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Complete Guide to servicing Rooftop Units


Packaged Rooftop Unit - Routine Maintenance: Chapter 1


General RTU Routine Maintenance


In this module, we will learn about the need for routine maintenance of a packaged rooftop unit. We will also discuss, about general maintenance procedure for a packaged RTU. Skip to quiz!


Requirement of a Routine Maintenance


Recall that the packaged rooftop units are also known as RTUs. RTUs provide cool or hot air along with ventilation. We generally find RTUs in commercial buildings like office buildings and supermarkets.


Recall some standard components of a Packaged RTU includes:

  1. Electrical controls,

  2. Blower motor,

  3. Fan motor,

  4. Condenser coils,

  5. Gas-fired unit,

  6. Evaporator coils,

  7. Air filter, dampers, and

  8. Compressors.

Let us look at a video that explains these components.


Recall that packaged rooftop units are installed on the roof. They are affected by harsh weather conditions like wind, dust, snow, and rain. So, they have to be checked and maintained at regular intervals.


Regular maintenance of RTUs leads to:

  • Longer life,

  • Lower power consumption,

  • Better performance, and

  • Higher efficiencies.


We generally do a complete maintenance of an RTU quarterly, seasonal, or twice a year. We follow routine maintenance as per the manufacturer’s guidelines or manuals. However, some components might need a more frequent check-up than others.


While going for any HVAC systems’ routine maintenance, we need to acquire permission to access the equipment. Some safety precautions we need to always follow are:

  1. Wear a helmet,

  2. Wear safety glasses,

  3. Wear gloves, and

  4. Wear safety boots.


Some of the steps while doing a routine maintenance are;

  • All electrical connections should be switched off or Lockout during the whole process.

Recall that lockout ensures that equipment are properly shut off and not able to be started up again prior to the completion of maintenance or repair work.


  • We should observe a waiting period before maintenance, as some equipment like capacitors have power even after shutting off.

  • Use proper tools for accessing different components.

A complete maintenance is always recommended for an RTU at least once in a year. For example, a new car runs smoothly for the first year. However, after a year, it will need some maintenance. Let us look at a video showing an RTU’s routine maintenance.



Routine Maintenance Process


Some of the common problems in an RTU are:

  • Less cooled air or heated air,

  • Malfunctioning of dampers,

  • Non working thermostat and controls,

  • Dirty air filters, and

  • Issue in starting the equipment after a long time.


We usually follow a general checklist for most of the problems during a routine maintenance. Most of the RTU manufacturer’s have their own inspection methods and maintenance checklists.


The maintenance procedure for common components in a residential HVAC system and RTU is the same. However, the location of components and the procedure to access them is different. Some components and procedures will also be completely different.


Common points in a RTU maintenance checklist includes:

  • Cleaning or replacing of air filters,

  • Cleaning of grilles,

  • Cleaning of dampers,

  • Cleaning of both the coils,

  • Cleaning of Economizers and other components.


Remember the general maintenance of a car when we take the car to the service center or garage. The technician will first inspect the car, as per the general checklist for all the cars, then proceeds with the specified issue. The same way we will do the RTU.


We generally find RTUs in commercial buildings like office buildings and supermarkets. We generally do a complete maintenance of an RTU quarterly, seasonal, or twice a year.


Common points in a RTU maintenance checklist includes:

  • Cleaning or replacing of air filters,

  • Cleaning of grilles,

  • Cleaning of dampers,

  • Cleaning of both the coils, and

  • Cleaning of Economizer.



 

Air Distribution Components - Part 1


In this module, we will learn how to inspect the air distribution components. We will also look at the cleaning and routine maintenance of these components in a packaged rooftop unit. Skip to quiz!


Air Distribution Components


The air distribution system in an RTU includes:

  • Grilles,

  • Air filters,

  • Ductwork, and

  • Dampers.

Let us take a look at the maintenance of each of these components.


Maintenance of Grilles


Recall that grilles are the endpoint of the air distribution system from which hot or cool air is provided. The two types of grilles are:

  • Fixed grilles, and

  • Removable grilles.

We cannot remove fixed grilles as they are installed in the walls and ceiling. Removable grilles are the ones that can be removed by unscrewing or by unlocking the clips of the grille.


