The water is too cold! The water is too hot! The water is not hot enough!
The major reasons for heating a pool are for swimmer comfort, relaxation, exercise and therapy. Aquatic facility managers must regulate pool heating based on the various usages of the facility.
As seen in the following table, competitive swimmers enjoy a cooler temperature while students in “teaching children to swim” programs desire 84 degrees.
Efficient use of energy is prominent in today’s news. The pool industry is no different, and is faced with the challenge of creating products that will heat a pool and spa with a minimum amount of cost and harm to the environment.
Today’s aquatic facility management has many choices available for heating options: gas (fossil fuel), electric, boilers, solar, and heat pumps. And there are new approaches that allow managers to provide heat by geothermal heating (taking heat from the ground).
To begin, let’s look at the history of the various heating processes:
· Gas (1620)–French missionaries recorded that Indians in what is now New York State ignited gases in the shallows of Lake Erie and in the streams flowing into the lake. It was in this same area that the natural gas industry in America began.
· Electric (1882)–Thanks to Thomas Edison, the first electric power plant opened in New York, making it possible to have an inexpensive source of energy for residential and commercial buildings.
· Solar (18th century)–Though civilizations have long sought to capture the sun’s rays for uses ranging from weapons to cooking, the first solar water heating collector appeared over 200 years ago.
· Heat Pumps (1977)–New technology allowed heat pumps to operate at lower outdoor temperatures while heating on the reversed refrigeration cycle.
The first heated swimming pool is believed to have been built c. 40 B.C., by the wealthy Roman diplomat, Gauis Cilnius Maecenas, at his palace and gardens on the Esquiline Hill in Rome. ¹
(¹Famous First Facts, International, Edition, edited by Steven Anzovin and Janet Podell, Section 5817)
Fossil-fueled (gas) heaters have been the most prominent source of heating for several decades due to low gas prices. However, this has changed with the increase in fossil fuel costs, as much as $100 per barrel, according to recent figures. Gas heaters operate by burning fuel–either natural gas or propane. The major advantages of this type of heat are: fast heat-up time, quiet operation, and providing heat regardless of the ambient temperature. The major disadvantage to gas heaters is the burning of fuel, which must be vented to the outside air; the burning of gas creates carbon monoxide, which can cause death without proper ventilation. There have been serious accidents and/or deaths in aquatic environments due to inadequate ventilation. The diagram below shows an example of proper installation of a gas heater within a room. Aquatic facility managers should consult the specific heater manufacturer installation manual for accurate measurements.
Outdoor installations must also provide adequate clearances from any adjoining structure, and manufacturers’ installation manuals should be consulted to be sure that carbon monoxide does not enter into public areas.
Major strides in engineering of heat pumps have been made due to higher fossil fuel costs. Heat pumps provide the advantages of maintaining heat with a low cost of operation; the heater can operate day or night (unlike solar), and is environmentally friendly (no admittance of carbon monoxide). Although electricity is used to operate the compressor and the fan, the energy source to heat the pool is either air or water– geothermal. The only limitations are the heat pumps must be installed outdoors to obtain air for operation. In addition, the heat pump is not a fast heat machine; however, once it heats up, the heat will remain more stable than that of gas heaters. Aquatic facilities with adequate outdoor space are now installing these systems on their pools as shown in the photo. The sizing of heat pumps is based on the number of gallons of water and desired temperature. The aquatic operator should obtain a sizing calculation from the heater manufacturer. One of the factors in sizing is Coefficient of Performance.
Solar heating obtains its heat source from the sun, which offers free heat. The solar (collector) panels are installed either on the roof of a facility or in an area near the pool. The pool water is heated as it travels through these collector panels. Another major advantage of solar heat is that it is environmentally friendly. The disadvantages are the amount of space required for the collector panels and the need for sunshine to operate. Auxiliary heaters are usually installed to enable the facility to maintain the desired pool temperature.
Gas heaters, solar heating and heat pumps are the most widely used forms of pool heating in the 21st century. Electric resistance heaters have proven to be very expensive in heating large volumes of water. Spa and hot water therapy pools are able to utilize this type of heating due to the small volume of water.
Any discussion of pool heating should include ways by which heat is lost in a pool. Evaporation, convection, radiation and conduction all play a part in heat escaping from a pool. The major heat loss (50 percent) comes from evaporation. Designers and engineers are constantly looking at ways in which to minimize evaporation. Outdoor installations experience evaporation and convection. To visualize convection, imagine blowing on a cup of coffee to cool down the temperature. Outdoor environments experience convection with the wind blowing over the surface of the pool. This is one of the reasons landscape architects surround pools with hedges and fencing to eliminate the wind factor. Indoor pools have three interacting factors–the water, the indoor air and the ventilation system. Maintaining the relative humidity at 40 to 60 percent and the air temperature at 2 degrees Fahrenheit above the water temperature, and keeping indoor ventilation air exchanges 8 to 10 times per hour will eliminate some of the evaporation loss.
Maintaining a facility’s pool temperature is one of the greatest challenges of any pool operator. Achieving swimmer comfort and an enjoyable aquatic experience is vital. It is of the utmost importance that the operator investigates all the advantages and disadvantages of each type of heating prior to making any renovation or equipment change to the facility. Also, with such an emphasis on energy conservation, as well as on the critical need to eliminate toxic air into the atmosphere, it is prudent for the operator to review all considerations.
Connie Gibson Centrella is Program Director for the online Aquatic Engineering Program at Keiser College eCampus. She is an industry veteran with over 40 years experience in the pool and spa industry. She is a former pool builder with extensive knowledge in pool construction and equipment installation as well as manufacturing.
About the Keiser College Aquatic Engineering Degree
The Keiser College Associate of Science Aquatic Engineering Degree is a two-year degree consisting of 60 semester hours. Each student is required to complete 36 credit hours of major courses and 24 credit hours of general education courses. The degree program encourages students to broaden their knowledge in all aspects of swimming pool and spa management and operation. It is offered exclusively online, making the degree program available to the national and international community of pool and spa professionals, and those seeking employment in the field. The online format enables schedule flexibility and increased access to those currently employed.