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How to properly care for your rooftop AC unit and lower your overall operating/repair costs.

There are many reasons why regular maintenance is especially important for rooftop AC units. Having an improperly heated or cooled building can result in a variety of problems, including a loss of employee productivity and computer malfunctions. Mechanical failure of commercial HVAC systems can result in thousands of dollars in damages. These incidents, and the majority of service calls involving rooftop HVAC units, can be prevented through proper maintenance. 

Unlike most HVAC units found in indoor mechanical rooms, package units are typically mounted on the rooftop of buildings or on concrete slabs at ground level. Because of its location, this equipment is oftentimes exposed to harsh weather conditions due to its proximity to the elements. And because of their remote location, it is harder to see and hear the signs and signals that indicate it is time for a service call. Most people tend to not think about what they do not regularly see. For this reason, a rooftop AC unit usually has to malfunction for them to remember that it needs to be serviced (out of sight, out of mind).

Make sure a routine maintenance schedule is in place before operation begins. Only qualified service professionals should handle maintenance. Include a service log and schedule based on the hours of operation and conditions under which the units run. Keeping detailed service logs for each unit can help you troubleshoot issues in the future, track its maintenance, and maintain valuable information about its history.

There’s also a lot of value in properly maintaining your rooftop AC unit. Doing so can save you a great deal of money by lowering your overall annual operating/repair costs. This article examines the major components of gas heat/electric cooling rooftops and the seasonal maintenance requirements to take care of them. Maintenance should be performed according to the manufacturer’s recommendations.

Service tools

Several tools are needed to perform seasonal maintenance on rooftop air conditioning units. These include a ladder with various extension sizes for access to the building roof; an accurate manifold pressure gauge and thermometer to determine and verify the correct refrigerant charge; and a belt tension gauge and straight edge to measure belt tension and pulley alignment. 

Service safety

Prior to beginning service on any rooftop unit, you’ll want to start off by first shutting off all electrical power to the unit and tagging the disconnect to avoid a shock hazard or injury from rotating parts. It might sound pretty basic, but it’s still worth mentioning since it is, by far, your most important step.

Overall unit

Considering that the units are located outdoors, the unit exterior should be checked at the beginning of every heating and cooling season. You’ll want to make sure you clean off any debris, such as leaves, paper, etc. Check that all access panels have been securely fastened in place. Should the unit not have hinged doors, look for missing screws and replace them if necessary.

Inspect air filters and inlet screens

Inspect, clean or replace your AC unit’s air filters every 3 to 4 weeks, or, at the very least, at the start of each cooling and heating season. You will also want to clean outdoor air inlet screens annually.

AC Spring Maintenance

Dirty filters: One of the primary causes of significantly reduced system efficiency and air flow blockages is dirty filters. When normal air flow becomes completely obstructed, air carrying dirt bypasses the filter, carrying that dirt directly into the AC unit’s evaporator coil, which impairs the coil’s heat-absorbing capacity.

Keeping the filter clean: By keeping your air conditioner’s filter clean, you can lower its energy consumption by 5%-15%, which saves you money on your monthly energy bill. When your AC unit is in cooling mode and doesn’t have enough air moving over the indoor coil, the coil’s temperature begins to drop. In the event that the temperature drops below the freezing point, ice then begins to form on the coil, which has a significant impact on normal airflow and coil temperature.


Your air conditioner’s compressor is a pump that is designed to pump a vapor. When airflow through your indoor coil begins to decrease, not enough heat is being removed from the air passing over the coil to vaporize the liquid refrigerant. So instead of receiving a vapor, your air conditioner’s compressor receives the liquid refrigerant. An excess of refrigerant in your compressor creates a danger called slugging. 

Because liquids are not compressible, when all that extra refrigerant floods into the piston cylinders of the compressor while in a liquid state, it can create many different problems, such as broken valves, broken connecting rods, and significant damage to the compressor itself. The liquid refrigerant entering the compressor will fall directly into the crankcase oil, which raises the pressure inside the crankcase far beyond its design limits. As a result, the valves, pistons, or other internal components are destroyed. Over time, slugging will cause an air conditioner’s compressor motor to completely burnout. In this scenario, the air conditioner started out only requiring a filter replacement. But should you fail to do so, and your unit’s compressor motor ends up failing, your only option is to fully replace the HVAC unit.

On the flipside of things, in heating mode, low airflow causes the heat exchanger to overheat. At higher temperatures, the heat exchanger begins to oxidize and its life-span is drastically reduced, or it cracks and breaks. When we are considering cost, it makes much more sense to replace your AC unit’s air filters regularly than it does to replace a heat exchanger. 

There is no need to make the diagnosis of an overcharged air conditioner yourself. If you suspect there might be an issue, call Miranda Plumbing & Air Conditioning. We will send one of our licensed HVAC experts to you and they will get to the bottom of what’s causing the problem and come up with the best options to fix the issue.

If you live in Port St. Lucie or the Treasure Coast and need AC repairs, call Miranda today at 833-514-8083.