Wow - Thanx Richard.
I really regret not coming here first and asking questions before my solar system was installed.
Answers to your questions are as follows:
1. I do have 1.5" pvc piping for the supply and returns for the solar system. All the piping is the black piping which I'm assuming is ABS rather than PVC. I do not know what schedule it is. The supply and returns lines coming off the roof to the booster pump is 1.5" PVC, Schedule 40.
2. The system pump is a StaRite DuraGlas, P2RA5F-125L. This pump/motor combination is a 1.5 HP, but the motor was replaced some time ago before my ownership with a GE 1 HP motor.
3. The filter is a StaRite Posi Flo, PTM100.
4. The pressure gauge on the filter housing reads 15 psi without solar and 20 psi with solar enabled.
Thanx again for all your help - you would be a very valuable asset here in SW FL!
Energy Efficient Pool Pump?
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chem geek
- Pool Industry Leader
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The Sta-Rite P2RA5F-125L is a 1-1/2 HP Dura-Glas PR2A series up-rated pump. The service factor for an up-rated pump is usually lower, say around 1.1 or so. Your replacement motor GE 1 HP is probably full-rated with a service factor of 1.5 to 1.65 or so. So basically it is the same. What is most relevant is the Total Brake Horsepower which is the product of the Horsepower and the Service Factor (SF) -- you can see the HP and SF on the plate that should be on the pump motor.
The pump curves for the Sta-Rite Dura-Glas may be found here where the P2RA5FL is curve "D". It shows that the maximum head is around 90 feet and the best efficiency sizing is between 43 GPM 85 feet and 80 GPM 47 feet. With your long 1.5" pipe runs, this means that you aren't getting near the 75 GPM that is more efficient for your solar panels and you are wasting a LOT of energy with friction in the "too narrow" pipe.
The Pentair Intelliflo should have no problem at least emulating your current pump, but could be fine tuned to the desired flow. That is, even with your existing pipe, the Intelliflo would work in your system but would be pumping at a flow rate that is lower than optimal for your solar panels, just like your existing pump is doing. By replacing the 200' round-trip pipe, you can increase your flow rate to your panels with lower electricity usage -- a real win-win. You can get a LOT of energy savings with the Intelliflo if you use a lower flow rate when the solar is off.
Your pressure reading when solar is on doesn't make sense. 15 psi with solar off is reasonable and is 35 feet of head so with suction head added it's perhaps around 40-45 feet of head and a GPM of 80. That's a higher flow rate than you need (with solar off), but is due to not having a variable speed pump. However, with the solar on, 20 psi is only 46 feet of head so with suction head it's perhaps around 55-60 feet of head so 70 GPM but there's no way that this is going only through your solar system. The psi should have been much higher. In my own pool, for example, my older 1 HP full-rated pump (somewhat similar to your 1-1/2 up-rated pump) had around 15 psi with the solar off and around 28 psi with the solar on with fairly long runs but using 2" pipe. A 10 psi increment is more typical, but 5 psi is strange given your long narrow pipe runs.
If your current pump were just flowing through the 200' round-trip of 1.5" pipe with nothing else (and no suction head), it would be at around 73 GPM with 52 feet of head or 22.4 psi. So adding in everything else (the solar, the suction head, the baseline head to the pool without the solar), there's no way that all the water is going through that 1.5" 200' round-trip of pipe. When the solar is on, is ALL of the water going through the solar or is there a bypass valve that only has only SOME of the water going through the solar?
A psi increment of 5 is 11.6 feet of head. If there were no friction in the solar panels themselves (which isn't true), then the 200' of 1.5" pipe would have a flow rate of about 32 GPM to produce that head loss. So this implies that the flow rate through the panels (overall, not per panel) at <32 GPM is less than the flow rate from the pump overall at around 70 GPM. This is why I'm asking if some of the flow bypasses your solar when it is "on".
