Troubleshooting Air Handling Units: Chapter 3
Condensing Drain Issues
A condensate drain is placed at the bottom of the cooling coil in an air handling unit. It drains out the condensate water out the AHU. An AHU won’t work well if there are any condensate drain issues. By the end of this module, you should be able to troubleshoot the condensate drain issues of an air handling unit. Skip to quiz!
Introduction
Recall that condensate drains consist of a drain pan and a drain line. The water that drips off a cooling coil is collected in a drain pan. Then, from the drain pan, a condensate drain line moves the water out of a house.
It’s no wonder that condensate drain problems happen so often. The average 4 TR air handling unit produces more than 20 gallons of condensate water daily. It can even more if the humidity is high.
Condensate drain problems can cause health problems to the occupants and damage to the home.
A clogged condensate drain symptoms include:
Moldy smell near the AHU,
Standing water near the AHU, and
AHU shuts down and doesn’t turn on.
Additional symptoms of clogged are:
High humidity in the home,
Higher energy bills,
Mold growth, and
No water is coming from the condensate drain line.
Problems
The main problems that can be caused by condensate drain are:
Overflows, and
Coil icing.
Let’s learn more about these problems.
Sometimes there is dust and other particles in the air that drips out with the water as air passes through the coils. Other times, mold grows up in the drain line or the drain trap.
Blockages in the condensate drain slow or stop the flow of water and can accumulate in the drain pan. If this goes on for too long, the water will overflow. Depending on where the AHU is located, this can lead to leaks and water damage in the floors ceilings.
Some technicians also suggest installing a safety float switch if the AHU does not have it. Recall that float switches automatically shut down the AHU if the condensate pan reaches the overflow stage. This stops the damage of the AHU components.
When the evaporator coil runs too cold or airflow over it is low, water vapor in the air freezes instead of dripping down into the drain pan. The growing layer of ice expands outward beyond the extent of the drain pan underneath.
When the AHU turns off, and ice rapidly melts, water drips directly onto the floor. Common causes of frozen evaporator coil are insufficient airflow and low refrigerant levels.
Causes
Condensate drains are almost always wet during the cooling season. Warm and wet inside the drain line forms the perfect environment for mold growth. Mold causes health problems, so it is important to keep the condensate drain clean and to flow freely not to affect indoor air quality.
Recall that the condensate drain has a U-shaped trap. The condensate drain must work properly so that water flows of the AHU. The U-shaped traps can become blocked or dry out if water does not flow through them properly. This can cause dust particles to get into the AHU.
If the drain line is blocked, the condensate pan can become filled with water and eventually overflow. The flooding of water can damage flooring, walls, and even AHU components. This is particularly true if it goes unnoticed for a long period of time.
Cleaning Condensate Drains
We check drain lines to see whether the water is flowing freely or not. Recall that when air passes through a cooling coil, moisture in the air converts into water. This condensate water is moved out of an AHU using a drain line.
When cleaning drain lines, we first switch off the air handler. We then pour distilled vinegar in a drain line through the opening and let the solution sit for half an hour.
After that, we have to flush the pipe with water to make sure that it is clean and functioning normally. If a drain line is still dirty after this process, we can use a vacuum cleaner to further clean it.
We have to locate the end of a drain line outside a building. We then connect a vacuum hose to the end of the drain line and turn on the vacuum pump. Lastly, we pour water into the drain line to clean it.
A technician needs to check the condensate drain in an AHU if there are problems like:
Overflows, and
Coil icing.
He needs to consider cleaning the condensate drain if an AHU has condensate issues.
Cooling Coil Issues
In some air handling units, refrigerant is used with cooling or heating coils. The refrigerant flows through the coils to give cooling or heating. An AHU won't work well if there are any refrigerant issues. By the end of this module, you should be able to troubleshoot the refrigerant issues of an air handling unit. Skip to quiz!
Introduction
Recall that a refrigerant is a substance or mixture that absorbs heat by using it to boil, changing the phase from liquid to vapor.
Refrigerant leaks can happen simply due to the age of the air handling unit. There can be a refrigerant leak if the AHU is not cooling well even though the blower is running and the air is flowing out the vents.
Refrigerant Leaks - Consequences
We should not ignore refrigerant leaks. Refrigerant leaks can cause
AHU system damage,
Energy consumption,
Environmental damage, and
Potential health concerns.
When the AHUs have low refrigerant levels, they try to compensate by running longer to cool indoor space. This causes increased load within the system that may damage many other components and eventually cause the compressor to fail.
The more AHU runs to reach the set temperature, the more energy they consume. This increases the electricity bill.
Recall that refrigerants are dangerous chemicals that can deplete the earth's ozone layer. That is why the handling and disposal of refrigerants are controlled by Environmental Protection Agency (EPA).
It is fine if the refrigerant stays inside the HVAC system. When there is a refrigerant leak, the refrigerant goes to the atmosphere, where it contributes to global warming.
Recall that refrigerants are hazardous chemicals. Breathing evaporated refrigerant can damage our lungs. Refrigerant contact with skin may cause serious burns. So if we suspect a leak, we should not touch the coils.
