Multi Speed/Two Speed Swimming Pool Pumps

DWP in Los Angeles is giving $500.00 rebates on these pumps

Links near bottom of page for various pumps

So how do multi speed pumps save electricity and how do they work?

Here is some real world examples:...on a 28,000 gallon pool I installed a Pentair PEN011012 variable speed pump and set pump to turn entire volume of pool over once a day running 18 hours a day using less than 300 watts while running. Her old pump had a 2 HP motor drawing 11.5 amps and ran 8 hours a day at an average of over 21 kilowatts a day....she now runs at 5 kilowatts a day. So she saves about 75% a year. At an average of 14.5 cents a kilowatt,thats over 800.00 a year savings.

On another customer,he was running a 1.5 HP pump 8 hours a day at around 15 kilowatts at .20 cents a kilowatt hour or $3.00 a day....his new pump (Pentair PEN011018) runs at 2000 RPM's for a half hour in the morning and a half hour at the end of day to run pool cleaner,and 7 hours a day in skimmer mode at 1400 RPM's for a total of 2 kilowatts a day or .40 cents a day for a savings of about 949.00 a year - however when he uses his solar heating he uses a higher speed (2500 RPM's to pump water up to second story roof) which comes to 7 kilowatts a day for lets say four months of the year so the ACTUAL savings is probably a little over 800.00 a year give or take depending on how many months or days of the year he uses his solar heating. He COULD solar heat his pool at a much lower speed but he wanted a waterfall like effect from his raised spa overflowing to his pool even in solar heat mode.

The examples above were in southern california which may have a higher rate than your area,and were large upper middle class homes that may have been on a higher tier rate - also the pumps were running in the middle of the afternoon which is the peak rate especially in summer. Its quite possible their savings are actually higher but I just went by an average kilowatt rate.

I have installed many 2-speed pumps and have come to the conclusion they are an inefficient compromise compared to multi speed pumps for several reasons:

1)Although they are less expensive,they require some type of automation to prime in high speed for a minute or two before going to low speed to prime. The automation devices can negate the cost savings.

2)A two speed pump is about 1750 rpms at low speed...a multispeed pump can run much lower.

3)Even at the same speed,the permanent magnet multi speed pump is more efficient.

4)The rebates from ultility companies (up to 1000.00) usually only apply to multiple speed pumps.

Pump Affinity Law

Speed R.P.M.(revolutions per minute) = Flow G.P.M (gallons per minute)

Speed R.P.M. = Power3 (energy used)

Example: Reduce speed

3000 RPM --> 1500 RPM

1/2 Speed RPM = 1/2 GPM

1/2 Speed RPM = 1/2 x 1/2 x 1/2 = 1/8 energy used

3000 RPM -> 1000 RPM

1/3 Speed RPM = 1/3 GPM

1/3 Speed RPM = 1/3 x 1/3 x 1/3= 1/27 energy used

On the last example above,you can see how you must run pump 3 times longer because you are pumping only 1/3 the gallons per minute....however,you are only using 1/27 the energy so even if you run pump three times as long,you are only using 1/9 the energy and thats where the savings are!

Multi speed pumps offer several advantages over single speed pumps

1)Much quieter(can be run at night even if next to a bedroom window and will run cooler)

2)In some areas electricity is less expensive at night especially in summer

3)Water filters better at low speed,resulting in smaller particles being filtered out(especially noticeable at night with pool light)

However,there are some circumstances where low speed on a 2-speed motor cannot be used:

1)If your swimming pool equipment is much higher than pool level (unless you have a "programmable" system where the pump can come on at high speed for a few minutes to catch prime and then switch to low speed. (many varible speed pumps have the programming built in)

2)If you have solar panels and water must be pumped up to roof (again if you have programmable system with valve that closes when solar panels are not being used then the pump can be switched to a low speed at these times,and if you have a multiple speed pump the speed can be set somewhere in between high and low for pumping up to roof)

3)If you have a suction type automatic pool cleaner,it may not work on low speed. It depends on the type of cleaner and the HP of pump. For example,I have found that Kreepy Krauly pool cleaners work great on low speed,however some cleaners like Pool Vac or Navigator may work on a 2 HP low speed pump but not a 1.5 HP low speed pump. If you have a dedicated line for a pool cleaner and automatic controls,the pool cleaner can be programmed to come on high speed for an hour, and then the valve turned by actuator to skimmer and motor switched to low speed for rest of night. Also, some multi speed pumps (such as Pentair models) have a 3 H.P. sized impeller, unlike most two speed pumps, so the impeller pulls more water even at lower speeds.

