Carrier 48AK Installation, Start-up And Service Instructions Manual

Also see for 48AJ: Installation instructions Operation and service guide Started guide Operating and service guide

Contents

31Features with Thermostat Control of Unit• two-stage heating• two-stage cooling• control of unit using Y1, Y2, W1, W2, and G thermostatinputs• control of the indoor fan• outdoor-air temperature/supply-air temperaturemonitoring• control of an outdoor air condenser fan based on out-door-air temperature• control of modulating economizer damper to providefree cooling when outdoor conditions are suitable, usingsupply-air temperature as a control point• control of the economizer damper and indoor fan toobtain unoccupied free cooling• provide power exhaust output to an external powerexhaust controller• support a field test for field checkout• control of 2 stages of CV power exhaust• compressor Time Guard® (power up, minimum off andon times)• compressor lockout during low supply-air temperatureAdditional features are provided by accessing the standardunit control board via software with a computer. These featuresare:• electronic expansion board features (if installed)• control board diagnostics• ability to change supply air set point (economizer control)• ability to change high outdoor temperature lockout setpoint (economizer control)• ability to change power exhaust set pointsNOTE: A CV unit without a thermostat requires a field-supplied sensor for operation.Features with Sensor Control of Unit (Stand-Alone Applica-tions — Unit control is limited to CV unoccupied default setpoints, 90 F for cooling, 55 F for heating unless a computer hasbeen used to change the set points. There are 2 sensor optionsavailable:• T-55 sensor will monitor room temperature and provideunoccupied override capability (1 hour)• T-56 sensor will monitor room temperature, provideunoccupied override capability (1 hour), and provide atemperature offset of 5° F.Standard features are:• support of remote occupied/unoccupied input to start andstop the unit• cooling capacity control of 3 stages using economizerand 2 compressors to maintain space temperature to anoccupied or unoccupied set point• enable heating or cooling during unoccupied periods asrequired to maintain space temperature within the unoc-cupied set points• adjustment of space temperature set points of ±5° F whenusing a T-56 sensor• provides CCN (Carrier Comfort Network) IAQ (Indoor-Air Quality) participation• control of modulating economizer damper to maintainindoor air quality (IAQ) when outdoor conditions aresuitable (this function is provided in the base unit con-trols on units with serial number 0600F or later)NOTE: The IAQ sensor must be set for current output (4 to20 mA), not voltage output. Ensure the jumper on the sensor isin the upper position. See Fig. 25.Additional features with sensor control of unit (with com-puter access or Remote Enhanced Display) are:• 365-day timeclock with backup (supports minute, hour,day of week, date, month, and year)• daylight savings time function• occupancy control with 8 periods for unit operation• holiday table containing up to 18 holiday schedules• ability to initiate timed override from T-55 or T-56 sen-sors for a timed period of 1 to 4 hours• ability to use multiple space temperature sensors to aver-age the space temperature• supply-air temperature reset for the supply-air tempera-ture set point• temperature compensated start to calculate early starttimes before occupancy• access to the Display, Maintenance, Configuration, Ser-vice, and Set Point data tables through network software• loadshed and demand limitingWhen the unit is equipped with a field-supplied space tem-perature sensor and a remote contact closure (remote start/stop) on the base control board, the occupied default set pointswill monitor unit operation. The occupied default set points are78 F cooling and 68 F heating (if heating is present). SeeFig. 26 for remote start/stop wiring.NOTE: For units with a field-supplied space temperature sen-sor which have not had the base unit control board accessedvia software to set an occupancy schedule, the remote start/stop closure will allow the unit to operate in the pre-configuredoccupied default set points of 78 F cooling and 68 F heating.Without this feature, the unit will control to the unoccupieddefault set points of 90 F cooling and 55 F heating.Fig. 24 — Supply-Air Thermistor Connections