Economi$Er Iv Input/Output Logic; Supply Air Temperature (Sat) Sensor; Outdoor Air Temperature (Oat) Sensor; C7660 Temperature Sensor - Carrier 50FC Series Service And Maintenance Instructions

INPUTS
Demand Enthalpy*
Controlled
Ventilation
Outdoor
(DCV)
High
(Free Cooling
LED Off)
Below set
(DCV LED
Off)
Low
(Free Cooling
LED On)
High
(Free Cooling
LED Off)
Above set
(DCV LED
On)
Low
(Free Cooling
LED On)
* For single enthalpy control, the module compares outdoor enthalpy to
the ABCD set point.
† Power at N terminal determines Occupied/Unoccupied setting: 24
vac (Occupied), no power (Unoccupied).
** Modulation is based on the supply-air sensor signal.
†† Modulation is based on the DCV signal.
*** 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).
††† 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$er IV can be used for free cooling. The sensor has 8
selectable temperature changeover setpoints, ranging from
48°F to 78°F. The temperature changeover is set using the 3
dip switches on the sensor See Fig. 59.
Fig. 59 — C7660 Temperature Sensor
Table 6 — EconoMi$er IV Input/Output Logic
Compressor
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
OUTPUTS
Stage 2 Occupied
On
Off Minimum position
Off
Off
Modulating** (between
min. position and full-open)
Off
Off Minimum position
On
Modulating†† (between min.
Off
position and DCV maximum)
Off
Off
Off Modulating***
Off

Supply Air Temperature (SAT) Sensor

The supply air temperature sensor is a field-installed 3 K
thermistor located on the fan deck. See Fig. 60. This sensor is
factory installed. The operating range of temperature measure-
ment is 0°F to 158°F (–18°C to 70°C). See Table 7 for sensor
temperature/resistance values.
SUPPLY AIR
TEMPERATURE
SENSOR
Fig. 60 — 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.
Outdoor Air Lockout Sensor
The EconoMi$er IV is equipped with an ambient temperature
lockout switch located in the outdoor airstream which is used
to lock out the compressors below a 42°F (6°C) ambient tem-
perature. See Fig. 54 on page 30.
33
N Terminal†
Unoccupied
Closed
Modulating** (between
closed and full-open)
Closed
Modulating†† (between
closed and DCV maximum)
Modulating†††