is generally worth getting an automation system that knows how to talk to the pump so it can raise the speed when in solar mode and lower it again when solar is off.

So maybe some automation systems can do that, so maybe Aqualink can. And even if there were a way to variably switch between high and low speed based on the solar heater's needs, that might make it difficult to set a SWG level, given that the SWG would be producing lower or higher levels based on the pump hp depending on the solar heater's needs. The solar heater and SWG's needs would be opposite: when things were colder outside, the pump would switch into high-speed to send water to the solar heater, which in turn would boost the chlorine production, whereas probably less chlorine would be necessary given the colder and therefore less sunny climate at that time. I guess I might be able to find an appropriately low SWG setting that would account for the higher flow rate during that season, although it sounds like it would mean lots more adjustments that usual.
So with the goal of trying to be energy and cost efficient, this could actually be very inefficient if I have to maintain the pump at 2.0 hp’s. So my questions are:

• 
  1. Does anybody know if there is a way to have Aqualink change the speed of a two-speed pump when the solar heater needs to run?
  2. Would you agree that 0.25 hp’s is too little to prime the solar system I was thinking of installing? I read in other posts people priming with around 0.5 hp, but I don’t know about 0.25.
  3. If so, would it make sense to switch out the pump e.g. for a 0.75 hp one? And if so, would there be any reason not to get a one-speed say 0.75 pump for the pool (again, I have a 3.0 hp pump for the spa, and I don’t use the pool cleaner that uses the pump). I haven’t looked into the cost of doing so, but maybe the solar heater installer could do so, and hopefully he might give me some value for the almost-new existing 2-speed pump.
  4. Given the costs of a solar heater installation plus the fact that they are not free to use as they require higher pump settings, and installing one might make me need to consider changing my pump, maybe a solar heater is not as energy efficient and beneficial as initially thought. I have a natural gas heater, and natural gas is relatively inexpensive and clean. I wonder if anyone has compared the costs of regularly heating the pool with natural gas in a generally warm climate like South Florida versus the extra electricity of pumping water up to the roof for solar heating, possibly at a significantly higher horsepower setting than one would use otherwise.

Any help would be greatly appreciated!

 

[Isaac-1]

I just installed 11 4x12 TechnoSolis panels about a month ago along with a 2 speed 1.5 HP Jandy FloPro pump, the top of my roof top panels is located about 16 feet above ground level. I have an Aqusolar AQ-LV-TC solar controller set up to run the pump on high when solar is on and low the rest of the time (unless manual override switch is flipped) using the booster pump relay connection on the controller with a RIB relay to switch pump speeds. When on high and all flow diverted through the panels I am getting about 45 gpm of flow (just over 4 gpm per panel) , but I do have a Hayward Perflex series DE filter which generates more back pressure than many other filter designs. Optimal flow for most 4x12 panels is around 5 GPM per panel and acceptable flow is 3-8 GPM , so as you can see even with full flow on high mine is not reaching optimal flow performance for 11 panels, but is well above minimum.


Ike

p.s. I suspect .75 HP would allow flow through the panels, but I really doubt it would be enough pump to reach optimal flow rate of about 5 gpm per panel to maximize heat exchange.

Also that seems like a lot of panels for such a small pool, are you attempting to get 12 month operation with these panels?

 

[jblizzle]

Solar efficiency is higher at higher flow rates. Low speed is rarely enough. But you could only divert some on high speed if it was too much flow.

I would not replace the pump. That is extra cost and in the winter or dead of summer when solar is not needed, you can take advantage of the electrical savings using low speed.

The SWG should really be wired to work on either speed. You could set a long-ish run time on low, with a high speed override when solar is needed. That way the pump would always be on the same amount of time and the SWG would produce the same amount of FC.

Not sure if this is possible with that controller ... Certainly possible with the pro logic.

 

[Isaac-1]

One more question, which Aqualink model do you have?

