For techs at St. Charles, Missouri-based Wiegmann Associates, the process begins with the coils and refrigeration circuits.

“Our techs make sure a rooftop unit’s coils are clean and its refrigeration circuits are functioning properly, in addition to a number of other items,” said Rex Hutchinson, service technician, Wiegmann Associates. “We ensure the system is ready to keep up with the demands of summer as energy efficiently as possible. RTUs are exposed to a lot of dirt and debris, so the most important first step is to make sure the coils are clean. If service has been done regularly, and the unit has been properly maintained, we can usually have an RTU ready for summer within a day.”

Many contractors feel it’s imperative to make a checklist in order to guarantee all aspects of a rooftop unit are properly covered.

Technicians at Haller Enterprises Inc. in Lititz, Pennsylvania, carry an actual document with check boxes that can be physically checked off to ensure each step is completed when they service RTUs.

“We expect to catch many potential problems before they become operating malfunctions,” said John Hogarth III, commercial service group HVAC field manager, Haller Enterprises Inc.

According to Mark Strahan, commercial account manager, Midstate Energy, Phoenix, there are several items to address in order to properly prepare a rooftop unit for summer use.

“Check to make sure the system is clean, including the coils, filters, blower wheels, and fan blades,” said Strahan. “Check the electrical system, including the electrical disconnect, wiring, connectors, capacitors, and other components; take a look at the mechanical parts, such as motors, bearings, belts, shafts, blower wheels, and fans; and ensure the unit has proper airflow. Inadequate airflow is often the first domino that falls in a string of events, which results in more serious system component failure modes. Finally, check the operation of the refrigeration circuit, including the compressor, metering device, evaporator coil, condenser coil, and interconnecting piping. For example, an indication of an improper refrigerant charge during this portion of the inspection may trigger a leak test or require the removal of excess refrigerant.”

Lauren Dagostino, senior marketing manager, Allied Air Enterprises, said a priority should be placed on cleaning coils, cleaning drains, replacing filters, confirming system performance by checking pressures and temperatures, checking and tightening electrical connections, and cleaning economizer coils and operation.

“Scheduled preventive maintenance should take one to three hours, depending on the size of the unit and should be done prior to temperatures rising,” said Dagostino.

Beyond the checklist, contractors and manufacturers recommend quarterly inspections to avoid any negative surprises when the summer arrives. The amount of inspections throughout the year depends on several factors, such as weather and environmental conditions.

“The frequency of cleaning and preparing a unit for peak load demands will depend on the operating demands and the environmental conditions the rooftop unit is operating in,” said Steve VanPeursem, director of packaged systems, Daikin Applied. “For instance, if your building is based in a particularly hot or humid climate, it may require more frequent routine cleaning simply because of a higher operating demand required during peak weather. In general, for buildings in moderate or mild climates, typical periodic maintenance on RTUs is performed on a quarterly basis.”

PROBLEM SOLVING

Once it’s time to run through the checklist and prep the RTU, various issues can arise that may impede the process. However, many have found ways to solve the issues to make sure the units are prepped and ready to go.

“It’s extremely important to determine the root cause of any issues that are found and perform a system diagnostic and not a symptom diagnostic,” said Mary Flake, service manager, Comfort Systems USA Southeast, Savannah, Georgia. “We are very careful not to stop at the first issue we come across but rather determine what caused the failure. The most common issues we encounter are clogged evaporator coils and algae buildup in the drain lines. Sometimes, as temperatures heat up, we will see capacitors starting to fail if they are older due to the extreme temperatures outside.”

In addition, properly trained technicians allow problem solving to go smoothly as well as support from other departments and software.

“We, at Trane, turn to our Trane service technicians, who are incredibly knowledgeable,” said Bryan Ware, portfolio leader, light commercial package products, Trane. “Our technicians have immediate access to the HUB, a knowledge-based online solution center with a highly efficient search tool. We also have multiple factory support teams of highly experienced technical service engineers on hand to provide additional in-depth technical support via phone, email, instant messaging, or through social media discussion groups.”  

