Variable Speed Pool Pump Savings: Part 2

Last week we started to share an incredible resource that outlines how you can save money by switching your single speed pool pump out with a variable speed pool pump.  This week we will wrap up with the report that we had found.  We truly hope that we have been able to show you how amazing the savings can be just with this swap out.  When you consider how our technology has advanced since this report has come out and how the cost of energy delivery has risen, you will see the sense that it makes to contact us for this change to your pool!  You will be able to enjoy your pool all summer long and not have to stress over energy consumption.

Installation of Variable Speed Pool Pumps

The pool pump replacement process requires a complete inspection of the outdoor swimming pool area followed by an evaluation of the energy usage and filtration flow rate of the existing pump. It also requires the removal of the existing pump and, finally, the installation and calibration of the variable speed pump. This section will include safety and health practices as well as pool volume calculation methods that are required during the inspection and replacement of the pool pump.

Inspecting the Pool Area

The health and safety of the pool pump installer, as well as the occupants, should be a critical part of the pool pump replacement process. Prior to beginning pump installation, the installer should carefully inspect the entire pool area for exposed wiring, trip hazards, pests, or animals. A thorough inspection of the pool pump containment area and any exposed plumbing should also be done to ensure that any leaks or damage to existing pool plumbing is identified and repaired. Finally, the installer should locate the main electrical circuit breaker panel and identify and confirm which breaker is designated for the pool pump.

Measuring the Pool and Calculating Pool Volume

There are two important reasons why an installer must accurately calculate the volume, in gallons, of water in the pool. First, the pool pump must have the correct flow rate (volume of water that passes through the pump) in order to meet the proper turnover rate and maintain clarity and sanitary conditions in the pool. If the pump is unable to turn over the entire volume of water within a 24-hour period, the risk of algae and pathogens can increase. A turnover every 24 hours is the minimum flow rate for the pool pump. To calculate the minimum flow rate of the pool pump, divide the total volume of the pool in gallons by 1,440 (total minutes in a day).

Total volume of pool / 1440 = Minimum Filtration Flow Rate (gpm)

The minimum filtration flow rate is the least amount of water (gpm) the pool pump must circulate through the filtration system in order to achieve the minimum daily turnover.

The second reason for calculating the pool volume is to determine the maximum pool filtration rate. The pool pump should not have a filtration rate greater than the rate needed to turn over the pool water volume in six hours, or 36 gallons per minute (gpm), whichever is greater. This equation was developed by the California Energy Commission and was adopted by the Association of Pool and Spa Professionals to help set guidelines for achieving the maximum energy efficiency in pool pump operation. To calculate the maximum filtration flow rate, divide the total volume of water in the pool by 360.

Total volume of pool /360 = Maximum Filtration Flow Rate (gpm)

For pools with less than 13,000 gallons, the pump must have a gpm rating of 36 gpm or less.

In order to determine the maximum and minimum pool filtration rates, the installer must first calculate the entire volume of pool water in cubic feet and then multiply by 7.48 (number of gallons of water contained in one cubic foot of water) to determine the total number of gallons. For simple, flat-bottomed, rectangular swimming pools this is a relatively easy calculation to perform by simply measuring and multiplying the length, width, and depth of the pool.

length x width x depth of water = cubic feet of the pool (volume of water)

The volume of water in cubic feet x 7.48 = Total volume in gallons

For instance, a rectangular pool that is 24 feet long by 16 feet wide with a consistent depth of 5 feet would have a total volume of 1,920 cubic feet of water when completely filled.

24 x 16 x 5 = 1,920 cubic feet

Once the total cubic feet of water has been calculated, that amount can be multiplied by 7.48 (gallons per cubic foot of water) to determine the total number of gallons in the pool.

1,920 x 7.48 = 14,362 gallons of water

However, because pools come in countless designs, shapes, and depths, calculating pool volume is rarely so simple. In order to calculate oblong, circular, sloped, nonlinear sloped and custom pool designs, more advanced mathematical calculations are required. There are several free pool volume calculation tools available online, including on the Pentair Pool and Spa website.

Once the total pool volume in gallons has been determined, the installer can calculate the maximum and minimum filtration rates. This information will help calibrate the new pool pump to make sure it is operating at peak performance from both a healthful and energy efficient standpoint.

Evaluating Energy Usage of Existing Pool Pump

The conventional way to calculate the amount of watts an appliance or electrical device uses is to multiply amps times volts. While this method works for an electrical direct current (DC) circuit, it is not an accurate way to calculate energy use of alternating current (AC) motors.

