Air conditioning systems typically consume the most energy in commercial facilities and can be responsible for 35% – 50% of a building’s electricity consumption. Water-cooled chillers are a big part of this consumption and can consume half of this electrical use. That’s why it’s important to understand potential problem areas early and implement corrective maintenance processes which prevent costly problems from developing.
Potential Problem Areas
1. Condenser Tube Fouling
This is the number one reason water-cooled chillers have difficulty in their operation, thereby increasing energy usage. Tube fouling is caused by not brushing the tubes regularly or by ineffective water treatment. Tube fouling leads to compressor surge which damages the compressor and motor. Worse yet, if fouling continues, it can lead to a tube leak which results in water entering the chiller causing a catastrophic machine failure.
To resolve tube failure, chiller maintenance companies (such as CM3) remove debris, sediment, scale, and corrosion. Yearly maintenance of dropping both condenser heads, then brushing the tubes and removing the scale allows the chiller to run efficiently. Afterward, during operation, careful monitoring of the condenser log readings will detect the need for repeat tube cleaning during the operating season.
2. Condenser Water Temperatures
Not only does the water from the condenser need to be cleaned and properly treated but the temperature coming from the cooling tower should be as low as the chiller will allow. For most manufacturers of chillers, lowering the condenser water temperature increases the efficiency of the compressor and the overall capacity of the machine. Gone are the days of having to maintain 85 degrees entering condenser water temperature; lowering the condenser water temp saves money.
High efficiency cooling towers allow water temperatures to get much lower, and this should be taken advantage of whenever possible. A study of your chiller should be undertaken to identify what the maximum point of operation should be for lower condenser temps. Some chillers can go as low as 55 degrees while others must be higher due to potential oil loss problems. (Contact CM3 for this evaluation.)
3. Refrigerant Charge and Refrigerant Leaks
A proper refrigerant charge is important to achieve 100 percent capacity of the chiller. Over time, leaks lead to a reduced refrigerant charge which causes the chiller to run outside of its design parameters. Not having a full refrigerant charge reduces efficiency and the overall cooling capacity of the chiller.
Refrigerant loss is due to many issues, such as loose fittings, worn gaskets, and seals. Each of these issues contributes to refrigerant leaks which over time require expensive refrigerant addition or sometimes a costly full replacement. An annual leak test is a minimum requirement along with the testing of your refrigerant alarm systems to provide you with an advance warning of problems, so this does not happen.
4. Electrical Issues
The electrical system within a chiller is carefully designed and must be maintained to prevent expensive failures. Improper phase operation, low or high incoming line voltage, blown fuses, voltage surges, or general wear on electric contactors can all cause serious electrical problems. Electrical issues can cause frequent chiller shutdowns – usually at the worst possible times. Electrical overloading causes overheating and a likely failure. Wires and connections can come loose over time, which can result in nuisance chiller malfunctions.
In addition to being good practice to maintain the entire electrical system of a chiller, the safety of all the people around the machine will benefit. Good electrical preventive maintenance is a critical part of chiller maintenance and a comprehensive safety program.
5. Deficient Operating Practices
Having a good maintenance program is essential to trouble-free chiller operation. Performing yearly periodic maintenance of condenser tubes, refrigerant charge and electrical systems will save an owner money in the long run. Having an early warning system that alerts you to small problems before they become larger ones will pay off in uninterrupted chiller operation and extended chiller life. Contact a reputable chiller servicing company (like CM3) to design a maintenance program that fits your budget and takes care of the heart of your HVAC system.
Best Practices
A comprehensive maintenance plan is essential for the efficient operation of your system and maximizing its lifespan. In addition to conducting regular maintenance and inspection, here are a few tips for facility managers:
1. Maintain a Daily Operating Log – The Federal Energy Management Program (FEMP) recommends updating the log four times a day to monitor key operating parameters that will help indicate if any problems are developing. If four times a day is unfeasible, a minimum of once a day is suggested. This data will help raise any red flags in case something needs to be addressed. Careful logging of refrigerant temperatures, pressures, flows and voltages will all be early identifiers of problems.
2. Keep Tubes Clean – The presence of scale and fouling can greatly impact efficiency. Even the smallest amount of scale can add thousands of dollars in additional energy expenses. It is recommended to clean chiller tubes at least once a year, but regular monitoring can help identify when cleaning should take place. With regular cleaning, you can reduce the effort on the compressor and motor, thereby increasing efficiency while simultaneously avoiding catastrophic problems such as the tubes eroding away.
3. Ensure a Leak-Free Unit – In addition to scale, leaks can also be detrimental to the efficiency and operation of the system. Having a leak-free unit means that hazardous refrigerants are NOT released into the air. Keep refrigerant levels within the manufacturers’ recommendations. Refrigerant levels can be tracked by noticing purge run time, checking the refrigerant sight-glass for bubbles, and using a gas analyzer to assess all the joints and connections. Frequent leak checks of the chiller and of your refrigerant monitoring system will ensure that 1. you are NOT leaking refrigerant and 2. You know right away if it’s happening before it becomes a bigger problem.
4. Maintain Proper Water Treatment – A water treatment program can help maintain efficiencies between cleanings. It helps to reduce the buildup of contaminants on heat-transfer surfaces and slow the growth of harmful bacteria.
Bottom line: A good preventative maintenance plan either conducted internally or by a reputable company (such as CM3) is essential to the long-term efficiency and lifespan of your equipment