31
Return Gas Temperature (RGT)
— These sensors are factory
installed in a friction fit well located in the suction line of each
circuit. The sensor is a 5,000 : at 77 F (25 C) thermistor con-
nected to the main base board. These thermistors are used in
the suction superheat calculations. The thermistor must be in-
sulated with cork tape insulation to reduce the effects of ambi-
ent temperature on the sensor.
Outdoor-air Temperature Sensor (OAT)
— This sensor is
factory installed on a bracket which is inserted through the
base pan of the unit on unit sizes 025-060 (see the section Sen-
sor Locations on page 32) or mounted to the back of the con-
trol box on the unit sizes 065-130. This sensor is a 5,000 :
thermistor at 77 F (25 C) connected to the main base board.
Outside Air Temperature can be forced to a value at the
scrolling marquee or Navigator device. To force the value, ac-
cess the parameter Temperatures
UNIT
OAT. Press
to view the current value. Press again and
use the up and down arrow keys to display the desired value;
then press to accept the value. On the scrolling mar-
quee, the “.” in the lower right corner will flash. On the Navi-
gator device, a flashing “f” will be displayed next to the value.
To clear the forced value, press followed by the up
and down arrow keys simultaneously. The value will revert to
the actual reading and the flashing “.” or “f” will be removed.
Discharge Temperature Thermistor (DTT)
— This sensor is
only used on units with a digital compressor. The sensor is
mounted on the discharge line close to the discharge of the dig-
ital compressor. The thermistor must be insulated with cork
tape insulation to reduce the effects of ambient temperature on
the sensor. It attaches to the discharge line using a spring clip
and protects the system from high discharge gas temperature
when the digital compressor is used. This sensor is an
86,000 : at 77 F (25 C) thermistor connected to the AUX
board (see Table 9).
Space Temperature Sensor (T55, T56)
— Space temperature
sensors are used to measure the interior temperature of a build-
ing.
Space Temperature can be forced to a value at the scrolling
marquee or Navigator device. To force the value, access the
parameter Tempe ratures
UNIT
SPT. Press to
view the current value. Press again and use the up
and down arrow keys to display the desired value; then press
to accept the value. On the scrolling marquee, the “.”
in the lower right corner will flash. On the Navigator device, a
flashing “f” will be displayed next to the value. To clear the
forced value, press followed by the up and down ar-
row keys simultaneously. The value will revert to the actual
reading and the flashing “.” or “f” will be removed.
The following three types of SPT sensors are available:
• Space temperature sensor (33ZCT55SPT) with timed
override button (see Fig. 27)
• Space temperature sensor (33ZCT56SPT) with timed
override button and set point adjustment (see Fig. 28)
• Space temperature sensor (33ZCT59SPT) with occu-
pancy override button, space temperature offset, and
LCD (liquid crystal display) display (see Fig. 29)
All of the above sensors are 10,000 : at 77 F (25 C), Type II
thermistors and are connected to the low voltage terminal
(LVT). The sensor should be mounted approximately 5 ft
(1.5 m) from the floor in an area representing the average tem-
perature in the space. Allow at least 4 ft (1.2 m) between the
sensor and any corner. Mount the sensor at least 2 ft (0.6 m)
from an open doorway.
2
3
45
61
SW1
SEN
BRN (GND)
BLU (SPT)
RED(+)
WHT(GND)
BLK(-)
CCN COM
SENSOR WIRING
TIMED OVERRIDE
BUTTON (SW1)
Fig. 27 — Space Temperature Sensor
Typical Wiring (33ZCT55SPT)
2
3
45
61
SW1
SEN
SET
Cool Warm
BRN (GND)
BLU (SPT)
RED(+)
WHT(GND)
BLK(-)
CCN COM
SENSOR WIRING
JUMPER
TERMINALS
AS SHOWN
BLK
(T56)
TIMED OVERRIDE
BUTTON (SW1)
Fig. 28 — Space Temperature Sensor
Typical Wiring (33ZCT56SPT)
Fig. 29 — Space Temperature Sensor
Typical Wiring (33ZCT59SPT)
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