WIN 2017/18

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Page 19 of 38

UNDERSTANDING, ACCELERA TED TSI provides the most accurate, dependable and versatile ventilation and indoor air quality measurement instruments on the market today. TSI offers a full line of: + Hydronic Manometers + Capture Hoods + Thermal Anemometers + Indoor Air Quality Monitors + Micromanometers To learn more, visit www.tsi.com/comfort ACCURATE. DEPENDABLE. VERSATILE. CIRCLE ID #17 ON READER SERVICE CARD OR GO TO HVACPPRODUCTS.COM/MARKET opposed to hydrof luorocarbon based. Hydrocarbon-based refrigerants include propane (R290), isobutane (R600a) and R32, which is a blend of R290 propane and another refrigerant. These naturally occurring chemicals operate in mid-pressure ranges of 10- 50 bar. Hydrocarbons have no ozone depleting properties and low GWP. However, they are highly f lammable and therefore require different and safer technologies for HVAC systems and components. CO2 — CARBON DIOXIDE: CO2 operates at almost twice the pressure of hydrocarbons in a typical air conditioning system, making it much more difficult to manage. But, CO2 has a GWP of one, whereas hydrocarbons have three times more global warming potential. AMMONIA: Another natural refrig- erant is ammonia, which measures zero for both ODP and GWP and breaks down rapidly. However, as ammonia is toxic and is extremely corrosive, installation and mainte- nance staff need to be appropriately trained in how to safely handle this material. It is important that proper maintenance techniques be used while charging the system and that all air is properly evacuated from the system. It is also critical that impurities be kept out of the ammonia system to prevent stress corrosion of steel components. When working with ammonia, material selection for overall system design needs to be taken into consid- eration. Most ammonia refrigeration systems are designed with either alu- minum or steel (carbon and/or stain- less) components with welded joints. Copper-based components and brazes are not typically selected as ammonia can corrosively attack those metals with the added presence of contami- nants like water or air. COMPATIBILITY AND SAFETY Each type of natural refrigerant comes with challenges that manufacturers have had to overcome with techno- logical innovation. To meet these challenges, industry leaders have developed HVAC systems with new types of compressors and components compatible with the latest common refrigerants — hydrocarbons, CO2 and ammonia. New products created for this market include a variety of pressure switches and sensors to meet different application requirements. HIGH PRESSURE Every component in today's HVAC systems is specified to certain operating conditions and pressure ranges. While CO2 is not poisonous like ammonia and not combustible like hydrocarbons, it does pose a different set of problems in that it operates at a higher pressure. This necessitates designing specialized components like pressure switches, tubing and other mechanical compo- nents specified to reliably work at these higher pressure levels. Safely working with CO2's extremely high pressure re- quires special training and equipment. It is essential that contractors and facility managers working with these next-generation "green" natural refrig- erants fully understand not only the benefits, but some of the technological challenges these new materials offer. William Bentley is engineering director at Sensata Technologies. HVACPproducts.com Winter 2017/2018 \ HVAC & Plumbing Product News 17

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