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Blower and Air Vent Issues


Troubleshooting Air Handling Units: Chapter 2


Blower Issues


A blower in the air handling unit circulates the cool or hot air heat to the building. An AHU would not be able to maintain the temperature in the room if there are any blower issues. By the end of this module, you should be able to troubleshoot the thermostat issues of an air handling unit. Skip to quiz!


Introduction


Recall that blowers are a type of fan that forces air to move through the ductwork into rooms and office spaces. Manufacturers generally use centrifugal type blowers in AHUs. Blowers are located beside cooling or heating coils to pull or push the air.


If the blower is not working, it could be because of several things. We have to go over a few things to check before calling for troubleshooting.


Preliminary Checks


First, we have to make sure that there is a power supply to the air handling unit and the breaker is not off. Then we have to make sure that the air filter and condensate drain are not clogged.


We also have to make sure that the fan switch in the thermostat is in on condition. We have to check the air coming out of air vents.


If cooling mode is selected in the thermostat, we have to check for ice around the evaporator coil. If the evaporator coil is frozen, the blower could be working, but the air wouldn’t circulate through the ice until it melts.


Sometimes AHU blowers can’t move enough air within the space that needs to be heated or cooled. This can be caused by:

  • malfunctioning blower unable to properly circulate air throughout the system, or

  • a layer of dirt on the blower blades makes the blower run at a slower speed.


Recall that some AHUs use belt-driven motors. V-belts wear out, crack and eventually break. We have to check for the condition of the V-belt. If it is damaged, we have to replace it.



V-Belts


We need to inspect V-belts for signs of cracking. If a belt is damaged or looks worn, replace it right away.


After replacing a V-belt, we should assess pulley alignment. Good pulley alignment increases the lifespan and efficiency of an AHU by reducing the wear of pulleys, belts, and bearings.


We can check the tightness of a belt by pushing it down in the middle with a finger. If it goes beyond a half-inch, we should make an adjustment.


Recall that bearings support loads and also help them to rotate.



Blower Faults


The main reasons for blower faults are:

  • Dirty or damaged blower blades, and

  • Blower motor failure.

Let us look into how to troubleshoot these problems.


A dust layer on the blower blades decreases the blower speed and won’t circulate air efficiently. Damaged blower blades can strike the edge of the casing and create terrible noise. When we hear a loud noise coming out of the AHU cabinet, we should shut down the AHU and troubleshoot the problem.


The blower motor can suffer from a number of mechanical and electrical issues. The most common is motor freeze from the stress on the moving parts due to wear and tear or excess dirt. If there is too much stress on the motor, it could burn out and fuse its wiring. In this case, we must replace the motor.



A technician needs to check the blower if an AHU is not able to maintain the desired temperature in the room. This can be caused by:

  • malfunctioning blower, or

  • a layer of dirt on the blower blades.

A technician needs to troubleshoot the blower issues and make the blower run well again.


 

Air Vent Issues


Air vents are the terminal devices where hot or cold air is supplied to the room. An AHU won’t work well if there are any thermostat issues. By the end of this module, you should be able to troubleshoot the air vent issues of an air handling unit. Skip to quiz!


Introduction


The air vents are where hot or cold air is supplied to a room. This is where the air leaves a ductwork system through either grilles or diffusers. Grilles release air at a controlled rate. Diffusers release air in all directions.


Clogged air vents cause air handling unit problems as they do not allow air to pass through them easily. The main problems that can be caused by troubled air vents are:

  • Frozen evaporator coils,

  • High energy bills,

  • Blower motor issues, and

  • Poor cooling or heating.


Dirty air vents do not allow air to pass through them easily. This reduces return airflow over evaporator coils. AHU’s evaporator might not receive enough heat from the return air, resulting in the frozen evaporator coils.


In our homes, if a table fan grill is dirty, the fan motor has to work harder to push air through it. This increases energy consumption. In the same way, if air vents are dirty blower motor has to work harder to push air through them. This increases the overall energy consumption of an AHU.


As the blower works harder to push or pull air from dirty air vents, it increases the load on the blower motor. This causes the blower motor to overheat and leads to system failures.


Dirty air vents do not allow hot or cold air to pass through them easily. This causes hot and cold spots in a room.


Cleaning Air Vents


For cleaning air vents, we need to switch off the air handling unit connected to them. We’ve to unscrew it and wash it with soap. Then we rinse it with water and let it dry for some time. We screw air vents in their places.



Sweating Air Vents


Sweating air vents happens when outside air comes in contact with air vents. This happens due to the lack of insulation around the air vents.


Sweating of air vents reduces air handling unit efficiency because cooling air is wasted for condensation. So we need to insulate air vents without any gap.



A technician needs to check air vents in an AHU if there are problems like:

  • Frozen evaporator coils,

  • High energy bills,

  • Blower motor issues, and

  • Poor cooling or heating.

He needs to consider cleaning or insulating air vents if an AHU has air vents issues.


 

Question #1: Worn out blower V-belts in an air handling unit _________.

  1. can be sealed together and reused again

  2. should be replaced with new V-belts

  3. does not affect the working of blower

  4. Outdoor atmosphere temperature

Scroll down for the answer...

















Answer: should be replaced with new V-belts

If a V-belt in an air handling unit is damaged or looks worn, it should be replaced right away.


Question #2: Which of the following increases the wear of pulleys, belts, and bearings of a belt-driven blower?

  1. tightness of fittings

  2. lubrication of bearings

  3. wrong pulley alignment

  4. All the above

Scroll down for the answer...
















Answer: wrong pulley alignment

Wrong pulley alignment increases the wear of pulleys, belts, and bearings of a belt-driven blower.


Question #3: Which of the following decreases the blower speed of an air handling unit?

  1. Clogged air filters

  2. Dust on blower blades

  3. Outdoor air temperature

  4. Refrigerant level in the system

Scroll down for the answer...
















Answer: Dust on blower blades

A dust layer on the blower blades decreases the blower speed and won’t circulate air efficiently.


Question #4: Which of the following problems can be caused by clogged air vents?

  1. Frozen evaporator coils

  2. High energy bills

  3. Blower motor issues

  4. All the above

Scroll down for the answer...


















Answer: All the above

The main problems that can be caused by troubled air vents are:

  • Frozen evaporator coils,

  • High energy bills,

  • Blower motor issues, and

  • Poor cooling or heating.


Question #5: For cleaning air vents, we need to switch off the ________ connected to them.

  1. air handling unit

  2. cooling tower

  3. tube light

  4. water pump

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Answer: air handling unit

For cleaning air vents, we need to switch off the air handling unit connected to them.


Question #6: Which of the following can happen if there is no insulation around the air vents?

  1. No filtration of indoor air

  2. Sweating around air vents

  3. Hot or cold air leakage

  4. All the above

Scroll down for the answer...
















Answer: Sweating around air vents

Sweating around air vents can happen if there is no insulation around air vents.

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