• SkillCat Team

Residential Maintenence: Inspect & Replace Furnace Components

Updated: Jul 12


Routine Maintenance: Residential Systems: Chapter 5


Furnace Components


In this module, we will look at how to inspect and replace furnace components including:

- burner,

- blower belt,

- humidifier pad,

- UV light bulb, and

- gas valve Skip to quiz!


Inspecting Burner


Recall that the burner is a section of the gas furnace where air and fuel are combined and burned with a flame. This produces the heat that warms our home.

First, we have to observe the flames of the burner. The flames should be burning with a steady blue color. The flames that are yellow indicate a dirty burner.


For further inspection, we need to turn off the power supply to the furnace. We have to find

the gas supply line that goes to the burner and close its valve. We have to open the burner and check it visually, whether it is clean or not and if any rust is formed on it.


Burners usually clog up with dust, dirt, and lint from the air. This blocks the gas from entering the burners. Recall that the burners are made of metal. So, rust can form on them. Rusty burners wear much faster and can be costly to replace.


We have to clean the dirt and rust on the burners. Let us see how to clean the burners.


Cleaning Burner


For cleaning the burner, we have to shut off the power to the furnace. We need to close the gas supply line to remove the metal access panel. We then have to remove the burners from the furnace assembly.


We use the brass brush to clean the rust and soot from the burner’s face. Next, we blow compressed air to remove any debris stuck inside the burners. We put back the clean burners onto their places and reassemble everything.


We turn the gas valve to an open position and switch on the furnace. We make sure that the burners are working properly.



Inspecting Belt


Recall that the blower in the furnace forces the hot air to move throughout the home. In HVAC systems, there are motors that are directly connected to the blower wheel.


In some cases, motor is connected to the belt, and the belt is connected to the blower. As the motor operates and the shaft rotates, it turns the belt. This, in turn, rotates the blower.


To inspect the blower belt, we have to switch off the furnace and turn off the gas line valve. Now, we have to remove the blower cover. Then we will disconnect the motor wires and pull out the blower motor assembly.


First, we will visually inspect the belt for any sign of cracking or worn-out edges. We have to replace the belt if anything abnormal is found.


Next, we have to check the tightness of the belt. We do this by pushing downward on the belt with a finger between two pulleys in the middle.


For good performance, the belt should not go more than a half inch after we push. If it goes beyond a half inch, we should make the adjustment. Let us see how to tighten the loose belt.


Finally, we will check the alignment of pulleys, whether they are in a straight line or not. The belts can wear out more quickly than they should when pulleys are not aligned properly. If the pulleys are not lined up perfectly, we have to make an adjustment.



Replacing Belt


We have seen how to inspect the belt and make proper adjustments. Let us see how to replace the old belt with a new belt on pulley wheels.

As shown video, we need to loosen the belt and replace with new belt. We then check the alignment of the belt and place the blower assembly back. After we reconnect the motor wiring, we place back the furnace cover.


We then switch on power to the furnace and gas line valve. Finally, we make sure that the furnace is running normally.



Replacing Humidifier Pad


Recall that humidifier is a device that increases the moisture content in the air. It is very useful in winter when the air can be very dry.


Portable humidifiers run in specific areas of the home, such as bedrooms. Furnace humidifiers are installed in the ductwork to distribute moisture throughout the house.


Water is constantly dripped across the humidifier pad in small amounts while the furnace operates. The humidifier pad holds a certain level of water inside it. The air passing through the humidifier pad picks up moisture in order to increase humidity levels in the room.


We have to replace the humidifier pad if it is clogged. For replacing the humidifier, we have to make sure that the humidistat is turned off. Recall that a humidistat is a device that regulates the humidity of air in a room.


We have to install the new humidifier pad and connect the water pipe to it. We open the damper and reattach the humidifier cover. Finally, we turn on the humidistat and make sure that the humidifier operating perfectly.



Replacing UV Light


UV light bulbs kill microorganisms such as bacteria, mold, and viruses that are harmful to health. They are installed in some HVAC systems. They burn just like the bulbs that are used for lighting in homes. So, we have to change the bulbs.


For the replacement of the UV light bulb, we first switch off the furnace and open the door close of the UV light bulb. We unplug the wiring of the UV light bulb and remove it. We then replace it with the new UV light bulb as shown in the video.



Replacing Gas Valve


Recall that a valve is a device that opens and closes to control the flow of liquid or gas. Thermal expansion valve, reversing valve, and gas valve are some of the examples of valves used in HVAC systems. Let us see how to change a gas valve in the furnace.


For the replacement of the gas valve, we first switch off the furnace and shut off the gas supply. We have to remove the old gas valve and replace it with the new gas valve as shown in the video. Finally, open the gas supply line and switch on the furnace and check if the new gas valve is working.


The burner flames should be in steady blue color. Burners usually clog up with dust, dirt, and lint from the air. We use the brass brush to clean the rust and soot from the burner’s face.


We visually inspect the belt for any sign of cracking or worn-out edges. The humidifier pad holds water inside it. UV light bulbs kill microorganisms such as bacteria, mold, and viruses that are harmful to health.




Question #1: The flame of the burners should be in _______ color.

  1. Red

  2. Blue

  3. Yellow

  4. Orange

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Answer: Blue

The flame of burners should be in blue color. When the flame turns yellow or orange, it means that the burners are dirty.


Question #2: For cleaning the burners, the power supply should be____ and gas supply should be____ to the furnace.

  1. ON, ON

  2. ON, OFF

  3. OFF, OFF

  4. OFF, ON

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Answer: OFF, OFF

Before cleaning the burners, we should switch off the power supply and close the gas supply line. This is because power to the furnace will us electric shock and gas supply to the furnace may cause fire hazard.


Question #3: During the inspection of the belt, we check for

  1. Damage of belt

  2. Tightness

  3. Alignment

  4. All the above

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Answer: All the above

During the inspection of the belt, we check for damage of the belt, tightness, and alignment.


Question #4: We can loosen the blower belt by rotating the ______ .

  1. Blower wheel

  2. Adjustment screw

  3. Motor shaft

  4. Mounting screws

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Answer: Adjustment screw

An adjustment screw in the blower is used to tighten or loosen the belt.


Question #5: Humidifier damper connected to air duct is opened in

  1. Summer

  2. Winter

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Answer: Winter

In the winter season, the humidity of the air around is low. The humidifier damper should open condition. Air from ductwork passes through the humidifier and absorbs moisture to increase the humidity in the living room.


Question #6: UV light bulbs installed in HVAC systems to kill

  1. Bacteria

  2. Viruses

  3. Mold

  4. All the above

Scroll down for the answer...










Answer: All the above

UV light bulbs installed in HVAC systems to kill microorganisms such as bacteria, mold, and viruses that are harmful to health.


Question #7: Before replacing the gas valve, we have to shut off the gas supply to the furnace.

  1. True

  2. False

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Answer: True

Before replacing the gas valve, we have to shut off the power supply and gas supply to the furnace.

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