How Exactly Does A Heat Pump Water Heater Work?

Heat pump water heaters are special hot water appliances that can produce nearly three times the electric energy needed to run them. That is most astonishing because the basic laws of physics tell us no energy can be created out of nothing. As a matter of fact, a heat pump water heater does not create heat. It pumps the heat from one medium to another, as the name implies.

Heat moves from one place to another all the time but almost always, the movement is from hotter medium to cooler medium. The specialty of heat pumps is luring the heat into the hot water tank so the water keeps getting hotter while the air in the room gets cooler. This is possible by harnessing an interesting property of gaseous substances. Gases heat up when exposed to pressure and will eventually condense to a very hot liquid form. That means you can compress a gas to create a hot liquid, which in turn could be used to heat other stuff. Naturally, a continuous supply of the substance in gas form would be required because it is being converted to a liquid in the process. It is the heat of the ambient air that ensures the substance evaporates back to gaseous state.

To make things a little more clear, let use first name the substance we are talking about. Heat pump water heaters contain a special chemical called a refrigerant. For instance, Steibel Eltron Accelera 300 model, deemed as the best heat pump water heater, uses R134a. What makes a refrigerant special is having the right boiling and condensation temperatures for efficiently tranferring the heat. The refrigerant begins its cycle as a cool liquid that moves out of the water heater’s heat exchanger after losing its heat to the water in the tank.

The refrigerant passes through pipes exposed to the ambient air and evaporates due to the ambient heat. The process is often faciliated through the use of mechanical fan that blow the air onto the evaporator. At this stage, the refrigerant picks up a lot of heat and gets back to gas state, too but it is still far too cool to heat any water. Its energy has to be concentrated by the compressor.

The compressor is a mechanism that applies pressure on the gaseous refrigerant and forces it to get back to liquid state. This causes the chemical to become hot enough to heat the water in the tank. Sent into pipes that run through the water heater. Moving through the heat exchanger, our hot liquid friend gets back to its cool state and is ready to restart the cycle.

Heat pumps water heaters do not produce free hot water. They need electric energy to run the fan and the compressor and can even activate their electric resistance heaters if the normal heat pump funtion is unable to heat the water fast enough.