DOE-2 Reference Manual Version 2.1 - DOE2.com

o. Unitary Hydronic Heat Pump System (HP)TO ADD I TJ ONAlr------r---r------~----------_r----------~----z~O~"'~sHEATREJECTIONUNlTSUPPLY -I-zONE -I ZONEAiR No.2 No.31"EAO (i) I (i)~U I RETURN PUMPCIRCULATING I -~'--;'=l:;;;J:::' _~__ ~=~ -PUMP,- • I : 1- 41I OUTSIDE I I I IL~I~_I L ___ ~ I ___ ~ITEMS SHOWN IN DASHED BOXESARE OPTIONAL COl~"ONENT$The Unitary Hydronic Heat Pump System, illustrated above, providesheating and cooling for a number of individually controlled zones by operationof heat pump units located in each space to be conditioned. Each heat pumpunit may provide a fixed quantity of outside air ventilation, or merelyrecirculate conditioned air.Each heat pump consists of a refrigerant compressor, a room air-to-refrigerantheat exchanger, a working fluid-to-refrigerant heat exchanger (connectedto the pipe loop), controls to switch the evaporating and condensing functionsfrom one heat exchanger to the other, a supply air fan, and a two-set pointZONE thermostat. When the heat pump is in the room heating mode of operation,the room air-to-refrigerant heat exchanger is used for refrigerant con dens ing.In the room cooling mode, this same heat exchanger is used for refrigerantevaporating. Each heat pump provides dehumidihcation in the cooling mode buthas no dehumidification control.Temperature is controlled in each zone by on-off operation of the heatpump unit (fan and compressor). The type of thermostat used for this systemhas two individual set points. The heat pump unit provides cooling when spacetemperature increases to the upper set point, and heating when the space temperaturefalls to the lower set point; it does not operate when space temperatureis between set points. If outside air is specified the fan operatescontinuously; otherwise, the fan cycles on and off with the refrigerationcompressor.•A piping system with circulating fluid is connected to the water-torefrigerantheat exchanger in the heat pump. The circulating fluid absorbsheat from those units that are operating in the cooling mode, and gives upheat to those units that are operating in the heating mode. Because some zoneunits may be cooling, while others are heating, the temperature of the fluidcirculating will depend on the relative quantities of each. When coolingdemand exceeds heating demand and the fluid temperature increases to thehighest allowable value (see keyword MAX-FLUID-T in the SYSTEM-FLUIDinstruction), heat is dissipated to the atmosphere through an evaporativecooler, (or a cooling tower). When heating demand exceeds cooling demand andthe fluid temperature decreases to the minimum allowable value (see keywordI V. 71 (Revised 5/81)