The dust in the room can accumulate on the grilles. This dust blocks the airflow through the grille. So, proper inspection and cleaning of the grilles can improve the flow and quality of air.


While grilles inspection, we:

  • Locate all grilles

  • Check visually for dust.

  • Remove the removable grilles.

  • Clean the grilles.

  • Refixing of grilles.

  • Cleaning the area.

Unscrew removable grilles and check whether there is dust on the blades and integral damper. Dampers installed on the inner side of the grille for controlling the airflow is known as Integral dampers. For fixed grilles, use a white cloth to see if some dust is present on the grilles.


Prepare the area where the grilles are installed, like covering other parts with large polythene where dust can fall. Use proper cleaning tools like a soft brush, vacuum machine, water jet pump, and dust collector. Fixed grilles are cleaned with the brush connected to the vacuum, where they are installed.


Removable grilles are removed by unscrewing in an anti-clockwise direction. Take the removed grilles outside to the garden or open space for cleaning.


Kitchen grilles may have grease on them, so wash them with detergents or liquid cleaners. Clean the grilles with a medium pressure water jet and let them dry. Reinstall the removed clean grilles and clean the covered surface if any dust is left after removing all the coverings.



Maintenance of Air Filters


An air filter is a device that removes solid parts like dust from the air. They are usually made up of fiberglass material. Advanced air filters also remove pollen, bacteria, and allergens from the air.


Similarly to grilles, air filters are also two types:

  • Washable filters, and

  • One-time use filters.

However, most of the RTUs use one-time use filters. The quantity of filters depends on the size of the RTU.


Air filters can collect dust particles. As the filters trap more dust, it gets clogged.


Imagine putting on a dirty mask that makes you gasp for breath. Similarly, if the air filter is clogged with dust, it does not allow air to flow easily via the ducts in the entire system. So, the RTU has to work harder to provide you the same cooling or heating effect.


Check visually for air filters if they are clean or dirty. The steps are as follows:

  • Locate the access door for the air filter on the RTU as per manufacturer’s guidelines.

  • Open the access door using a handle or door key.

  • Check whether they have to be replaced or washed as per the owner’s manual.

Recall that some air filters are reusable and can be cleaned. We can clean an air filter with water. We can use a garden hose with a medium pressure water jet to clean the reusable air filters. High-pressure water might tear and damage the filter.


Cleaning of air filter includes:

  • Locate the access door for the air filter on the RTU as per manufacturer’s guideline.

  • Open the access door using a handle or door key.

  • Remove the air filter from the guide slots.

Cleaning of the washable filter is as follows:

  • Remove the filter and wash it with water.

  • Make sure the filter is dry before replacing it.

  • Insert the filter back.

We can only clean reusable filters and must replace other filters.


Non-reusable air filters cannot be washed and need to be replaced. You can pull out the air filters by opening the access door or sheet panel and insert a new one.


All air filters have an arrow marked on them. This arrow is the direction in which the air should flow through the filter. So while inserting the filter back, we should see the direction in which the air flows in the ducts and point the arrow in the same direction.


Grilles are of two types:

  • Fixed grilles, and

  • Removable grilles.

Grilles maintenance involves:

  • Inspecting an air filter.

  • Cleaning or replacing air filter.

If the air filters are filled with dust, they need to be cleaned or replaced.



 

Air Distribution Components - Part 2


This module teaches about inspecting and cleaning air distribution components during routine maintenance for Packaged rooftop units. We will look at the procedures to maintain dampers and ductwork. Skip to quiz!


Maintenance of Ductwork


Recall that ductwork is a closed pathway made of thin metal sheets.


Some purposes of the ducts are:

  • To provide a path for the cold or hot air to reach the rooms from the entire system.

  • Not to allow the transfer of heat between the air inside and outside of the ductwork.


Some common problems in the ductwork that need to be inspected during routine maintenance are:

  • Dents,

  • Leaks, and

  • Clogs

All types of ducts have these problems. We will talk in detail about these problems.


Recall that ducts are made of thin sheets of metal. It’s just how hitting a car can put a dent on it, a heavy blow on the ducts can quickly put a dent on it. We can find damages on the duct inspecting visually.


