this prior art arrangement has some significant problems these problems are icing of the direct expansion coil compressor seizure or occupant discomfort icing of the direct expansion coil 10 may occur as a result of a low load condition a direct expansion cooling system is inherently limited in its ability to throttle cooling capacity because of this cooling is limited to discrete capacity steps as the cooling load drops below the minimum throttling capacity of the cooling stage icing of the coil 10 occurs it has also been determined that loose fan belts or dirty filters can result in icing of the coil 10 in all three cases the air flow through the coil 10 is reduced and the result may be icing additionally if valves 15 and 16 stay open such that cooling water always flows to coil 8 the load on the direct expansion coil 10 is reduced if condenser 12 cooling water valve controlled by head pressure sticks open this can lead to compressor failure this condition will cause excessive compressor cycling due to automatic safety cutouts a stuck condenser cooling valve can result in the condenser cooled to a lower temperature than the direct expansion coil these conditions result in oil migration from the compressor seizure and permanent failure valves 15 and or 16 commonly stick open as a result of scale or dirt build up in the valves resulting from the use of water which flows directly from cooling tower 9 compressor failure as evidenced by compressor seizure may result from several causes.