Carrier 25VNA Installation Instructions Manual page 9

Crankcase Heater Operation
This unit has an internal crankcase heater that will be energized
during the off cycle and is intelligently demanded by the system to
prevent the compressor from being the coldest part of the system
thus enhancing the reliability. The crankcase heater will function
as needed any time the outdoor unit is powered. The indoor unit
and UI do not need to be installed for the crankcase heater to
operate properly.
NOTE: Contactor may close intermittently without the unit
starting. This is done to determine whether the control needs to
energize the crankcase heater. Closing the contactor powers the
inverter and allows the system to check compressor temperature.
Outdoor Fan Motor Operation
The outdoor unit control (Fig. 11) energizes outdoor fan anytime
compressor is operating, except for defrost and as needed during
low-ambient cooling operation. The outdoor fan remains
energized if a pressure switch opens or compressor scroll over
temperature should occur. This OD fan is an ECM motor which
operates at varying speeds depending on the ambient and the
demand.
Time Delays
The unit time delays include:
• Five minute time delay to start cooling or heating operation
when there is a call from the user interface. To bypass this
feature, momentarily short and release Forced Defrost pins.
• Five minute compressor re-cycle delay on return from a
brown-out condition.
• See Tab le 7 for other delay information.
General Information
Infinity Controlled low ambient cooling:
This unit is capable of low ambient cooling down to 0°F (-17.8°C)
with Low Ambient enabled on the Infinity Control. A low
ambient kit is not required. The only accessory that may be
required is wind baffles in locations which are likely to experience
cross winds in excess of 5 miles an hour. This generally occurs
only on roof and open area applications. The Infinity Control
provides an automatic evaporator freeze thermostat. Low ambient
cooling nmst 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:
• Fan is OFF when outdoor coil temperature is too low (+
55 ° F/12.7 ° C), the saturated suction pressure indicates a freezing
indoor coil or outdoor fan has been ON for 30 minutes. (Fan is
turned off to allow refrigerant system to stabilize.)
Utility Interface With Infinity Control
The utility curtailment relay should be wired between UTIL and C
connections on the control board for this Infinity Communicating
System (see Fig. 19). 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 User Interface
will display, "Curtailment Active". See UI installation instructions
for setup details.
Communication and Status Function Lights
Infinity Control_ Green Communications (COMM)Light
A green LED (COMM light) on the outdoor board (see Fig. 11)
indicates successful communication with the other system
products. The green LED will remain OFF until conmmnication is
established. Once a valid command is received, the green LED will
turn ON continuously. If no conmmnication is received within 2
minutes, the LED will be turned OFF until the next valid
communication.
Amber Status Light
Amber colored STATUS light indicates operation and error status.
See Table 7 for definitions.
• Two minute time delay to return to standby operation from last
valid communication.
• One minute time delay of outdoor fan at termination of cooling
mode when outdoor ambient is greater than or equal to 100°F
(37.8°C).
• Fifteen second delay at termination of defrost before the
auxiliary heat is de-energized.
Fig. 11 - Variable Speed Control Board
Al1139
• Fan is ON when outdoor coil temperature is too high
(+80°F/26.7°C), the high side pressure is too high or if outdoor
fan has been OFF for 30 minutes. (Fan is turned on to allow
refrigerant system to stabilize)
• Low pressure indication by the suction pressure transducer is
ignored for first 3 minutes during low ambient start up. After 3
minutes, if low pressure trip occurs, then outdoor fan motor is
turned off for 10 minutes, with the compressor running. If
pressure condition is satisfied 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
suction pressure condition is not satisfied within 10 minutes, then
the normal trip response (shut down cooling operation and
generate LP trip error) will occur.
Defrost
This user interface (UI) offers 5 possible defrost interval times: 30,
60, 90, 120 minutes, or AUTO. The default is AUTO.
Defrost interval times: 30, 60, 90, and 120 minutes or AUTO are
selected by the Infinity Control User Interface (dip switches are not
used.)
AUTO defrost adjusts the defrost interval time based on the last
defrost time as follows:
• 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.