Carrier 25HPA6 Infinity Controlled low ambient cooling, Defrost Hold, Forced Defrost

GENERAL INFORMATION

Infinity Controlled low ambient cooling:

This unit is capable of low ambient cooling down to 0°F (-17.8°C) without a kit ONLY when using an Infinity Control. A low ambient kit is not required for Infinity controlled low ambient operation. The Infinity Control provides an automatic evaporator freeze thermostat. Low ambient cooling must be enabled in the User Interface setup. Fan may not begin to cycle until about 40°F (4.4°C) OAT. Fan will cycle based on coil and outdoor air temperature.

Infinity controlled low ambient mode operates as follows:

SFan is OFF when outdoor coil temperature is less than outdoor air

temperature (+ 3 _F/1.7_C) or outdoor fan has been ON for 30 minutes. (Fan is turned off to allow refrigerant system to stabilize.)

SFan is ON when outdoor coil temperature is less than outdoor air temperature (+25_F/13.9_C) or outdoor coil temperature is more than 80_F (26.7_C) or if outdoor fan has been OFF for 30 minutes.

(Fan is turned on to allow refrigerant system to stabilize.)

S Low pressure switch is ignored for first 3 minutes during low ambient start up. After 3 minutes, if LPS trips, then outdoor fan motor is turned off for 10 minutes, with the compressor running. If LPS closes within 10 minutes then cooling continues with the outdoor fan cycling per the coil temperature routine listed above for the remainder of the cooling cycle. If the LPS does not close within 10 minutes, then the normal LPS trip response (shut down cooling operation and generate LPS trip error) will occur.

Defrost

This control offers 5 possible defrost interval times: 30, 60, 90, 120 minutes, or AUTO.

Defrost intervals are selected by dip switches on the unit control board or by the Infinity Control User Interface. The Infinity Control selection overrides the control board dip switch settings.

Defrost interval times: 30, 60, 90, and 120 minutes or AUTO are selected by the Infinity Control User Interface (the dip switches are not used.)

AUTO defrost adjusts the defrost interval time based on the last defrost time as follows:

SWhen defrost time <3 minutes, the next defrost interval=120

minutes.

SWhen defrost time 3-5 minutes, the next defrost interval=90

minutes.

SWhen defrost time 5-7 minutes, the next defrost interval=60 minutes.

SWhen defrost time >7 minutes, the next defrost interval=30 minutes.

The control board accumulates compressor run time. As the accumulated run time approaches the selected defrost interval time, the control board monitors the coil temperature sensor for a defrost demand. If a defrost demand exists, a defrost cycle will be initiated at the end of the selected time interval. A defrost demand exists when the coil temperature is at or below 32_F (0_C) for 4 minutes during the interval.

The defrost cycle is terminated when the coil temperature reaches 65_F (18.33_C)or 10 minutes has passed. When OAT is > 25°F (-3.9°C), defrost will occur in low or high stage as demanded by the thermostat or User Interface.

If OAT is ≤25°F (3.9_C), defrost will occur in high stage only, regardless of thermostat or User Interface demand, and will terminate at 50_F (10_C) coil temperature with a minimum of 2.5 minutes in defrost.

If the coil temperature does not reach 32_F (0_C) within the interval, the interval timer will be reset and start over.

SUpon initial power up the first defrost interval is defaulted to 30 minutes. Remaining intervals are at selected times.

SDefrost is only allowed to occur below 50_F (10_C) outdoor ambient temperature.

The outdoor fan output (ODF) will remain off for 20 seconds after termination. This delay will allow time for the system to capture the heat from the outdoor coil and reduce the “steam cloud” effect that may occur on transition from defrost to heating cycle. The outdoor fan output OFF delay of 20 seconds may be defeated to enable the fan to energize immediately at the time of termination and 12 seconds prior to the reversing valve de-energizing through the User Interface setup screen (available with SYSTXCCUID01-C), or forced defrost pins as follows:

The ODF fan delay defeat can be toggled by shorting the forced defrost pins for >15 seconds while in the standby mode (status LED on solid). The LED will start to flash when the toggle has taken place.

Status code 4 shows the fan delay defeat is active (no delay). Status code 3 shows that it si not active (20 second delay).

The code will continue to be displayed until after the short is removed. There is a 5 second wait before the code is cancelled once the short is removed. the code that is flashing will finish before going back to solid LED. The control is shipped with the ODF fan delay defeat NOT active.

The change in status is remembered until toggled to a new status. A power down/power up sequence will not reset the status. It may be necessary to do the toggle twice to cycle to the desired state of the defeat.

Defrost Hold

On a non-communicating system, if the thermostat becomes satisfied (Y1 or Y1 and Y2) before the defrost cycle is terminated, the control will “hold” in defrost mode and finish the defrost cycle on the next call for heat.

On models with communicating Infinity Control, defrost hold is not needed because the User Interface will complete the defrost cycle before shutting down the system.

Forced Defrost

On a system with non-communicating (non-Infinity) control, forced defrost can be initiated by manually shorting the 2-pin header labeled FORCED DEFROST (see Fig 6) on the control board for 5 seconds then releasing.

On a system with communicating (Infinity) control, forced defrost is initiated with the User Interface.

On all models, during a Forced Defrost:

SIf coil temperature is at defrost temperature of 32_F (0_C), and

outdoor air temperature is below 50_F (10_C), a full defrost sequence will occur.

SIf coil temperature or outdoor air temperature does not meet the above requirements, an abbreviated 30 second defrost will occur.

Quiet Shift

Quiet Shift is a field-selectable defrost mode which may eliminate occasional noise that could be heard at the start of the defrost cycle and restarting of the heating cycle. On a non-communicating system, this feature must be enabled by selecting the 3rd position of the 3-position dip switch. For communicating (Infinity) systems, it must be enabled at the User Interface. When activated, the following sequence of operation will occur. Reversing valve will energize and compressor will turn off for 30 seconds, then turn back on to complete defrost. At the end of the defrost cycle, the reversing valve de-energizes, compressor will turn off for another 30 seconds, and the fan will turn off for 40 seconds, before starting in the heating mode.

Liquid-Line Solenoid Accessory

In heat pump long-line applications, a liquid-line solenoid is required to control refrigerant migration in the heating mode. The solenoid should be installed near the outdoor unit with the arrow facing the outdoor unit. This is the direction of flow control. See application manual for long-line application details.

Accessory Liquid Solenoid with Infinity Communicating Control: When using the Infinity Control, the liquid-line solenoid

25HPA6

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