Commercial rooftop units, or RTUs, typically last 15-20 years, as long as they’re properly serviced and maintained. In fact, HVAC contractors in different climates and regions all over the U.S. agree that irregular upkeep is the most problematic issue when it comes to rooftop unit failure.
PREVENTING PREMATURE FAILURES
Edward McFarlane, vice president of marketing and development at Haller Enterprises Inc. in Lititz, Pennsylvania, said a lack of proper maintenance is by far the most common cause of failure.
“To be clear, this is not on accounts that are performing maintenance, but rather that maintenance is not being performed to the correct standards,” he explained. “This is apparent by the usual dirty filters and clogged coils, which lead to premature compressor failures. And it’s because of simple issues like a lack of water access, since many companies are not going to send 250 feet of hose along or the technician is not going to drag it out. There is also a lack of understanding beyond the most basic of controls.”
Eric Fleming, service manager at Colorado Climate Maintenance Inc. in Englewood, Colorado, said the two most frequent issues he encounters are severe hail damage to the condenser and compressor failure.
“Both of these issues are preventable,” Fleming said. “Compressor failure can be caused by electrical phase problems, elevated refrigerant pressures, and low refrigerant pressure. These items can typically be corrected at a much lower cost than the compressor replacement would ultimately cost. Electrical issues can be corrected in a lot of cases by replacing a worn contactor, which would be detected during routine maintenance. Elevated pressures can be caused by dirty or damaged condenser coils as well as a failing condenser fan motor. Low pressure situations can be caused by a dirty evaporator coil, dirty filters, or a loss of refrigerant issues, which may require a leak check and repair. All of these issues can be easily detected during routine maintenance inspections and, in most cases, can be easily corrected.
“Condenser coil damage from inclement weather can be prevented by simply installing a hail guard to protect the face of the coil,” he continued. “This is something we include as a standard upgrade on all of our rooftop unit replacements, and it’s also a good source of revenue on existing rooftop equipment. This is a very easy and low-cost solution that can save customers thousands of dollars in coil repairs or replacement costs.”
Aside from worn belts, dirty filters, and faulty coils, techs at Willow Street, Pennsylvania-based JK Mechanical frequently encounter damaged blower sheaves and contactors.
“These are what I call ‘wear items,’” said Chris Broyles, commercial service manager at JK Mechanical. “They are designed to wear with use and be replaced on a regular basis. They would be analogous to brake pads and rotors in the automotive industry. As blower sheaves wear, they alter the blower wheel’s RPMs as well as increase friction on the belt. This speeds up the degradation of the belt, reduces blower efficiency, and affects the overall efficiency and capacity of the unit.
“Worn contactors are an often overlooked item, because the amount of pitting and wear they should achieve before being replaced is subjective and can differ greatly from technician to technician,” he continued. “Compressor manufacturers are highly aware of the danger of a worn contactor on a compressor. So much so that Copeland voids any and all warranties on its three-phase compressors due to single-phase burnouts that are almost exclusively caused by faulty or worn contactors. In my opinion, spending a couple of hundred dollars on a new contactor is cheap insurance against a possible compressor replacement that could exceed $10,000.”
Broyles said he commonly discovers failed heat exchangers. “A high percentage of the HVAC units in our area are gas-fired, including packaged rooftop units. Unlike split-system furnaces that may get their combustion air from inside a conditioned space or by way of polyvinyl chloride (PVC) vent piping, the burners and inducer outlet on packaged rooftop equipment are much closer to the outside ambient. The body of the heat exchanger is typically directly in the supply airstream with temperatures as low as 45°-50°F during the cooling cycle. This causes any moisture from the ambient air that enters the heat exchanger to condense and corrode the heat exchanger. It’s not uncommon for a packaged rooftop unit to have one or more heat exchanger replacements in its 12- to 15-year lifespan. A failed heat exchanger in a unit that is more than 12-15 years old typically results in a full unit replacement.”
CONTINUAL MAINTENANCE IS KEY
Ann Kahn, president of Kahn Mechanical Contractors in Dallas, said clients may encounter numerous issues caused by dirty condensers and evaporator coils. These issues can all be prevented with regular cleaning through a preventive maintenance program, she said. Other common issues include compressor and motor failures, which are also typically caused by a lack of regularly scheduled preventive maintenance.
“Coil cleanings and filter changes allow the air to pass freely to condition the air,” said Kahn. “Belt replacements help avoid downtime, occupant discomfort, and possible motor damage. Preventive checks also allow the owner to know what parts are likely to fail in the near future as well as to budget for replacement units down the line.”
Additionally, preventive maintenance benefits building owners with less downtime due to breakdowns and emergencies. “It also ensures better energy efficiency, which results in more affordable running costs and the ability to more easily budget for replacement equipment,” Kahn noted.
Dustin Upmore, service manager at Capstone Mechanical in Waco, Texas, said the lack of basic maintenance is a widespread problem. He suggested mechanical contractors have a dedicated salesman pursue planned maintenance contracts with customers.
“Regular maintenance keeps a unit running at the highest capacity possible,” Upmore said. “It cuts down on run time of the equipment and helps keep the area cool with less effort. In my opinion, planned maintenance is one of the most important things that can be done to help prevent issues, and it is probably the one thing that is also most overlooked.”
Preventive maintenance also benefits building owners by reducing costs in the long run, Fleming noted.
“Not only can routine maintenance detect issues that could ultimately cause major component failure, it also reduces utility costs and wear and tear on the unit,” he said. “While utility costs may not be the driving force with the way that many leases are structured today, it can prevent many major issues that ownership may ultimately be responsible for, including repair or replacement of the equipment. With routine maintenance and filter/belt replacement, a rooftop unit may see an additional three to five years of life. The owner will most likely have a tenant who is more willing to stay in a long-term lease situation if they have fewer breakdowns and a more comfortable work environment.”
So, what are some best practices when it comes to rooftop unit maintenance?
Broyles advises safety is always the top priority on a job site. “The only real difference between servicing rooftop equipment versus equipment mounted in other locations is the increased safety concerns of being on a roof. Being aware of the extra danger and practicing proper safety procedures is critical. Safety is increasingly being made the responsibility of the building owner and not just the contractor. It’s in the building owner’s best interest to contract with vendors that are safety conscious.”
Kahn said her technicians practice a set of best practices that include power washing coils when needed, leaving an extra belt in the unit cabinet for emergencies, and keeping customers updated on the equipment’s condition.
Additionally, it’s important to consider the entire unit when diagnosing a problem, Upmore noted. “Anytime we are called out to look at a unit, it’s important that we not only address the problem at hand, but go ahead and look at all system components.”
Fleming said Colorado Climate Maintenance has implemented a digitally formatted checklist customized to each property the company performs maintenance on in order to make sure the equipment is operating properly and as efficiently as possible.
“Our technicians use a smartphone or tablet to fill out the form, and these are provided as an added value to our customers,” he explained. “The digital forms include a list of which pieces of equipment have been inspected, an itemized inspection list, and any problems found during the inspection. We also have our technicians look at the big picture while performing maintenance. We try to anticipate future needs with the building equipment and controls and advise management to budget accordingly.”
Fleming said technicians also make cost- and equipment-saving suggestions to the building owner or tenant that may help them save money and increase the unit’s longevity. Additionally, they also report on any non-HVAC-related issues they may discover.
“Many buildings are remote, and ownership/management may not be on-site except for occasional site visits,” he said. “We routinely find broken doors/locks, signage, lighting issues, and plumbing leaks. Again, we provide these details to our customers as an added value, and this ultimately helps build a trust-based partnership with the customer.”
Publication date: 6/13/2016