C NC NO M B 1 IN IN OUT 1 M 2 3 4 5 6 7 8 1 1 2 3 4 5 6 7 8 COL SEQUENCE OF OPERATION The cold deck is always maintained cold. Outside air is used in winter and the cooling valve (V2) is used in summer. The hot deck is always maintained hot, to varying degrees, based only on the outside temperature. The thermostats modulate their respective zone damper motors, mixing hot and cold air, attaining the desired supply air temperature to satisfy the zone requirements. BASIC LOGIC PROBLEMS The cold deck temperature will satisfy the maximum cooling requirement the system will experience; therefore, it is too much cooling for all other conditions. The hot deck temperature will satisfy the maximum heating requirement the system will experience at each specific outdoor temperature; therefore, it is too much heating for all other conditions. The system produces cooling and heating, at times, when no zone requires either. The system runs during unoccupied times. 8.84 ORIGINAL DESIGN RETURN FAN SUPPLY FAN SPH SPH OUTDOOR AIR EXHAUST AIR RETURN AIR NC NO NC TT4 TT1 LLI PUMP TT2 TT3 DM4 3# - 13# T1 CWR CWS HWR HWS C NC NO NC C NO V2 4# - 11# V1 5# - 12# M COLD DECK HOT DECK TO ZONE (TYPICAL) MIXED HOT OSA COLD TEMP. DECK TEMP. DECK EP1 PE1 NO TC1 B M 1 2 3 B M 1 2 3 B M 1 2 3 TC4 (DA) TC2 (RA) TC3 (DA) HOT DECK OSA HD -27˚F 108 F 60˚F 77˚F LS1 MPR1 70˚F M 55˚F P B DRAWING TWO MIXED AIR 55˚F RESTRICTOR
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