Carrier Infinity 50XT-A Installation Instructions Manual page 19

Fig. 14, 16 and 17). This input allows a power utility device to
interrupt compressor operation during peak load periods. When the
utility sends a signal to shut the system down, the UI will display
"Curtailment Active".
COMPRESSOR OPERATION
When the compressor is operating in low stage, the modulating
ring is de- -activated, allowing two internal bypass ports to close off
33% of the scroll compression area so the system operates at part
load capacity. The 24- -volt solenoid coil is de- -energized in
low- -stage operation.
When the compressor is operating at high stage, the modulating
ring is activated, sealing the bypass ports, which allows the
compressor to operate at full load capacity. The 24- -volt solenoid
coil is energized in high stage operation.
CRANKCASE HEATER OPERATION (IF APPLICABLE)
The crankcase heater is energized during off cycle below 65_F
(18_C) outdoor air temperature.
OUTDOOR FAN MOTOR OPERATION
The outdoor unit control energizes the outdoor fan any time the
compressor is operating, except for defrost. The outdoor fan
remains energized if a pressure switch or compressor overload
should open. Outdoor fan motor will continue to operate for one
minute after the compressor shuts off when the outdoor ambient is
greater than or equal to 100_F (38_C).
TIME DELAYS
The unit time delays include:
S Five 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.
S Five minute compressor re- -cycle delay on return from a
brown- -out condition.
S Two minute time delay to return to standby operation from last
valid communication (with Infinity only).
S One minute time delay of outdoor fan at termination of cooling
mode when outdoor ambient is greater than or equal to 100_F
(38_C).
S Fifteen second delay at termination of defrost before the
auxiliary heat (W1) is de- -energized.
S Twenty second delay at termination of defrost before the outdoor
fan is energized.
S Thirty second compressor delay when quiet shift enabled.
S There is no time 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 as demand dictates.
INFINITY CONTROLLED LOW AMBIENT COOLING
NOTE: When this unit is operating below 55_F (13_C) outdoor
temperature, provisions must be made for low ambient operation.
This unit is capable of low ambient cooling down to 0_F (18_C)
ONLY when using the Infinity control. A low ambient kit is not
required, and the outdoor fan motor does not need to be replaced
for Infinity controlled low ambient operation. Low ambient
cooling must be enabled in the UI set- -up. Fan may not begin to
cycle until about 40_F (4_C) OAT. Fan will cycle based on coil
and outdoor air temperature. Infinity controlled low ambient mode
operates as follows:
S In high stage, fan is off when outdoor coil temp is <outdoor air
temperature plus 3_F (1.6°C) or outdoor fan has been ON for 30
minutes. (Fan is turned off to allow refrigerant system to
stabilize.)
S In low stage, fan is off when outdoor coil temp is <outdoor air
temperature plus 1_F (- -6°C)or outdoor fan has been ON for 30
minutes. (Fan is turned off to allow refrigerant system to
stabilize.)
S In high stage and low stage, fan is on when outdoor coil temp >
outdoor air temperature plus 25_F (13.8°C) or outdoor coil temp
> 80_F (27_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.
The 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 HP/AC 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_C) or 10 minutes has passed.
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.
DEFROST HOLD
Defrost hold is not needed in a communicating system because the
User Interface will complete the defrost cycle before shutting down
the system.
FORCED DEFROST
Forced defrost is initiated with the User Interface.
During a Forced Defrost:
S If coil temperature is at defrost temperature of 32_F (0_C), and
outdoor air temperature is below 50_F (10_C), a full defrost
sequence will occur.
S If coil temperature or outdoor air temperature do not meet the
above requirements, an abbreviated 30 second defrost will occur.
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