FC FC Combustion & Fuel Systems 2

Question 1

What instrument is used to measure gas manifold pressure on a furnace?

Accepted Answer

Manometer

Answer

Ammeter

Answer

Flue gas analyzer

Answer

Anemometer

Question 2

What is the typical supply gas pressure (upstream of the gas valve) for a natural gas furnace?

Accepted Answer

5–7 inches W.C.

Answer

1–2 inches W.C.

Answer

3.5–5 inches W.C.

Answer

10–14 inches W.C.

Question 3

A cracked heat exchanger is most likely to allow which dangerous gas to enter the living space?

Accepted Answer

Carbon monoxide

Answer

Propane

Answer

Nitrogen dioxide

Answer

Sulfur dioxide

Question 4

What is the primary purpose of a draft inducer motor on a high-efficiency furnace?

Accepted Answer

To pull combustion gases through the heat exchanger and exhaust them outdoors

Answer

To circulate warm air through the ducts

Answer

To pre-heat incoming combustion air

Answer

To control burner ignition timing

Question 5

Which type of ignition system uses a resistance element heated to approximately 1,800°F to ignite the gas?

Accepted Answer

Hot surface igniter

Answer

Standing pilot

Answer

Intermittent pilot

Answer

Spark igniter

Question 6

What causes delayed ignition (a loud boom or puff) when a furnace starts up?

Accepted Answer

Gas accumulating in the combustion chamber before igniting

Answer

Excessive gas pressure

Answer

A faulty limit switch

Answer

Low blower speed