How Water Heaters Work
Hot water heaters convert energy into heat. This heat is transferred to water, which makes the water hot. A cold water supply pipe connects to the heater and a system of hot water pipes going out from the heater supplies water to various taps or appliances. A thermostat controls the temperature of the water.
Most water heaters use natural gas as fuel to heat the water, while others use propane, electricity or even fuel oil. Natural gas-powered heaters are less expensive than electric water heaters. Conventional water heaters store hot water in a cylindrical tank. If the tank is not insulated properly, heat escapes via the sides of the tank, resulting in energy waste.
Types Of Water Heaters
Storage-type water heaters use electricity, natural gas, propane, or oil. Water is heated in the tank to the specified temperature. The heater turns on and off to maintain the heat. When hot water is used, the heater switches on to heat the incoming cold water to make up for what you have used. Since the water is being heated continuously, it can waste energy, even if you are not using it -- this is called standby loss.
Tankless instant water heaters, or demand water heaters, heat water instantly and do not store hot water. Cold water goes into the unit through a pipe and a gas burner or an electric element heats the water when required. You can get continuous hot water through this type of water heater. Since there are no standby losses, energy is not wasted. If your hot water needs are not much larger than normal, the low flow rate won't matter to you.
Heat pump water heaters transfer heat from one place to another instead of generating heat directly. They use electricity to do this. Heat pump water heaters can be integral units with built-in water storage tanks or add-ons that can be retrofitted to an existing water heater tank. Initial cost is high and heat pump water heaters must be installed in specific locations.
Tankless coil and indirect water heaters use your home space heating system to heat water. Water heats inside the boiler and then flows through a heat exchanger every time you turn the tap on. Indirect water heaters require a separate storage tank because heated water flows to an insulated storage tank.
Solar water heaters, when properly designed, installed, and maintained, can take care of your hot water needs. They have a storage tank and a collector and use the sun's energy for heating water. Passive solar heaters don.t use pumps and controls and are said to be more reliable, easy to maintain, and less expensive than active systems. Active solar heaters use pumps and controls to pass the heat transfer fluids from the collectors to the storage tanks, which have an inlet and outlet.
Heat recovery units (HRU) use air conditioners' hot refrigerant to make hot water. The compressor's hot refrigerant and the cooler water from the bottom of the water heater enter the HRU. Heat from the air conditioner heats the water.
While choosing a new water heater, you need to consider the capacity, efficiency and cost, as well as the actual usage pattern. Water heaters can use 15-20% of the total energy you use, so it's important to choose the type of heater that is most appropriate for your needs.