B M 1 2 1 2 3 3 RESTRICTOR C NC NO BMM123 1 2 3 BB M 1 2 3 1 2 3 RESTRICTOR RESTRICTOR RESTRICTOR M 2 3 4 5 6 7 IN IN OUT 1 2 4 5 6 7 P M B P M B 1 1A RESTRICTOR 2 3 1 1 2 3 . . SEQUENCE OF OPERATION -The fan runs continuously to suit laboratory operation. -Solenoid air valve (EP1) passes control air to the fan controls when the fan runs. -Receiver controller (RC1) senses the return air temperature via transmitter (TT1) and receives a set point demand from (SP ADJ 1). RC1 sends its signal to biasing relays (BR1), (BR2), (HS4 on drawing three), as well as to cooling valve (V2). The instrument arrangement causes the heating valve (V1) to close first, then the free cooling dampers (D1) and (D2) to be maximized and then the mechanical cooling valve (V2) to be used on a demand for cooling. -BR1 sends its signal to high selector (HS1) which also receives a signal from regulator (PRV1) to assure the system of at least minimum ventilation. -Receiver controller (RC3) senses the outside air temperature via transmitter (TT3). RC3 passes main air to receiver controller (RC2) only when free cooling is available based on the outside air temperature to economize on mechanical cooling. RC2 senses the mixed air temperature via transmitter (TT2). RC2 limits the mixed air temperature to a minimum of 58°F by limiting the main air to BR1. -Turndown ratio relay (BR3) is set to limit the degree of set point demand from the laboratory. -Static pressure controller (SPC1) senses the differential pressure between the outside air and the lab. SPC! Sends its signal to limiting relay (LM1) which limits the vanes to not close beyond LM1’s set point. LM1 sends its signal to modulate vane motor (D3). -If low limit (LL1) senses a temperature below its set point on any one foot of its element the fan will shut down. If high limit (HL1) senses a temperature above its set point, the fan will shut down. Both HL1 and LL1 require resetting after they have tripped. 7.51 MIXED AIR FAN EXAMPLE FROM SINGLE ZONE CASE STUDY PAGE 8.63 RETURN FAN SUPPLY FAN RETURN AIR NC NC NO HL1 LL1 OSA EX. D2 3# - 13# D1 3# - 13# TT3 TT2 TT1 TT4 M 1A V2 V1 5# - 12# PP 13# - 16# NO C NC NC NO C PUMP HWS HWR CWR CWS HEATING COIL COOLING COIL SP ADJ. 1 LOCATED ON COLUMN IN LAB. EP1 RET. TEMP. MIXED TRMP. OSA TEMP. SUPPLY TEMP. M S B BR3 RETURN RC1 MIXED RC2 OSA HL RC3 BR2 1:2 RATIO 6# IN = 12# OUT HS1 PRV 1 SET 5# BR1 1:2 RATIO 8# IN = 3# OUT DA 70˚F DA 58˚F RA 70˚F 2 POS. 3
RkJQdWJsaXNoZXIy ODY1ODQy