A thermal system is used for heating fluids. An open-loop system heats domestic water directly and is used in tropical regions where freezing never occurs. A closed-loop system, used in colder climates, is a pressurized system that heats a 50/50 mixture of glycol and water. The heat is transferred through conduction to the domestic water. Thermal panels will generally be connected with copper pipes and fittings and may have low-voltage control wiring attached. The most common-sized module is four feet by eight feet; several can be tied together in a system. The hazards that a thermal system presents for firefighting operations, for the most part, are obvious: hampered vertical ventilation if the system is installed on the roof; structural collapse because of the added weight; tripping and slipping hazards; inhalation hazards from combustion by-products; and a potential for burns from hot fluids (generally 50°-90°F on a cold cloudy day and 120°-180°F on a hot and sunny day).
(1) A pressurized rooftop thermal system with four foot by eight foot panels.
Wear a self-contained breathing apparatus when operating in the area of a module impinged by fire because of the materials used in the manufacturing of PV modules (i.e., phosphorous; gallium arsenide; and cadmium, a known carcinogen).
(2) A PV system mounted on the roof.
(3) A PV system designed to look like conventional roof shingles.