 

[haz]

The pool installers kept referring to the Aqualink as "PDA-4", and from Jandy's website this looks like the name of the model, so I think it's: PDA-PS4. Apparently I need to change to a PDA-PS6, if I hook up solar, since all of the auxiliaries are used on the 4. It's manual is here:
http://www.zodiacpoolsystems.com/~/medi ... 72300.ashx

I see something called Solar Priority, but from reading that manual, I don't see anything about changing the speed of the pump if the solar is on. It does say, strangely:
Solar temperature must be at least 5° F above the water temperature and the water must be cooler than the thermostat setting.
So... if I want 85 degree water and the water is at 82 degrees, I have to put 90 degree temp so that it heats to 85? Strange.

In terms of the number of panels needed, maybe I don't need so many. This contractor originally recommended 8 panels for 400 ft2 after his tech saw my pool. I afterwards let him know that I would be installing a screen, and part of the SE exposure side and half of the top will be 80% UV (and therefore solar heat) blocking, and the standard screen around the rest of the pool blocks 10-15% of UV/heat. I asked him if he would then suggest more panels, and he said yes, but mostly because I was asking about it. He didn't make a real calculation.

An Aquatherm installer recommended 9 4’x12’ EcoSun panels (432 ft2), and he also offered to increase the surface area to 12 4’x10’ (480 ft2) or 14 4’x10’ (560 ft2). Do you guys suggest fewer panels, maybe 8 or fewer 4' x 12.5' Heliocol? That would allow more GPM per panel. The solar installers I met with didn't seem to consider that.

Maybe I'm hijacking my own thread and should post my question about number of panels in the solar section...

 

[jblizzle]

The solar sensor is not a water temp, it is really sensing the sun hitting the panels. So you would set the desired temp to 85 and if the water temp is less than that and Sun is hitting the solar sensor making it read 90, then the solar will turn on. This is done to prevent the panels from cooling the water.

The more panels, the more heat you get ... assuming you can get close to the 4-5 gallons per minute that is ideal for each panel.

Keep your questions here.

 

[Isaac-1]

Let me try to put that another way, a standard solar controller has 3 inputs,

A, a knob where you set your desired temperature
B, a sensor that measure pool water temperature (usually in the pipe at the pad just after the filter)
C, a roof mounted sensor that measures the temperature of the solar panel

assuming you are at below your desired temperature (A >B) the controller will divert water to the solar panels if the solar panels are more than 4 degrees warmer than the pool water [s:2xir701m](C+4>B)[/s:2xir701m](C>B+4), Most will also turn off at some point when the Solar panel is still slightly warmer than the pool, by something like 1 degree, I suspect this is done due to accuracy limits of the sensors. The point being so that you don't quickly cycle the control system in a situation where the panels are just a little warmer than the pool due to sun exposure, pump cold water through the panels, cool them off and then loose heat by radiating heat from the panel faster than the sun warms them.

As to size, bigger is better, to a point, the problem with sizing correctly is it depends on a number of variables, then you get certain engineering decisions, do you design for worst case, best case, average case...

The biggest factor here is what is your goal for extending the swim season are you talking 9-10 month season, 11-12 month, or true year round heating your pool to desired temperature on the coldest day of the year, there can be a big difference in required number of panels for each of those 3 since the intensity of sunlight can be MUCH lower in the winter, which is also when you need the most heat. (this again depends on where you live), add to this local issues like wind exposure, shading of the pool, and even owner preference (desired 88 degree temperature vs 78 can make for another big difference), even if the owner desires to swim in the morning vs in the evening.

Ike

I edited your equation, jblizzle

 

[haz]

Got it, thanks for the explanations of how the solar heater works.

From reading the manual of Aqualink, I do not see a way to run the filter in high-speed only when the solar system needs to run. So during the few months of the year in which I would never plan to use the pool in South Florida, I could leave the system on low speed, i.e. 0.25 hp. But if my Aqualink can't change the speed of the pump, I will have to run the pump the rest of the year at high speed, i.e. 2 hp, in order to get enough GPM to the solar heater. This high speed is both energy inefficient and loud; I can hear the pump in my bedroom at 2 hp. If I try to do something like say run five hours at high speed with the solar capable of working then five hours at low speed, then it seems like in the colder seasons I might not be able to sufficiently keep the pool warm enough as five hours maximum will be not enough time for the solar panel to run.