Recall that air contains many impurities like dust particle and soil particles. As air continuously flows inside the ductwork, the particles stick to the walls of the ducts. You can use a flashlight to check for dust and debris stuck inside the ducts.


As ductworks are made by joining thin metal sheets, there is a chance that they may open. A small opening in the ducts will cause the hot or cold air flowing inside to leak out. An anemometer measures the airflow through the grille; by this, we can find leakages.


Recall that ducts are made of metal. They have a chance of corrosion or rust. You can visually inspect the insides of a duct for signs of corrosion using a flashlight. Sign of corrosion usually means that you will have to replace that part of the duct.


As ducts are closed, there are chances of mold and fungus growing inside the ducts. This would be a common problem if the unit were shut down for a long time. We can clean the mold with a cloth or mop dipped in a regular bleach solution.


You may face a situation where you suspect that you can find problems

  • In an area that cannot be seen easily, using a flashlight, or

  • deep inside the ductwork.

In such cases, we use an inspection camera to look inside the ducts. An inspection camera has a camera attached to a long cable inserted inside the ducts for inspection.


We always clean the ducts during regular maintenance. Duct cleaning involves cleaning grilles and the insides of the ducts using a vacuum cleaner. Recall that the grilles are found on the walls at the end of the duct.


While cleaning, we switch off the RTU. Then, we need to unscrew the grilles with a screwdriver. We have to clean the walls with a brush as far as possible. We need to collect the loosened dust and dirt with a vacuum cleaner by inserting the hose into the duct.


Take the removed grilles to the garden or cleaning area. Clean the grille using low pressure water jet. Rinse the grilles after washing. Reinstall the grilles once the cleaning of ductwork is done.


Recall that air filters are of two types, reusable or replace filters. We would also need to clean any dust that might have fallen on the floor out of the ducts. Finally, we will screw the grilles as before and clean the dust falling on the floor.



Maintenance of Dampers


Dampers are the tools that help to regulate the amount of cooled or heated air required to be fed into different areas of ductwork. A dampers' work is to control the amount of air distributed to the specified area. Let us see different types of a damper.


Recall that there are many types of dampers based on their use and operation. Dampers based on its uses in RTU are;

  • Backdraft damper,

  • Intake damper,

  • Exhaust damper,

  • Return air damper, and

  • Economizer damper.

Generally, dampers cleaning and inspection are usually based on their operation. Types of dampers based on operation are;

  • Manual dampers and

  • Motorized dampers.


Manual damper are operated with the locking quadrant or by hand using a lever. The locking quadrant is a lever by which the airflow is regulated. The lever is locked at a particular position on the guideways. Each position allows a specific quantity of air to pass through the dampers locked at a particular position.


Motorized damper are the dampers having an actuator attached to it. Recall that an actuator is a device that helps to obtain physical movement or control the damper operation.


Some of the common damper failures are;

  • Gasket blockage in between damper blades.

  • Blades damaged.

  • Reverse operation of automatic damper.

  • Dust is collected at the end of the blades.

  • Locked or jammed locking quadrant.

Some dampers are easy to access by opening the access door. But, for some dampers we need to unscrew the section to access the damper.


Inspection of dampers:

  • Damper location can also find in the manual.

  • Check whether the damper is operating smoothly with a lever.

  • Check if the damper blades have dust on them.

  • Check for the wirings of motorized dampers connected to the controls.

  • Visually check whether the damper closes completely or some gap is present in between the blades.

  • Close the access door after inspection of the damper.

These dampers need to be cleaned for better operation and higher efficiency of the RTU.


The steps involved are:

  • Access the damper by removing the access door or unscrew the damper section.

  • Clean the damper with a medium pressure water jet for dust cleaning.

  • Remove any debris present in the damper.

  • Remove the extended gasket in between the damper blades.

  • Remove any damaged blade present and need to be replaced upon approval of the authorized person.

  • Close the access door or screw the damper section which has opened for cleaning.


Ductwork is an essential part of an air distribution system, and it connects all the parts of conditioned areas. Ductwork maintenance includes cleaning and inspection of the entire ductwork. Common problems of duct are dents, leaks, and clogs.