The equation for motors is:
Amps x Volts x Power Factor = Watts

Although every motor has a power factor rating, it can be difficult to access this information for every pump on the market, as the service factors and load factors all vary.

The best way to determine kW usage is with an RMS kilowatt meter, which tells you instantly how many kW’s the pump is using. Using a kW meter is just like using an Amp meter but you must measure both volts and amps. First, put the meter dial on kW and turn the pump on. Next. place the black and red leads on the terminals supplying voltage to the pump (this can be done at the time clock or relay, depending on the installation). Then, clamp the meter around one of the hot wires and read the pump’s kW usage. As with any electrical wiring evaluation, extreme care should be taken when using the RMS kilowatt meter, especially around areas that have standing water.

Once the wattage use of the pump has been determined, it is possible to calculate the kilowatt hours, daily and annual energy consumption of the motor, and the estimated cost of the pool pump operation.

For example, after using the RMS kilowatt meter on a 1½-hp single-speed pump; a reading of 2.07 kW is measured. In order to determine the energy consumption and estimated cost, first, convert that reading to kilowatt-hours.

2.07 kilowatts X 1 hour =2.07 kWh.

As such, in one hour, the pump will consume 2.07 kWh. Next, determine the average number of hours the pump is used daily. This can be done by reviewing the timer and by interviewing the homeowner. If the pump normally runs for six hours a day, then multiply 2.07 by 6.

2.07 kWh x 6 hours = 12.42 kWh per day

A common question related to pool pump power usage relates to how a 1½-hp motor can draw 2.07 kilowatts. This is because motors also have a service factor (SF) rating or overload capacity designed into the motor. There is a practice in the swimming pool pump industry of using high service factors where the total horsepower (and subsequent kW demand) is much greater than the nameplate would imply. For general-purpose motors, service factors would rarely be higher than 1.15. However, swimming pool motors are definite purpose motors designed exclusively for use in the pool industry. These motors are designed with exceptionally large service factors as high as 1.65 or 1.9. The result is that a 1½-hp pump with a service factor (SF) of 1.47 can easily draw around 2,100 watts or 2.1 kW.

Rated HP x SF x 746 Watts per HP /Motor Efficiency = Watts

1.5 HP x 1.47 x 746 Watts per HP / 78% = 2108 Watts

Estimate Energy Usage and Savings of a New Pool Pump

Once the energy usage of the existing pool pump has been determined, it is easy to calculate the expected energy savings associated with installing the new variable speed pool pump. To do this, first, use the pool volume calculation to determine the acceptable filtration rate. Once the flow rate has been determined, you can calculate expected energy usage by referencing the product manual of the new pool pump.

In general, the slower turnover rates associated with variable speed pool pumps should reduce energy usage between 30% and 70% annually, however, there are many variables to consider. Because there is such a wide range of pool circulation systems, conditions, and filtration needs, specific savings and performance data can only be accurately determined after the variable speed pool pump has been installed. Pool volume, ambient temperature, use, the age of system, water quality, covering, local environment (trees, grass, dirt, sand) and accessories (waterfalls, cleaners, scrubbers, fountains) all impact potential cost savings. Calculating the exact energy savings before installation may not be possible; however, comparing the existing pump usage with potential savings based on the model and type of pool pump to be installed can help encourage homeowners to invest in pool pump replacement.

Remove an Existing Pool Pump

Being prepared for the removal of the existing pool pump and installation of the new variable speed pump can make the task simpler and faster. The actual process of removing and replacing the pump is not a difficult task; however, care should be taken to ensure the safety of the worker and occupants of the home and their property. Removal and replacement of the pool pump requires the tools needed for rewiring any basic electric circuit and cutting and gluing PVC pipe. These include:

• Electrical meter: preferably True RMS clamp-on kW and multi-function style meter.

• Miscellaneous: Screwdrivers, slip-joint pliers, channel-lock pliers, wire cutters, wire strippers, wrenches, sandpaper.

• Pipe cutter: ratcheting PVC cutter, reciprocating saw, chop saw or hacksaw.

Before removing the pump, verify the electrical supply voltage and wire and circuit breaker size and ensure that these are compatible with the replacement variable speed pump and in accordance with national, state, and local codes and permits.

