Energy Efficient Pool Pump?

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SarahSmile1

Energy Efficient Pool Pump?

Postby SarahSmile1 » Wed 07 Jan, 2009 18:04

Hey everyone.
So, I have just bought a new house which has a pool. I don't know a huge amount about pool pumps, but I have been told that I need to get a new pump as the current one is about to die. I have been looking for the most energy efficient pump as I'd love to do my bit to reduce my energy bills.

Can anyone tell me if the Pentair Intelliflo is worth the money over the Whisperflo? A guy in the shop said they were pretty much as efficient as each other, but would love to hear a second opinion.
Many thanks for your help!!


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Postby chem geek » Wed 07 Jan, 2009 21:39

See my response here.
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Postby Rick Sass » Thu 08 Jan, 2009 13:00

So Richard -

I have an elevated spa spilling over into my IG pool in SW FL. I do have solar and currently I'm using a 3/4 hp booster pump in addtion to my single speed 1 hp sta-rite pump. This pump and motor are about 13 years now and I was wondering if it would be a wise idea to replace the system pump and solar booster pump (which is 1 year old) with the Intelliflo VS or VF?

I am using the Aqua Logic automation system with their salt generator. The return lines are all 1.5" and the suction line for the spa is 2" and the suction line for the pool is 1.5" up to the pump and then it's 2" between the pump and filter which is a 100 sq. in. cartridge filter. The solar is 1.5" supply and return.
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Postby chem geek » Thu 08 Jan, 2009 15:31

You may be able to use a single Intelliflo for your pool and solar, though 1.5" pipe for solar, if the system is large and on a roof, isn't very good. That's a lot of wasted energy due to the high dynamic head and 2" lines would have been much better to/from the solar. You should have a competent PB review your situation for pump sizing.

You mentioned that you have a spa and that's another matter. Usually to get enough flow for multiple jets you need a separate pump for the spa. However, it doesn't sound like you are using a separate pump for your spa so if you are happy with the current spa situation then the Intelliflo may be able to handle that as well though probably not being able to have the spa jets on at the same time as the solar. Again, a competent PB should be able to help you figure that out.

The Intelliflo pump, either the VF or VS, has variable speeds (the VF just has a flow meter to adjust the speed to maintain constant flow rate) and can go up to 3450 RPM. The flow rate at this speed drops quickly above around 90 feet of total head (at 89 feet it's 60 GPM, but drops to 0 GPM at 96 feet). Peak efficiency at this RPM is at 100 GPM and 77 feet of head. Dynamic head loss with 1.5" pipe at 100 GPM is about 46 feet of head per 100 feet so that means an effective pipe length of around 170 feet which isn't very much. If you had 2" pipe, then at 100 GPM this is about 13.5 feet of head per 100 feet so an effective pipe length of around 570 feet which is much better.

Having individual return lines at 1.5" is OK if there is more than one and they come together into a 2" (or larger) pipe to the pump. Having 1.5" suction lines is also OK if there is more than one which there usually is since you've typically got a skimmer and floor drains, but again these should come together into a 2" (or larger) pipe to the pump. It sounds like your plumbing situation may limit your options and require you to have more pump power than you would otherwise need.

Richard
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Postby Rick Sass » Fri 09 Jan, 2009 12:40

Thanx Richard -

Competent PB and SW FL is not going to happen. It's pretty bad over here considering all the pools we have down here.

I do not have a separate pump for the spa - the flow with the solar enabled is just fine and I do have a "blower" which when turned on really does the trick.

So would you recomend replacing the 1.5" supply and return lines for the solar? I have 16 "panels" and the distance as the pipe goes from the panels to the booster pump is a run of 50' per run.
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Postby chem geek » Fri 09 Jan, 2009 23:45

Well, you could replace the 50' 1.5" pipe (each way, so 100' total) with 2", but let's see what that does. This will also help you save on electricity costs. I'm not sure what kind of solar panels you use, but if they are like these, then the optimal flow rate is 4 GPM per panel. 16 panels is a lot and would be 64 GPM. The head loss through 100' of round-trip 1.5" pipe at 64 GPM is 20 feet while the head loss using 2" pipe at 64 GPM is only 6 feet. So it's a difference of 14 feet of head (6 psi). That's not horrible so unless you can do it relatively inexpensively, it's probably not worth it. In terms of energy savings, it might save you around 200 Watts or so of pump electricity power.

