H Block Expansion Valve System
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| Illustration 1 | g01077020 |
In the H Block expansion valve system the thermostatic expansion valve is replaced with the H Block expansion valve.
When the H Block expansion valve opens, liquid refrigerant is metered into the bottom of the evaporator. The low pressure refrigerant begins to boil as the refrigerant flows through the evaporator coil. The refrigerant vapor attracts the heat from the warmer air that is circulated by the evaporator fan. The compressor draws the refrigerant vapor out of the top of the evaporator and past the temperature sensor. The cooler vapor cools the temperature sensor. As the temperature sensor cools, the gas in the sensor condenses. Then, the gas decreases the pressure on the top of the temperature sensor diaphragm. The diaphragm expands upward moving the rod away from the ball and the spring. The ball and the spring starts to close restricting flow through the expansion valve.
The temperature sensor controls the operation of the air conditioning system by allowing the exact amount of liquid refrigerant to be metered past the ball and spring.
H Block Expansion Valve
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| Illustration 2 | g01077021 |
Some air conditioning systems use the H Block expansion valve in order to control the amount of refrigerant into the evaporator.
During the compressor cut-out mode, the pressure on the bottom of the temperature sensor diaphragm increases above the pressure on top of the diaphragm. The diaphragm expands upward retracting the rod and allowing the ball and the spring to close the valve.
During the compressor cut-in mode, the pressure on the bottom of the temperature sensor diaphragm decreases rapidly. The higher pressure on the top of the diaphragm causes the diaphragm to contract downward moving the rod against the ball and the spring. This causes the valve to open.