Similarly, Wiegmann Associates turns to its team to address any issues that arise.

“When we run into more complex issues, our technicians can usually troubleshoot the problems,” said Hutchinson. “If not, we can bring in others on our team, including our engineering department or the manufacturer, for support.”

Many manufacturers now provide advanced technology that eases the troubleshooting process for technicians in the field.

“Daikin Applied’s rooftop units have Microtech DDC unit controllers that are designed to be user-friendly so technicians have more time to make specific modifications or check certain functions of the unit during routine maintenance checks. This may include operating all motors to confirm they are working independently of environment temperatures,” said VanPeursem.

In addition, the design of the RTU can make addressing issues and preparation easier on technicians. Manufacturers are striving to create RTUs that are easy to troubleshoot, maintain, and prepare.

“Daikin Applied has designed its RTUs to provide easy access to the various critical components that require inspection and maintenance,” said VanPeursem. “We’ve learned by listening to feedback from the industry and our customers that making a maintenance operation as easy as possible will make it more likely to be accomplished. In addition, our RTUs provide trend information to technicians that help them make maintenance more efficient. For example, our MicroTech DDC controls provide detailed information, like alarm history and other trends, that allow technicians to provide intelligent diagnostics.”

Similarly, Trane has designed its RTUs to make it easier for contractors to maintain the units.

“The Trane RTUs are designed with optional hinged access panels for easier access to subsystems and tool-less hail guards to protect coils while providing easy coil access,” Ware said. “It also features single-row microchannel coils, which are easy to clean. For applications where coated coils are used or required, they are easier to clean. Microprocessor controls also help pinpoint any system issues that may be present. These thoughtful design elements assist contractors when performing maintenance, so they can get in and address any problems quickly.”

ENERGY SAVINGS

At the end of the day, properly preparing RTUs is done to deliver significant energy and cost savings to customers.

“We strongly encourage maintenance staff to stick to a routine schedule in order to keep the condenser coils clean and confirm all stages of the compressor are operational,” said VanPeursem. “An improperly running refrigerant circuit can consume as much as 10-20 percent more energy alone, which is why checking to confirm the refrigerant pressure and temperatures are operating properly can be crucial to keeping those costs down.”

Maintaining the unit increases the likelihood it will operate at the performance level it was designed for, Ware said.

“This can help owners avoid service calls during the summer season and ensure the system is well-tuned and operating efficiently,” he said.

“The goal of effective maintenance is to keep equipment in optimum operating condition,” continued Strahan. “Air conditioning is all about airflow and heat transfer. If a belt is loose or a filter or coil is dirty, it impacts both. If a system is overcharged or undercharged, it takes more energy to achieve the same cooling effect and it is hard on the system,” said Strahan. “If humidity is not properly removed by the air conditioning system, the comfort index will suffer, often resulting in the thermostat being set lower to achieve comfort. Lower set points cause an air conditioning system to operate more hours over any given 24-hour period. Additional operating time, outside of what should be required to meet the cooling demand, results in additional energy expense. Properly maintained equipment is more likely to deliver the right amount of cooling for the least amount of cost.”

Clean systems run more efficiently, and efficient systems decrease power consumption and system down time, said Flake, emphasizing the importance of proper, timely maintenance.

“By properly maintaining your system, you are also extending its life cycle, so you will get extended use out of it opposed to a system that is not on a routinely scheduled maintenance program,” she said.

Wiegmann Associates’ Hutch-inson summed it up: “When the unit is properly maintained, it runs less often or not as hard. That is easier on the equipment, lowers energy consumption, and saves the owner money.” 

Publication date: 6/19/2017

Want more HVAC industry news and information? Join The NEWS on Facebook, Twitter, and LinkedIn today!