Which statement correctly describes the heat source in a residential forced-air heating system?
- AIt must be a gas-fired water heater
- BIt must include central air conditioning to provide heat
- CIt must be a gas-fired boiler
- Forced air describes heat distribution and does not by itself require a direct-vent gas furnace
Where to look it up
https://www.energy.gov/sites/default/files/2013/11/f5/hvac_guide.pdf
Why D is correct
Forced-air heating moves heated air through an air-distribution system. It does not specify a single fuel or appliance: an electric furnace is one example that uses forced-air distribution without gas combustion. The actual equipment and installation must meet their applicable requirements; the distribution label alone does not establish a gas-furnace mandate. Source: https://www.energy.gov/sites/default/files/2013/11/f5/hvac_guide.pdf