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When it comes to large equipment that powers HVAC systems, the old saying “an ounce of prevention is worth a pound of cure” definitely rings true. And nowhere is an ounce of prevention more beneficial than with chiller maintenance.
Chiller downtime can be very costly for many reasons, but contractors who work regularly on chillers say with vigilant maintenance, failures may be prevented.
Causes of Chiller Failure
In Greg Crumpton’s experience, many chiller system failures have proven to be oil related. Crumpton, president and founder of AirTight Mechanical Inc., in Charlotte, N.C., explained that these failures are more likely when the machines have become oversized for the load.
“Perhaps a significant retrofit has reduced the load, lighting loads have decreased, maybe even a data center has moved some of its load to another site, thereby causing the machine to run unloaded, etc.,” he said. “Oil in the compressor, or a lack of oil, may cause significant losses, which may saturate the refrigerant with oil, therefore exacerbating the problem.”
Ken Bodwell, leadership team member, Innovative Service Solutions, Orlando, Fla., agreed. “On centrifugals, we often find that the oils have not been changed,” he said.
Bodwell added that he also sees chiller failures when annual maintenance has not been performed or there is no eddy current history to determine barrel condition.
Russ Donnici, president, Mechanical Air Service Inc., San Jose, Calif., said he generally sees centrifugal chiller failures that have been caused by noncondensables in the system, lack of condenser and evaporator tube cleanings, and poor cooling-tower maintenance. “These units operate in a vacuum, so noncondensables are a big issue,” he explained.
Donnici added that for reciprocating and screw chillers, he commonly sees dirty condensers and evaporator tubes that haven’t been cleaned.
Dennis Purvis, service manager, Mechanical Services Inc. of Central Florida, in Orlando, Fla., pointed to a few more causes of failure, including “refrigerant leaks, condenser-fan motor failure, and electrical components like contactors.”
Aaron York Sr. of Aaron York’s Quality Air, Indianapolis, summed it all up, stating that the most common cause of chiller downtime is “a lack of timely and appropriate preventive maintenance.”
To prevent chiller failures, York said that, at a minimum, maintenance should include “regularly checking all operating components, safety controls, and controllers, as well as refrigerant system operation.”
It’s important to follow the manufacturer’s recommended maintenance timeline and procedures, Bodwell said.
Purvis recommended that chillers be inspected on a monthly or quarterly basis with annual condenser coil cleaning or tube cleaning.
Crumpton stressed the importance of an oil analysis, stating that the system should be inspected for metallic content and acidity. Refrigerant saturations should also be regularly monitored, he said.
“Keeping the machine loaded is still the most helpful way to ensure longevity and reduced repair costs,” Crumpton said. “These machines were built to run with a load, not coasting and having to work less. The kilowatt cost per ton is best when running as designed.”
While keeping a daily chiller log has long been recommended as a standard maintenance procedure, some contractors acknowledged that this approach is oftentimes difficult to maintain.
“Unless there is a site engineer, this is very expensive,” Purvis said.
Bodwell noted, “As a general practice, we do not keep daily logs because in most cases there is not a technician on site daily. We record data on every visit, and it is electronically recorded in the equipment history. A lot of our chiller systems have remote monitoring, should equipment exceed set points.”
Crumpton also noted the increasing importance of digital data logging.
“With the onset of automated controls and overall control of plants, we think trending is best done digitally. However, that being said, nothing beats an experienced eye and ear walking throughout the environment, looking and listening for anything abnormal,” he said. “So really, a good mix is most likely the right balance.”
To aid clients in preventing chiller failures, many contractors offer full-coverage maintenance contracts.
York said that his preferred method is to offer a contract that covers “100 percent on all parts and labor for preventive maintenance and repairs.” But for customers who are not interested in full coverage, he suggests regular inspection and reporting agreements.
“Full coverage is far and away the best investment for both the customer and the company,” said York. “The customer’s needs are met and our interest is served in assuring the prevention of failures by regular and thorough inspection services. If there is a major failure, which is in our best interest to avoid, the customer is better served and happier because they are not subjected to a major expense. Their service is promptly returned, without the wait for someone to authorize major expense allocation.
“We are better served by prevention of such failures, but, if such does occur, we already have cash reserves to offset the costs of repair. We are then accorded the opportunity to determine why we had the failure and what is needed to ensure we never have another one.”
At Innovative Service Solutions, Bodwell said, “After a thorough evaluation, we will cover all components including the motors of chillers under 10 years old. Equipment older than 10 years, which often is lacking maintenance history, is risky. In some cases, we will purchase insurance coverage to minimize our risk.”
For the client, Bodwell said, the benefit of such a contract is peace of mind.
“They typically understand that the equipment will be properly maintained because we are minimizing our exposure and risk. We have developed a relationship with the client that puts us in a position of trust when the time for replacement or retrofit occurs.”
Purvis noted that these contracts are very expensive due to the risk involved. “With these contracts, we schedule monthly visits with the annual cleanings. Typically, the heat exchangers and non-moving non-maintainable parts are excluded from coverage. For the client, it can help them plan a fixed budget, but they still need an emergency contingency fund,” he said.
Donnici offered an opposing viewpoint on full-coverage contracts. “I know our industry promotes them and views them as a great money maker; however, my personal opinion is that someone loses on full service contracts,” he said. “Either the customer pays too much or the contractor underestimates the cost and suffers from it.”
Another approach is to offer contracts customized for the client, said Crumpton.
“We offer full coverage on centrifugal chillers and screw machines, as well as any other type of chiller,” he said. “We provide all of the manufacturers-recommended services, as well as water treatment, as the customer desires. Tube brush cleaning and eddy-current analysis is in the mix as well. Some customers want to do some of this internally with their own staff, so we work to customize a program for them specifically. We are not about a rigid set of rules per type of contract.”
Publication date: 5/13/2013