Figure 15-10. - A DHW system with heat exchanger in hot-water storage tanks.

heat exchanger cannot be used effectively in this system.

Space Heating and DHW Systems

Space heating systems are a simple extension of the domestic hot-water (DHW) systems (fig. 15-10). The collectors and storage tank need to be resized to provide greater loads. A heat delivery system is added and the auxiliary heater (or existing heater) is connected into the system as backup. The design of the space heating system, if a retrofit, depends on the existing system. Water-to-air heat exchangers may be placed in existing ductwork, in which case, an unpressurized, unlined tank may be used. This represents a minimum heating system, as shown in figures 15-11 and 15-12.

Domestic hot water could be added to the system shown in figure 10-33 by adding a preheat coil in the storage tank. Figure 10-31 has the potential to provide some cooling to the building by using the collector at night to radiate heat to the sky and store cool water for use during the day. A heat pump is another option that could be used to cool the building, reject the heat to the storage tank during the day, and then, as before, cool the tank at night through the solar collectors. Unglazed collectors are superior to glazed collectors for this application. There are many variations that can be used with the configurations shown.

Air types of space heating systems are receiving increased attention, and a typical system