By Connie Gibson Centrella
With environmental and cost concerns still top of mind in the pool and spa industry, technological changes intended to promote the energy efficiency of pool heaters are being required by many jurisdictions throughout North America. Whether prompted by legislation or just good sense, the pool and spa industry is taking steps to improve efficiency on everything from pumps and filters to pool heating and air circulation. After all, promoting energy efficiency is good business.
The energy efficiency boom
Energy efficiency is defined as using less energy to provide the same result. Energy conservation in new construction or renovation requires an understanding of hydraulics; lower velocities, larger pipe diameter, larger filters and backwash valves are all critical when developing an energy conservation plan.
When it comes to heaters, new building codes propose natural gas models cannot be equipped with constantly burning pilots. They must also deliver a thermal efficiency of no less than 80 per cent and have an accessible on-off switch mounted on the outside of the heater, allowing shut off without adjusting the thermostat. The same codes also propose heat pumps must produce a co-efficient of performance (COP) of no less than 4.0. (Industry professionals should review energy codes in their area for any recent changes.)
People are not likely to change behaviour when it comes to temperature comfort. Recreational swimming traditionally mandates water temperatures ranging from 27 to 29 C (82 to 84 F). Facilities will continue to face the challenge of maintaining a preferred temperature without prostrating their budgets. Energy-efficient heaters provide an opportunity to make commercial facilities more profitable, while keeping customers happy.
Understanding energy loss
In both indoor and outdoor pool environments, maintaining the temperature depends on elimination of heat losses; there are constant heat gains and heat losses causing the temperature to rise or fall. Understanding the effects of energy losses is important in the determination of which type of heating is the most desirable.
Energy loss primarily occurs from four different means: evaporation, convection, radiation and conduction. Ninety-five per cent of energy loss comes from the surface of the pool, while conduction heat loss of five per cent moves through structural components. Historically, energy loss has been controlled through sheltering the surface of the pool from wind, thereby eliminating surface temperature loss.
The pool environment itself also affects energy loss. In indoor pools, humidity control and ventilation produce a comfortable surrounding for bathers. Outdoor facilities are affected by wind and rain, ultraviolet (UV) rays, ambient temperatures and humidity. Relative humidity is important in heating efficiency. When the air temperature is high and relative humidity is low, evaporation (energy losses) increases; conversely, when the air temperature is high and relative humidity is high, evaporation is low. Most indoor facilities encourage a relative humidity of 40 to 60 per cent.