Lennox Combination Temperature / Humidity (RH) Sensor Kit
Installation Instructions
For LG/LC/SG/SC Units
Model Numbers: 21W06 and 101046
Document Number: 505196M
Revision: Supersedes 03/2023 (11/2023)
⚠ WARNING
Improper installation, adjustment, alteration, service, or maintenance can cause personal injury, loss of life, or damage to property.
Installation and service must be performed by a licensed professional installer (or equivalent) or a service agency.
⚠ CAUTION
ELECTROSTATIC DISCHARGE (ESD) Precautions and Procedures
Electrostatic discharge can affect electronic components. Take precautions during unit installation and service to protect the unit's electronic controls. Precautions will help to avoid control exposure to electrostatic discharge by putting the unit, the control, and the technician at the same electrostatic potential.
Neutralize electrostatic charge by touching hand and all tools on an unpainted unit surface before performing any service procedure.
Shipping and Packing List
- 1 - Sensor (A37)
- 2 - Screws
Cable Applications and Wiring
Wire runs of 150' (46m) or less:
Use three separate shielded cables containing 18AWG minimum, twisted pair conductors with overall shield (e.g., Belden type 8762 or 88760 [plenum] or equivalent). Connect cable shield drain wires as shown in Figure 1.
Figure 1. Field Wiring [150 ft. (46m) or Shorter Runs]
Textual description of Figure 1 wiring diagram: Shows connections from a sensor (A37) to a controller (M1 M2/M3/M4 TB1 P298). Key connections include VIN, GND, VOUT. Twisted pair conductors with overall shield are specified. Drain wires are shown connected to the controller's shield terminal.
Wire runs over 150 feet (46m):
Use a local, isolated 24VAC transformer (e.g., Lennox cat #18M13, 20VA minimum) to supply power to the sensor, as shown in Figure 2. Use three shielded cables containing 20AWG minimum, twisted pair conductors with overall shield [e.g., Belden type 8762 or 88760 (plenum) or equivalent].
Figure 2. Field Wiring [150 ft. (46m) or Longer Runs]
Textual description of Figure 2 wiring diagram: Similar to Figure 1 but shows the use of an isolated 24VAC transformer supplying power to the sensor.
Wall-Mount Installation
Install the sensor on a standard handy box or directly on the wall. Locate the sensor in the conditioned space approximately 5 feet (1-1/2m) above the floor in an area with good air circulation at average temperature.
Avoid locating the sensor where it might be affected by:
- Drafts or dead spots behind doors and in corners
- Hot or cold air from ducts
- Radiant heat from sun or appliances
- Excessive moisture
- Corrosive fumes
- Excessive vibration
- Extremely high temperatures
- Route shielded cables from the rooftop unit to the appropriate location in the conditioned space.
- Loosen screws and remove sensor cover (see Figure 3).
- Center opening in baseplate over opening in wall.
- Mark holes for screws (see Figure 4).
- Remove baseplate and drill holes.
- Insert wall anchors (field provided) and align baseplate over opening in wall.
- Pull wiring through opening in baseplate.
- Secure baseplate to wall with screws.
- Connect wiring for appropriate length of run as shown in Figure 1 or 2.
- Replace humidity sensor cover and turn set screws counterclockwise to secure cover in place.
Figure 3. Temperature/Humidity Sensor (A37)
Textual description of Figure 3: Shows the sensor unit (A37) with a cover that can be removed by turning set screws clockwise. It indicates the sensor has terminals for VIN, GND, VOUT, and connections for HUM and TMP.
Figure 4. Wall-Mount Sensor Baseplate
Textual description of Figure 4: Illustrates the sensor baseplate, showing where to route wiring from a rooftop unit, where to mark holes for screws, and the terminal block for wiring connections (24 VAC, GND, 0-10V OUT).
DIP Switch Settings
DIP switches are set at the factory. Proper settings are shown in Figure 5.
Figure 5. Wall-Mount DIP Switch Settings
Textual description of Figure 5: Shows a diagram of DIP switches, typically labeled ON/OFF, indicating their factory default or recommended settings for operation.
Check-Out
Check the sensor output annually for accuracy. Keep the air intake openings on the sensor clean and free of obstructions and debris.
NOTE:
The temperature thermistor should read a resistance of 11K Ohm at 77F (+/- 1.5%).
Verify the humidity reading is proper by using the L-Connection PC Software, the NCP (A105), the controller (A55), or by measuring the sensor output voltage. Relative humidity should correspond to the sensor (A37) output voltage listed in Table 1. For example: if indoor air relative humidity is 80% + 3%, the humidity sensor output should read 8.00VDC.
Table 1. RH to Sensor Output Voltage
| Relative Humidity (%RH ± 3%) | Sensor Output (VDC) |
|---|---|
| 20 | 2.00 |
| 30 | 3.00 |
| 40 | 4.00 |
| 50 | 5.00 |
| 60 | 6.00 |
| 70 | 7.00 |
| 80 | 8.00 |
| 90 | 9.00 |
Display zone sensor reading on the controller
M1 IMC:
- Turn the "TMP" DIP switch ON.
- Press the pushbutton 4 times. The IMC readout will alternate between A2 (output being read) and the temperature.
- Press the pushbutton 5 more times. The IMC readout will alternate between rH (output being read) and the zone sensor humidity reading.
M2:
- Use the scroll buttons to locate DATA->SENSORS -> ZAT. The Zone Air Temperature (ZAT) displays (e.g. ZAT:79F).
- Refer to the controller manual for more details.
M3:
The current ZAT reading when enabled is always displayed on the status screen. It can also be displayed using the following procedure:
- Use the scroll buttons to locate DATA > IN/OUTPUTS > SENSORS > LOCAL. From the LOCAL SENSOR screen, scroll down to the ZAT information. The Zone Air Temperature (ZAT) displays (e.g. ZAT: 79F).
- Refer to the controller manual for more details.
M4:
The current ZAT reading (when enabled) displays on the system overview screen of the Lennox CORE Service App. The ZAT reading can also be found in the Data Menu (after connecting to the RTU with the app):
- Navigate to the RTU Menu.
- Select SYSTEM DATA / SENSOR DATA/ OUTPUTS.
- Select LOCAL INPUTS, SENSORS. The Zone Air Temperature will be listed (e.g. ZAT: 79F).
- Refer to the controller manual for more details.
