VARIABLE SPEED POOL PUMPS *Info courtesy of energy.gov
If you own a pool, then the pool pump is probably the largest electric motor in your home. It also consumes up to a few thousand kilo-watt hours per year, making it second only to to your air conditioner or heat pump. You can save energy and maintain a comfortable swimming pool temperature by using a smaller, higher efficiency pump and by operating it less.
In a study of 120 pools by the Center for Energy Conservation at Florida Atlantic University, some pool owners saved as much as 75% of their original pumping bill when they used these energy conservation measures (see table below).
Table 1. Savings from Pump Conservation Measures
|CONDITION||ENERGY USE (KWH/YEAR)||COST OF ENERGY ($/YEAR)||ENERGY SAVINGS|
|Pump replacement (downsizing)||1800||140||40%|
|Reduced time (60%)||1200||100||60%|
|Combination of above||720||60||75%|
Table courtesy of Home Energy magazine. These savings represent a typical pool in Florida. The average pool pump energy bill is probably higher in Florida than in many other areas of the country because of the long swimming season. While the absolute savings here will be greater there than elsewhere, the percentage savings should apply nationwide. Note that the savings for the combination of measures are not simply the sum of savings for the individual measures. When both are implemented, the energy use is 60% of 40% of the original use-percent savings.
The larger the pump, the greater your pumping and maintenance costs. Therefore, you want to use the smallest size pump possible for your swimming pool. To choose the right size pump, you can consult a pool supplier's design chart. Using the chart, match the hydraulic characteristics of the pump to both the piping and the pool's flow characteristics. For a solar pool heating system, you also need to consider the need to pump the pool's water to and through the collector(s).
The Florida study shows that a 0.75 horsepower or smaller pump is generally sufficient for residential pools. Smaller pumps, which cost less, can be used if you decrease the pool circulation system's hydraulic resistance by doing the following:
- Substituting a large filter (rated to at least 50% higher than the pool's design flow rate)
- Increasing the diameter or decreasing the length of the pipes, or replacing abrupt 90-degree elbow pipes with 45-degree ones or flexible pipes.
By decreasing the pool circulation system's hydraulic resistance, you can reduce the pump's electricity use by up to 40%.
Operating the Pump
Pool pumps often run much longer than necessary. Circulating your pool's water keeps the chemicals mixed and removes debris. However, as long the water circulates while chemicals are added, they should remain mixed. It's not necessary to recirculate the water everyday to remove debris, and most debris can be removed using a skimmer or vacuum. Furthermore, longer circulation doesn't necessarily reduce the growth of algae. Instead, using chemicals in the water and scrubbing the walls are the best methods.
Reduce your filtration time to 6 hours per day. If the water doesn't appear clean, increase the time in half-hour increments until it does. In the Florida study, most people who reduced pumping to less than 3 hours per day were still happy with the water's quality. On average, this saved them 60% of their electricity bill for pumping.
You can install a timer to control the pump's cycling. If debris is a problem, use a timer that can activate the pump for many short periods each day. Running the pump continuously for, say, 3 hours leaves the other 21 hours a day for the pool to collect debris. Several short cycles keep the pool cleaner all day.
Keep the intake grates clear of debris. Clogged drains require the pump to work harder, which uses more energy. Backwash your filter appropriately. Backwashing too frequently wastes water, while not backwashing wastes energy by requiring the pump to work harder.
HEAT PUMP POOL HEATERS *Info courtesy of energy.gov
A heat pump is a device that uses a small amount of energy to move heat from one location to another. Heat pumps used for heating pools transfer heat from the outdoors into the water. Because they use heat that is already available and just move it from one place to another, they use less electricity.
How a Heat Pump Pool Heater Works
As the pool water circulates through the pool pump, it passes through a filter and the heat pump heater. The heat pump heater has a fan that draws in the outside air and directs it over the evaporator coil. Liquid refrigerant within the evaporator coil absorbs the heat from the outside air and becomes a gas. The warm gas in the coil then passes through the compressor. The compressor increases the heat, creating a very hot gas that then passes through the condenser. The condenser transfers the heat from the hot gas to the cooler pool water circulating through the heater. The heated water then returns to the pool. The hot gas, as it flows through the condenser coil, returns to liquid form and back to the evaporator, where the whole process begins again.
