Carrier 58MSA Installation, Start-up, And Operating Instructions Manual

Also see for 58MSA Series: Service and maintenance instructions User manual Instruction manual Installation, start-up, and operating instructions Installation, start-up, and operating instructions

Carrier 58MSA Installation, Start-up, And Operating Instructions Manual Manual pdf 33 page image

SEQUENCE OF OPERATIONFurnace control must be grounded for proper operation, orcontrol will lock out. Control is grounded throughgreen/yellow wire routed to gas valve and burner box screw.Failure to follow this caution will result in minor unitoperation.Using the schematic diagram in Fig. 32, follow the sequence ofoperation through the different modes. Read and follow the wiringdiagram very carefully.NOTE: If a power interruption occurs during a call for heat (W),the control will start a 90-second blower-only ON period twoseconds after power is restored, if the thermostat is still calling forgas heating. The red LED light will flash code 12 during the90-second period, after which the LED will be ON continuous, aslong as no faults are detected. After the 90-second period, thefurnace will respond to the thermostat normally.The blower door must be installed for power to be conductedthrough the blower door interlock switch ILK to the furnacecontrol CPU, transformer TRAN, inducer motor IDM, blowermotor BLWM, hot-surface igniter HSI, and gas valve GV.1. Heating(See Fig. 30 for thermostat connections.)The wall thermostat ″calls for heat″, closing the R to Wcircuit. The furnace control performs a self-check, verifies thepressure switch contacts PRS are open, and starts the inducermotor IDM.a. Inducer Prepurge Period- As the inducer motor IDMcomes up to speed, the pressure switch contacts PRS close,24 vac power is supplied for a field installed humidifier atthe HUM terminal and the control begins a 15-secondprepurge period.b. Igniter Warm-Up- At the end of the prepurge period, theHot-Surface Igniter HSI is energized for a 17-secondigniter warm-up period.c. Trial-for-Ignition Sequence- When the igniter warm-upperiod is completed, the main gas valve relay contacts GVRclose to energize the gas valve GV, the gas valve opens.The gas valve GV permits gas flow to the burners where itis ignited by the Hot Surface Igniter HSI. Five seconds afterthe GVR closes, a 2-second flame period begins. The HSIigniter will remain energized until the flame is sensed oruntil the 2-second flame proving period begins.d. Flame-Proving- When the burner flame is proved at theflame-proving sensor electrode FSE, the furnace controlCPU begins the blower-ON delay period and continues tohold the gas valve GV open. If the burner flame is notproved within two seconds, the control CPU will close thegas valve GV, and the control CPU will repeat the ignitionsequence for up to three more Trials-For-Ignition beforeTable 7—Maximum Allowable Exposed Vent Pipe Length (ft) With and Without Insulation in Winter DesignTemperature Ambient*FURNACESIZEWINTER DESIGNTEMPERATURE(°F)MAX PIPEDIAMETER(IN.)WITHOUTINSULATIONWITH 3/8–IN. ORTHICKER INSULATION†04020 1.5 51 700 1.5 28 70-20 1.5 16 7020 2 45 700 2 22 70-20 2 10 5806020 2 65 700 2 35 70-20 2 20 7008020 2 55 550 2 48 55-20 2 30 5520 2.5 70 700 2.5 47 70-20 2.5 28 7010020 2.5 40 400 2.5 40 40-20 2.5 38 4020 3 70 700 3 50 70-20 3 28 7012020 3 70 700 3 61 70-20 3 37 7020 4 70 700 4 48 70-20 4 23 70* Pipe length (ft) specified for maximum pipe lengths located in unconditioned spaces. Pipes located in unconditioned space cannot exceed total allowable pipe lengthas specified in Table 7.† Insulation thickness based on R value of 3.5 per in.33→→