Richard
The pump curves for the Sta-Rite Dura-Glas may be found here where the P2RA5FL is curve "D". It shows that the maximum head is around 90 feet and the best efficiency sizing is between 43 GPM 85 feet and 80 GPM 47 feet. With your long 1.5" pipe runs, this means that you aren't getting near the 75 GPM that is more efficient for your solar panels and you are wasting a LOT of energy with friction in the "too narrow" pipe.
The Pentair Intelliflo should have no problem at least emulating your current pump, but could be fine tuned to the desired flow. That is, even with your existing pipe, the Intelliflo would work in your system but would be pumping at a flow rate that is lower than optimal for your solar panels, just like your existing pump is doing. By replacing the 200' round-trip pipe, you can increase your flow rate to your panels with lower electricity usage -- a real win-win. You can get a LOT of energy savings with the Intelliflo if you use a lower flow rate when the solar is off.
Your pressure reading when solar is on doesn't make sense. 15 psi with solar off is reasonable and is 35 feet of head so with suction head added it's perhaps around 40-45 feet of head and a GPM of 80. That's a higher flow rate than you need (with solar off), but is due to not having a variable speed pump. However, with the solar on, 20 psi is only 46 feet of head so with suction head it's perhaps around 55-60 feet of head so 70 GPM but there's no way that this is going only through your solar system. The psi should have been much higher. In my own pool, for example, my older 1 HP full-rated pump (somewhat similar to your 1-1/2 up-rated pump) had around 15 psi with the solar off and around 28 psi with the solar on with fairly long runs but using 2" pipe. A 10 psi increment is more typical, but 5 psi is strange given your long narrow pipe runs.
If your current pump were just flowing through the 200' round-trip of 1.5" pipe with nothing else (and no suction head), it would be at around 73 GPM with 52 feet of head or 22.4 psi. So adding in everything else (the solar, the suction head, the baseline head to the pool without the solar), there's no way that all the water is going through that 1.5" 200' round-trip of pipe. When the solar is on, is ALL of the water going through the solar or is there a bypass valve that only has only SOME of the water going through the solar?
A psi increment of 5 is 11.6 feet of head. If there were no friction in the solar panels themselves (which isn't true), then the 200' of 1.5" pipe would have a flow rate of about 32 GPM to produce that head loss. So this implies that the flow rate through the panels (overall, not per panel) at <32 GPM is less than the flow rate from the pump overall at around 70 GPM. This is why I'm asking if some of the flow bypasses your solar when it is "on".
Richard
Richard -
Here are more details of my system:
1. I do not have a bypass for the solar. The solar is controlled by a valve actuator which is controlled by the Aqua Logic.
2. The GE system pump is 1 HP with a SF of 1.25.
3. The booster pump for the solar is a Waterway SVL56, A.O. Smith motor, 3/4 HP and a SF of 1.65.
4. With the solar enabled and no booster pump the psi is 28.
5. With the solar enabled and the booster pump on, the psi is 20.
6. With solar not enabled and just running the system pump, the psi is 17.
Does using the booster pump change your previous psi concerns from your earlier reply?
Here are more details of my system:
1. I do not have a bypass for the solar. The solar is controlled by a valve actuator which is controlled by the Aqua Logic.
2. The GE system pump is 1 HP with a SF of 1.25.
3. The booster pump for the solar is a Waterway SVL56, A.O. Smith motor, 3/4 HP and a SF of 1.65.
4. With the solar enabled and no booster pump the psi is 28.
5. With the solar enabled and the booster pump on, the psi is 20.
6. With solar not enabled and just running the system pump, the psi is 17.
Does using the booster pump change your previous psi concerns from your earlier reply?
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chem geek
- Pool Industry Leader
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- Joined: Thu 21 Jun, 2007 21:27
- Location: San Rafael, California
Rick,
Thanks for the info. I forgot about the booster pump and even if I had remembered, I didn't realize that (apparently) it is coming after your filter (probably just on the line to the solar) so it would reduce the pressure reading at the filter when it was on. The pump curve for your main pump with the smaller GE motor is probably closer to the "C" curve in the link I gave.
