Refrigeration Compressors and Air Conditioning Compressors - Insights

Refrigerants and refrigeration systems have to be modified in order to address environmental requirements related to technical progress. These changes provide equipment manufacturers and practitioners with opportunities to better meet the needs of their customers. These needs have also been changing quite a lot, in particular in terms of: · Humidity control: it is difficult to control both temperature and humidity. Nevertheless, there is increasing demand in this field. This is the case of the following in particular: * food preservation, namely chilled food, flowers and in display cabinets, * plant and processing rooms, * all air conditioning systems, where humidity control has led to choosing temperatures that are far too low in many cases, with discomfort and high energy consumption as consequences. · Hygiene: requirements related to hygiene have become increasingly stringent in the food sector as well as in air conditioning. · Reliable cold chain: in particular during transport, at interfaces, etc., with the need for monitoring, recorders and/or integrators. · Energy savings: in relation to economic efficiency as well as with regulatory requirements about global warming. a lot of progress can be achieved in air conditioning design for example. The IIR Congress in Sydney will focus on this point in particular.

The Energy efficiency and low maintenance over the lifetime of a compressor would be the dominating factor in today's selection of hermetically sealed compressors. The commercial refrigeration sector, while still using hermetically sealed piston compressors on small applications, is drifting towards the Scroll type compressor for medium to large type chill temperature applications. Scroll technology is very efficient on medium refrigeration and Air-conditioning applications with low noise levels and can be started with very low inertia because they remain unloaded during the Off period. They are also lightweight for the amount of power they deliver and have very few mechanical parts. There is also the option of capacity control on Scroll compressors that allow them to run at reduced capacity on larger applications when the work load conditions fall in demand. (A) rated air-conditioning systems are generally fitted with hermetically sealed Rotary type, Inverter driven compressors for capacities up to 10.00 KW and run on R410a refrigerant gas. This design of the motor has enhanced the power output of these new compressors which are delivering very high COP's which make them the more chosen type for all new split air-conditioning & heatpump manufacturing companies.

I think the biggest driver of compressor design comes from developments in refrigerants. New, higher-pressure refrigerants that are better for the environment necessitate materials and processing improvements that improve the strength of compressor components. Another important push for new compressor technologies is the eternal quest for improved efficiency.

Mitsubishi, Sanyo, Hitachi, Toshiba are all front runners in the area of Rotary and scroll type Inverter compressors with Copeland, Bitzer and Danfoss specializing generally in the Scroll fixed speed type compressor. Although this new concept is producing very efficient machines, the cost of replacing Inverter type compressors is expensive and requires an upgrading in skills to recognize and understand the workings of inverter drive technology.

At the moment the modern compressors are of a poor quality compared to units built in the sixties and seventies. I have purchased three compressors in the last two years and all three have failed. My old units were bought secondhand with over eleven years of use, and lasted over twenty years before failing.

DC inverter compressors and digital scroll. Adapt the power to the refrigeration or air conditioning needs, using displacement or variable speed control.

Air conditioning engineers broadly divide air conditioning applications into comfort and process. Comfort applications aim to provide a building indoor environment that remains relatively constant in a range preferred by humans despite changes in external weather conditions or in internal heat loads. Air conditioning makes deep plan buildings feasible, for otherwise they would have to be built narrower or with light wells so that inner spaces receive sufficient outdoor air via natural ventilation. Air conditioning also allows buildings to be taller since wind speed increases significantly with altitude making natural ventilation impractical for very tall buildings. Comfort applications for various building types are quite different.

I have encountered various types of air compressor in ships where they supply high pressure and low pressure ringmains and control and servo air to pneumatic control systems. I have selected and applied most types of refrigeration compressor from 1/2 HP up to 200 HP in a wide variety of applications including cacade and 2 stage systems, cold rooms, dx air conditioning, water/fluid chilling, all at temperatures ranging from -70ºC to +30ºC and with all CFC, HCFC, HFC and HC refrigerants.

That I know of, the compressors that are equipped with our valves go on trains, buses, airplanes, ships, industrial and conditioning.

Industrial heat pump to produce hot water for sterilization Heating applications using waste heat as heat source and replacing the use of fossil fuel (boilers)

Ice machine applications are different where as a "reverse run" hot cycle is used to melt ice off of the evaporator where ice cubes are formed.

Air condition condenser and compressor of the same freon used with a walk in cooler evaporator.

Yes, if the compressor supplier buys valves from a source other than Selco he runs the risk of having its unit fail for any assembly detail taken not into consideration. If the compressor fails so will the unit.

Yea, never rebuild a 70 hp semi-hermetic on a 40 year chiller without replacing the evap barrel. Now pricing a replacement chiller.

Van blew up after lighting cigarette, R600 leeched from oil in replaced compressor which was being returned for warranty....

The problem with Inverter driven compressors is matching them up with other Manufacturer's systems. You simply cannot buy an "off the shelf" standard Inverter compressor replacement for your system via the Wholesalers. They all have particular characteristics to their designer and inverter driver and so you need to replace like for like via the Manufacturer/agent of your particular system. My wish list would be to standardize this feature on some of the leading brands, but I am sure this has more complicit implications than we could possible imagine.

Design and produce solar air condition at a simple and low price that every one can install without thinking of comparing with grid connected solid units.

Lowest power consumption per ton of refrigeration along with reliable service.

Always buy machines that you can repair on site, because it is very difficult to bring them to a workshop. In critical applications, it is better to install two or three smaller of the same type machines than one big because: 1). in part loads these are more flexible 2). in case of failure of one, you have the others 3). You can have a limited stock of spare parts.

Get in touch with a sales representative to help figure out exactly how much cooling capacity you need, what special features would help tailor the system to your needs, and don't be afraid to tell them you don't quite know what you need.

Just don't oversize. Ohm out windings and if necessary test fire the compressor momentarily before installation. Always check that the compressor delivered to your job is the one that was ordered.

The older design compressors are more reliable and much easier to repair than the new ones. Try to avoid electronic controls (if it is possible) because in case of failure, it will be very costly to change them. Before your decision to buy any type of machine, research the availability and cost of the spare parts. The better machine is the machine that is in operation easily, soon and with logical cost after a failure.

Do your homework for reliability testing of selection for your applications. Compressors failing in only three to five years will not delight your customers.

Sizing and number of units. 3 to 5 units for total required capacity should be ideal. Depending on criticalness and reliability standby unit can be added.