Carrier 25HPA6 instruction manual Time Delays, Compressor Operation

25HPA6

Time Delays

The unit time delays include:

SFive minute time delay to start cooling or heating operation when there is a call from the thermostat or user interface. To bypass this feature, momentarily short and release Forced

Defrost pins.

SFive minute compressor re-cycle delay on return from a brown-out condition.

STwo minute time delay to return to standby operation from last valid communication (with Infinity only).

SOne minute time delay of outdoor fan at termination of cooling mode when outdoor ambient is greater than or equal to 100_F

(37.78_C).

SFifteen second delay at termination of defrost before the auxiliary heat (W1) is de-energized.

STwenty second delay at termination of defrost before the outdoor fan is energized (unless fan delay defeated).

SThirty second compressor delay when quiet shift enabled.

SThere is no delay between staging from low to high and from high to low capacity. The compressor will change from low to high and from high to low capacity “on the fly” to meet the demand.

Compressor Operation:

The basic scroll design has been modified with the addition of an internal unloading mechanism that opens a by-pass port in the first compression pocket, effectively reducing the displacement of the scroll. The opening and closing of the by-pass port is controlled by an internal electrically operated solenoid. The modulated scroll uses a single step of unloading to go from full capacity to approximately 67% capacity.

A single speed, high efficiency motor continues to run while the scroll modulates between the two capacity steps. Modulation is achieved by venting a portion of the gas in the first suction pocket back to the low side of the compressor, thereby reducing the effective displacement of the compressor.

Full capacity is achieved by blocking these vents, thus increasing the displacement to 100%. A DC solenoid in the compressor controlled by a rectified 24 volt AC signal in the external solenoid plug moves the slider ring that covers and uncovers these vents.

The vent covers are arranged in such a manner that the compressor operates at approximately 67% capacity when the solenoid is not energized and 100% capacity when the solenoid is energized. The loading and unloading of the two step scroll is done ”on the fly” without shutting off the motor between steps.

NOTE: 67% compressor capacity translates to approximately 75% cooling or heating capacity at the indoor coil.

The compressor will always start unloaded and stay unloaded for five seconds even when the thermostat is calling for high stage capacity.

MODEL

PLUG

UTILITY RELAY *

UTILITY SIGNAL

OPEN RELAY

MODEL

PLUG

LLS

* SUPPLIED BY UTILITY PROVIDER	Liquid Line Solenoid
A06525	A06526

Fig. 6 - 2-Stage Control Board

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