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Tankless Water Heater Information

Tankless Water Heaters
Tankless water heaters, also called combination or "combi" boiler, instantaneous, continuous flow, inline, flash, on-demand or instant-on water heaters, are gaining popularity. The main advantages of a tankless water heater is a continuous flow of hot water and energy saving heating. Tankless water heaters heat the water as the water flows through the device, and do not retain any water internally except for what is in the heat exchanger coil. Point-of-use (POU) heaters are typically installed right at the faucet or in the bathroom, far form the central water heater.

Tankless water heaters are divided into two categories: "full on/full off" and "modulated". Full on/full off units do not have a variable power output level; the unit is either on or off. Modulated tankless water heaters base the heat output on the flow of water running through the unit. This is usually done through the use of a 'flow sensor', modulating gas valve, inlet water temperature, sensor and outlet water temperature sensor-choke valve and means that the occupants should receive the same output temperature of water at differing velocities.

Tankless heaters are generally more efficient than storage water heaters. In both kinds of installations (centralized and POU) the absence of a tank saves energy as conventional water heaters have to reheat the water in the tank as it cools off, called standby loss.

Point of use tankless water heaters are located right where the water is being used, so the water is almost instantly hot, which saves water. They also save energy because no hot water is left in the pipes after the water is shut off. However, point of use tankless water heaters are usually used in combination with a central water heaters since they are usually limited to 1.0 - 2.5 gallons/minute, as the expense of buying a heater for every kitchen, laundry room, bathroom or sink, often outweighs the money saved in water and energy bills.

Since the water in a tankless water heater must be heated instantly, tankless water heaters use a very large amount of electricity or gas while they are on. If a storage water heater is being replaced with a tankless one, the size of the electrical wiring or gas lines may have to be increased to handle load.

    Main advantages of tankless water heaters:
  • Virtually endless how water
  • Easy to install
  • You are not paying energy costs to heat water 24 hours a day
  • Electrical units can be installed at the point of use
Resources
- U.S. Department of Energy Water Heating Guidance
- How It Works - Water Heaters, Popular Mechanics

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