5 Major Threats to Chiller Efficiency
Building chillers are the largest energy-consuming component in most institutions, businesses and facilities. In many facilities, more than 50% of the annual electricity consumption can be attributed to building coolers. Therefore, the correct operation and maintenance of building chillers should be a high priority in any facility energy management plan.
However, it is surprising to see the frequency of inefficient or ineffective operation or maintenance of chillers, resulting in increased energy costs, reduced system performance and reliability, and shortened equipment life.
Although there are many factors that can reduce the efficiency of the cooler, the five most common factors include: poor operating practices, neglected or postponed maintenance, neglected cooling tower maintenance, oversized and neglected cooler with spare fuel. Although all these factors pose a real and major threat to the efficiency of the chiller, maintenance managers can easily control or eliminate all of these factors.
1. Bad operating habits
Poor operating practices will not only reduce the efficiency of the chiller, but also reduce the service life of the chiller. Most of these practices are the result of one of two situations: trying to get the cooler to perform an operation it is not intended to perform or not understanding the consequences of a particular operation.
For example, when trying to provide more cooling water to the facility, a common practice is to increase the flow of cooling water through the cooler. It is believed that as the flow rate increases, more cooling water will be available.
However, in fact, increasing the flow through the cooler beyond the manufacturer’s recommendations actually reduces the operating efficiency of the cooler. It is also important that a flow rate higher than the recommended value will increase the corrosion rate of the cooler tube, leading to early damage to the tube.
The problem with poor operating habits is that their effect on the operation of the cooler is usually not noticed. The chiller continues to run and can meet various building loads under various conditions. However, soon, poor operating habits were accepted as standard operating procedures, and one day, the operating problems of the chiller may become obvious, or the chiller may not be able to meet the cooling load that has never occurred before. When this happens, technicians usually blame the weather or the cooler itself. It is not how the cooler is operated and maintained.
It is necessary to ensure that poor operating specifications will not become standard operating procedures, and personnel need to be trained in maintenance and operating specifications. Proper training can help operators and maintenance personnel to efficiently set up and operate the cooler.
It also allows maintenance personnel to develop ongoing cooler maintenance procedures to ensure the long-term effective service life of the equipment. It enables maintainers to detect and correct problems early before they develop into broader, more expensive problems. Finally, training can help operators and maintenance personnel identify poor operating habits before they are recognized as standard operating procedures.
2. Ignore maintenance
Although good maintenance habits are important to the effective operation of all construction equipment, they are more obvious than maintaining building chillers in a few areas. For example, consider the impact of good maintenance on the efficiency of the cooler.
The full-load efficiency rating of most new high-efficiency centrifugal chillers is about 0.50 kW per ton. If the chiller is well maintained, its full load efficiency is expected to be 0.55-0.60 kW per ton within five years.
If the maintenance of this cooler is neglected, it is not surprising to find that the full-load efficiency has dropped to 0.90 to 1.0 kW/ton. On an annual basis, this means that poorly maintained chillers will use 20-25% more energy each year to produce the same cooling capacity.
Good cooler maintenance starts with keeping the cooler running log. Regularly recording the operating parameters of the cooler can provide a valuable diagnostic tool for maintenance personnel. Over time, most chiller problems will slowly develop. By tracking the chiller data and performing regular inspections, operators can identify trends in chiller performance and help maintainers find the root cause. Although it is common for most facilities to maintain operational logs of chillers, few people regularly check them, which is important. Refrigerant leaks, air leaks, pipe fouling and other problems can be determined by thoroughly checking the operation log.
Another important factor in the chiller maintenance plan is regular inspections. These inspections performed daily, weekly, monthly or yearly help determine the operating conditions and operating efficiency of the cooler. They form the basis of any refrigerator maintenance program.
Most operations can be performed without stopping the cooler. Some requirements, such as the annual inspection of the chiller pipeline, require that the chiller be shut down for a few days. Although the inspection will determine the maintenance activities that need to be performed, the inspection itself cannot ensure the condition of the cooler. Maintenance personnel must thoroughly track and perform the activities required for maintenance.
