How Does A Hot Water Heater Work?

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Understanding How Water Heaters Work

Water heaters are obviously an essential part of our plumbing systems. They are also something that most people never really give much thought to. With this in mind, we’re going to take an in-depth look at the different types of water heaters and how each one works to ensure you have a steady supply of hot water.

Women soaking baby in tub with hot water from water heater

Types Of Water Heaters

Traditional water heaters are the kind that most homes use, and these units depend on either gas or electricity to heat water inside a large storage tank. There are also tankless water heaters that don’t store any hot water. Instead, they only heat water on demand when it is called for. You can also find electric heat pump water heaters as well as indirect water heaters. The latter are passive units that rely on the heat from a boiler to keep water inside the tank hot.

How Traditional Water Heaters Work

Traditional water heaters work in essentially the same way regardless of whether the unit is powered by gas or electricity. Whenever any hot water is used, the same amount of cold water flows into the tank. It flows through a long pipe known as the drip tube and into the very bottom of the tank. This prevents the cold water from mixing with the hot water higher up in the tank, which is important since the hot water is always drawn from the top. The only issue is that if you use most of the hot water, the tank will fill with cold water, and then you may need to wait 30 minutes or more before the water reheats.

Gas units have a burner that combusts natural gas or propane to create heat. This process causes the heating element in the bottom of the tank to become extremely hot, and the heating element in turn raises the temperature of the water in the tank. The combustion chamber at the bottom of the unit is connected to a large exhaust pipe that runs up through the tank and out of the top. The combustion fumes created by burning gas flow up through this pipe and are eventually vented outside the building.

Electric units work similarly except that they use electric resistance coils to make the heating elements warm enough. Electricity flows through the coils and causes them to become glowing hot, and this heat is then used to keep the water inside the tank warm. Most electric water heaters have two heating elements, one at the bottom of the tank and another near the middle.

The main issue with traditional water heaters is that the units need to run at least a few times every hour in order to keep the water in the tank hot. This leads to lots of energy waste since the unit will continue heating whether you’re using any hot water or not. Traditional units are also prone to leaking as they age. This happens because minerals in the water slowly corrode the tank and can weaken it to the point where it eventually develops a leak.

How Tankless Water Heaters Work

Tankless water heaters are far more energy efficient than traditional units since they only ever heat water when hot water is needed. Compared to traditional units, a tankless water heater will typically use anywhere from 10% to 40% less energy. Tankless heaters can either be whole-house units or point-of-use, which means they only provide hot water to one faucet or fixture.

Gas tankless units work using a metal heat exchanger similar to that found in gas furnaces. Burning gas produces extremely hot combustion fumes, which travel through the heat exchanger and then out through the exhaust flue. The combustion fumes cause the heat exchanger to become extremely hot in just a few seconds. Electric tankless units work basically the same way except that they use an electric resistance coil to make the heat exchanger extremely hot.

Whenever hot water is needed, the water heater opens up a valve so that cold water begins flowing through the unit. This cold water flows over the heat exchanger, which then heats the water up instantly to anywhere between 120 and 160 degrees Fahrenheit. As soon as no more hot water is called for, the unit turns off and closes the valve to shut off the water flow.

The main issue with whole-house tankless units is that they typically have a longer lag time. Depending on the distance between the water heater and the plumbing fixture, it can take anywhere from 15 seconds to a minute or two from the time that you turn on the hot water until it actually starts flowing out of the fixture. Traditional units typically only have a few seconds of lag time since they always keep the water hot instead of only heating on demand.

How Heat Pump Water Heaters Work

Heat pump water heaters are a relatively new type of unit that uses electricity and refrigerant to absorb heat from the surrounding air and transfer it to heat the water inside the tank. A fan draws warm air into the unit and forces it over a coil filled with cold refrigerant. Heat energy from the air is absorbed by the refrigerant, which eventually causes the refrigerant to boil and turn into a hot gas. Inside the water heater tank are additional refrigerant coils. The hot gas refrigerant flows through these coils, and the heat energy is released to heat the water inside the tank.

Heat pump water heaters are far more energy efficient than traditional water heaters, and they usually have similar operating costs to tankless units. Many heat pump water heaters are hybrid units that also have electric heating elements. The unit can switch over to using these in colder conditions when there is very little heat energy in the air.

How Indirect Water Heaters Work

Indirect water heaters work alongside a boiler to supply hot water. These units are unique in that they don’t use any power on their own. Boilers are employed to heat water for radiant heating systems, but most boilers can’t also supply hot water for plumbing because the system is a closed loop. For a traditional boiler to also supply hot water, it requires a passive water heater located next to it.

A passive water heater has a large storage tank where the water is heated. A pipe runs from the boiler into the tank. Inside the tank are several coils just like in a heat pump water heater. Hot water from the boiler is pumped into the pipe, through the coils, and eventually back to the boiler, and this process works to heat the water inside the indirect water heater tank.

If you need any water heater service in the Morgantown or Pittsburgh areas, our team at Absolute Air is here for you. We repair and maintain most types and brands of water heaters, and our experts can also assist with installation and replacement. In addition, we offer a full range of heating, cooling, and indoor air quality services, including inspection, testing, installation, maintenance, and repair. To schedule any water heater or HVAC service, give us a call today.

Published: December 20, 2022

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