With the solar off, 17 psi pressure head is 39 feet of head so with suction head it might be around 45-50 feet of head and 65-70 GPM. Again more than you need when solar is off so the Intelliflo would clearly help there. If your pool was 15,000 gallons, then your current turnover rate with the solar off is under 4 hours. With the Intelliflo, you can run the pump for a longer time at a lower flow rate for a lot of energy savings (at least when the solar is off). The implied equivalent 1.5" pipe length is 190-240 feet which sounds about right going to/from your pool and fittings.
With the solar on and the booster pump off, 28 psi pressure head is 65 feet of head so with suction head it might be around 75 feet of head and 35 GPM. This implies a 1.5" pipe length of around 1200 feet. It's possible that the pump with your new motor has a higher GPM and also flowing through the booster pump with it off could have significant resistance. With the booster pump on, the 20 psi is from the first pump and about 46 feet of head which with suction head is around 55 feet of head and 60 GPM. The second pump is similar to the 1st (with the replacement motor) in HPxSF so the 60 GPM means another 55 feet of head. 60 GPM with 110 feet of head implies 600 feet of 1.5" equivalent pipe length and that sounds about right given the roughly 200 feet equivalent to/from the pool and fittings leaving 400 feet for the solar -- 200 feet to/from the solar and 200 feet round-trip through the solar panels.
So with your booster pump, the 60 GPM is a decent flow through the panels -- less than ideal, but not bad. It's pretty clear that if you replace your two pumps with the Intelliflo and don't change your piping, then you won't be able to achieve this flow rate. Even at peak 3450 RPM with the Intelliflo, the 600 feet of 1.5" equivalent pipe length implies around 55 GPM with 91 feet of head and around 2100 Watts. If you replace your 200' round-trip with 2" pipe, then you could get your current 60 GPM with 82 feet of head at around 3300 RPM and around 1850 Watts which may be only a little more than half of what your current pumps are using in energy.
Well, that makes a lot more sense so thanks for straightening me out. There's no question that your plumbing should have been using 2" for long runs. I'm a little surprised that your solar panel headers are 1.5", but that depends on the manufacturer. My Fafco solar panels have 2" headers (at least -- they are awfully thick and could be even larger). Anyway, it seems pretty clear that if you want to replace your two pumps with one Intelliflow, you're going to have to replace your 200' of round-trip piping to/from your solar panels with 2" pipe.
Richard
Thanks for the info. I forgot about the booster pump and even if I had remembered, I didn't realize that (apparently) it is coming after your filter (probably just on the line to the solar) so it would reduce the pressure reading at the filter when it was on. The pump curve for your main pump with the smaller GE motor is probably closer to the "C" curve in the link I gave.
With the solar off, 17 psi pressure head is 39 feet of head so with suction head it might be around 45-50 feet of head and 65-70 GPM. Again more than you need when solar is off so the Intelliflo would clearly help there. If your pool was 15,000 gallons, then your current turnover rate with the solar off is under 4 hours. With the Intelliflo, you can run the pump for a longer time at a lower flow rate for a lot of energy savings (at least when the solar is off). The implied equivalent 1.5" pipe length is 190-240 feet which sounds about right going to/from your pool and fittings.
With the solar on and the booster pump off, 28 psi pressure head is 65 feet of head so with suction head it might be around 75 feet of head and 35 GPM. This implies a 1.5" pipe length of around 1200 feet. It's possible that the pump with your new motor has a higher GPM and also flowing through the booster pump with it off could have significant resistance. With the booster pump on, the 20 psi is from the first pump and about 46 feet of head which with suction head is around 55 feet of head and 60 GPM. The second pump is similar to the 1st (with the replacement motor) in HPxSF so the 60 GPM means another 55 feet of head. 60 GPM with 110 feet of head implies 600 feet of 1.5" equivalent pipe length and that sounds about right given the roughly 200 feet equivalent to/from the pool and fittings leaving 400 feet for the solar -- 200 feet to/from the solar and 200 feet round-trip through the solar panels.
