Infinity Controlled Low Ambient Cooling; Utility Interface With Infinity Control; Communication And Status Function Lights - Carrier 25VNA Service Manual

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
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 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 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.)
S 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)
S 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.

Utility Interface With Infinity Control

The utility curtailment relay should be wired between the two
UTIL connections on the control board for this Infinity
Communicating System. 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. 3)
indicates successful communication with the other system
products. The green LED will remain OFF until communication is
established. Once a valid command is received, the green LED will
turn ON continuously. If no communication 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 5 and Table 6 for definitions.
Two minute time delay to return to standby operation from last
S
valid communication.
S 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).
S Fifteen second delay at termination of defrost before the
auxiliary heat is de- -energized.
Infinity Control. A low
1
BRN
RED
SEC1 SEC2
CC
PL3
HPS
PL2
RVS
PL1
COMM STATUS
C LS Y
UTIL
A B C NO
USE
Fig. 3 – Variable Speed Control Board
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:
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. 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 defrost cycle is terminated as described below.
When OAT is > 30°F (- -1.1 °C), defrost terminates if outdoor
S
coil temperature (OCT) > 50°F (+10°C)
S When OAT is </= 30°F (- -1.1°C), defrost terminates if outdoor
coil temperature (OCT) > 40 °F (+4.4°C)
S Or 10 minutes has passed.
At the defrost termination, the outdoor fan output (ODF) will turn
on 15 seconds before the reversing valve switching.
NOTE: Compressor speed during defrost varies based on outdoor
conditions.
6
YEL
BLU
EXV
PWM2 PWM1
PL4
SPT
PL11
CB
OST
PL6
OCT
OAT
J2
O
PL8
FORCED
MODEL DEFROST
A11139