HVAC Heating Systems

Question 1

What is the Annual Fuel Utilization Efficiency (AFUE) rating used for?

Accepted Answer

Rating the seasonal efficiency of fossil-fuel heating equipment

Answer

Rating the efficiency of air conditioning systems

Answer

Measuring airflow in forced-air systems

Answer

Calculating heat loss through building walls

Question 2

What is the minimum AFUE required for a gas furnace to qualify as high-efficiency in the US?

Accepted Answer

90%

Answer

80%

Answer

95%

Answer

78%

Question 3

In a gas furnace, what is the purpose of the heat exchanger?

Accepted Answer

To separate combustion gases from the conditioned air while transferring heat

Answer

To mix combustion gases with supply air

Answer

To control the flow of gas to the burners

Answer

To recover heat from the flue gases in the chimney

Question 4

What type of venting is typically required for a 90%+ AFUE condensing gas furnace?

Accepted Answer

PVC plastic pipe venting

Answer

Category I metal flue venting

Answer

Type B double-wall vent

Answer

Masonry chimney

Question 5

What is the ignition system called that replaced the standing pilot light in modern gas furnaces?

Accepted Answer

Hot surface ignitor (HSI)

Answer

Thermocouple ignition

Answer

Glow plug ignition

Answer

Piezo ignition

Question 6

What safety device shuts off a gas furnace if the heat exchanger area overheats?

Accepted Answer

High-limit switch

Answer

Pressure switch

Answer

Flame sensor

Answer

Rollout switch