Carrier 39L specifications CO2 Sensor Accessories, CGCDXSEN002A00, CGCDXSEN003A00, CGCDXGAS001A00

Filter Status Switch Ð The ®lter status switch (FLTS) is factory-installed in the ®lter section on all PIC-equipped units. The switch is a snap-acting SPDT switch. When dirty ®lter elements cause the pressure drop across the ®lter me- dia to exceed the switch setting, the switch closes and sends an alarm signal to the PIC.

The 39L units use a single switch. In 39NX units, up to 3 switches can be connected in parallel. When the switches are wired in parallel, it is not possible to isolate an alarm signal to a single switch.

The FLTS has an operating range of 0.05 to 2.0 in. wg. Factory settings for the switch are as follows:

Filter Type	Setting (in. wg)
Flat	0.5
Bag/Cartridge	1.0
Final	1.5

The FLTS electrical ratings are as follows:

300 va pilot duty at 115 to 277 vac

10 amps non-inductive to 277 vac

Rated for NO (normally open) and NC (normally closed) contacts.

High-Pressure Switch (Fig. 38) Ð The high- pressure switch (HPS) is factory installed in the PIC control box on VAV units only. It is a snap-acting SPDT switch with manual reset that is used to shut down the supply fan when- ever the duct pressure reaches the switch setting. The manual reset is used to restart the fan after the problem has been corrected.

The switch is factory set at 3.0 in. wg. It has a range of

1.4to 5.5 in. wg and can be ®eld adjusted for speci®c applications.

Adjust the high-pressure switch setting as follows:

1.Loosen conduit enclosure retaining screw, pull ®rmly on the bottom end and snap off cover.

2.Raise set point by turning slotted adjustment screw (located at top of range spring housing) clockwise. Turn adjustment screw counterclockwise to lower set point.

Fig. 38 Ð High-Pressure Switch (P/N HH02WC001)

3.To change or check calibration, use a T assembly with 3 rubber tubing leads. Attach one lead to the HPS and another to an accurate manometer with the appropriate range. Apply pressure through the third lead and ap- proach set point slowly.

4.Adjust set point to at least 0.5 in. wg greater than con- ®gured static pressure set point.

Air Quality Sensors (Fig. 39) Ð The air quality (AQ) sensors are shipped inside the fan section for ®eld installa- tion. Two types of sensors are supplied; one sensor monitors the conditioned air space, and the other sensor monitors the return air duct. Both sensors use infrared technology to de- tect the levels of CO2 present in the air.

Sensor descriptions and part numbers are shown in Table 6. To mount the sensor, refer to the installation in- structions shipped with the sensor.

Table 6 Ð CO2 Sensor Accessories

CO2 SENSOR ACCESSORY	DESCRIPTION
PART NUMBERS
CGCDXSEN001A00	Wall Mount Sensor (No Display)
CGCDXSEN002A00	Wall Mount Sensor with Display
CGCDXSEN003A00	Duct Mount Sensor (No Display)
CGCDXGAS001A00	Sensor Calibration Service Kit
CGCDXPRM001A00	User Interface Program (UIP)

The CO2 sensors listed in Table 6 are all factory set for a range of 0 to 2000 ppm and a linear voltage output of 2 to 10 vdc. Fig. 40 shows ventilation rates for various CO2 set points when outside air with a typical CO2 level of 350 ppm is used to dilute the indoor air. Refer to the instructions sup- plied with the CO2 sensor for electrical requirements and terminal locations.

Any changes to the sensor's factory con®guration require the purchase of the User Interface Program (UIP) or Sensor Calibration Service Kit, which also contains the UIP.

To accurately monitor the quality of the air in the condi- tioned air space, locate the sensor near the return air grille so it senses the concentration of CO2 leaving the space. The sensor should be mounted at least 1 ft above or 1 ft below the thermostat to avoid direct breath contact.

Do not mount the space sensor in drafty areas such as near supply ducts, open windows, fans, or over heat sources. Al- low at least 3 ft between the sensor and any corner. Avoid mounting the sensor where it is in¯uenced by the supply air; the sensor gives inaccurate readings if the supply air is blown directly onto the sensor or if the supply air does not have a chance to mix with the room air before it is drawn into the return air stream.

To accurately monitor the quality of the air in the return air duct, locate the sensor at least 6 in. upstream or 15 in. downstream of a 90 degree turn in the duct. The downstream location is preferred. Mount the sensor in the center of the duct.

If the sensor is mounted in the return air duct, readjust the mixed-air dampers to allow a small amount of air to ¯ow past the return air damper whenever the mixing box is fully open to the outside air. If the damper is not properly ad- justed to provide this minimum air¯ow, the sensor may not detect the indoor-air quality during the economizer cycle.

49