Higher efficiency heat pump pool heaters usually use scroll compressors versus the reciprocal compressors of standard units.
Heat pump pool heaters work efficiently as long as the outside temperature remains above the 45ºF–50ºF range. The cooler the outside air they draw in, the less efficient they are, resulting in higher energy bills. However, since most people use outdoor pools during warm and mild weather, this usually isn't an issue.
Selecting a Heat Pump Pool Heater
Heat pump pool heaters cost more than gas pool heaters, but they typically have much lower annual operating costs because of their higher efficiencies. With proper maintenance, heat pump pool heaters typically last longer than gas pool heaters. Therefore, you'll save more money in the long run.
When selecting a heat pump pool heater, you should consider its:
Sizing a Heat Pump Pool Heater
You should have a trained pool professional perform a proper sizing analysis for your specific pool to determine pool heater size.
Sizing a heat pump pool heater involves many factors. Basically, a heater is sized according to the surface area of the pool and the difference between the pool and the average air temperatures. Other factors also affect the heating load for outdoor pools, such as wind exposure, humidity levels, and cool night temperatures. Therefore, pools located in areas with higher average wind speeds at the pool surface, lower humidity, and cool nights will require a larger heater.
Heat pump pool heaters are rated by Btu output and horsepower (hp). Standard sizes include 3.5 hp/75,000 Btu, 5 hp/100,000 Btu, and 6 hp/125,000 Btu.
To calculate an approximate heater size for an outdoor swimming pool, follow these steps:
- Determine your desired swimming pool temperature.
- Determine the average temperature for the coldest month of pool use.
- Subtract the average temperature for the coldest month from the desired pool temperature. This will give you the temperature rise needed.
- Calculate the pool surface area in square feet.
- Use the following formula to determine the Btu/hour output requirement of the heater:
Pool Area x Temperature Rise x 12
This formula is based on 1º to 1-1/4ºF temperature rise per hour and a 3-1/2 mile per hour average wind at the pool surface. For a 1-1/2ºF rise multiply by 1.5. For a 2ºF rise multiply by 2.0.
Determining Heat Pump Pool Heater Efficiency
The energy efficiency of heat pump pool heaters is measured by coefficient of performance (COP). The higher the COP number, the more efficient. The federal test procedure for heat pump pool heaters sets the test conditions at 80ºF ambient dry bulb, 63% relative humidity, and 80ºF pool water. COPs usually range from 3.0 to 7.0, which converts to an efficiency of 300%–700%. This means that for every unit of electricity it takes to runs the compressor, you get 3–7 units of heat out of the heat pump.
Estimating Heat Pump Pool Heater Costs and Savings
For an outdoor pool, use the following tables to help estimate your annual heat pump pool heater costs and savings compared to using an electric resistance or a gas pool heater.
Table 1. Costs by Location of Heating Outdoor Pools with a Heat Pump*
*Figures based on a 1,000 square foot, outdoor pool heated with an air to water heat pump with an average COP of 5.0 at $.1301/kwh.
Table 2 estimates the savings for every $1000 in annual pool heating costs using a heat pump pool heater compared to using an electric resistance or gas pool heater with an efficiency of 55% (baseline).
Table 2. Annual Savings Comparisons of
Gas and Electric Pool Heaters*
|EFFICIENCY||ANNUAL COST||COST W/ 5.0 COP||HEAT PUMP SAVINGS|
|Gas Pool Heater|
*Based on an electric resistance heated pool, which costs $1,000 per year at an electric cost of $.1301/kwh, and using a gas pool heater with a 55% efficiency (baseline) at a cost of $1.09/therm. A seasonal average COP of 5.0 was used to determine heat pump savings.
Installation and Maintenance
Proper installation and maintenance of your heat pump pool heater can optimize its efficiency. It's best to have a qualified pool professional install the heater, especially the electric hookup, and perform complicated maintenance or repair tasks.
Read your owner's manual for a maintenance schedule and/or recommendations. You'll probably need to tune up your pool heater annually. Because of a heat pump pool heater's many moving and electrical parts, it will probably require periodic service by an air conditioning technician.
With proper installation and maintenance, heat pump pool heaters can last 10 or more years.
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$75- $600 Rebates
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