So with your booster pump, the 60 GPM is a decent flow through the panels -- less than ideal, but not bad. It's pretty clear that if you replace your two pumps with the Intelliflo and don't change your piping, then you won't be able to achieve this flow rate. Even at peak 3450 RPM with the Intelliflo, the 600 feet of 1.5" equivalent pipe length implies around 55 GPM with 91 feet of head and around 2100 Watts. If you replace your 200' round-trip with 2" pipe, then you could get your current 60 GPM with 82 feet of head at around 3300 RPM and around 1850 Watts which may be only a little more than half of what your current pumps are using in energy.
Well, that makes a lot more sense so thanks for straightening me out. There's no question that your plumbing should have been using 2" for long runs. I'm a little surprised that your solar panel headers are 1.5", but that depends on the manufacturer. My Fafco solar panels have 2" headers (at least -- they are awfully thick and could be even larger). Anyway, it seems pretty clear that if you want to replace your two pumps with one Intelliflow, you're going to have to replace your 200' of round-trip piping to/from your solar panels with 2" pipe.
Richard
Well thanx again Richard for your input and explanation. Just to make it clear, the headers for my solar panels are 2". Also, the pool is about 15,000 gallons.
You are correct, the BP is after the the filter and is on the line to the solar only.
The electric rate on my bill is about 6.5 cents per kw.
By replacing the 1.5" piping with 2" piping and replacing the two pumps with one IntelliFlo pump, it's clear there would be an energy savings and a lower electric bill to go with it. Would this scenario also give me more "heated" pool water and would it heat the pool quicker?
You are correct, the BP is after the the filter and is on the line to the solar only.
The electric rate on my bill is about 6.5 cents per kw.
By replacing the 1.5" piping with 2" piping and replacing the two pumps with one IntelliFlo pump, it's clear there would be an energy savings and a lower electric bill to go with it. Would this scenario also give me more "heated" pool water and would it heat the pool quicker?
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chem geek
- Pool Industry Leader
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- Joined: Thu 21 Jun, 2007 21:27
- Location: San Rafael, California
That's good that the solar panels have 2" headers. Your electricity costs are very low so if you save 1000 Watts (and you could save 1500 Watts) when the solar is on, then that's 6.5 cents per hour so that's about $15 per month if you were running the pumps 8 hours a day. In addition, you would save another 2000 Watts or so when the solar is off which may be 2-4 hours per day so about $8 to $16 per month in additional savings. So with your low energy costs, it will take a lot longer to achieve payback for a new pump and piping. In my pool, my marginal electric rates were about 32 cents per KWh so I was saving about $600 per year -- your savings obviously won't be that high at perhaps $200 a year or thereabouts. [EDIT] If you run the pump during the off-season (winter) with the solar off, then the Intelliflo and 2" pipe will save about another $100 so the overall per year savings is around $300. [END-EDIT]
It's not clear if you will be able to get that much more than 60 GPM from the single Intelliflo pump even after replacing the 1.5" pipe. It will certainly be far less energy than the two pumps, but you might not get that much higher a flow rate. Even if you did get to 75 GPM, the difference in efficiency in the solar panels isn't huge. Faster flow rates are more efficient in solar heating, but it's diminishing returns.
You can see in this Fafco SunSaver spec in the "EFFICIENCY vs. FLOW" chart the drop in efficiency at lower flow rates. For this panel, 4 GPM is recommended and yields 80% efficiency. For your panels, 60 GPM vs. 75 GPM would be like 3.2 GPM in this chart so perhaps 76-77% efficiency compared to 80% so perhaps 5% less efficient. So if after getting 2" pipe and a Pentair Intelliflo you were able to get up to 75 GPM, then the heating would be 5% faster -- not that much. You'll find a trade-off in energy savings vs. this efficiency.
