Carbon Dioxide (Co2) Sensing - T775U - Honeywell T775 Series 2000 Application Manual

Carbon Dioxide (CO
T775U
Application Description
In this application, the T775U is controlling an outside air
damper based on CO sensing input, to maintain reasonable
2
CO levels.
2
Sensor Designation
This device application requires one sensor.
• Sensor A is sensing CO
Operation
In this example, as the CO
opened to allow fresh air to enter the facility.
Many CO sensors are used with a 0-2,000 ppm output range.
2
Parts per million (ppm) units not available on the T775U.
• Set the units for Ppm and enter 0 for a minimum and 2,000
for a maximum. The controller will simply convert the input
signal (0-10 Vdc or 4-20 mA) into the correct ppm value
and display it on the screen.
Programming Example
Program in Setup:
Press and hold the MENU button for 5 seconds to enter
Setup mode, and then select:
→
— Sensors Sensor A:
Type = 0-10V
Units = PPM
Minimum Value = 0.0
Maximum Value = 2000
NOTE: Sensor A is a 0-10 Vdc CO
range of 0 to 2,000 PPM
) Sensing –
2
in parts per million
2
level increases a damper is
2
sensor (C7232) with a
2
T775 SERIES 2000 ELECTRONIC STAND-ALONE CONTROLLERS
IMPORTANT
After the desired value is selected, be sure to press
the  or  or HOME button in order to save that
value in the controller's memory.
Wiring
See Fig. 33 for wiring connections for the T775U and the CO
sensor.
–
+
USE SEPARATE 24 V TRANFORMER TO POWER THE C7232 CO2 SENSOR.
1
PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
Fig. 33. T775U wiring — carbon dioxide sensing control.
27
SHIELDED CABLE
NOTES:
1. SHIELDED CABLE MUST BE
SENSOR A
CONNECTED TO A SEPARATE
EARTH GROUND. HOWEVER,
DO NOT GROUND SHIELDED
CABLE AT SENSOR END.
2. TO MINIMIZE NOISE PICKUP,
MAKE SENSOR CONNECTION
FROM SHIELDED CABLE AS
CLOSE AS POSSIBLE TO
SENSOR BODY.
+ –
+ –
24 V
ANALOG
OUT
C7232 CO2 SENSOR
(0-10 VDC CONNECTION)
1
L1 (HOT) L2
2
M24882
63-7147—05