York SUNLINE MagnaDRY DR180 Installation Manual

Also see for SUNLINE MagnaDRY DR 180: Submittal data sheet Installation manual

Contents

York SUNLINE MagnaDRY DR180 Installation Manual Manual pdf 56 page image

127915-YIM-A-040556 Unitary Products Grouplow return air temperature, (opens at 26 ± 5 °F andresets at 38 ± 5°F).2. A high-pressure switch to protect against exces-sive discharge pressures due to a blocked con-denser coil or a condenser motor failure, (opens at405 ± 7 psig and resets at 265 ± 20 psig).3. A low-pressure switch to protect against loss ofrefrigerant charge, (opens at 22 ± 5 psig and resetsat 45 ± 5 psig).The above pressure switches are hard-soldered to theunit. The refrigeration systems are independently mon-itored and controlled. On any fault, only the associatedsystem will be affected by any safety/preventive action.The other refrigerant system will continue in operationunless it is affected by the fault as well.The unit control board monitors the temperature limitswitch of electric heat units and the temperature limitswitch and the gas valve of gas furnace units.COMPRESSOR PROTECTIONThe compressors also have inherent (internal) protec-tion. If there is an abnormal temperature rise in a com-pressor, the protector will open to shut down thecompressor. The UCB incorporates features to mini-mize compressor wear and damage. An anti-shortcycle delay (ASCD) is utilized to prevent operation of acompressor too soon after its previous run. Addition-ally, a minimum run time is imposed any time a com-pressor is energized.The ASCD is initiated on unit start-up and on any com-pressor reset or lock-out.FLASH CODESThe UCB will initiate a flash code associated witherrors within the system. Refer to UNIT CONTROLBOARD FLASH CODES Table 33.RESETRemove the call for cooling, by raising thermostat set-ting higher than the conditioned space temperature.This resets any pressure or freezestat flash codes.REHEAT MODE SEQUENCE OF OPERATIONThe reheat control board allows the user to select twodifferent modes of operation via a jumper connectionon the board. (See Figure 19.) Each mode is describedbelow. Refer to Figures 19 - 21 when reading this sec-tion.“NORMAL” MODEWhen the reheat control board (RCB) detects a needfor dehumidification (24VAC) at "HUM" via the fieldsupplied dehumidistat connected to RHTB-1 andRHTB-2 and there is not a call for cooling, it energizesthe hot gas relay (HGR), which energizes the 3-wayvalve (SOL 3), the condenser coil valve (SOL 2), andde-energizes the reheat coil bleed valve (SOL 1). TheY1 signal is passed to the unit control board (UCB),which engages circuit # 1, resulting in circuit #1 reheatmode operation.When the room thermostat calls for first stage cooling,with or without a call for dehumidification, the RCBsenses a signal through "Y1", de-energizing the HGR,which de-energizes SOL 3 and SOL 2, and energizesSOL 1, engaging circuit # 1, resulting in circuit #1 cool-ing mode operation.When the room thermostat calls for second stage cool-ing, the RCB senses a signal through "Y1" & "Y2" andengages circuit #1 and circuit #2 in the cooling mode.Indoor blower operation is initiated upon a call for firststage cooling, second stage cooling or dehumidification.Anytime there is a call for 2 stages of cooling, the unitwill not operate in the reheat mode, even if there is acall for dehumidification at "HUM".The unit will not operate in the reheat mode if there isany call for heating.On units with economizers, the unit will not operate inthe reheat mode if there is a call for cooling and theeconomizer is operating as first stage of cooling.All safety devices function as previously described."ALTERNATE” MODEWhen the RCB detects a need for dehumidification(24VAC) at "HUM" via the field supplied dehumidistatconnected to RHTB-1 and RHTB-2, and there is not acall for cooling, it energizes the HGR, which energizesthe SOL 3, SOL 2, and de-energizes SOL 1. The unitthen operates with circuit #1 in reheat mode and circuit#2 in cooling mode.