Maintenance of dampers is essential for an RTU. Dampers are of two types based on operation, manual and motorized dampers. Maintenance of dampers includes inspection, cleaning and adjusting the dampers.



 

Question #1: Which of the following is the best routine maintenance time period? (Select all that apply)

  1. Quarterly.

  2. Annually.

  3. Seasonal.

  4. Once in five years.

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Answer: Quarterly.

Annually.

Seasonal.

We generally do a complete maintenance of an RTU quarterly, seasonal, or twice a year.


Question #2: Routine maintenance of commercial HVAC systems like an RTU is recommended at least after ___ year(s).

  1. 1

  2. 2

  3. 3

  4. 4

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Answer: 1

A complete maintenance is always recommended for an RTU at least once in a year as per the standard organizations.


Question #3: General RTUs routine maintenance checklist includes:

  1. Cleaning of grilles.

  2. Cleaning of air filters.

  3. Clening of coils.

  4. All of these.

Scroll down for the answer...















Answer: All of these

General RTU routine maintenance checklist includes:

  • Cleaning or replacing of air filters,

  • Cleaning of grilles,

  • Cleaning of dampers,

  • Cleaning of both the coils,

  • Cleaning of Economizers and other components.


Question #4: How many types of grilles are there?

  1. One

  2. Five

  3. Three

  4. Two

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Answer: Two

A grille refers to any air outlet or intake that consists of a square or rectangular face and neck at the end of ductwork. There are two types of grilles:

  • Fixed grilles

  • Removable grilles


Question #5: We clean the kitchen grilles with grease on them using ____?

  1. Oil.

  2. Water jet.

  3. Detergents or liquid cleaner.

  4. Glass cleaner.

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Answer: Detergents or liquid cleaner.

Kitchen grilles may have grease on them, so wash them with detergents or liquid cleaners.


Question #6: While inspecting an air filter, which of these components will you remove first?

  1. Air Filter

  2. Access Panel

  3. Grilles

  4. Duct Joints

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Answer: Access Panel

The access panel is the outer cover of the filter. It is the first component you should remove to gain access to the air filter.


Question #7: During routine maintenance for a system with a reusable air filter, you should ____ the filter and see that the ____.

  1. Wash; filter arrow is pointing the same as the direction of airflow.

  2. Wash; filter arrow is opposite to the direction of airflow.

  3. Change; filter arrow is opposite to the direction of airflow.

  4. Wash; filter arrow is pointing the same as the direction of airflow.

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Answer: Wash; filter arrow is pointing the same as the direction of airflow.

During routine maintenance for a reusable air filter system, you should wash the filter and see that the filter arrow is pointing the same as the direction of airflow. Recall that reusable filters can be washed with water and need not change them.


Question #8: An RTU had been shut down for three months as the owners were on vacation. What should you likely check duing routine maintenance?

  1. Air Filter.

  2. Access Panel.

  3. Traces of mold and fungi in the ducts.

  4. Dust on the air filters.

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Answer: Traces of mold and fungi in the ducts.

Gain access to the duct from the access panel or grilles and inspect for traces of mold and fungi. It is the first component you should remove to gain access to the duct.


Question #9: What do we clean during the ductwork cleaning?

  1. Air Filter

  2. Grilles

  3. Ducts

  4. All the above

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Answer: All the above

We clean the insides of the ducts, grilles, and air filters during ductwork cleaning.


Question #10: Types of dampers based on their working are: (Select all that apply)

  1. BDD damper.

  2. Manual damper.

  3. Motorized damper

  4. Fresh air damper.

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Answer: Manual damper.

Motorized damper

Dampers' work is to control the amount of air distributed to the specified area. There are two types of dampers based on operation:

  • Manual damper and

  • Motorized damper.


Question #11: Cleaning of damper includes:

  1. Cleaning off the dust on blades.

  2. Removal of debris, if present.

  3. Cleaning with a water jet.

  4. All of the above.

Scroll down for the answer...

















Answer: All of the above.

Dampers cleaning includes:

  • Cleaning off the dust on blades.

  • Removal of debris, if present.

  • Cleaning with a water jet.

  • Removing of the extended gasket.


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