Question 21Refrigeration/AC - Assistant Engineer70% to pass
If the needle and seat assembly is excessively eroded, the valve cage assembly can be replaced. In replacing the original valve cage assembly rated at 1/2 tons, what would be the result if the replacement valve cage was oversized at 5 tons? Illustration GS-RA-07
AI Explanation
The correct answer is D) The expansion valve would hunt excessively, alternately starving and overfeeding the evaporator coil.
This is because an oversized valve cage assembly (5 tons) compared to the original (1/2 ton) would cause the expansion valve to be unable to properly regulate the flow of refrigerant to the evaporator. The excessive capacity of the replacement valve would cause it to alternate between starving and overfeeding the evaporator, leading to inconsistent superheat levels and the expansion valve "hunting" - rapidly adjusting in an attempt to maintain proper superheat. This would result in unstable operation and potential equipment damage over time.
The other answer choices are incorrect because: A) the evaporator would not be consistently underfeeding, and B) the expansion valve would not function normally with such a mismatch in capacity. C) is also incorrect, as the evaporator would not consistently overheat but rather experience fluctuating superheat levels.
Related Questions
#19 An obstructed expansion valve may be indicated by an incompletely cooled evaporator and what other symptom? #20 Which of the following conditions will occur if the power element of the thermostatic expansion valve shown in the illustration loses its charge? Illustration GS-RA-07 #22 If the superheat value of the thermostatic expansion valve is adjusted too high, what would be the result? #23 If the superheat setting of a thermostatic expansion valve is set too low, what would be the result, assuming that the system has a single evaporator? #24 Which of the illustrated valves is used to gain access to a hermetic system and features a Schrader core valve which is unseated by the core depressor of hose fitting when attached? Illustration GS-RA-69