Jan 27, 2017
In this episode, we talk with Jeff Nieman about chillers and how they work.
For those of you who primarily work in residential or light commercial HVAC, chillers may be unfamiliar at best and terrifying at worst. However, centrifugal chillers' parts are actually quite similar to those of HVAC units. They have an evaporator, compressor, condenser, metering device, and control system, just like the HVAC units we see every day. Jeff believes that breaking a chiller down into its parts is the easiest way to become comfortable with it.
Chillers are used for comfort cooling and process cooling. In comfort cooling, chillers discharge cool water (44°F) to the building. From there, air blows over the water to cool the space. For process cooling, chilled water flows through machines that require constant cooling to operate correctly, such as laser-cutting machines and MRIs. As you can see, chillers simply absorb and reject heat, just like standard compression-refrigeration HVAC systems. However, unlike traditional compression-refrigeration units, chillers have an independent oil circuit.
Preventive maintenance is a major part of chiller work. You can tell a lot by listening to a chiller and looking for oil or water on it. You also check superheat, subcooling, and water temperatures. Service calls also require technicians to engage their senses. Most issues deal with low water flow, building issues, and dirty strainers in the condenser water piping.
Bryan and Jeff also discuss:
- Two-way and three-way valves
- Glycol and freeze protection
- Alarms (float switch, low evaporator pressure, high condenser pressure)
- Chiller troubleshooting
- Impellers and inlet guide vanes
- Suction in negative pressure
- Fan coils
- Chiller water
- Screw chillers
Also, Bert and the Testo 770-3 make an appearance.
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