P B M B M 1 3 2 B M 1 3 2 B M 1 B M 1 B M 1 C 3 2 1 SUBR1 SET (P3 = P2) = 9PSIG M M RH TEMP. 60% 80°F 40% 70°F VALUE 33.80 BTU 23.70 BTU RC5 3 9 15 6 12 5 4 7 8 10 11 13 14 21 39 30 23 24 26 27 28 31 33 34 36 37 RES. 22 25 29 32 35 38 SEQUENCE OF OPERATION When the fan is off, solenoid valve (EP1) is de-energized. The outside air and exhaust air dampers close and the return air damper opens. Receiver controller (RC5) senses the outside air humidity and temperature via transmitters (HT2) and (TT2) respectively. RC5 produces a signal representing the outside enthalpy as the humidity and temperature vary according to the reset schedule. RC4 senses the return air humidity and temperature via transmitters (HT1) and (TT1). RC4 produces a signal representing the return air enthalpy as the humidity and temperature varies according to the reset schedule. Both RC4 and RC5 send their signals to low selctor (LS1). RC4 also sends its signal to RC2. RC2 receives its main air from receiver controller (RC3), which senses the return air temperature via TT1. RC2’s signal provides the main air for receiver controller (RC1) which senses the mixed air temperature via transmitter (TT3). RC1 sends its signal to minimum positioning relay (MPR1), which sends its signal through EP1 to modulate the mixing dampers. The safeties will shut down the fan when the temperature exceeds their set points. NOTE: The proportional band and authority may have different values, depending on the controller manufacturer. B M 1 2 B M 1 B M 1 2 3 B M 1 2 3 IN IN OUT LS1 The Kreuter subtraction relay became obsolete; therefore, this circuit was developed allowing enthalpy comparison. Alternate relay to achieve circuit intent. EP1 NC 6# MPR1 RC1 RC2 RC3 RC4 OSA ENTHALPY RETURN AIR ENTHALPY RETURN AIR SET 72˚F (22˚C) ENTHALPY SWITCH (DA) 2 POS. PB<4% AUTH. 100% MIXED AIR LOW LIMIT SET 55˚F (13˚C) MIXED AIR TEMP. RETURN TEMP. RETURN %RH OSA TEMP. OSA %RH 0-100˚F 0-100% 0-100˚F 0-100% RES. RES. RES. RES. RC4 AND RC5 RESET PB= 25.8% AUTH. = 41.4% RETURN ENTH. OSA ENTH. 21-39 BTU 21-39 BTU PSIG ENTHALPY BTU/LB RETURN AIR FAN SUPPLY FAN NC NO NC OSA EX. RETURN AIR HL1 TT1 HT1 TT2 HT2 LL1 HL2 6# - 10# 4# - 9# M 7# - 12# M M 1 3 4 5 6 1 2 3 4 5 6 2 8-112
RkJQdWJsaXNoZXIy ODY1ODQy