Carrier 50GCQ Series - Page 36

36
Outdoor Air Temperature (OAT) Sensor
The outdoor air temperature sensor (HH57AC074) is a 10 to
20 mA device used to measure the outdoor-air temperature. The
outdoor-air temperature is used to determine when the
EconoMi$er IV can be used for free cooling. The sensor has
8 selectable temperature changeover setpoints, ranging from 48°F
to 78°F. The temperature changeover is set using the 3 DIP
switches on the sensor. See Fig. 58.
Fig. 58 — C7660 Temperature Sensor
Supply Air Temperature (SAT) Sensor
The supply air temperature sensor is a field-installed 3 K thermis-
tor located on the fan deck. See Fig. 59. This sensor is factory in-
stalled. The operating range of temperature measurement is 0°F to
158°F (–18°C to 70°C). See Table 12 on page 37 for sensor tem-
perature/resistance values.
Fig. 59 — Supply Air Sensor Location
The temperature sensor looks like an eyelet terminal with wires
running to it. The sensor is located in the “crimp end” and is sealed
from moisture.
Table 11 — EconoMi$er IV Input/Output Logic
INPUTS OUTPUTS
Demand
Controlled
Ventilation
(DCV)
Enthalpy
a
NOTE(S):
a. For single enthalpy control, the module compares outdoor enthalpy to the ABCD set point.
Y1 Y2
Compressor N Terminal
b
b. Power at N terminal determines Occupied/Unoccupied setting: 24 vac (Occupied), no power (Unoccupied).
Outdoor Return Stage 1 Stage 2 Occupied Unoccupied
Below Set
(DCV LED
Off)
High
(Free Cooling
LED Off)
Low
On On On On
Minimum position ClosedOn Off On Off
Off Off Off Off
Low
(Free Cooling
LED On)
High
On On On Off
Modulating
c
(between minimum
position and full-open)
c. Modulation is based on the supply-air sensor signal.
Modulating
c
(between
closed and full-open)
On Off Off Off
Off Off Off Off Minimum position Closed
Above Set
(DCV LED
On)
High
(Free Cooling
LED Off)
Low
On On On On
Modulating
d
(between minimum
position and DCV maximum)
d. Modulation is based on the DCV signal.
Modulating
d
(between
closed and DCV maximum)
On Off On Off
Off Off Off Off
Low
(Free Cooling
LED On)
High
On On On Off
Modulating
e
e. Modulation is based on the greater of DCV and supply-air sensor signals, between minimum position and either maximum position (DCV) or fully open (supply-air signal).
Modulating
f
f. Modulation is based on the greater of DCV and supply-air sensor signals, between closed and either maximum position (DCV) or fully open (supply-air signal).
On Off Off Off
Off Off Off Off
Supply Air
Temperature
Sensor