When selecting common PVC fittings, use of schedule 40 or 80 pipe is recommended. It is not advisable to use lower pressure rated drain, waste, vent (DWV)-style pipe and fittings for pool circulation systems. Though rare, occasionally copper pipe may be found in older pools.

To expedite the installation process, installers should have ample inventory of common materials such as 90° elbows, 45° elbows, couplings, unions, valves, pipe, PVC glue and primer, threaded nipples to attached to the pump, pipe thread compound or Teflon tape. Prior to installation, it is important to inspect and note the threaded fitting size of the replacement pump housing. Most are 2” male pipe thread (MPT), and some pumps come equipped with the threaded fittings and unions.

When inspecting the area, also measure the overall pump dimensions and compare the existing pump to the replacement variable speed unit. Pay special attention to the suction port height, and distance from pump suction port to discharge port as these critical dimensions vary amongst pumps. Have a plan for how the replacement pump will fit and where it is best to make cuts before the old pump is removed from service. Also, note locations of junction boxes to ensure sufficient wire and conduit is available.

Once preparation is complete and current electrical consumption has been measured and recorded, removal of the existing pump can begin. The process for removing the pump is as follows:

1. Open the circuit breaker to disconnect electricity to the pump.

2. Verify that the pump has been de-energized by checking with an electrical meter.

3. Disconnect electrical wires at the pump junction box.

4. Mark the location and use a pipe cutter or hacksaw to cut the discharge and suction pipe.

5. Remove the existing pump.

Installing a Variable Speed Pump

Once the existing pump is removed, ensure that the work area is clean and free of obstructions. Place the replacement pump in position and align the suction and discharge pipes. Shims may be required to compensate for varying pump heights and should be used to create a level and stable connection height. Install threaded fittings in pump suctions and discharge ports using thread sealant.

Avoid installation of 90° elbows directly into the pump inlet as these greatly increase friction or total dynamic head (TDH). If the installation allows, install a length of straight pipe at the pump’s suction port that is equal to five times its diameter. For example, with a 2” diameter pipe, it is recommended to install a straight pipe 10” long prior to entering the pump’s inlet. This practice will aid in the pump’s priming and general performance.

Connecting Fittings and Making Electrical Connections

After all fitting and connections have been made, reconnect the electrical conduit and wires per national, state, and local codes. Also, ensure the ground bonding wire is connected to the pump’s bonding lug.

Most existing single-speed pumps are electrically powered through a timer or automation system to schedule their daily operation. Newer variable speed pumps have the time clock and scheduling feature inherent in their control system. For these pumps, it is preferable to wire them directly, bypassing the existing time clock. For installations with remotely operated automaton systems, the pump may be powered through relays. This is done to ensure that the pump has a continuous uninterrupted power supply.

Calibrating Variable Speed Pump for Optimum Performance

After installation is complete, the installer must program the new pump to obtain adequate filtration, in-pool circulation, and water clarity while using the lowest possible motor speed.

Filters only capture what is suspended in the water passing through them, and only what is large enough to collect on the filter media. Once debris and sediment enters the water, one of three things will happen: it will float, sink, or get suspended in the water. Floating matter can be skimmed off the surface to be collected and removed, but once it sinks to the floor, it will stay there without some kind of help to remove it. Variable speed pumps need to run longer to accomplish the required turnover due to their lower flow rates. As a result, the pool spends much more time skimming the water and preventing debris from sinking.

The result is a cleaner pool with improved water clarity and is another benefit derived from running pumps at a slower rate and for longer periods of time. The variable speed pump should be set up to operate at a speed that will turn over the pool volume at least once during every 24-hour period. For pools with high debris and/or bather loads, additional turnovers may be required to maintain adequate water quality. In no event should the turnover time be less than six-hours during normal operation.

Reducing the flow through main drains by throttling the drain’s return line valve (if applicable) can improve skimmer performance by providing the pump with most, or all of the water from the skimmer. However, this configuration must be tested to confirm the pump is supplied with enough water when operating the pump at the highest speed needed by the pool. This is often not the highest speed at which a pump can operate and should only be high enough to achieve the intended purpose, such as operating cleaner therapy jets, or a water feature. Essentially, the goal is always to provide sanitation and to accomplish the desired feature operation at the lowest flow rate.

The start-up flow rate may need to be higher for several minutes to fully prime the pump, purge air from the filter, and fill solar panels with water. Once these start-up tasks have been completed, the pump speed can be reduced to the energy efficient low-speed setting.

