Question 44Refrigeration & AC - Assistant Engineer

The correct answer is C) the highest. When all four evaporators of a multi-box refrigeration system are actively being fed with liquid refrigerant, the control oil pressure acting on the hydraulic relay piston will be at its highest value. This is because the compressor is working at full capacity to meet the demand from all four evaporators, resulting in the maximum oil pressure being exerted on the hydraulic relay piston. The other options are incorrect because: A) the lowest oil pressure would occur when only one evaporator is active, not when all four are active; B) the mid-range oil pressure would occur during partial load conditions, not full load; and D) the lube oil is used in the operation of the unloader, so its pressure is relevant.