Sensor Locations; Typical Spt Wiring; Thermostat Input - Carrier 38APS025 Manual

To connect the space temperature sensor (Fig. 30):
1. Use a 20 gage wire to connect the sensor to the controller.
The wire is suitable for distances of up to 500 ft (152 m).
Use a three-conductor shielded cable for the sensor and
set point adjustment connections. The standard CCN
communication cable may be used. If the set point
adjustment (slidebar) is not required, then an unshielded,
18 or 20 gage, two-conductor, twisted pair cable may be
used. Connect one wire of the twisted pair to one SEN
terminal and connect the other wire to the other SEN ter-
minal located under the cover of the space temperature
sensor.
2. Connect the other ends of the wires to terminals 21 and
22 on LVT located in the unit control box. Sensor wiring
should not be in conduit wth other control voltages, or er-
roneous or erratic readings may result.
3. Connect the T56 set point adjustment between the SET
terminal and LVT terminal 23.
Units on the CCN can be monitored from the space using
the RJ11 connector provided with the space sensor, if desired.
To wire the RJ11 connector into the CCN (Fig. 31):
IMPORTANT: The cable selected for the RJ11 connector
wiring MUST be identical to the CCN communication bus
wire used for the entire network. Refer to Table for accept-
able wiring.
1. Cut the CCN wire and strip ends of the red (+), white
(ground), and black (–) conductors. (If another wire color
scheme is used, strip ends of appropriate wires.)
2. Insert and secure the red (+) wire to terminal 5 of the
space temperature sensor terminal block.
3. Insert and secure the white (ground) wire to terminal 4 of
the space temperature sensor.
4. Insert and secure the black (–) wire to terminal 2 of the
space temperature sensor.
5. Connect the other end of the communication bus cable to
the remainder of the CCN communication bus.
In lieu of a single sensor providing space temperature, an aver-
aging sensor array of either 4 or 9 sensors may be employed to
provide a space temperature as shown in Fig. 32. With this
control scheme, only T55 space temperature sensors (P/N
33ZCT55SPT) can be used. Total sensor wiring must not
exceed 1,000 ft (305 m). Do not use T56 space temperature
sensors (P/N 33ZCT56SPT) for space temperature averaging
because the 5-degree offset function will not work in a multi-
ple sensor application.
NOTE: The Timed Override feature from a space temperature
sensor requires a single space temperature sensor connected to
the unit. This feature does not function when used with aver-
aging space temperature sensor arrays.
N
SPT
SENSOR
SEN
SEN
SET
Fig. 30 — Typical SPT Wiring
TO CCN
COMM 1
BUS (PLUG)
AT UNIT
Fig. 31 — CCN Communications Bus Wiring to
Optimal Space Sensor RJ11 Connector
THERMOSTAT INPUT — A two-stage thermostat can be
used for constant volume applications to provide Y1 and Y2
cooling inputs. A thermostat can also be used in a variable air
volume application to determine supply air set point with Y1
and Y2 cooling inputs. For dual circuit machines, two separate
systems can be controlled independently from two 2-stage
thermostats. Y1 and Y2 cooling inputs control circuit A. Y3
and Y4 cooling inputs control circuit B. Thermostat connec-
tions depend on the machine control type which is discussed
later in this book.
Sensor Locations —
32
LVT
T-55 SPACE
SENSOR
6
CCN+ 5
CCN GND 4
3
CCN-
2
1
See Fig. 33-49.
21
22
23