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Storage Water Heaters
With a storage water heater cold water from the home.s water supply is heated by a thermostat controlled gas burner. The heated water rises to the top of the tank, where a delivery pipe sends it where it is needed. When hot water leaves from the top and cold water replaces it at the bottom, the burner, lit by a pilot light or electronic spark ignition, automatically comes on. The burner will also come on if the water in the tank drops below a pre-set temperature. A relief valve protects against temperature or pressure that is too high for the tank.The insulated storage tank is usually made of steel and is lined with glass or another material to prevent corrosion. The tank also contains an "anode" rod composed of one or more metals that attract corrosion away from the rest of the tank.s components.
Storage water heaters are freestanding, and offer a wide variety of venting configurations, allowing homeowners may installation and location choices. Some models can even be installed outdoors without any kind of housing or cover. Because installation is relatively simple, they're a good choice for homes converting to a natural gas water heating system.
Considerations:
- Capacity. Don.t buy a water heater larger than you need. While many consumers base their purchase on storage tank size, the first-hour rating (FHR) is actually more important. FHR, required by law to appear on the Energy Guide label, is the measure of how much hot water the heater will deliver in an hour. Before you shop, estimate your household.s hot water needs and look for a water heater with an FHR in that range.
- Efficiency. The energy efficiency of a storage water heater is indicated by its "Energy Factor" (EF). The higher the EF, the more efficient the water heater. Most gas water heaters have an EF between 0.50 and 0.60, with some high-efficiency models around 0.80. Also, look for tanks with at least 1.5 inches of foam insulation.
- Cost. It may be tempting to buy an inexpensive water heater and ignore the operating cost. This is not recommended. Often the least expensive water heaters are the most expensive to operate. A high-efficiency water heater may cost a little more, but reduced operating costs will more than make up for the higher outlay. Use the Energy Guide label to help you choose an energy-efficient heater.
- Venting. All natural gas water heaters must be vented to the outdoors to remove the by-products of combustion. A wide variety of venting options are available.
- Atmospherically vented gas water heaters are the most common type. Because the flue gases from the water heater are warmer than the surrounding air, they will rise naturally through a vertical vent pipe or chimney. These units don.t need help from fans or other mechanical boosters, which keeps installation and operating costs down. All atmospherically vented gas water heaters can use either a standard metal vent or a masonry chimney.
- Direct-vent or horizontally vented water heaters are designed for installations where vertical chimneys or flues are not available or would be more expensive to install. The vents go directly through an outside wall, and also can bring combustion air to the gas burner. Most of these units require zero-clearance at the sides and rear, which allows them to be installed in a small area.
- Fan-assisted or power-vented gas water heaters use an electric fan or blower to push out combustion gases. This type of venting allows gas water heaters to be installed as far as 40 feet away from an outside wall and in homes without existing vertical vents. The flue or vent pipe can be hidden behind walls and cabinets. Other gas equipment installed with the water heater can use the same power venting system.