Install Instructions

T775P SERIES 2000 CONTROLLER WIRING
62-0256–03 4
Temperature Sensor Wiring
CAUTION
Electrical Shock Hazard.
Can short equipment circuitry.
Make sure that metal tube of sensor does not
short against T terminals in wall-mounted case.
IMPORTANT
Poor wiring practices can cause erratic readings
from the sensor. Avoid the following to ensure
proper operation:
• Do not route the temperature sensor wiring
with building power wiring.
• Do not locate the temperature sensor wiring
next to control contactors.
• Do not locate the temperature sensor wiring
near electrical motors.
• Do not locate the temperature sensor wiring
near welding equipment.
• Make sure good mechanical connections are
made to both the sensor and the controller.
• Do not mount the sensor with the lead wire
end pointing up in an area where condensa-
tion can occur.
If any of the above conditions cannot be
avoided, use shielded cable.
NOTE: Each temperature sensor must be wired to a
single T775 controller. However, a benefit of the
T775 controller’s accuracy is that there is no
more than a 2°F differential between any two
T775 controllers.
Reset Temperature Control
If you are implementing two-sensor reset control, Sensor
A or C must always be the controlled temperature and
Sensor B must always be the controlling temperature.
For example, in a reset control based on outside
temperature, Sensor A or C must be the inside sensor
(supply, boiler, chiller, or return) and Sensor B must be the
outside sensor.
Multiple Parallel Sensors
Multiple sensors can be parallel-series wired to sense
average temperatures in large spaces. To maintain
control accuracy, the number of sensors to be parallel-
series wired must be of the n
2
power (for example, 4, 9,
16, etc.). See Fig. 3.
Fig. 3. Parallel-series wiring of sensors.
Temperature Sensor Wire Type and Size
Temperature sensors use standard AWG 18/2 unshielded
wire. For cable runs greater than 25 feet or where
electrical interference may be a problem, shielded cable
is recommended. See Fig. 4.
Refer to “Temperature Sensor Calibration” on page 8 for
wire size selection where cable runs are longer than 25
feet.
Fig. 4. Sensor Wiring — Showing shielded cable connection to Sensor A.
TO T775 CONNECTIONS (SENSOR A) OR (SENSOR B).
SENSORS
M24380
M24374
SHIELDED
CABLE
SHIELDED
CABLE
NOTE: TO MINIMIZE NOISE PICKUP,
MAKE CONNECTION FROM
SHIELDED CABLE AS CLOSE AS
POSSIBLE TO SENSOR BODY.
SENSOR
T
T
T
T
SENSOR A
SENSOR B
SENSORS A, B, AND C USE THE TWO TT CONNECTIONS AND
ARE POLARITY INSENSITIVE.
1
1
T
T
SENSOR C
NOTE: SHIELDED CABLE MUST BE
CONNECTED TO AN EARTH
GROUND.
HOWEVER, DO NOT GROUND
SHIELDED CABLE AT SENSOR END.