8
UTILITY RELAY
*
UTILITY SIGNAL
OPEN RELAY
* SUPPLIED BY UTILITY PROVIDER
A B C
A B C
A12260
LLS
Liquid Line Solenoid
A B C
A B C
A12261
Fig. 7 -- 2--Stage Control Board
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:
S
Fan 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.)
S
Fan 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:
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. 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.
S
Upon initial power up the first defrost interval is defaulted to 30
minutes. Remaining intervals are at selected times.
S
Defrost 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
SYSTXBBUID01--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.
25H
N
B
6
/25H
N
B
9
