Compressor Delay Mode (P5)
The demand defrost control has a field−selectable function to reduce occasional sounds that may occur while the unit is cycling in and out of the defrost mode. When a jumper is installed on the DELAY pins, the compressor will be cycled off for 30 seconds going in and out of the defrost mode. Units are shipped with jumper installed on DELAY pins.
NOTE − The 30 second off cycle is NOT functional when jumpering the TEST pins.
OPERATIONAL MODE OVERVIEW
The demand defrost control has three basic operational modes. Those modes are:
1.Calibration Mode The demand defrost control is considered uncalibrated when power is applied to the demand defrost control, after cool mode operation, or if the coil temperature exceeds the termination temperature when it is in heat mode (see figure 26 for further details).
2.Normal Mode
monitors the O line, to determine the system operating mode (heat/cool), outdoor ambient temperature, coil temperature (outdoor coil) and compressor run time to determine when a defrost cycle is required.
Calibration of the demand defrost control occurs after a defrost cycle to ensure that there is no ice on the coil. During calibration, the temperature of both the coil and the ambient sensor are measured to establish the temperature differential which is required to allow a defrost cycle.
3.Defrost Mode aragraphs provide a
detailed description of the defrost system operation.
DEFROST CYCLE ACTUATION
The demand defrost control initiates a defrost cycle based on either frost detection or time.
1.Frost Detection
30 minutes and the actual difference between the clear coil and frosted coil temperatures exceeds the maximum difference allowed by the demand defrost control, a defrost cycle will be initiated.
2.Time
time has elapsed since the last defrost cycle while the coil temperature remains below 35°F (2°C), the demand defrost control will initiate a defrost cycle.
Actuation
When the reversing valve is de−energized, the Y1 circuit is energized, and the coil temperature is below 35°F (2°C), the demand defrost control logs the compressor run time. If the demand defrost control is not calibrated, a defrost cycle will be initiated after 30 minutes of heating mode compressor run time. The control will attempt to self−calibrate after this (and all other) defrost cycle(s).
Calibration success depends on stable system temperatures during the 20−minute calibration period. If the demand defrost control fails to calibrate, another defrost cycle will be initiated after 45 minutes of heating mode compressor run time. Once the demand defrost control is calibrated, it initiates a demand defrost cycle when the difference between the clear coil and frosted coil temperatures exceeds the maximum difference allowed by the control or after six hours of heating mode compressor run time has been logged since the last defrost cycle.
Termination
The defrost cycle ends when the coil temperature exceeds the termination temperature or after 14 minutes of defrost operation. If the defrost is terminated by the 14−minute timer, another defrost cycle will be initiated after 30 minutes of run time.
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XP16 SERIES