includes end-to-end encrypted features that help protect your data from unauthorized access. Their Unlimited pricing on the Pro Teams Unlimited plan is simply unbeatable because it includes both unlimited storage AND unlimited data transfer for each user. It appears to be based primarily on obsolete Carrier chiller technology and outdated thinking about open-drive chiller operation and maintenance.One of the best things about is that it’s really easy to use, and works much like Dropbox, but with better security, privacy and pricing. Parsnow’s article lacking in both expertise and objectivity. This lowers chiller capacity or increases the chiller-system power requirement. What about the heat generated by a hermetic motor? It must be absorbed by the chiller and exhausted to the cooling tower. The heat generated by the open-drive chiller is simply factored into the ventilation calculation. ASHRAE 15 Safety Code for Mechanical Refrigeration has a similar provision. Local codes already require sufficient equipment-room ventilation to ensure operator comfort. An open motor obviously adds heat to the equipment-room ambient, as does other equipment such as pumps and air-handling units. Parsnow states that open-motor chillers generate more ambient heat than hermetic chillers, and implies that is a serious concern. The bottom line is, refrigerant loss through open-drive chiller shaft seals is negligible.ĥ. The oil used to lubricate the seals has had the refrigerant previously removed. Positive-pressure chillers are equipped with double seals that also keep the seal faces moist during shutdown. Today’s shaft seals are made of advanced materials that are better lubricated throughout chiller operation. Contributing to this leak-tight performance are vastly improved open-drive shaft seals. All new chillers have leak rates of less than 1%, with no difference between open and hermetic drives.Ĥ. Replacing compression-fit connections with brazed connections andįurther, EPA’s acceptable chiller leak rate of 5% per year is well above field experience with all types of chillers.Replacing pipe-thread connections with face-seal fittings.Reducing length of piping and number of fittings.York engineers have systematically reduced the number of potential leak points in all our chillers. Leaks can occur in any chiller at pipe connections, screw-thread connections, and gasketed areas on compressor castings. Today’s open-drive chillers are as leak-tight as both semi-hermetic and full-hermetic designs. In fact, chillers from all the major manufacturers in the late 1990s are designed, built and tested to be leak-free. Parsnow states that open-drive chillers tend to have the highest leak rates in the industry. If the motor ever needs to be removed from the chiller for repair, alignment is automatic when the motor is re-bolted to the compressor.ģ. The flange provides factory alignment of the compressor and motor shafts, eliminating concern about thermal growth from either component the two work as one unit. However, open motors on York factory-packaged chillers up to 2,200 tons use a flange arrangement whereby the motor casting is bolted directly to the compressor casting (see accompanying photograph). This might be true on chillers with an external gear, such as shown in the picture accompanying the April 26 article. Parsnow states that open motor-compressor alignment is a field-engineering challenge. Open, constant-speed chillers get the same amount of cooling at both full-load and part-load conditions.Ģ. Thus, all hermetic chillers need and have high-temperature motor protection. So, a lot of owners, engineers and contractors are moving to open-drive chillers, including systems below 2,000 tons of refrigeration, and with good reason.Īt low-load operation, adequate motor cooling is an issue with hermetic systems because less refrigerant is being circulated to the motor windings. Inherent flexibility of open-drive systems for resizing and retrofit, parallel-drive and hybrid-drive applications.Proven energy efficiency of open-drive designs.Lower cost and less downtime in the event of motor burnout, which is considered a catastrophic failure in hermetic systems.Less downtime for routine service, because the motor is not tied to the refrigerant circuit.Accessibility and serviceability of open motors, without the need to disassemble the compressor.Reliability of heavy-duty ODP motors (open, drip-proof), with their simple cooling and lubrication systems.Chiller buyers and specifiers must have good reasons for switching to open-drive chillers in such large numbers, and they do. That’s a 50% market-share increase from the 1980s. Parsnow states, open-drive centrifugal and screw chillers represented over one-third of the large-tonnage chillers sold in the U.S.
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