Three-pipe air conditioning system and control arrangement therefor

Claim 1

AN AIR CONDITIONING SYSTEM COMPRISING A PLURALITY OF HEAT EXCHANGE COILS; MEANS FOR FLOWING ROOM AIR OVER SAID COILS IN HEAT EXCHANGE RELATION THEREWITH; A CHILLED LIQUID CIRCUIT INCLUDING A COOLER FO SUPPLYING A CHILLED HEAT EXCHANGE FLUID TO SAID COILS; A HEATED LIQUID CIRCUIT INCLUDING A HEATER FOR SUPPLYING A HEATED HEAT EXCHANGE FLUID TO SAID COILS; VALVE MEANS RECEIVING SAID HEATED AND SAID CHILLED HEAT EXCHANGE FLUIDS, SAID VALVE MEANS BEING SELECTIVELY OPERABLE FOR FLOWING EITHER CHILLED OR HEATED HEAT EXCHANGE FLUID THROUGH SAID HEAT EXCHANGE COILS; A RETURN SYSTEM INCLUDING CONDUITS WHICH FORM A PART OF BOTH SAID CHILLED LIQUID CIRCUIT AND SAID HEATED LIQUID CIRCUIT FOR RETURNING BOTH HEATED AND CHILLED LIQUID FROM SAID COILS TO SAID HEATER AND COOLER, SAID RETURN SYSTEM FURTHER INCLUDING BRANCH CONDUITS WHICH FEED SAID HEATER AND SAID COOLER, RESPECTIVELY, FROM A CONDUIT WHICH IS COMMON TO BOTH SAID CHILLED LIQUID CIRCUIT AND SAID HEATED LIQUID CIRCUIT; AND TEMPERATURE RESPONSIVE VALVE MEANS DOWNSTREAM FROM EACH HEAT EXCHANGE COIL FOR SUBSTANTIALLY PREVENTING THE FLOW OF FLUID FROM SAID HEAT EXCHANGE COILS TO SAID HEATER AND COOLER WHEN THE TEMPERATURE OF SAID FLUID RISES, BY SOME PREDETERMINED AMOUNT, ABOVE THE NORMAL TEMPERATURE OF FLUID LEAVING SAID HEAT EXCHANGE COILS AND WHEN THE TEMPERATURE OF SAID FLUID FALLS, BY SOME PREDETERMINED AMOUNT, BELOW THE NORMAL OPERATING TEMPERATURE OF FLUID LEAVING SAID HEAT EXCHANGE COILS.