Tank water heaters 219
Reversed connection 219
Relief valve 220
Rumbling noise 222
Exhaust stack 222
Operational inspection 223
Water heater replacement 224
Water heater capacity and recovery 225
Tankless coil water heaters 226
Inspection procedure 228
Indirect-fired storage water heater
Checkpoint summary 229
Hot water for bathing and washing (domestic hot water) is produced through a separate tank-type water heater, through the heating-system boiler (steam or hot water) by a tankless coil, or through an indirect-fired storage water heater. Domestic hot water is considered by manufacturers as cold water whose temperature has been raised 100° F. An important consideration in the design of water heaters is the ability of the unit to raise the temperature of 1 gallon of water 100° F. This criterion is used in evaluating the recovery rate for tank heaters and the water-flow rate for tankless coil heaters. These items will be discussed in the sections that follow.
The temperature of domestic hot water is important for energy conservation and safety. The operating temperature range for most water heaters is between 120° F and 160° F, although in some cases it is possible to achieve temperatures of 180° F. Normally, a thermostat setting that produces a water temperature of 140° F will be adequate for household chores, including the use of automatic clotheswashers and dishwashers. However, for washing dishes by hand or bathing, temperatures of 120° F are more than adequate. In fact, a 120° F water is above the tolerance level of most people and will have to be mixed with cold water. Setting the thermostat so that the water temperature exceeds 140° F is wasteful of energy and will shorten the life of the water heater. In addition, a water temperature in excess of 160° F is a potential hazard because of the possibility of being scalded while showering (if the mixing valve should be faulty).