[EDIT] By the way, what do you have for a pool cleaner? Does it have yet another pump -- a booster pump for a pressure-side pool cleaner? [END-EDIT]
Richard
It's not clear if you will be able to get that much more than 60 GPM from the single Intelliflo pump even after replacing the 1.5" pipe. It will certainly be far less energy than the two pumps, but you might not get that much higher a flow rate. Even if you did get to 75 GPM, the difference in efficiency in the solar panels isn't huge. Faster flow rates are more efficient in solar heating, but it's diminishing returns.
You can see in this Fafco SunSaver spec in the "EFFICIENCY vs. FLOW" chart the drop in efficiency at lower flow rates. For this panel, 4 GPM is recommended and yields 80% efficiency. For your panels, 60 GPM vs. 75 GPM would be like 3.2 GPM in this chart so perhaps 76-77% efficiency compared to 80% so perhaps 5% less efficient. So if after getting 2" pipe and a Pentair Intelliflo you were able to get up to 75 GPM, then the heating would be 5% faster -- not that much. You'll find a trade-off in energy savings vs. this efficiency.
[EDIT] By the way, what do you have for a pool cleaner? Does it have yet another pump -- a booster pump for a pressure-side pool cleaner? [END-EDIT]
Richard
Richard -
Regarding your questions:
1. I run the pump during the summer and winter for 8 hours/day and solar is enabled during the summer and winter as well.
2. I do not have a pressure-side pool cleaner. I'm using an AquaJet robot cleaner.
3. So, after all this analysis, it appears that swithing to one InteliFlow pump and replacing the 1.5" piping with 2" piping will require a longer payback period with a very minimal amount of solar heat efficiency - is that correct?
Regarding your questions:
1. I run the pump during the summer and winter for 8 hours/day and solar is enabled during the summer and winter as well.
2. I do not have a pressure-side pool cleaner. I'm using an AquaJet robot cleaner.
3. So, after all this analysis, it appears that swithing to one InteliFlow pump and replacing the 1.5" piping with 2" piping will require a longer payback period with a very minimal amount of solar heat efficiency - is that correct?
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chem geek
- Pool Industry Leader
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- Joined: Thu 21 Jun, 2007 21:27
- Location: San Rafael, California
Yes, due to your low electricity rates, the payback period is longer. Using the presumed flow rates from your two pumps through your system, will show little INCREASE in solar efficiency -- I wouldn't say that you are currently at minimal or low efficiency, just that the new system won't increase the efficiency by very much -- it mostly just lowers energy costs.
Since you are running year-round, your energy savings would possibly be around $400 per year. The Intelliflo pump you can get for around $800 or $1200 depending on the variable speed or variable flow model. You can get the former plus install a flow meter and do OK. You'll also need an IntelliComm module for around $350. These prices do not include installation.
According to the Florida electric rates I see here, the rate appears to be closer to 10.5 cents per kilowatt-hour. If that were the case, your annual energy savings could be closer to around $650 per year. How much you actually saves depends a lot on how long your solar is on per day (I assume the solar booster pump only runs when the solar is on) and I assume that your solar turns on via some thermocouple measurement (i.e. when the panels are warmer than the general pool water).
Richard
Since you are running year-round, your energy savings would possibly be around $400 per year. The Intelliflo pump you can get for around $800 or $1200 depending on the variable speed or variable flow model. You can get the former plus install a flow meter and do OK. You'll also need an IntelliComm module for around $350. These prices do not include installation.
According to the Florida electric rates I see here, the rate appears to be closer to 10.5 cents per kilowatt-hour. If that were the case, your annual energy savings could be closer to around $650 per year. How much you actually saves depends a lot on how long your solar is on per day (I assume the solar booster pump only runs when the solar is on) and I assume that your solar turns on via some thermocouple measurement (i.e. when the panels are warmer than the general pool water).
Richard
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