Below are a few different types of multi speed pumps

Below are the keypads-an LCD screen denotes it has the built in controller to qualify for rebate programs.

1)Easy to install because it comes with unions,a handle to carry,multiple base options to match the plumbing height of several different manufacturers existing pumps. Probably a good choice for a do-it-yourselfer with limited tools

2)Can work with thinner wiring (14 gauge) because its limited to 2 HP (the Pentair needs 12 gauge in case its run at full speed but can be programed with a speed limit)....again,if you are installing yourself and have thinner 14 guage wiring this is one less thing to do.

3)Jandy is a well known name with excellent factory support

The Cons:

1)Cost the same as the Standard Pentair varible speed 3 HP pumps - even though most existing pools can never use that much horsepower,I would think running a 3 HP motor/impeller combination at a slightly lower speed would be more efficient or at least less wear on the motor than running a 2 HP motor/ impeller at a higher speed for the same flow rate...but then again I am not an electrical engineer so perhaps I am wrong.

2)Pump portion of pump/motor combo is not as hydraulically efficient as existing Pentair pumps so you probably have to use a few watts more for the same flow..its probably not a huge number,but if they are close to the same price,why not get the more efficient pump and more powerful motor combination?

Shown below is the Pentair Whisperflo XF pump,which is NOT a multi-speed pump YET...but when the multi-speed version comes out,I expect it to dominate the market:

1)It will have one of the best permanent magnet motors available

2)High hydraulic efficiency

3)Unions for easy intall

4)A large,hard basket which keeps it shape

5)A carrying handle

6)Able to except 2.5" or 3" plumbing

7)Because of its market domination,parts will be easy to acquire

1)Can save more electricity than 2 speed pumps(depending on speed selected and 2 speed pump's HP). With multi speed pumps you get a lower low setting and a higher high setting. A two speed pump has a set horsepower at high speed,and low speed is half the RPM's...so with a multi speed pump you can use less electricity than a two speed pump on day to day filtering, but get higher flow than a two speed pump for something like a waterfall or spa jets.

2)Have built in software that shuts pump off if it runs dry saving costly repairs

3)Built with permanent magnet motors that produce less heat than regular induction motors,and also 30% more efficient (even at high speed)

4)Has software that automatically finds the most efficient speed to run(RPM's)

5)If you have automatic controls,you set a different speed for different functions(low speed for filtering,high speed for spa jets,medium for a waterfall or other water feature,etc.

6) Rebates that now apply for 2 speed/multi speed pumps may only apply to multi speed pumps in near future

7)Also available with software that shuts off pump in case of cavitation (such as a child getting stuck on main drain) or pump running dry

Disadvantages:

1)More expensive than two speed pumps (however with the controls now required by utility companies to qualify for rebates they are about the same or at least not much different)

2)If you are in an area where electrical rates are cheap,it may not be worth it to buy a multi speed pump (instead of an efficient SINGLE SPEED 1/2 HP fully rated pump running at the time of day or night with the best electical rate) unless:

A):You have a waterfall,fountain,spa,or the equipment is raised above the level of pool or some other reason you may need a higher horsepower or more rpm's than a two speed pump or 1/2 HP single speed pump

B):You have a large pool which requires more time to turn over water

C):You simply want the MOST energy savings and the best equipment.

The link below will take you to a pool pump energy cost calculator that will give you a basic idea of energy savings with one of these type of pumps:

Pool Pump Energy Calculator

Pentair Multi Speed Pumps

Hayward Ecostar Pump

Marathon Impower Motor

Jandy VS Flo Pro Pump

Jandy E Pump (shown at top of page)