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Table 7—Ambient Temperatures for High- and
Low-Speed Operation
AMBIENT TEMPERATURE (°F)
UNIT SIZE
High Speed
036
30 or less
048
33 or less
060
40 or less
LED FUNCTION LIGHTS
System control function LED indicator lights are available at
outdoor unit 2-speed control board. The indoor thermostat may
provide indicator signals for high- and low-speed operation,
system malfunction, and auxiliary heat (if equipped to do so). The
2-speed control board has an LED which provides signals for
several system operations. See Table 8 for LED functions and
definitions. Table 8 also provides the order of signal importance if
more than 1 signal should occur. If equipped and properly wired,
the signal to indoor thermostat is supplied by the low-voltage L
lead.
NOTE: A signal (code) is not sent through the L lead to
thermostat unless a failure has occurred.
Table 8—LED Control Function Light Code
CODE
Constant flash
No pause
1 flash
Low-speed operation
w/pause
2 flashes
High-speed operation
w/pause
3 flashes
Outdoor ambient thermistor failure
w/pause
4 flashes
Outdoor coil thermistor failure
w/pause
3 flashes
pause
Thermistor out of range†
4 flashes
5 flashes
Pressure switch trip (LM1/LM2)
w/pause
6 flashes
Compressor PTC's out of limit
w/pause
Constant light
No pause
No flash
* Function light signal order of importance in case of multiple signal request; 1
is most important.
† Check both thermistors to determine which is faulty.
FACTORY DEFAULTS
Factory defaults have been provided in the event of failure of
ambient thermistor, outdoor coil thermistor, and/or furnace inter-
face jumper. Refer to Table 9 for default and function.
THREE-SEC TIME DELAY
Any time the control receives a 24-v input, such as Y1 or Y2, there
is a 3-sec time delay before control function is initiated. This helps
prevent nuisance trips from thermostat jiggling.
ONE-MINUTE SPEED CHANGE TIME DELAY
When compressor changes speeds from high to low or low to high,
there is a 1-minute time delay before compressor restarts. The
outdoor fan motor remains running.
FIVE-MINUTE TIME DELAY
The 2-speed control logic contains a 5-minute time delay that
prevents unit from short cycling after a thermostat off cycle or
power interruption. The unit can be forced to operate immediately
Low Speed
31 or greater
34 or greater
41 or greater
DEFINITION
*
No demand
9
Stand by
8
7
6
5
4
3
2
Board failure
1
by momentarily touching a jumper between speed-up terminals of
control board. (See Fig. 9.) The speed-up feature does not bypass
any other function or time delay.
LM1 LM2
DFT1 DFT2 T1
1
K7
SPEED-UP
Fig. 9—Two-Speed Control Board
TWO-MINUTE LOW-SPEED MINIMUM
If unit has not operated within the past 30 minutes, upon the next
thermostat high- or low-speed demand, unit operates for a mini-
mum of 2 minutes in low speed.
CRANKCASE HEATER OPERATION
The 2-speed control energizes crankcase heater during unit's off
cycle when outdoor ambient is below 75°F.
OUTDOOR FAN MOTOR OPERATION
The 2-speed control energizes outdoor fan any time compressor is
operating. The outdoor fan remains energized during the 1-minute
speed change time delay and if a pressure switch or positive
temperature coefficient (PTC) overload should trip.
After termination of a defrost cycle, the outdoor fan delays coming
on for 20 sec. This allows refrigerant system to recover outdoor
coil heat and minimize the "steam cloud" effect.
SECOND-STAGE LATCHING
Mechanical thermostats operate with a staging differential of 2°F
(droop). Carrier electronic thermostats are droopless, meaning that
they maintain room temperature at set point without latching
second stage. If system is installed with a mechanical thermostat or
second stage latching is desired, the following information applies.
During normal operation, the compressor operates at low speed to
satisfy first stage of indoor thermostat. If indoor thermostat
temperature increases 2 degrees, the compressor shifts into high-
speed operation. When indoor thermostat temperature is satisfied,
the compressor returns to low-speed, first-stage operation.
The installing technician can select high-speed compressor opera-
tion until first stage of indoor thermostat is satisfied. This
eliminates the temperature droop of indoor thermostat between
first- and second-stage operation and holds room temperature
closer to set point when load requirements are high. To select this
option, rotate the STAGE 2 LATCH potentiometer (pot) to desired
temperature. (See Fig. 10.) The pot is factory set at OFF; however,
a temperature of 85°, 90°, 95°, 100°, or 105°F can be selected. The
selected temperature is the outdoor temperature at which the
structure's cooling load requires high-speed operation.
Unit high- and low-speed capacities should be plotted versus
cooling load (heat gain) of structure to accurately determine the
STAGE 2 LATCH temperature to be selected. Unit capacities
16
T2
S2
S1 PW2 PW1
P1
18
FURN INT
OFF
ON
50
STAGE 2
DEFROST
BALANCE
LATCH
TIME
POINT
A93568
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