Richard
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Postby Rick Sass » Sun 11 Jan, 2009 13:18

Thanx Richard -

This is the solar system I'm using: http://www.heliocol.com/.
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Postby chem geek » Mon 12 Jan, 2009 00:10

Unfortunately, I couldn't find any detailed specs so I don't know the efficiency vs. flow graph nor the flow rate vs. head graph for your panels. Such detailed data is provided for FAFCO panels here, for example.

So I don't know what to tell you. If you were to save 200 Watts when your pump is running with solar, say at least 4 hours a day, then at 20 cents per killowatt-hour, that would be 16 cents per day or about $4.80 per month. So it would take a while to pay back replacement of your pipes so wouldn't be worth it unless you were concerned about lowering your energy profile (i.e. how much energy you use) even if it cost you to do so.
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Postby Rick Sass » Mon 12 Jan, 2009 14:36

Richard

I re-read one of my earlier posts to you and I mistyped the length of the return and supply pipes for my solar system. It is 100' for the supply and 100' for the return. Does this make a difference in your calcualtions?
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Postby Rick Sass » Mon 12 Jan, 2009 15:42

Richard -

Here is the technical info my solar system. FYI - I am using 11 of the HC-50 and 5 of the HC-40.

Thanx again.

Well I thought I send the info, but it's in a pdf format and I don't know how to include that file type into this message...

When I look at the technical info, it state that the flow is 5 gpm and the chart for the head loss per flow rate shows at 5 gpm a head loss of .420. Does this help?
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Postby chem geek » Mon 12 Jan, 2009 23:30

Doubling the pipe length doubles the head loss. So just for the 100' of pipe each way (200' round-trip) at 5 GPM for each of 16 panels in parallel, that's 80 GPM. In 1.5" pipe the head loss in 200' is 60 feet (26 PSI) which is quite a lot. In 2" pipe the head loss would be 18 feet (8 PSI) which is much more reasonable. I suspect that with your current pump, you may not be at 80 GPM because of the high head loss so your heating may not be quite as optimal.

I assumed that each panel truly needs or is optimal at 5 GPM and that they are plumbed in parallel. Though that's how it is normally done, you could instead plumb two banks in series which is less efficient for heating since the second bank is hotter and radiates out more heat, but it would have about half the flow rate requirement though a little more loss of head through two sets of panels. The net result would be less total head which in your situation would be better. However, getting larger pipe would be a better option.

So having your pipe replaced with larger pipe would certainly save a lot more energy, perhaps over 1000 Watts. I'm quite surprised that you have a solar system hooked up with 1.5" pipe in the long runs to/from the system.

Richard
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Postby Rick Sass » Tue 13 Jan, 2009 13:26

Thanx again Richard -

I'm not sure what serial and parallel piping is, but I do have two banks of "panels." One bank is above the other bank and there is piping going to the lower panel which has a tee and then another pipe goes from the tee up to the other sets of panels. The same scenario holds true for the other piping except that tee is at the upper panel. The reason I have two sets of panels is because I ran out of roof area in a straight line so they were doubled up.

I should have asked questions about piping and head loss on this forum first, but I really didn't know what to ask.

So, would you suggest that I replace all the 1.5" piping with 2" piping and go with a different pump to handle both the system and solar pumping and eliminate the solar booster pump?

Just to clarify, I have 11 panels that flow 5 gpm and 5 panels that flow 4 gpm.
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Postby chem geek » Tue 13 Jan, 2009 14:44

The diagram shown here has 3 individual solar panels plumbed in parallel. This means that the cold water input to the panels is evenly distributed among all of the panels and that the output from the panels is collected equally from all of the panels.

You will also notice that in order to have the total pipe length be the same regardless of which panel water goes through, that the plumbing input goes in the opposite direction from the plumbing output. That is, the input pipe at the bottom of the panels is going from left to right while the output pipe at the top of the panels is going from right to left.

If these panels were connected in series, instead of parallel, then the output of one panel would feed the input to the next panel so you'd have a pipe at the top of the first panel go to the bottom of the second panel, etc. Connecting in series creates a higher flow resistance (head), but a lower total flow requirement since the total flow is equal to the flow through each panel. When you connect in parallel as shown in the diagram, the flow resistance (head) is lower, but the total flow requirement is higher since it is the sum of the individual panel flows.

