York R-410A Cooling Sequence Of Operations, Heating Sequence Of Operations, Fan Only CFM

288429-YIM-A-0307

Fan Only CFM:

When the connection is made from “R” to “G”, the fan only mode is activated. In this mode, the blower will deliver 75% of the cooling system CFM. This connection is factory set from the manufacturer and cannot be field adjusted.

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Figure 10: Control Board Speed Tap Location

Table 19: Delay Profile

Delay Tap	Regional Climate Type
Jumper at “A”	Standard Setting
Jumper at “B”	Humid Climate
Jumper at “C”	Dry Climate
Jumper at “D”	Temperate Climate

Operation

Cooling Sequence Of Operations

1.If the fan switch on the thermostat is in the "ON" position, the 24 volts at "G" signals the ECM motor controller to operate the blower at 75% of the rated airflow. If the fan switch on the thermostat is in the "AUTO" position, the blower operates only when there is a call for cooling by the thermostat.

2.If the 2-stage thermostat calls for the first stage of cooling, the 24 volts at "Y1" signals the ECM controller to operate the blower at low speed and closes the contactor coil M1. Power is supplied to the compressor and outdoor fan motor. When the fan switch on the thermostat is in the "AUTO" position, the indoor blower motor is energized at the low-speed cooling airflow.

3.If the 2-stage thermostat calls for the second stage of cooling, the 24 volts at "Y2" signals the ECM controller to

operate the blower at high speed and energizes the compressor solenoid to close the bypass ports so that the compressor operates at full capacity. If the outdoor fan motor has an ECM controller, the 24 volts at "Y2" signals the motor to operate at high speed.

4.When the cooling demand is satisfied, the 24 volt "Y1" and "Y2" signals are removed and the M1 contactor is de- energized. If the fan switch on the thermostat is in the "ON" position, the blower will continue to run at 75% of the rated airflow. If the fan switch is in the "AUTO" position, the blower will continue to run for a short period as determined by the "DELAY" jumper setting on the CFM Selector board.

Heating Sequence Of Operations

1.If the fan switch on the thermostat is in the "ON" position, the 24 volts at "G" signals the ECM motor controller to operate the blower at 75% of the rated airflow. If the fan switch on the thermostat is in the "AUTO" position, the blower operates only when there is a call for heating by the thermostat.

2.For units equipped with supplementary electric heat, 24 volts at "W" sends 24 volts to "W2" on the fan control board. The 24 volt signal energizes all stages of electric heat.

3.When the heating demand is satisfied, the 24 volt "W" signal is removed and the electric heat is de-energized. The M1 contactor is de-energized when the 24 volt "Y" signal is removed. If the fan switch on the thermostat is in the "ON" position, the blower will continue to run at 75% of the rated airflow. If the fan switch is in the "AUTO" position, the blower will continue to run for a short period as determined by the "DELAY" jumper setting on the CFM Selector board.

Please refer to Tables 20 and 21 for more information.

Electric Heat Limit Switch Operation

The limit switch responds to over-temperature conditions in the air duct. Opening the device results in dropping power to the relays. The control logic will also respond by turning off the relays. After four limit cycle trips the unit goes into a 1 hour soft lockout period. If the control "sees" another limit cycle during this period, the unit will go into a hard lockout condition. Once in a hard lockout state, the fan is locked on and the heaters are disabled. Only a power cycle will clear this state.

During the soft lockout period, the fan responds to thermostat input but the heaters are enabled. This is to sense a failed heater relay. The limit cycle count is reset at the start of a heat request. If the limit remains open for period of 80 seconds or more, the control is immediately put into a hard lockout condition. Only a power cycle will clear this state.

18 Unitary Products Group