Carrier 40UV Installation, Start-Up And Service Instructions Manual page 36

RELATIVE HUMIDITY SENSOR (Field-Installed Acces-
sory) — The relative humidity (RH) sensor is used to measure
the relative humidity of the air within the occupied space. The
sensor is ordered separately from the unit, is field-installed and
should be wired in the control compartment below the control
module. It may be mounted directly on an interior wall if
acceptable by local codes. See Fig. 23.
The sensor uses bulk polymer resistance technology, which
eliminates the effect of surface contamination and helps to
maintain sensor accuracy over a long period of time. It has a
long-term stability of less than 1% drift per year.
The relative humidity sensor has a range of 10 to 90% with
an accuracy of ±3% at 77 F. It generates a 2 to 10 vdc signal
which is sent to the controller.
If the sensor is installed directly on a wall surface, install the
humidity sensor using 2 screws and 2 hollow wall anchors
(field-supplied); do not overtighten screws. See Fig. 17. The
use of a standard 2 x 4-in. electrical box to accommodate the
wiring is recommended for installation.
DO NOT touch the sensing element or clean with chemical
solvents; they can permanently damage the sensor.
The sensor must be mounted vertically on the wall. The
Carrier logo should be oriented correctly when the sensor is
properly mounted.
DO NOT mount the sensor in drafty areas such as near the
unit's discharge grille, open windows or fans, or over heat
sources such as baseboard heaters, radiators, or wall-mounted
light dimmers. Sensors mounted in those areas will produce
inaccurate readings.
Avoid corner locations. Allow at least 4 ft between the
sensor and any corner. Airflow near corners tends to be
reduced, resulting in erratic sensor readings.
Sensor should be vertically mounted approximately 5 ft up
from the floor.
For distances up to 500 feet, use a 3-conductor shielded,
20 AWG cable. A CCN communication cable can be used. The
shield and drain wire must be removed from the sensor end of
the cable. See Fig. 24 for wiring details.
The power for the sensor is provided by the control board.
The board provides 24 vdc for the sensor. No additional power
source is required.
To wire the sensor, perform the following:
1. At the sensor, remove 4-in. of jacket from the cable. Strip
1 / -in. of insulation from each conductor. Route the cable
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through the wire clearance opening in the center of the
sensor. See Fig. 24.
2. Connect the RED wire to the sensor screw terminal
marked (+).
3. Install one lead from the resistor (supplied with the sen-
sor) and the WHITE wire, into the sensor screw terminal
marked (–). After tightening the screw terminal, test the
connection by pulling gently on the resistor lead.
4. Connect the remaining lead from the resistor to the
BLACK wire and secure using a closed end type crimp
connector or wire nut.
5. Using electrical tape, insulate any exposed resistor lead to
prevent shorting.
6. At the control end, remove the jacket from the cable and
route the RED conductor over to the left side of the con-
trol board. Route the remaining conductors to the right
side of the control board.
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7. Strip / -in. of insulation from each conductor and equip
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each with a / -in. female quick connect terminal.
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8. Connect the RED wire to terminal T26 on the control
board.
9. Connect the BLACK wire to terminal T16 on the control
board.
10. Connect the WHITE/CLEAR wire to terminal T15 on the
control board.
11. Equip the shield wire with a no. 8 fork-type lug and
secure to the control module mounting screw between
terminals T16 and T17.
Fig. 23 — Wall-Mounted Relative Humidity Sensor
(Part No. HL39ZZ003)
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