It seems like changing the Aqua link controller to pro logic or Aqusolar, which you guys say could change the speed to high only when the solar needs to run, might be expensive.

Isaac-1 said:

I suspect .75 HP would allow flow through the panels, but I really doubt it would be enough pump to reach optimal flow rate of about 5 gpm per panel to maximize heat exchange.

So it sounds like I would need something at least 1 hp to get sufficient water to the solar heater, no? If so, what about changing the pump from Jandy Zodiac FloPro FHPM 2.0-2 dual speed to something like a 1 hp max version:
Jandy Zodiac FloPro FHPM 1.0-2 dual speed

That way I can leave it at 1 hp for the majority of the year when I have the solar on and go to low power for the remaining few months.

I can't tell from their documentation what the hp is for the low speed on that, but from the diagram in the manual, it does not seem like the GPM is much less than the low speed on my 2 hp version, so I hope the low speed could work when solar is not needed.
http://www.zodiacpoolsystems.com/~/medi ... /SA/SA6220

And given the cost of installing a solar heater and the fact that I will apparently have to go from 0.25 hp to maybe one horsepower during most of the year, does anybody have a sense of how the costs of installing solar would compare to just heating the pool with my natural gas (relatively cheap and clean) heater regularly?

 

[Isaac-1]

You say you never use high speed on your pump now, coming up with a hack to make it switch to high speed when in solar mode should be easy. 2 or 3 ways come to mind immediately, one might be as simple as connecting a pressure or flow switch to the cold side plumbing that activates a DPDT relay that switches the pump into high speed mode.

It would work something like this:

Aqua Link would select solar on the diverter valve actuator, this would let flow start trying to go through the solar panels (may need a small limited flow bypass loop (say 1/2 inch PVC looping past the panels to work)), flow or pressure switch would make contact and this would drive a relay that would in turn switch the pump to high speed mode

Pool gets to desired temperature or a cloud blocks the sun and the Aqua Link switches the diverter valve back to direct pool return / no solar, panel drains down and pressure switch turns off switching the pump back to low speed mode. This is the simple version, reality may require the use of an additional time delay relay to keep the pump from switching back and forth too fast, due to air bubbles, etc.

Alternatively you could just buy a stand alone solar controller and not have solar control through your current Aqua Link

I have not read through the manual for your Aqua Link yet, but also if it supports a relay to control a booster pump for solar operation that contact could be connected to a DPDT (or SPDT) relay to switch between low and high speed on the 2 speed pump The standard relays these units tend to use are SPST, which is what you would normally use to turn a booster pump on and off.

Ike

 

[haz]

Makes sense what Issac-1 says about coming up w/ a hack to make my Aqualink controller be able to be in low-speed mode and then switch to high-speed only when solar heating is needed. The solar installer wanted to install his own controller, but I told him the Aqualink should be able to do more with it than his stand-alone controller would, but will less capability. If I got a stand-alone controller, how would/wouldn't that help create a way for the Aqualink to change pump speeds based on the need for solar heating? And it terms of the hack, I'm sure many of you could do that yourselves, but it's beyond my technical abilities unfortunately. My pool and solar people don't seem to be that capable with that either - who might be a good type of person to help with something like that?

And does anyone suggest changing the Aqualink for something else? don't know what that would run - may not make sense.

 

[Isaac-1]

I use a Hayward Aquasolar AQ-LV-TC controller with the addition of an aftermarket $20 SPDT RIB relay connected to the speed control leads on my 2 speed pump to switch to high speed when in solar mode and back to low when solar is off. The more basic $200 Aquasolar AQ-LV model (same but without timeclock or included SPST relay) would likely work for your needs. If your interested I would gladly send photos of the wiring on my setup and draw out the connections.

Simply put the RIB SPDT relay is connected to the 24V relay output intended to turn on a solar booster pump by way of the optional plain on/off SPST relays.

