MODEL |
PLUG |
UTILITY RELAY * |
UTILITY SIGNAL
OPEN RELAY 
MODEL |
PLUG |
LLS |
286A / 288A
* SUPPLIED BY UTILITY PROVIDER | Liquid Line Solenoid |
A06525 | A06526 |
Fig. 6 - 2-Stage Control Board
GENERAL INFORMATION
Low Ambient Cooling
When this unit is operating below 55_F (12.78_C) outdoor temperature, provisions must be made for low ambient operation.
Evolution Controlled low ambient cooling:
This unit is capable of low ambient cooling without a kit ONLY when using Evolution control. A low ambient kit is not required, and the outdoor fan motor does not need to be replaced for Evolution controlled low ambient operation. The Evolution Control provides an automatic evaporator coil freeze protection algorithm that eliminates the need for an evaporator freeze thermostat. Low ambient cooling must be enabled in the User Interface set up. Fan may not begin to cycle until about 40_F (4.4 _C) OAT. Fan will cycle based on coil and outdoor air temperature.
Evolution controlled low ambient mode operates as follows:
SFan is OFF when outdoor coil temp is < (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 temp > (outdoor air temperature + 25_F / 13.9_C) or outdoor coil temp > 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.)
SLow 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.
For 288A models, the PWM output for both high and low stage equals the value for low stage operation below 55_F (12.8_C).
Defrost
This control offers 5 possible defrost interval times: 30, 60, 90, 120 minutes, or AUTO.
These are selected by dip switches on the unit control board or by the Evolution Control User Interface. The Evolution Control selection overrides the control board dip switch settings.
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
SWhen defrost time
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.
On 286A models, defrost will occur in low- or
On 288A models, when OAT is >25_F
On 288A models, if OAT is ≤25_F
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.
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