Carrier 48DD User Manual

Both heating and cooling stages offer 50% or 100% capacity ranges, reducing operating costs.

Air delivery options include bottom or side discharge for flexible building integration.

Shuts off main gas valve on pilot/combustion failure or heat exchanger overheating.

Unaffected by winds/drafts, with safety shut-off for combustion air failure or blockage.

Pilot flame automatically relights upon interruption of power or gas supply.

Resist corrosion, provide long, quiet, safe, efficient operation with a ten-year warranty.

Prevents rapid cycling, extending compressor life by delaying restarts after power interruption.

Cycles condenser fans to permit cooling down to 35 F ambient temperature.

Includes crankcase heaters, accumulators, filter-driers for compressor protection and charge monitoring.

Modulates condenser fan motor speed for saturated condensing temp at low outdoor temps.

Two-step heating/two-step cooling thermostat with auto/manual changeover.

Allows manual unit control from a remote location.

Frames roof opening, providing a watertight connection for unit installation.

Provides outside air cooling when temp is below 60 F, potentially replacing refrigerant system.

Used to convert the unit from natural gas to LP gas usage.

Used to relieve positive building pressure.

Identify cooling and heating needs at specific design conditions.

Choose a unit by matching required cooling capacity to table data.

Verify the selected unit's heating capacity meets design requirements.

Calculate required fan speed and motor horsepower based on airflow and static pressure.

Choose the unit that matches the available electrical characteristics.

Presents cooling capacities based on various air temperatures and airflow rates.

Details input and bonnet capacities for heating stages.

Provides fan RPM and motor horsepower data for different airflow and static pressure conditions.

Describes how the unit operates during cooling mode, including compressor staging.

Explains how the two-step thermostat controls compressor staging based on load.

Details the sequence of operation for heating, including pilot ignition and burner stages.

Explains how the unit automatically switches between heating and cooling modes.

Describes continuous indoor fan operation for air circulation when set to 'Fan' mode.

Details damper operation during cooling, including 'Vent' and closed positions.

Explains damper repositioning based on mixed air temperature during intermediate seasons.

Describes damper behavior during heating, staying at 'Vent' unless night switch is open.

Provides voltage, current, and motor data for unit operation.

Illustrates rooftop unit installation with separate supply and return ductwork.

Shows alternative air flow configurations for unit installation.

Details cooling operation strategies for low outdoor temperatures, including economizer use.

Protective devices that shut off gas supply or limit discharge air temperature.

Open control circuit if compressor current is excessive, with automatic reset.

De-energizes circuit if extreme temperatures develop in compressor windings.

Protects unit from excessive compressor discharge pressures and overheating.

Provides short circuit protection for control circuits.

De-energizes circuit if refrigerant pressure drops below setting.

Opens power circuit if temperatures or current become excessive on motors.

Protects against excessive pressures or temperatures in the refrigerant system.

De-energizes gas valve in case of combustion air failure.

Specifies total net cooling, sensible capacity, and casing construction materials.

Details hermetic compressors with vibration isolators and copper tube coils with aluminum fins.

Describes indoor centrifugal fan and outdoor propeller fan specifications.

Specifies corrosion-resistant heat exchanger and Bunsen-type burners with warranty.

Lists safety features for cooling and heating sections, including timing devices.

Defines maximum unit dimensions and lists available accessories.