Carrier 48FC M20 Series Service And Maintenance Instructions page 50

INPUTS
Demand Enthalpy
Controlled
Ventilation
Outdoor
(DCV)
High
(Free Cooling
Below Set
LED Off)
(DCV LED
Low
Off)
(Free Cooling
LED On)
High
(Free Cooling
Above Set
LED Off)
(DCV LED
Low
On)
(Free Cooling
LED On)
NOTE(S):
a. For single enthalpy control, the module compares outdoor enthalpy to the ABCD set point.
b. Power at N terminal determines Occupied/Unoccupied setting: 24 vac (Occupied), no power (Unoccupied).
c. Modulation is based on the supply-air sensor signal.
d. Modulation is based on the DCV signal.
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).
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).
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$er IV can be used for free cooling. The sensor has 8
selectable temperature changeover setpoints, ranging from
48°F to 78°F. The temperature changeover is set using the 3
dip switches on the sensor See Fig. 66.
Fig. 66 — C7660 Temperature Sensor
Supply Air Temperature (SAT) Sensor
The supply air temperature sensor is a field-installed 3 K
thermistor and is installed through the heat section partition ex-
tending into the supply airstream. See Fig. 67. The operating
range of temperature measurement is 0°F to 158°F (–18°C to
70°C). See Table 13 for sensor temperature/resistance values.
Table 12 — EconoMi$er IV Input/Output Logic
a
Y1 Y2
Return Stage 1
On On On
Low On Off On
Off Off Off
On On On
High On Off Off
Off Off Off
On On On
Low On Off On
Off Off Off
On On On
High On Off Off
Off Off Off
Compressor
Stage 2 Occupied
On
Off Minimum position
Off
Off
Modulating
min. position and full-open)
Off
Off Minimum position
On
Modulating
Off
position and DCV maximum)
Off
Off
Off Modulating
Off
Fig. 67 — Supply Air Temperature 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.
50
OUTPUTS
N Terminal b
Unoccupied
c (between Modulating
closed and full-open)
d (between min. Modulating
closed and DCV maximum)
e Modulating
Supply Air Temperature Sensor
Closed
c (between
Closed
d (between
f