Monthly Archives for January 2011

Discharge-Bypass Valves Operation

Discharge-bypass valves (DBV) respond to changes in downstream or suction pressure (see Fig. 11-37). When the evaporating pressure is above the valve setting, the valve remains closed. As the suction pressure drops below the valve setting, the valve responds and … Continue reading

17. January 2011 by admin
Categories: Controlling Refrigerant | Tags: | Leave a comment

Discharge-Bypass Valves

On many air-conditioning and refrigeration systems it is desirable to limit the minimum evaporating pressure. This is so especially during periods of low load either to prevent coil icing or to avoid operating the compressor at lower suction pressure than … Continue reading

17. January 2011 by admin
Categories: Controlling Refrigerant | Tags: | Leave a comment

Nonadjustable ORO/ORD system operation

The nonadjustable ORO head pressure-control valve and the ORD pressure-differential valve offer the most economical system of refrigerant side head-pressure control. Just as the ORI/ORD system simplified this type of control, the ORO/ORD system offers the capability of locating the … Continue reading

17. January 2011 by admin
Categories: Controlling Refrigerant | Tags: | Leave a comment

Head-Pressure Control Valve Test and operating pressures

Excessive leak testing or operating pressures may damage these valves and reduce the life of the operating members. For leak detection, an inert dry gas such as nitrogen or carbon dioxide can be added to an idle system to supplement … Continue reading

17. January 2011 by admin
Categories: Controlling Refrigerant | Tags: | Leave a comment

Head-Pressure Control Valve Brazing procedures

Any of the commonly used brazing alloys for high-side usage are satisfactory. It is very important that the internal parts be protected by wrapping the valve with a wet cloth to keep the body temperature below 250°F (121°C). Also, when … Continue reading

17. January 2011 by admin
Categories: Controlling Refrigerant | Tags: | Leave a comment

ORD valve operation

The ORD valve is a pressure differential valve. It responds to changes in the pressure difference across the valve (see Fig. 11-34). The valve designation stands for opens on rise of differential pressure. Therefore, the ORD is dependent on some … Continue reading

17. January 2011 by admin
Categories: Controlling Refrigerant | Tags: | Leave a comment

ORO valve operation

The ORO head pressure-control valve is an outlet pressure–regulating valve that responds to changes in receiver pressure. The valve designation stands for opens on rise of outlet pressure (see Fig. 11-33). The inlet and outlet pressures are exerted on the … Continue reading

16. January 2011 by admin
Categories: Controlling Refrigerant | Tags: | Leave a comment

Head-Pressure Control Valves Operation

The ORI head pressure-control valve is an inlet pressure regulating valve. It responds to changes in condensing pressure only. The valve designation stands for opens on rise of inlet pressure. As shown in Fig. 11-32, the outlet pressure is exerted … Continue reading

16. January 2011 by admin
Categories: Controlling Refrigerant | Tags: , | Leave a comment

Head-Pressure Control Valves

Design of air-conditioning and refrigeration systems using air-cooled condensing units involves two main problems that must be solved if the system is to be operated reliably and economically. These problems are high-ambient and low-ambient operation. If the condensing unit is … Continue reading

16. January 2011 by admin
Categories: Controlling Refrigerant | Tags: , | Leave a comment

OBIT valve test and operating pressures

As with other pressure valves, it is possible to introduce nitrogen or carbon dioxide in an idle system to check for correct pressure settings. The usual precautions for working with gases apply here. The standard factory setting for the 0/50 … Continue reading

16. January 2011 by admin
Categories: Controlling Refrigerant | Tags: | Leave a comment

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