Course: HET 130 Heating Residential Appliances

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Lab Assignment

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Week 8 Lab Assignment: High Efficiency Furnaces

Recommended Materials

1. PPE
2. Hand Tools
3. Notepad
4. Pencil
5. Hot Surface Ignition
6. Hot Surface Igniter
7. High Efficiency furnace
8. VOM
9. High Temperature Thermometer

Scope

The student will discover how to identify components found on high efficiency furnaces, test a high limit switch, check the draft switch with an ohm-meter, and check the gas valve with a manometer.

Procedures

1. Turn the power off.
2. Locate a high efficiency furnace.
3. Remove the door panels.
4. List out all the components and its location on this furnace.
5. Put the door panels back on except the burner section door panel.
6. Locate the high limit switch.
7. Record the temperature setting on the high limit.
8. Insert a high temperature thermometer in the supply plenum.
9. Turn the power source on and set the room thermometer above the room temperature.
10. Once the burners start operating, time how long it takes before the burner cycle off on high temperature.
11. Turn the unit off.
12. Turn off the gas.
13. Remove the leads on the draft pressure switch and with alligator clips on the ohm-meter leads, clip it on the pressure switch.
14. Make sure the leads are not touching anything and not grounding the unit.
15. Start the furnace up and check the ohm-meter and record the reading.
16. Turn the furnace off and restore the leads on the pressure switch.
17. To check the gas pressure on the gas valve, you will need to install the manometer on the gas valve gas port.
18. Make sure that the hose and fittings are secured.
19. Turn the power source on, gas on, and set the thermostat above the room temperature.
20. Once the burners are turned on, record the gas pressure at the gas valve.
21. Turn the unit off by the power source and the gas pressure.
22. Replace the door panels.

Research Questions

1. What are the components found on a high efficiency furnace?
2. How can you tell if a furnace is a high efficiency type?
3. What was the ohm reading on the draft pressure switch?
4. What position was the switch in?
5. What temperature did the limit switch trip on?
6. How long did it take to trip?
7. What is the purpose of the high limit switch?
8. What was the pressure reading on the manometer for the gas valve?
9. Was this pressure in range?

Click on the file below to download the Lab Assignment
- HET 130 Wk 8 Lab.docx (16.16 KB)