If your panels are connected in parallel, then the total flow needed is 11*5 + 5*4 = 75 GPM which is close to the 80 GPM I used in the previous post's calculation. The way you described the piping with a Tee sounds like the two banks of panels are connected in parallel.

Anyway, as to what to do, you really do need to speak to a professional about this. I do not work in the pool industry. However, moving to 2" pipe should help a lot in your particular system and is what should have been done in the first place (in fact, if you're replacing the pipe anyway, you could even go with 2.5" pipe if you wanted to). If you do this, then you should be able to run with a single variable-speed or variable-flow pump, such as the Intelliflo, and not need a separate booster pump for the solar and you should save quite a bit on energy costs and possibly improve your solar efficiency as well (depending on current flow rates in your system).

Richard
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Postby Rick Sass » Fri 16 Jan, 2009 12:27

Thanx Richard -

Based on your description, I am using a parallel system. Since, the headers for the solar panels are 2" should I continue with 2" returns and supplies or should I increase to 2.5" piping? Would the increase in piping size to 2.5" produce a noticable benefit or is just that if I'm replacing the piping I should go with 2.5".

The contractor has already been paid about 6 months ago - do you think I have any recourse with the contractor to replace the piping or is it going to be "if I know so much, then you do it" scenario.

Thanx again for your help.
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Postby chem geek » Fri 16 Jan, 2009 13:29

There is absolutely nothing wrong with having parts of the piping be larger than other parts, especially if the longest pipe run can be larger. In fact, the most common situation is to have 2" pipe out of the pump that then gets split into individual 1.5" pipes near the pool where each goes to a separate return (since the flow is split, smaller pipes can be used to each return). Another common situation is for separate 1.5" pipes to come from the skimmer(s) and floor drain(s) and then go to separate manual valves and then come together into a short 2" pipe that feeds the pump. Basically, the resistance to flow in a pipe is non-linear with respect to the flow rate and to the pipe diameter.

At 75 GPM, the head (pressure) loss in 200 feet of pipe of different sizes is the following (I also show velocity of the water in the pipe):

SIZE . HEAD(FT) . HEAD(PSI) . VELOCITY(FT/SEC)
1.5" ...... 54 .............23 ................ 11.8
2" ......... 16 .............. 7 ................. 7.2
2.5" ........ 7 .............. 3 ................. 5.0
3" ........... 2.4 ........... 1 ................. 3.3

You can see that the biggest bang-for-the-buck is to move from 1.5" to 2" pipe. So that's a no brainer. Going to 2.5" would only make sense if the incremental cost of doing so were fairly low. If the bulk of the cost were the labor, for example, then it might be worth it. It certainly isn't a requirement and the amount of energy savings will be somewhat small (I estimate that below).

If we assume that you've got 40 feet of head (17.3 PSI) with the solar panels, returns and suction head excluding the 200' of pipe (and that's just a very rough guess; it could be more), then this is a difference in feet of head (at 75 GPM) of 56 vs. 47 which is roughly an output power difference of about 16% which might translate to an input power difference that is similar in proportion. If I assume 50% overall pump efficiency, then that could be a difference between 1580 Watts vs. 1327 Watts or a difference of about 250 Watts. Remember that I assuming you are using an Intelliflo VF pump that adjusts its speed to keep the flow rate constant.

As for recourse with your contractor, I have no idea. At a minimum, you might ask him why he used 1.5" pipe for such a long run and whether he knew the effect that would have on pressure head loss and therefore energy efficiency.

By the way, do you have a pressure gauge on your filter showing, for example, PSI? That could give us a good idea of the current overall flow resistance in your system. I want to make sure that the Intelliflo pump will be able to handle what you've got. It may not be able to at all with the 1.5" pipe and should be OK with the 2" pipe, but knowing your current PSI would let me better estimate the unknown head associated with the solar panels and the pool return lines and fittings as well as the suction line and fittings. Also, do you know your current pump brand and model number or have specs on it including Horsepower and service factor and/or have pump curves?

You should also verify your pipe diameter. I assume you have Schedule 40 pipe and if so then 1.5" is a nominal pipe size with an actual inside diameter of 1.610" and an outside diameter of 1.900". The circumference which you can more easily measure is 5.969" (about 6"). For 2" nominal pipe size, the actual inside diameter is 2.067", the outside diameter is 2.375" and the circumference is 7.461" (about 7.5").

Richard

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