Carrier 25HNA Infinity
Series Installation Instructions Manual page 11

*
UTILITY RELAY
UTILITY SIGNAL
OPEN RELAY
* SUPPLIED BY UTILITY PROVIDER
GENERAL INFORMATION
Low Ambient Cooling
When this unit is operating below 55_F outdoor temperature,
provisions must be made for low ambient operation.
Infinity Controlled low ambient cooling:
This unit is capable of low ambient cooling without a kit ONLY
when using 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. The Infinity 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 OAT. Fan will cycle
based on coil and outdoor air temperature.
Infinity controlled low ambient mode operates as follows:
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Fan is OFF when outdoor coil temp is < (outdoor air
temperature + 3_F) or outdoor fan has been ON for 30
minutes. (Fan is turned off to allow refrigerant system to
stabilize.)
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Fan is ON when outdoor coil temp > (outdoor air
temperature + 25_F) or outdoor coil temp > 80_F 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.
For 25HNA9 models, the PWM output for both high and low
stage equals the value for low stage operation below 104_F.
MODEL
PLUG
A06525
Fig. 9 − 2−Stage Control Board
Defrost
This control offers 5 possible defrost interval times: 30, 60, 90,
120 minutes, or AUTO.
On 25HNA6 models, these 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.
On 25HNA9 , 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:
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S
S
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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 for 4
minutes during the interval.
The defrost cycle is terminated when the coil temperature reaches
65_F or 10 minutes has passed.
If the coil temperature does not reach 32_F within the interval,
the interval timer will be reset and start over.
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S
11
LLS
Liquid Line Solenoid
When defrost time <3 minutes, the next defrost
interval=120 minutes.
When defrost time 3−5 minutes, the next defrost
interval=90 minutes.
When defrost time 5−7 minutes, the next defrost
interval=60 minutes.
When defrost time >7 minutes, the next defrost
interval=30 minutes.
Upon initial power up the first defrost interval is
defaulted to 30 minutes. Remaining intervals are at
selected times.
Defrost is only allowed to occur below 50_F outdoor
ambient temperature.
MODEL
PLUG
A06526