9
UTILITY RELAY *
UTILITY SIGNAL
OPEN RELAY
* SUPPLIED BY UTILITY PROVIDER
MODEL
PLUG
A06525
LLS
Liquid Line Solenoid
MODEL
PLUG
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 fo r
Evolution controlled low ambient operation. The Evolution
Control provides an automatic evaporator coil freeze protection
algo rithm th at elim inates the need for an ev apo rator 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:
S Fan isOFFwhen outdoorcoiltempis <(outdoorairtemperature
+3_F/1.7_C)or outdoorfan hasbeen ON for 30 minutes. (Fan
is turned o ff to allow refrig eran t sy stem to stab ilize.)
S Fan is ON when outdoor coil temp > (outdoor air temperature +
25_F / 13.9 _C) or outdoor coil temp > 80_F/26.7 _Corif
outdoor fan has been OFF for 30 minutes. (Fan is turned on to
allow refrig eran t sy stem to stab ilize.)
S Low pressure switch is ignored for first 3 minutes during low
ambient start up. After 3 minutes, ifLPS trips, then outdoorfan
motoristurnedofffor10minutes,with thecompressor running.
If LPS closes with in 1 0 minutes then co o lin g con tin u es w ith the
outdoor fancyclingper thecoiltemperatureroutinelistedabove
fortheremainderof the cooling cycle. Ifthe LPS does notclose
within 10 minutes, then the normal LPS trip response (shut
down cooling operation and generate LPS triperror)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:
S When defrost time <3 minutes, the next defrost interval=120
minutes.
S When defrost time 3 -- 5 minutes, the next defrost interval=90
minutes.
S When defrost time 5 -- 7 minutes, the next defrost interval=60
minutes.
S When 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 high-- stage as
demanded by the thermostat or User Interface regardless of OAT
On 288A models, when OAT is >25_F(--3.9_C), defrost will occur
in low-- or high -- stage as demanded by the thermostat or User
Interface.
On 288A models, 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.
S Up o n in itial p o w er u p th e first defrost interval is d efau lted to
30 m in u tes. R em ain i n g in terv als are at selected tim es.
S Defrost is only allowed to occur below 50_F(10_C)outdoor
amb ient temp erature.
286A / 288A
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