The Department of Housing and Urban Development (HUD) residential solar heating and cooling demonstration program provided funding support for over 600 solar projects. These projects provide the largest single data base of solar heating and cooling experience now available. These data suggest that controls were problematic in many of the active and passive heating and domestic hot water systems in the program. This paper will assess the active system modes of operation and the control components as to their ability to perform as intended. A large number of systems in the demonstration program experienced control problems during testing, checkout, and operation (there were 238 reported control problems involving 192 systems). Frequently, trouble-shooting site visitors found control problems had disabled the whole system or caused a portion of the system to malfunction. The consequences are not as significant on the more carefully designed systems (i .e ., the auxiliary still functions) but, on systems with inappropriately designed solar-,auxiliary interfaces, the homeowners often were without adequate heat.

The most common control problems involved excessive modes in system and, therefore, control design ; errors in sensor set points, location, or installation; and poorly engineered or installed wiring to and from controller panels.

Units: Dual