Heating I Section#1 Furnace - Gas and Oil Quiz#11

This study session deals with gravity gas furnaces and combination furnaces. As well, life expectancies of furnaces are briefly discussed.

The estimated completion time for this study session is forty-five minutes.

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

• List the similarities and differences between gravity and forced air furnaces.
• List ten problems commonly found with combination furnaces.
• Describe the life expectancies of different efficiency gas furnaces.

Explain briefly how combination furnaces use the water heater to heat the house.

The combination furnace pumps hot water from the water heater when the thermostat calls for heat. This water passes through a water-to-air heat exchanger (coil), where the house air picks up heat from the water to deliver to the rooms. The cooled water is then returned to the water heater for reheating.

List 4 advantages of a combination system over a conventional furnace arrangement with a water heater.

1. One burner for water heater

2. No heat exchange, inexpensive

3. Safer

4. High efficiency

List 5 ways that gravity furnaces are similar to forced air furnaces.

1. The burners are the same. They can be coal, oil, gas or propane burners

2. The combustion air requirements are the same. Since the burners are the same, it makes sence that the combustion air requirements would be the same. 

3. The venting requirements are the same. Again, since the burners are the same, the way to take out exhuast is the same

4. The heat exchanger is the same

5. High-temperature limit switch works the same way

List at least 6 ways that gravity furnaces differ from forced air furnaces.

1. No blower fan

2. Gravity furnace is larger. 

3. Usually in the center of the house

4. Supply and return ducts are different 

5. no fan control switch 

6. no filter

7. humidifier is different

What is the function of a tempering valve in a combination furnace?

The tempering valve cools the domestic water if the water heater is set above 140F in order to heat the house air

Do our Standards require that we report on the life expectancy of furnaces?

No

What is the typical life span for a conventional gas furnace?

20 to 25 years