Final answer:
Heat traps should be installed on b. the hot and cold water piping above a storage water heater to prevent natural convection that can cause energy loss.
Step-by-step explanation:
The question pertains to the installation of heat traps in residential heating systems or appliances. Among the choices provided, heat traps should be installed on the hot and cold water piping above a storage water heater (option b). Heat traps are devices that prevent unwanted convective heat flow within water pipes. They are commonly installed in the piping above a hot water tank to prevent natural convection from drawing hot water into the piping system when there is no demand for hot water, thereby conserving energy.
Gravity furnaces and heat pumps use convective loops and work principles to transfer energy and maintain indoor temperatures. However, heat traps are not typically associated with the condensate drain from an air handler drip pan, the flue of a naturally-vented furnace, or the inlet piping to a washing machine. These are not locations where heat traps would be effective or necessary for energy conservation.