Fixing Refrigerant Leaks
If there is a slow refrigerant leak, we shouldn’t fix it by simply adding more refrigerant to the system. We shouldn’t follow this process because it is quick and relatively inexpensive. With this shortsighted solution, the AHU may work for a few months, but it raises other potential problems.
To keep recharging the system with refrigerant, it may cost more than fixing the refrigerant leak for the first time.
Some technicians try to fix the refrigerant leaks with sealants, which can temporarily stop a small refrigerant leak. This is also not a good solution since it won't last for a long time. Sometimes the sealants can cause a blockage within the system that may result in further damage.
The options for fixing the refrigerant leaks in the right way are:
Find and repair the hole, and
Replace the coil.
In the old days, it was time-consuming and expensive to find a refrigerant leak. This is because people used to manually inspect the entire length of the coil to find a tiny hole.
Nowadays, there are machines that can detect refrigerant leaks and making it quicker and less expensive to find and repair holes.
Replacing the Coil
If the coil is old and in poor condition, it has many leaks, recommended to replace the entire coil. This can happen when the coil has been exposed to contaminants or not cleaned in a long time. Replacing the coil is an expensive option, but we can experience much better performance, lower energy bills, and no more recurring leaks.
Chilled Water Coil
Some AHUs may also contain chilled water cooling cooling coil in the place of evaporator coil. Recall that chiller systems generate cold water. This cold water is circulated through cooling coils in AHUs.
We need to check for any debris on these coils. We should also check for damaged coil fins, coil leaks, mold growth, and unusual materials on a coil’s surface.
First, we clean coils with a brush. We spray coil cleaner onto the coils and let that sit for ten minutes. We then clean the coils with a water hose in the opposite direction of airflow,
Recall that we have to straighten coil fins with a fin comb if they’re bent. This process is similar to combing our hair. We should straighten fins slowly, or it could damage the coil.
A technician needs to check the refrigerant coils if the AHU is not cooling or heating well even though the blower is running and the air is flowing out the vents. He needs to consider
finding and repairing the hole, or
replacing the coil.
Question #1: Which of the following are the symptoms of clogged condensate drain?
Moldy smell near the AHU
Standing water near the AHU
High humidity in the home
All the above
Scroll down for the answer...
Answer: All the above
A clogged condensate drain symptoms include:
Moldy smell near the AHU,
Standing water near the AHU, and
High humidity in the home.
Question #2: Blockages in the _________ slow or stop the flow of water and can accumulate in the ________.
air filter; ductwork
ductwork; air filter
condensate drain; drain pan
drain pan; condensate drain
Scroll down for the answer...
Answer: condensate drain; drain pan
Blockages in the condensate drain slow or stop the flow of water and can accumulate in the drain pan.
Question #3: Which of the following components automatically shut down the AHU if the condensate pan reaches the overflow stage?
Antifreeze thermostats
Overload relays
Humidifiers
Float switches
Scroll down for the answer...
Answer: Float switches
Float switches automatically shut down the AHU if the condensate pan reaches the overflow stage.
Question #4: Which of the following are the common causes of frozen evaporator coil? (Select all that apply)
low refrigerant levels
high inline voltage
low humidity in the air
insufficient airflow
Scroll down for the answer...
Answer: low refrigerant levels
insufficient airflow
Common causes of frozen evaporator coil are insufficient airflow and low refrigerant levels.
Question #5: Which of the following environment in the drain line is perfect for mold growth?
warm and dry
cold and wet
warm and wet
cold and dry
Scroll down for the answer...
Answer: warm and wet
Warm and wet inside the drain line forms the perfect environment for mold growth.
Question #6: Which of the following is used to pull out clogs in a condensate drain?
Air purifier
Vacuum cleaner
Screwdriver
Bearing
Scroll down for the answer...
Answer: Vacuum cleaner
A vacuum cleaner is used to pull out clogs from a drain line.
Question #7: Which of the following are the causes of the refrigerant leaks in AHUs?
Environmental damage
High energy consumption
Health problems
All the above
Scroll down for the answer...
Answer: All the above
Refrigerant leaks can cause
AHU system damage,
Energy consumption,
Environmental damage, and
Potential health concerns.
Question #8: We can fix a slow refrigerant leak by adding more refrigerant to the system?
True
False
Scroll down for the answer...
Answer: False
We shouldn’t try to fix a slow refrigerant leak by adding more refrigerant to the system. With this shortsighted solution, the system may work for a few months, but it raises other potential problems.
Question #9: Which of the following are the ways to fix the refrigerant leak in an air handling unit? (Select all that apply)
Replacing the coil
Replacing breaker
Repairing the refrigerant hole
Applying leak sealant
Scroll down for the answer...
Answer: Replacing the coil
Repairing the refrigerant hole
The options for fixing the refrigerant leaks in the right way are:
Find and repair the hole, and
Replace the coil.
Question #10: Which of the following will happen if we spray a coil with high-pressure water?
Coil fins will bend
The condensate drain will be clogged
The air filter will tear off
Scroll down for the answer...
Answer: Coil fins will bend
AHU coil fins will bend if we spray a coil with high-pressure water.