3. Ignore the cooling tower
The cooling tower is a key component for the efficient operation of the cooler system. In most cases, the operation of the cooling tower largely determines the operating efficiency of the cooler. In good condition
, a properly functioning and well-maintained cooling tower allows the cooler to operate at maximum efficiency.
Even a slight drop in performance during the operation of the cooling tower will have a significant impact on the efficiency of the cooler. For example, for every degree of Fahrenheit increase, the condenser water supply from the tower will increase, and the chiller efficiency will decrease by an average of 2%.
Although cooling towers play an important role in the operation of coolers, they are often overlooked. Cooling towers, usually located on the roofs of buildings, often suffer from being invisible and annoying. Given the environment in which the cooling tower must operate, it is especially important to perform proper maintenance.
The cooling tower is exposed to the natural environment and can well collect dust, leaves and other debris, which can block the air and water channels. In addition, their operation in a warm and humid environment can promote biological growth, which can block the nozzles and reduce their heat transfer efficiency. The solids that accumulate in the cooling tower water can also block the nozzles and water passages.
Correct cooling tower operation requires management personnel to arrange regular inspections of the cooling tower and perform maintenance when needed. Water treatment procedures must be implemented to keep the suspended solids concentration in the tower water system within an acceptable range. In addition, the tower fan and water level controller must operate normally.
4. The size is too large
The correct selection of the size of the cooler is also very important for its effective operation, because as the load decreases, the efficiency of the cooler will drop rapidly. When the equipment is new, the size of the cooler may be slightly larger to allow the cooling load in the equipment to be increased without having to replace the cooler.
But in view of the agitated state of the equipment, even after only a few years, the load faced by the chiller may be very different from the load to be met by the design. This is especially true if the facility has been modified to improve its energy efficiency.
For example, installing new windows or energy-saving lighting systems usually results in a significant reduction in cooling load. As the cooling load decreases, the number of hours that the cooler operates under reduced load each year, so the efficiency decreases, which leads to a decrease in its annual operating efficiency.
When replacing the cooler, it is easiest to correct the problem of oversize. By studying the operation and performance of the existing chiller and the cooling load it actually serves, managers can more closely determine the size of the new chiller to meet these needs. If a facility is served by multiple chillers, the size of the replacement equipment can be determined so that different chillers of different capacities can be run as needed to meet the cooling load, so that the operator can perform phased operation as needed.
Between the replacement of the cooler, managers can help correct the problem of oversize by installing a variable frequency drive on the existing cooler. These drives will slow down the operating speed of the cooler as the cooling load decreases, so that the cooler can run close to full load under a certain range of loads.
5. Ignore the alternative fuel cooler
When the water chiller finally runs out, a common mistake is to simply replace it one-to-one. If the old cooler is an electric centrifugal unit, the administrator replaces it with a new electric centrifugal unit. Although it might be reasonable to install the type of chiller from 15 to 20 years ago, there have been so many changes since then to simply assume that the same type of chiller is the best choice for today's facilities.
Deregulation, real-time electricity prices, and technological advancement all provide managers with the option of replacing existing building chillers. The deregulation and real-time pricing of electricity provide managers with the motivation to manage their electricity load. Leveling the load, especially during peak usage periods, can reduce electricity costs.
Due to the high electrical load, the electric refrigerator is a very big goal when looking for ways to reduce the electrical load and control costs. New technology chillers, including natural gas-driven centrifugal chillers and steam or gas absorption units, allow managers to use alternative fuels during periods of high electricity bills. By investigating the cost of a new generation of chillers and their impact on operating costs, managers can save a lot of energy costs without sacrificing performance or reliability.
By understanding the five common threats to chiller efficiency, managers can take steps to improve the performance of the chiller system while improving the bottom line of the organization.