Carrier WeatherExpert Puron 50LC 08 Series Installation Instructions Manual page 34

demand for cooling, the outdoor-air damper will maintain its cur-
rent position, compressor C2 will run and the outdoor fan will run
at medium speed. The VFD-controlled indoor fan will operate at
high speed regardless of the cooling demand.
If the increase in cooling capacity causes the mixed-air tempera-
ture to drop below 45°F (7°C), the outdoor-air damper will return
to the minimum position. If the mixed-air temperature continues
to fall, the outdoor-air damper will close. Control returns to nor-
mal once the mixed-air temperature rises above 48°F (9°C). The
power exhaust fans will be energized and de-energized, if in-
stalled, as the outdoor-air damper opens and closes.
If field-installed accessory CO
omizer, a demand controlled ventilation strategy will begin to op-
erate. As the CO level in the zone increases above the CO
2
point, the minimum position of the damper will be increased pro-
portionally. As the CO level decreases because of the increase of
2
fresh air, the outdoor-air damper will be proportionally closed. For
economizer operation, there must be a thermostat call for the fan
(G). If the unit is occupied and the fan is on, the damper will oper-
ate at minimum position. Otherwise, the damper will be closed.
Low Ambient Cooling Operation down to 40°F (4°C)
In Low Ambient RTU conditions when the temperature is be-
tween 55°F (13°C) and 40°F (4°C), the Low Ambient Switch
(LAS) will be active and the outdoor fans will run to the pre-set
factory outdoor fan speed. When the temperature is greater than
65°F (18°C), the Low Ambient Switch will deactivate and the out-
door fans will run in the standard cooling mode. If the Outdoor
Fan Select Switch (see Fig. 53) is in the ON position, the outdoor
fans will run in the Fan Cycle Speed Mode (FCS) set to 250 rpm.
If the Outdoor Fan Select Switch is in the OFF position, the out-
door fans will run in the Minimum Fan Speed Mode (MIN) set to
160 rpm regardless of the cooling demand.
50LC Size 08 through 12 units have a SPDT Low Ambient
Switch wired to the OF terminal and the Outdoor Fan Relay (see
Fig. 54). The jumper across the PS terminal will be removed.
When the LAS is active, the switch will close making contact to
the OF terminal and will drop connection to the ODF Relay. When
electrical connection is removed from the ODF Relay, the PS con-
nection will be opened. This will place the third outdoor fan elec-
trically isolated from receiving any speed command, which will
then turn the motor off. This is done for units that only require two
outdoor fans to run at the same pre-set factory Low Ambient
Speed.
OF SPEED
Fig. 53 — Outdoor Fan Speed Select Switch
sensors are connected to the Econ-
2
SELECT
ON
FCS
MIN
OFF
24VAC
TB-4
Fig. 54 — Schematic of SPDT Low Ambient Switch
set-
2
Table 5 shows the operation of the outdoor fan for size 08, 09 and
12 units.
Table 5 — Low Ambient Temperature Outside Fan
NO. OF
LC SIZE
FANS ON
2
08
2
09
2
12
Heating
In the Heating Mode (W1 on the thermostat), power is applied to
the G and W1 terminal at the ISC board and energizes the first
state of electric heat. Upon more call for heat (W2 at the thermo-
stat), power is applied to the G and W2 terminal at the ISC board
and energizes the second state of electric heat. The VFD con-
trolled indoor fan will operate at high speed regardless of the heat-
ing demand.
EconoMi$er
®
The EconoMi$er X system is an expandable economizer control
system, which includes a W7220 economizer module (controller)
with an LCD and keypad (see Fig. 55). The W7220 can be config-
ured with optional sensors.
Fig. 55 — W7220 Economizer Module
The W7220 economizer module can be used as a stand-alone
economizer module wired directly to a commercial set-back space
thermostat and sensors to provide outside air dry-bulb economizer
control.
The W7220 economizer module can be connected to optional sen-
sors for single or differential enthalpy control. The W7220 econo-
mizer module provides power and communications for the
sensors.
34
ODF RELAY
OF PS
REMOVE JUMPER
LAS
SPDT
Control
NO. OF
SWITCH
FANS OFF
1 (1) SPDT
1 (1) SPDT
1 (1) SPDT
X (Factory Option)
PS
OUTDOOR
FAN
RPM
SELECT
SWITCH
Down 160
Down 160
Down 160