INSTALLATION INSTRUCTIONS
95-7557-04
C7770A/C7776A/C7778A
Air Temperature Sensor
OVERVIEW
The C7770A, C7776A, C7778A Air Temperature Sensors are
direct wired temperature sensors that are used to sense
discharge or return air in a duct.
The C7770A Sensors contain a temperature sensitive 20K
ohm NTC nonlinearized thermistor and are compatible with
the Excel 10 controller. The C7776As are 10 ohm NTC Type II
sensors that are compatible with TB7600, TB7300, and
TB7200 communicating thermostats. The C7778As are 10
ohm NTC Type III sensors that are compatible with WEBs-AX
I/O modules.
BEFORE INSTALLATION
All wiring must comply with local electrical codes and
ordinances or as specified on installation wiring diagrams.
Air temperature sensor wiring can be sized from 14 to
22 AWG (2.0 to 0.34 mm
2
) depending on the application. The
maximum length of wire from a device to a wall module is
1000 ft (305m). Twisted pair wire is recommended for wire
runs longer than 100 ft (30.5m). Run sensor wiring separately
from 50 VAC or greater power wiring to avoid electromagnetic
interference.
INSTALLATION
CAUTION
Electrical Shock or Equipment Damage Hazard.
Can shock individuals or short equipment
circuitry.
Disconnect power supply before installation.
The sensor assembly, see Fig. 1, consists of a stainless steel
sensor probe with an attached flange that can be mounted on
a flat duct or plenum surface using the type of screws
appropriate for the duct or plenum material. It can also be
mounted in a standard utility conduit box, 2 by 4 in. (51 by
102 mm) using No. 8 (4 mm) screws, see Fig. 2.
Location
The sensor should be located in the air duct or plenum where
it will sample an average air temperature. Avoid locations
where air stratification can cause sensing errors.
Mounting
See Fig. 2 for mounting a sensor on a flat duct or plenum
surface:
1.
Cut a 3/8 in. (9.5 mm) hole in the duct or plenum surface
at the desired location.
2.
Insert the sensor probe into the duct or plenum until the
flange rests against the duct or plenum wall.
3.
If necessary, use the flange as a template to mark and
drill two holes for the No. 8 (4 mm) mounting screws.
4.
Fasten the sensor to the duct or plenum surface with
two No. 8 (4 mm) sheet metal screws (not provided).
See Fig. 3 for mounting a sensor in a standard utility conduit
box:
1.
Cut a 3/8 in. (9.5 mm) hole in the duct or plenum surface
at the desired location.
2.
Remove the center knockout at the rear of the standard
utility conduit box. Insert the sensing probe through the
knockout with the flange flat against the box.
3.
Using the flange as a template, mark and drill two holes
in the standard utility conduit box and the duct or
plenum surface for No. 8 (4 mm) mounting screws.
4.
Insert the sensor probe through both the standard utility
conduit box knockout and the hole drilled in the duct or
plenum. Fasten the box and the sensor to the duct or
plenum surface with two No. 8 (4 mm) mounting screws
for sheet metal (not provided).
Fig. 1. C7770A/C7776A/C7778A Air Temperature Sensor
dimensions in in. (mm).
NOTES:
1.
Sensor probe diameter is 1/4 in. (6 mm) on all
models.
2.
6 ft. plenum rated cable is standard on the
C7770A1040, C7776A1040, C7778A1040.
1/4 (6)
DIAMETER (2 HOLES)
M17961
1
(25)
3/4 (19)
1-1/2 (38)
2 (51)
1 (25)
1/16 (2)
6 (152)
8 (203)
3/8 (9)
FITTING
NEOPRENE
GASKET
