Constant pressure valve is working as hot gas bypass of air dryer against ice block to protect evaporator (freeze protection)

The constant pressure valve is a vital component of many refrigeration and A/C systems. It automatically meters refrigerant to the evaporator at a rate equal to compressor pumping capacity.   The constant pressure valve contains a diaphragm, control spring , seat and valve needle or ball. The control spring, above the diaphragm, moves the diaphragm down. This moves the valve open. The opposing force is provided by low side evaporator pressure and a constant body spring force. This moves the valve closed. During the off cycle, evaporator pressure builds and overcomes spring pressure. This keeps the valve closed until the next ON cycle. At the start of the ON cycle, the compressor quickly reduces evaporator pressure. When this pressure equals the control spring pressure, the valve begins to open. The valve opens when evaporator pressure is just below the control spring pressure setting. This is the valve’s opening point, or setting.For plants with single injected evaporators and without a distributor, such as air conditioners, dehumidifiers, air driers,water coolers or ice-making machines. It is suitable for all CFC, HCFC, HFC, not for ammonia. The valves may be installed in any position.