This sort of solution would simply be connected to the pump for speed control instead of your existing controller, since your not using it to change speed now, it should not cause a problem, just disconnect the speed control outputs from your existing controller and connect these to the pump instead. Not the cheapest option, but less of a hack

Ike

p.s. I did have to scavenge a 2 pin header plug connector off an old dead computer fan to connect to the booster pump connection also.

 

[haz]

OK, sounds like you used an RIB SPDT relay like:
http://www.amazon.com/dp/B000LESCI2
http://www.amazon.com/Enclosed-Rela...qid=1370261578&sr=8-2&keywords=SPDT+RIB+relay

So it looks like you're recommending using a separate solar controller instead of the solar controlling ability of my Aqualink? I figure this is necessary in order to set up the relay workaround?

Sure, photos of the wiring would be very helpful. I will run it by the solar heater installer, whose company is a general pool heater (of all types) installer. If he has no idea how to do something like that, what type of person/contractor would be good to ask this type of thing?

Would anyone recommend changing to a different system, e.g. pro logic (jblizzle)?

 

[jblizzle]

It would not make sense to switch to a pro logic in my mind since you already have a Jandy SWG.

I am sure there are solar controllers that will do what you want, I just do not know which ones.

 

[Isaac-1]

Just putting it out there as an option that is less of a hack than using a pressure switch or flow switch to change the speed of the pump. One nice thing about the solution I am using is there is a 30 second delay after the actuator is told to switch position before the booster relay activates, so you minimized pressure flowing through the diverter as it switches.

The relay I used was a member of the 2401 series, but has an over ride manual / auto switch on the front that allows me to manually switch the pump to high without switching to solar it is the RIB 2401SBC

Ike
p.s. one thing about using a separate controller for solar is you don't really need all those bells and whistles, hand held remotes, etc. since nothing happens quick with solar, you want the pool a bit warmer, you turn the knob up on the controller and a couple of days later the average temperature on the pool is a bit warmer, it is not like walking into your house thinking its cold in here and turning up the heat then your toasty in an hour.

 

[haz]

I think I will be better off going for a separate solar controller. But changing the pump speed is a function of the main controller. Do some solar controllers have that ability, or I'd probably have to set up something like your RIB SPDT relay anyway? I will run it by the solar installers, but if they are confused by the idea of hooking up that type of relay, do you think a general electrician would be able to do that? I could try to find one w/ some comfort w/ pools - I'm sure that's possible here in South Florida.

I've never dealt much with pool controllers - with the relay, should most controllers be able to be switched from low to high speeds with it?

 

[haz]

BTW, my solar installer uses Hayward GL 236 auto control for the solar. I figure the work-around would be the same

 

[mas985]

Is your objective to run solar on low speed or just switch to high speed when solar is engaged?

Your current controller should be able to handle solar on high speed and switch it automatically to high speed when solar is engaged. Did you confirm with Jandy/Zodiac that this is not the case? My controller does this automatically and there is no setting for it.

Also, just to clarify, almost any pump will work for solar if the plumbing designed properly. I have a 1/2 HP pump that runs my solar system on a two story roof and I can still bypass some of the water around the solar system.

 

[Isaac-1]

BTW, my solar installer uses Hayward GL 236 auto control for the solar. I figure the work-around would be the same

I assume you mean a GL-235 (which is the most basic controller Hayward Gold Line sells), if so the relays are integrated on that model, not separate components, something similar to what I did could be done, but might be a bit more complicated, if your interested in going the route that I did, you might want to ask our installer if he could use a Hayward Goldine AQ-SOL-LV instead of the GL-235.

As to finding someone to do this sort of thing, I would look for people that do custom automation systems

 

[mas985]

So help me out here. Why is custom automation necessary?

 

[Isaac-1]

My understanding of the problem is that his version of the Aqualink will not support changing pump speed when switching to solar, and from my brief review of the documentation has no booster pump relay, etc. it just switches the valve position based on temperature differential. He also currently never runs his pump on high to save electricity, but does not want to have to switch it to run high all the time either.