Forced-Air Heating Systems 030203b

Question 1

What are the two most common materials used for electric heating elements and what are they generally encased in?

Answer 1

Nichrome & Tungsten.

Encased in a protective insulating material like ceramic, mica or glass.

Question 2

What is the control circuit voltage of a 120V heating system?

Answer 2

Control circuit power rating of 120V. Requires no 24V transformers. Gas valve is designed to operate at 120V.

Question 3

What is the purpose of a step open gas valve?

Answer 3

Limits the initial flow of gas to the ignition source to prevent a large explosion.

Question 4

What is the device called that stops the gas flow to the pilot flame as well as opens the circuit to the main gas valve?

Answer 4

100% shutoff valve, safety gas valve, or automatic pilot valve.

Question 5

What is the valve called that controls the flow of gas directly by means of an electrically operated plunger?

Answer 5

Solenoid valve.

Question 6

Where should solenoid and diaphragm valves be installed?

Answer 6

Downstream of the safety gas valve.

Question 7

What is the most common gas control device currently available?

Answer 7

Combination gas valve.

Includes a gas regulator, safety gas valve, power unit, main gas valve, and a manual gas shutoff all in one unit.

Question 8

What are the two types of fans in a forced air heating system?

Answer 8

Belt-driven type.

Directly coupled drive type.

Question 9

What is the range that the high limit switch is usually set to?

Answer 9

82 degrees Celsius to 93 degrees Celsius.

Resets when the temperature drops 11 degrees Celsius below the thermostat set point.

Question 10

What is the range setting for the Fan-on and fan-off function?

Answer 10

Fan-On - 49 degrees Celsius to 60 degrees Celsius.

Fan-Off - 32 degrees Celsius to 38 degrees Celsius.

Question 11

What is a down flow furnace?

Answer 11

Air is blows downward and force heated air through ductwork in or below the concrete slab floor.

Question 12

What is the electrical energy that comes from the thermocouple used for?

Answer 12

Operating the power unit.

Question 13

What safety pilot device provides 100% gas shutoff?

Answer 13

Safety gas valve.

Question 14

What is the AFUE (Annual Fuel Utilization Efficiency) rating of a high efficiency furnace?

Answer 14

90% to 98%

Question 15

What is the Annual Fuel Utilization Efficiency (AFUE) rating of a mid efficiency furnace?

Answer 15

80% to 83%

Question 16

What is the minimum Annual Fuel Utilization Efficiency (AFUE) rating for a new standard furnace?

Answer 16

78%