Chillers are an essential component in many building Heating, Ventilation and Air Conditioning (HVAC) systems. They provide cooling to the building by working in tandem with pumps and cooling towers in a water-cooled chiller plant. Because of the chiller’s complexity and its role in cooling facilities, it is arguably the most important piece of equipment to maintain.
Chillers are big energy users and are often not running at peak efficiency. Missed chiller energy savings opportunities can be as high as 40% and typically range between 10 to 20 percent. The U.S. Department of Energy (DOE) also estimates chillers consume more than 50% of a building’s electric energy use during seasonal periods. Unfortunately, the DOE also estimates chillers are wasting up to 30% of their energy use because of inefficiencies.
This article examines often overlooked or undiscovered energy waste with water-cooled chillers and the benefits of chiller monitoring and data analytics.
Multiple Reasons for Chiller Plant Inefficiencies
Energy (and money) is often wasted due to chiller inefficiency and underlying operational problems. There seems to be a general thinking that if a chiller is delivering chilled water at its setpoint, everything is fine and annual maintenance takes care of the rest. This thought process can lead to problems since annual maintenance is generally scheduled when the chilled water plant is not running anywhere near maximum capacity. This means issues can go unseen by the service technician. Frequently, issues remain hidden until chillers operate near their design capacity.
In many instances a chiller has poor operating efficiency – or worse – the chiller’s capacity is reduced. Reduced capacity doesn’t show itself until the plant can’t deliver on the hottest week of the year and chillers can fail at that time because they are pushed to or beyond their design limits. With such a critical piece of equipment, it’s better to know there is a:
- Performance issue before you’ve spent money operating under the pretense that everything is fine,
- a capacity problem before the chiller plant can’t deliver enough chilled water, and
- a reliability problem before a chiller fails at the least opportune time.
When we initially hook up chiller plants to a monitoring and analytics solution, we commonly find efficiency losses from 10 to 20 percent, and sometimes up to 40% on about half of the chillers we evaluate. It’s not that service contractors are doing something wrong; they just don’t have all the information served up in a way to help pinpoint problems. Service technicians know more about their machines than anyone. They just don’t have the same tools and are not specifically looking for energy waste and underlying problems.
Typical chiller issues we encounter include low refrigerant, which is more prevalent on high-pressure machines; fouled condenser and evaporator tubes; or issues with Variable Geometry Diffusers (VGDs), Inlet Guide Vanes (IGVs), sensors, and Variable Frequency Drives (VFDs). We also occasionally see liquid carryover and excessive compressor oil. We’ve even run across an older chiller control board causing reduced chiller performance. It all points to the need for chiller plant monitoring and analyses of analytics.
Implementing Chiller Plant Monitoring Solutions
The value of a monitoring and analytics solution will depend on the quality of the analytics and ultimately who is evaluating the data and delivering findings. All solutions we are familiar with collect data locally at the chiller and then send it to the cloud for analytics. Some good rules of thumb to follow to ensure the system is operating efficiently, include:
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