Choosing a system
Heating systems commonly used for pools include the following, each with its own advantages and drawbacks.
Fossil fuel heaters
Fossil fuel (gas and propane) heater manufacturers have made great strides toward improving product efficiency. Gas heater efficiency is based on the ratio of usable output to energy input. In other words, an 80 per cent efficient heater produces $80 worth of useable heat for every $100 of fuel. This increase in efficiency depends on the age of the existing heating unit. Within the past 20 years, the efficiency of gas heating appliances has increased from 60 to 80 per cent, a respectable improvement. Since gas heat offers the fastest heat, which can also be provided on demand, the increased efficiency is all the more noteworthy.
Solar-powered heaters
Solar energy is free once the system is in place and has passed through the payoff period—that is, the amount of time it will take to recoup the initial investment in the system. The design of solar heating depends primarily on how the sun reaches the pool area. The sizing of solar collector panels is vital to system efficiency. In addition, average regional temperatures, collector panel orientation and tilt and collector efficiency must be sized to fit the needs of the property. Solar heating efficiency is based on a solar performance rating, which is measured by the BTU per square foot, per day—the higher the rating, the greater the efficiency.
Most pool applications employ an open-loop system, which uses a single pump for both the pool and collector loops. When no heat is required, the pump bypasses the solar panels. A solar heating installation usually requires a backup heater to meet the desired temperature when cloud cover or cooler air temperatures prevail.
Air-source heat pumps
Air-source heat pumps are gaining acceptance even in cooler climates. A heat pump is actually a proactive collector of solar heat from ambient air. It does not burn energy to create heat; it only burns energy (electricity) to transfer heat from the outside air to the pool water. It is also considered an effective clean energy appliance.
Heat pump efficiency depends on the COP. Put simply, a COP of 5.0 means that for every dollar of energy input, $5 of heat will be gained. The COP varies depending on air temperature, relative humidity and pool water temperature. Therefore, the COP will not be high in cooler climates as it is in warmer ones.
The Montreal Protocol requires all heat pumps to be remanufactured to use R410A refrigerant as of January 1, 2010. The R-22 refrigerant is being phased out because of the chlorodifluoromethane (HCFC) affect on ozone depletion. The new R410A is a near-azeotropic, homogeneous mix that does not damage the ozone layer.