Pools sometimes need higher turnover flow rates. For example, following a storm or pool party, higher turnover flow rates may be required It is advantageous to have this feature set up in advance to provide the pool owner with a mode that will temporarily override the normal filtration flow rate without the need for reprogramming the pump controller.

Verification and Filtration Flow Rate Testing

Always follow the pump manufacturer’s instructions and guidelines, especially the warning and safety instructions. The instructions listed here are not intended to be comprehensive and do not substitute for adherence to the manufacturer’s instructions.

During the removal and installation process, air can enter the system and become pressurized. Before system start-up, the pump and system must be manually primed and evacuated of air. Care should be taken to vent system air through the filter’s manual relief valve.

Caution: do not run the pump dry. To prime, remove the strainer pot lid and fill the pump with water until the level reaches the suction port, and then replace the strainer pot lid. This prevents the pump from running dry, which will damage the mechanical seal. Start by opening the manual relief valve on top of the filter and then press the button to start the pump. Next, you must bleed air from the filter until a steady stream of water comes out, and then close the manual air relief valve.

Remember, the basic premise of variable speed energy-saving pump operation is “run it slower and run it longer.” By running the pump slower, a slight reduction in water flow (gpm) will greatly reduce the electrical demand (kW). By reducing the flow rate, the runtime will have to increase to ensure that the water is adequately filtered and mixed.

After the pump has been started and is successfully circulating water through the filtration system, filtration flow rates need to be verified. Water is supplied to the pump from both the skimmers and main drains; however, the skimmers should supply the majority of the flow. Minimum filtration flow rates need to ensure that the skimmers function adequately. Most skimmers take approximately 25 gallons per minute (GPM) of flow for adequate performance. Verification of performance can usually be accomplished by visually observing surface water drawn into the skimmer face and over the weir door. Skimmer baskets need to be checked and cleaned regularly. Main drain flow should complement the skimmer flow but should be minimized to prevent suction entrapment hazards. The main drain and suction covers should be visually observed. A broken or missing drain cover poses a serious health risk and should be replaced immediately, even before the pool is returned to service.

Programmable Pumps and Maintenance

Note that some variable speed pumps may be capable of producing a maximum flow rate higher than the existing single-speed pump. Excessive flow rates can present hazards such as suction entrapment. Use caution when installing and programming to limit pump’s performance potential with old or questionable equipment and to avoid suction entrapment hazards.

Many variable speed pumps have the ability to schedule features throughout the day. As such, the pump may unknowingly start to initiate a scheduled feature. Never leave the pump unattended and power supplied while the pump is in an unsafe condition unless the pump’s programming cycles are understood (for example, strainer pot lid removed or pipes not connected and system not primed).

Maintenance for variable speed pumps is generally the same as that for single-speed pumps.

Pump strainer baskets (sometimes referred to as “hair and lint pot”) must be kept clean of leaves and debris at all times. A dirty basket can impact pump and system performance and make the system difficult to prime.

Protect motors from heat by ensuring that there is shade from the sun and that ample ventilation is available. Particular attention should be paid to the motor’s fan cover and cooling fins to ensure there are no obstructions to air flow.

Motors should also be protected from dirt and moisture. Avoid splashing with water. Do not store or spill chemicals next to the motor. Avoid installations next to lawn sprinklers and protect them from the weather.

Some variable speed pumps come equipped with freeze protection to assist with winterization. This feature will automatically start the pump when temperatures reach a predetermined level to prevent freezing of the pipes. Whenever systems are drained, power should be removed from the pump to avoid inadvertent starting of the pump.

Once the variable speed pool pump has been successfully installed and tested, the next critical step is to train the homeowner on the capabilities, functions, operation, maintenance, programming, and potential risks associated with the new pump. In order to ensure that energy savings are actualized, the homeowner must understand that the lower flow rates will provide adequate filtration for the pool. However, it is also important to educate the homeowner on the signs of a potentially unclean pool and equip them with information and knowledge to maintain a healthy swimming environment.

The final step in installing the new pump is to accurately measure the energy use of the new pump and compare it the findings when you measured the energy use of the old pump. This comparison will act as a guide for the homeowner to understand optimum pump use and potential savings.

We are so grateful to the Department of Energy for conducting this study for all of us to benefit from.  If you want to read the entire report from them be sure to click here.  If you are ready to start talking to us about making this switch, be sure to contact us today!  We look forward to helping you save money on your energy bill and enjoying your pool all summer long!