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Boiler Technologies

How Boilers Work
Boiler water is chemically treated to maintain proper operation of the boiler and therefore is not usable for domestic hot water purposes. It can, however, be put to work heating potable water. One of two methods is employed.

Internal heat exchanger storage systems are equipped with a tank containing the water to be heated for service use. The high temperature boiler water (usually 180oF) circulates through a heat exchanger located in the storage tank where heat from the boiler water is transferred to the stored water. A higher capacity version, called a pumped external heat exchanger, employs a pump to achieve greater heat transfer in a smaller heat exchanger.

An alternative method is the tankless coil water heater system. A hot water coil is immersed in the hot water heating boiler. There is no external storage and the boiler operates each time there is a demand for hot water. Water flows through the coil and is heated continuously.

Unless the boiler provides a year round use, such as sterilization in a hospital, either method can be inefficient during the cooling season when a boiler, sized for a combined heating and water heating load, is used for water heating only. Seasonal efficiencies as low as 30% are possible. Tankless coil water heaters can be made more efficient by the use of a shell-and-tube type heat exchanger because the heat of the high-temperature water in the shell reduces the need to fire the boiler for every hot water demand.

Energy Types
Boilers can operate on natural gas, various types of fuel oil (#2, #4, #5 and #6), coal, wood and electricity.

For more information about Boilers, visit the Boilers module of the Industrial Advisor.