Today there are three main types of water heaters used in residential heating and cooling systems; quick-recovery, slow-recovery and heat pump water heaters.
This class of heater, as the name implies, has the ability to produce hot water at a more rapid rate than the slow-recovery type of heaters. It is frequently employed where repeated heavy requirement for hot water makes it essential to have a sufficient amount of water available on demand.
Thermostats used are of the throttling or snap-action type. Primarily the throttling thermostat is the one in which the amount of gas valve opening is directly proportional to the temperature changes of water in the tank. In the snap-action thermostat, the change from a completely open to a completely closed position of the valve, or vice versa, is accomplished by a snap action produced by a clicker diaphragm motivated by the temperature in the tank.
Slow-Recover Heaters:
The gas-fired slow recovery water heater is designed to keep a supply of how water in the storage tank and by means of a constantly burning gas flame, deliver hot water continuously to this tank.
Thermostats employed can be of the graduating or snap-action type. With the graduating thermostat, the burner operate between a low and high flame. The low position of the flame serving as a pilot light to keep the heater lighted and serving as a source of standby heat.
The slow-recovery automatic water heater is very economical since it can never burn more than a certain amount of gas, depending on the regulation offered by the thermostat. Also, the small amount of heating surface keeps the standby loss at a minimum, making this type of heater very advantageous where economy is the primary concern.
Heat Pump Water Heaters
A heat pump water heater consists of a small electrically operated compressor, the heat pump and domestic water supply controls, and a water storage tank. It uses the heat of the air in the room and energy used to operate its compressor to heat the water in its storage tank. Unlike conventional gas operated or electrical resistance water heaters, the heat pump water heater does not create heat. It transfers heat from one point to another. It is essentially a small heat pump that uses the room air as the heat source and the water in the storage tank as the heat sink. Because it is a heat pump, it can also cool the air and dehumidify it.
These three types of water heaters can be installed by any Denver hvac company. They are very common types of residential water heaters and have their own benefits.
(This article is from James Brumbaugh’s book “HVAC Fundamentals (Volume 3): Air conditioning, Heat Pumps and Distribution Systems”)
