Since water heating is a thermodynamic process using an energy source to heat water above its initial temperature and comprised of parts that can fail, maintaining its hot water production is crucial to your home needs. Typical domestic uses of hot water are for cooking, cleaning, bathing, and space heating. Commercial applications include both hot water and heated water to generate steam. Water heaters, boilers and heat exchangers are the mechanical processes used to heat water for a variety of domestic and commercial uses. Water heaters come in two basic forms: tanks and tankless.
Some of the more popular domestic water heaters are:
Conventional Tank Water Heaters
Most water heaters are tank water heaters which keep a cylindrical tank full of hot water in your home at all times. The typical sizes available for household water heaters that utilize a tank are between 20 and 100 gallons. When hot water is required the water is circulated to the open faucet. Conventional tanks utilize electric, natural gas, propane, oil, solar or geothermal power as an energy source to heat the water.
Electric Water Heaters
Water HeatersThe typical electric water heater is wired to a 220-volt circuit. To heat the water, the current passes through electrical-resistance heating elements—usually two, one at the middle of the tank and one at the bottom.
Power is delivered to each element through a thermostat—a switch that senses the water temperature. When the temperature drops, the switch closes to allow current flow, and it opens when the temperature reaches its preset limit. Thermostats have a dial for setting the maximum water temperature--generally between 130 degrees and 140 degrees F, or as low as about 120 degrees F for increased energy savings and scald protection.
When a hot water tap is opened, cold water enters the tank through the dip tube and the drop in temperature triggers the thermostat and element at the bottom. As the water at the top of the tank is replaced by cool water, the temperature at the top thermostat drops, and its element kicks in. When the tap is turned off, the heating elements continue to carry current until the thermostats are satisfied.
Gas-Fired Water Heaters
An alternative to electric water heaters is gas-fired, usually utilizing natural gas or propane. Instead of electrical-resistance elements, gas-fired heaters have a burner that's fed gas through a control valve and a thermostat switch. The burner is usually situated to throw a flame under the tank. The exhaust gases are vented either through a hollow core at the center of the tank or around the tank sides. Because gas-fired heaters heat the tank, which in turn heats the water, there will be more wear and tear on the tank than with electric heat. A gas-fired heater, therefore, may have a shorter life expectancy than an electric heater.
Tankless Water Heaters
A tankless water heater, also called instantaneous, only provides hot water as needed, saving energy and, therefore, saving you money. They are designed to heat water directly without the use of a tank and are more efficient than conventional water heaters. The primary energy sources for tankless heaters are natural gas and propane. Tankless heaters are typically more efficient than storage water heaters. 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. With a central water heater of any type, water is wasted waiting for water to heat up because of the cold water in the pipes between the faucet and the water heater. This water waste can be avoided if a re-circulating pump is installed, but at the cost of electricity to run the pump and wasted energy to heat the water circulation through the pipes. At Benjamin Franklin Plumbing® we offer our own brand of tankless water heater, goHot TM that delivers an endless supply of hot water through a piece of equipment the size of a briefcase.
Solar Water Heaters
For some areas, solar powered water heaters are used. Their solar collectors are installed outside the home, typically on the roof or nearby. Nearly all models are the direct-gain type, consisting of flat panels in which water circulates. Other types may use dish or trough mirrors to concentrate sunlight on a collector tube filled with water, brine or other heat transfer fluid. A storage tank is placed indoors or out to collect the heated water. Circulation is caused by natural convection or by a small electric pump. At night, or when there is insufficient sunlight present, circulation through the panel can be stopped by closing a valve and/or stopping the circulating pump, to keep hot water in the storage tank from cooling. Depending on the local climate, freeze protection, as well as prevention of overheating, must be addressed in the design, installation, and operation of the water heater.
Hot Water Circulating Pump
Hot water circulating pumps are often used to circulate domestic hot water so that a faucet will provide hot water constantly upon demand. Since water is piped from the water heater through the pipes to the tap, once the tap is shut off, the water remaining in the pipes cools, producing the familiar wait for hot water the next time the tap is opened. A circulator pump insures the hot water in the pipes is always hot, minimizing the wait.
Federal Tax Credits
Federal tax credits may be available for a number of home water heating improvements. Contact us for more information on available tax credits for energy-efficient installations.
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