Combination Space/Water Heater

Space heating can represent the largest use of energy in residential and small commercial applications. With space heating being a large portion of the energy budget, new technologies such as heat pumps, condensing furnaces, and pulse combustion are gaining in popularity. Water heating is a smaller portion of the energy budget, and standard efficiency water heating equipment is relatively inexpensive. As such, it is often difficult to justify hundreds (or thousands) of dollars of efficiency improvements on water heating systems.

Combination space/water heaters, also known as integrated systems, allow for the advances in heat pump, furnace and boiler technology to be used to efficiently heat water and provide space heating. There are three basic configurations for these systems: 1) Indirect space heating, or modified water heating systems that heat water for domestic use and also circulate hot water through a finned-tube coil, which transfers heat to air that is blown over the coil, 2) Indirect water heating, or modified systems that heat water for space heating and either utilize a heat exchanger in the boiler to heat domestic water or redirect the flow of heated water through the domestic hot water storage tank as necessary, 3) Integrated heat pump systems which provide space heating, domestic water heating, and space cooling, either in combination or independently.

Indirect space heaters employ a very high efficiency water heater to provide both domestic hot water and space heat. In gas-fired units, enhanced heat transfer results in flue temperatures so low that PVC pipe can be used as a vent pipe, and flue gases can be vented through sidewalls as well as through the roof.

Indirect water heaters employ a very high efficiency furnace or boiler and a water heater. An intermediate fluid passes from a coil in the furnace combustion chamber to a heat exchanger coil in the hot water tank heating the water. Combination space/water heaters can reduce hot water costs 5% to 10% annually.

Integrated heat pump systems utilize the vapor compression refrigerant cycle to heat domestic hot water while either heating or cooling the home. During the heating cycle, some of the heat absorbed from the outside air or ground is used for domestic hot water. During the cooling cycle the heat that would normally be rejected to the outside is used to heat domestic water. These devices utilize the relatively constant, mild temperature of the earth or ground water to enhance performance.

Combination space/water heaters are economically practical in most new installations and in many cases where the boiler or furnace must be replaced. Many combination space/water heaters offer quicker water temperature recovery rates than standard water heaters. As such, they can be made smaller to take up less space in basements, closets, and crawl spaces. With condensing combustion technology and integrated heat pump systems, a heating system and water heater can be installed without a single through-the-roof chimney.