Carrier 50CR Sequenceof Operation, Checkfor Refrigerant Leaks, Start-UpAdjustments

50CR

Check system wiring to be sure the User Interface is powered and connections are made A to A, B to B, etc., and wiring is not shorted. Mis-wiring or shorting of the ABCD communications wiring will not allow successful communications. Correcting wiring faults will clear the code and re-establish communications.

Shorting or mis-wiring the low voltage system wiring will not cause damage to unit control or to User Interface but may cause the low voltage fuse to open.

STATUS CODE 46, BROWNOUT CONDITION

If the secondary voltage of the transformer falls below 15-vac for a period exceeding 4 seconds, Status Code 46 will be displayed on STATUS LED and the User Interface will command the control board to turn off Y output controlling compressor.

When secondary voltage rises above 17-vac for more than 4 seconds, the brownout condition is cleared and normal system operation will resume subject to any minimum compressor off-delay function which may be in effect. Brownout does not affect blower or electric heater operation.

STATUS CODE 53, OUTDOOR AIR TEMPERATURE SENSOR FAULT

If an OAT sensor is found at power-up, input is constantly checked to be within a valid temperature range. If sensor is found to be open or shorted at any time after initial validation, Status Code 53 will be displayed at amber STATUS LED.

Check for faults in wiring connecting sensor to OAT terminals. Using an Ohm meter, check resistance of thermistor for a short or open condition.

If thermistor is shorted or open, replace it to return the system to normal operation. If fault is in the wiring connections, correcting the fault will clear the code and return the system to normal operation.

NOTE: If fault condition is an open thermistor or a wiring problem that appears to be an open thermistor and the power to the unit is cycled off, the fault code will be cleared on the next power-up but the fault will remain and system operation will not be as expected.

This is because on power-up, the unit control cannot discern the difference between an open sensor or if a sensor is not installed.

Step 2—Sequence of Operation

The packaged heat pump is designed for installation with a communicating User Interface. This unit will not respond to commands provided by a common thermostat except under certain emergency situations described in Step 1—Start-Up.

The User Interface uses temperature, humidity and other data supplied from indoor and outdoor system components to control heating or cooling system for optimum comfort. The unit will be commanded by User Interface to supply airflow. The unit will operate the indoor blower at requested airflow for most modes.

The nominal requested airflow will be 350 cfm per ton of nominal cooling capacity as defined by unit size. Actual airflow request will be adjusted from nominal using indoor and outdoor temperature and indoor humidity data to optimize the system operation for occupant comfort and system efficiency. Refer to User Interface literature for further system control details.

Airflow during electric heater operation must be greater than a minimum level for safe operation. If User Interface instructs unit to turn on electric heat and the requested airflow is less than the minimum level the unit control will override requested value.

NOTE: Once the compressor has started and then has stopped, it should not be started again until 4 minutes have elapsed. The cooling cycle remains “on” until the room temperature drops to point that is slightly below the cooling control setting of the user interface. Additionally, there is a 5-minute compressor delay built into the control for heat pump heating mode.

Step 3—Check for Refrigerant Leaks

Locate and repair refrigerant leaks and charge the unit as follows:

1.Use both high- and low-pressure ports to relieve system pressure and reclaim remaining refrigerant.

2.Repair leak following accepted practices.

NOTE: Install a bi-flow filter drier whenever the system has been opened for repair.

3.Check system for leaks using an approved method.

4.Evacuate refrigerant system and reclaim refrigerant if no additional leaks are found.

5.Charge unit with Puron (R-410A) refrigerant, using a volumetric-charging cylinder or accurate scale. Refer to unit rating plate for required charge.

Step 4—Start-Up Adjustments

Complete the required procedures given in the Pre-Start-Up section before starting the unit. Do not jumper any safety devices when operating the unit. Do not operate the unit in cooling mode when the outdoor temperature is below 40°F (unless accessory low-ambient kit is installed). Do not rapid cycle the compressor. Allow 5 min. between “on” cycles to prevent compressor damage.

CHECKING COOLING AND HEATING CONTROL OPERATION

Start and check the unit for proper control operation as follows:

1.Place room UI SYSTEM switch or MODE control in OFF position. Observe that blower motor starts when FAN mode is placed in FAN ON position and shuts down within 60 sec (030-060 size) or 30 sec (024 size) when FAN MODE switch is placed in AUTO position.

2.Place system switch or MODE control in HEAT position. Set control above room temperature. Observe that compressor, outdoor fan, and indoor blower motors start. Observe that heating cycle shuts down when control setting is satisfied.

3.When using an automatic changeover room thermostat, place both SYSTEM or MODE control and FAN mode switches in AUTO positions. Observe that unit operates in cooling mode when temperature control is set to “call for cooling” (below room temperature), and unit operates in heating mode when temperature control is set to “call for heating” (above room temperature).

IMPORTANT: Three-phase, scroll compressors are direction oriented. Unit must be checked to ensure proper compressor 3-phase power lead orientation. If not corrected within 5 minutes, the internal protector will shut off the compressor. The 3-phase power leads to the unit must be reversed to correct rotation. When turning backwards, the difference between compressor suction and discharge pressures may be dramatically lower than normal.

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