[jeff5may]

Running a cap tube metered circuit is always a trade-off. With a shorter tube, the system capacity is increased. With a longer tube, the balance point dT is increased. A longer cap tube will take longer to reach a colder box temperature; a shorter cap tube will reach a less cold box temperature faster. So with this freezerator application, shortening the cap tube would give you a faster pulldown of cabinet temp and shorter run times of the compressor.

This all sounds great, right? The only downside is that you run the risk of flooding the evaporator.Once the dT maxes out, the evaporator saturates. The liquid refrigerant cannot all boil off, so a fraction passes through, due to an increase in suction pressure (vs. a longer cap tube) . If this liquid reaches the compressor, bad things happen.

Better to starve the evaporator than to flood it. All refrigeration compressors are classified by the back (suction) pressure they are designed to operate with. Most freezers use low back pressure compressors, which are designed to cool themselves without much mass flow of refrigerant. This is why they are relatively larger in size than their heat pump counterparts of equal capacity: the motor and compressor head have more iron to shed their heat through.