With reference to main refrigeration plant give reason for each of the following operational irregularities and state how these are dealt with

(a) Rapid loss of lubricating oil from the crankcase of a " vee " block compressor (4)

(b) Steady "fall off" in refrigeration effect over a comparatively short period of time (4)

(c) Excessive "icing up " at compressor suction (4)

(d) Short cycling (4)