Free Sample
The Complete Handbook of Pool Heaters
A practical reference for installers, service technicians, facility managers, and pool owners who need to select, install, maintain, and repair pool heating systems with confidence.
by Alumigogo Books
Chapter 1: Understanding Pool Heaters
A pool heater is an engineered appliance designed to transfer heat into a body of water with a specific temperature goal in mind. Its job is not merely to make the water warmer; it is to maintain a target temperature across varying ambient conditions and to recover lost heat from evaporation, convection, and pool use. Understanding this starting point - that you are buying a heat-transfer device operating under changing loads, not a simple on/off appliance - separates good purchasing decisions from expensive mistakes.
What a pool heater actually does
Consider an in-ground residential pool in the northeastern United States. It is 20 by 40 feet, holds roughly 34,000 gallons of water, and is used from late May through early September. The owners want it at 84 degrees Fahrenheit. On a mild June day with an air temperature of 70 degrees and a light breeze, the pool will lose approximately 8 to 10 degrees Fahrenheit per day if left completely unheated, depending on the wind speed and humidity. That is the baseline you are fighting. On a windy, cooler night in early spring, the heat loss accelerates due to increased evaporation and convection from the water's surface. A heater must replace this energy loss, continuously, just to hold the set point, and it must supply additional energy to raise the temperature at the start of the season or after a cold snap.
That energy requirement is measured in British Thermal Units per hour, commonly abbreviated