HVAC Heating Systems 2 — Questions and Answers
Question 1: What is a heat pump's Heating Seasonal Performance Factor (HSPF) used to measure?
- The efficiency of heat pump cooling in summer
- The seasonal heating efficiency of a heat pump (Correct answer)
- The airflow capacity of a heat pump system
- The refrigerant charge level in a heat pump
Correct answer: The seasonal heating efficiency of a heat pump
HSPF measures the total heating output of a heat pump divided by the total electrical energy it consumes over a heating season.
Question 2: What is auxiliary (emergency) heat in a heat pump system?
- A backup cooling mode for the heat pump
- Electric resistance heating that supplements or replaces heat pump heating (Correct answer)
- A gas boiler connected in series with the heat pump
- The defrost cycle heating mode
Correct answer: Electric resistance heating that supplements or replaces heat pump heating
Auxiliary heat is typically electric resistance heating strips inside the air handler that assist the heat pump during very cold weather or emergency operation.
Question 3: At what outdoor temperature does a standard heat pump typically lose efficiency and need supplemental heat?
- 50°F (10°C)
- 32°F (0°C)
- Below about 35-40°F (2-4°C) (Correct answer)
- 20°F (-7°C)
Correct answer: Below about 35-40°F (2-4°C)
Standard heat pumps begin losing significant efficiency around 35-40°F, though modern cold-climate heat pumps can operate efficiently at much lower temperatures.
Question 4: What is the purpose of a defrost cycle in a heat pump?
- To cool the indoor coil during summer
- To remove frost that accumulates on the outdoor coil during heating mode (Correct answer)
- To defrost the expansion valve when iced over
- To warm the refrigerant before compression in cold weather
Correct answer: To remove frost that accumulates on the outdoor coil during heating mode
During cold weather, frost forms on the outdoor coil; the defrost cycle temporarily reverses the refrigeration cycle to melt this frost and maintain system efficiency.
Question 5: What type of heating system uses water as the heat transfer medium distributed through pipes to radiators or radiant floor tubing?
- Forced-air system
- Hydronic heating system (Correct answer)
- Steam heating system
- Geothermal system
Correct answer: Hydronic heating system
A hydronic heating system uses a boiler to heat water, which is then circulated through pipes to baseboard radiators, panel radiators, or radiant floor tubing.
Question 6: What is the purpose of a zone valve in a hydronic heating system?
- To control water pressure throughout the system
- To control the flow of hot water to a specific heating zone (Correct answer)
- To prevent backflow from the boiler
- To mix hot and cold water to achieve the correct supply temperature
Correct answer: To control the flow of hot water to a specific heating zone
Zone valves open and close in response to zone thermostats, allowing independent temperature control of different areas in a hydronic system.
HVAC Heating Systems 2
What is a heat pump's Heating Seasonal Performance Factor (HSPF) used to measure?