Heating I Section#1 Furnace - Gas and Oil Quiz#4

This study session deals with furnace heat exchangers, furnace cabinetry, fan controls and limit controls.

The estimated completion time for this study session is sixty minutes.

Objectives
At the end of this study session, you should be able to:

• List two problems commonly found with gas furnace heat exchangers.
• List six problems found with furnace cabinetry.
• Describe the setting and function of the three fan/limit controls.
• List six problems found with fan controls

List 3 reasons why cracks or holes may develop in furnace heat exchangers.

1. Rust
2. Metal fatigue
3. Manufacturing defects.

List 6 conditions commonly found with furnace cabinetry

1. Rust
2. Mechanical damage
3. Missing components
4. Inadequate combustible clearances
5. Obstructed air intakes
6. Scorching

List 6 conditions commonly found with limit switches.

1. Set wrong or defective
2. Scorching
3. Rusting
4. Mechanical damage
5. Improperly wired
6. Missing cover

List and describe the settings on the fan/limit switch.

Fan off - indicates the temperature at which the house air fan stops (typically 80F to 110F) Fan on - indicates the temperature at which the house air fan starts. (typically 120F to 150F) High limit - indicates the temperature at which combustion is stopped for safety (typically 170F to 200 F)

Most conventional gas furnaces have how many cabinet doors which we can easily remove to gain access to components?

Two - the blower compartment door, and the burner compartment door.

Where possible, you should watch the flame pattern of a gas furnace to:

Look for changes in the flame pattern when the house air fan turns on. This indicates heat exchanger failure.

Soot in a draft furnace heat exchanger can be caused by (check as many as apply):

incomplete combustion

misalignment of burner

over-firing of the burning

plugged vent

Using a mirror and flashlight to view the heat exchanger on a gas furnace allows you to see:

less than 20% of the heat exchanger

The use of electronic combustible gas analyzers is beyond the scope of our Standards.

true

Visual inspection of heat exchanger using a mirror and flashlight is required by the ASHI® Standards.

true