HVAC System (Heater, Ventilator and A/C)
EXPANSION VALVE
AC-36
2. FUNCTION
When the heat load to the air conditioning system increases, the refrigerant temperature at the
evaporator outlet rises and therefore the pressure P
1
around the temperature sensing area in-
creases. As this pressure P
1
becomes higher than the sum of the evaporator outlet (low-pressure
side) pressure P
2
and the spring force F (P
1
> P
2
+ F), the diaphragm is pressed down, moving
the valve ball connected to the diaphragm clear of its seat. This increases the flow of the refriger-
ant.
When the heat load is small, the action of the valve’s inner elements is contrary to the above; the
valve ball closes and the flow of the refrigerant decreases.
H4H1124
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