Fixed Length and Averaging Sensors

Image shows two duct temperature sensors. The sensor on the left is labeled 'TE-DFW (Temp Only)' and appears to be a fixed-length probe. The sensor on the right is labeled 'TE-AAG (Temp Only)' and appears to be an averaging sensor with a coiled tube.

Application

The Dwyer temperature sensors are used in conjunction with the Carel controller used on all model "DLV" Packaged Ventilation/Dedicated Outside Air System (DOAS) Units. The sensors are used as supply air sensors and are to be field installed in the supply air ductwork.

The sensors ship loose with a packing slip identifying the part numbers as shown in Table 1.1.

Sensor Installation Location

Location of the sensor is very important for proper control. Where possible:

• The sensor should be located between 8 and 20 feet downstream from the unit discharge connection.
• The sensor should be mounted in a single perimeter duct as shown in Figure 2.1. If the ductwork is split, the sensor should be mounted before the split is made. Locating sensors in a branch duct as shown in Figure 2.2 may cause poor temperature control.
• Avoid placing the sensor near turns in the ductwork.
• For the Fixed Length Probe Sensor, the sensor should be mounted in a position following Figure 2.1 and Table 2.1.
• For the Adjustable Length Averaging Sensor, the sensor should be mounted so it spans the width of the duct, from side to side of the duct.

Figure 2.1 - Duct Sensor Installation Locations: Diagram illustrating duct sensor installation locations. It shows a duct with numbered positions (1, 2, 3) for Fixed Length Sensor Locations, referenced in Table 2.1. An alternate location for an Adjustable Length Sensor is also indicated, spanning the duct width.

Figure 2.2 - Incorrect Split Duct Sensor Locations: Diagram showing incorrect split duct sensor locations. It depicts a duct splitting into two branches, with arrows pointing to areas within the branches labeled 'INCORRECT LOCATIONS', indicating that sensors should not be placed here.

Sensor Installation - Fixed Length Probes

Once the location of installation on the ductwork is determined from the previous section, install the sensor as follows:

1. Verify the sensor being installed is the correct sensor.
2. Drill a 1½" hole in the duct for the probe to be inserted.
3. Slide the sensor through the hole in the duct and mark where pilot holes are required to secure the sensor mounting tabs to the duct. Remove the sensor and drill 1/8" pilot holes.
4. Verify the gasket that came with the sensor is secured on the back of the sensor junction box. Slide the sensor back into place and secure with the screws included.

Figure 2.3 - Drill Locations for Sensor Mounting: Diagram illustrating drill locations for sensor mounting on a duct. It shows a circular sensor junction box (SENSOR J-BOX) mounted to the DUCTWORK. Pilot holes for mounting screws and the central hole for the sensor probe are indicated.

Sensor Installation - Adjustable Length

Once the location of installation on the supply air ductwork is determined from the "Sensor Installation Location" section, install the sensor as follows:

1. For all adjustable length averaging sensors, use the Sensor Mounting Plate included with the kit (see Figure 3.1) as a template to mark where to drill the required holes in the mounting location of the duct. Do not drill through the Sensor Mounting Plate, only use it for marking the ductwork. For the sensor hole in the center location, drill a hole between 1" and 4" in diameter. The end of the sensor needs to be mounted on the opposite side of the duct, so a larger hole will help with maneuvering the sensor during installation.

Figure 3.1 - Sensor Mounting Plate Drill Locations: Diagram of the Sensor Mounting Plate Drill Locations. It shows a rectangular plate with four corner locations for 1/8" pilot holes for #10 x 3/4" self-tap screws, two locations for 1/4" clearance holes for sensor mounting screws, and a center location for the sensor hole (diameter per instructions).

2. In the same location on the opposite side of the duct (directly across from where the holes were drilled in Step 1), repeat Step 1 for the (4) corner holes and the center location sensor hole. The (2) ½" clearance holes are not required. The center sensor hole should be between 1" and 4" in diameter as noted in Step 1.
3. The sensor length may need to be adjusted before installation in the duct. Measure the outside width dimension of the duct, across where the sensor will be installed, as shown in Figure 3.2.

Figure 3.2 - Adjustable Length Sensor Dimension: Diagram illustrating the dimensioning for an Adjustable Length Sensor. It shows the DUCT WIDTH and indicates that the sensor length should be DUCT WIDTH + 2".

Figure 3.3 - Adjusting Length of Sensor Tubing: Diagram showing how to adjust the sensor tubing length. It depicts the coiled aluminum sensor element tube being wrapped around a pipe (e.g., a 1-1/2" PVC pipe) to stretch or compress it to the desired length.

4. The sensor should be approximately 2" longer than the outside dimension of the duct, as shown in Figure 3.2. To adjust the sensor length, follow these steps:
   1. The aluminum sensor element tube is coiled when it ships. Straighten the sensor and measure the length.
   2. If the sensor needs to be shortened, the best way is to coil the tubing around a pipe, such as a 1-1/2" PVC pipe as shown in Figure 3.3. Like a spring, the coiled sensor tubing can be stretched or compressed to get the desired length.
5. Verify the gasket that came with the sensor is secured on the back of the sensor junction box. Slide the sensor through the center hole on the Sensor Mounting Plate and secure with (2) #10 x 1½" hex head screws included with the kit assembly as shown in Figure 3.4. Be sure that the gasket on the Sensor Mounting Plate is on the opposite side from the sensor junction box.

Figure 3.4 - Sensor to Sensor Mounting Bracket Installation: Diagram showing the installation of the sensor to the sensor mounting bracket. It shows the SENSOR J-BOX, the SENSOR MOUNTING BRACKET WITH GASKET, and the DUCTWORK. The INSTALLED AVERAGING SENSOR element is shown extending through the duct.

5. Slide the sensor element into the center hole drilled in the duct. Do not secure yet.
6. Carefully maneuver the sensor assembly to extend the end of the sensor through the hole on the opposite side of the duct. This may be easier with a second person located on the opposite side of the duct. Once the end of the sensor is through the hole in the duct, secure the Sensor Mounting Plate on the sensor junction box side to the duct with the (4) #10 x 3½" self-tapping screws included with the kit.

Adjustable Sensor End Support

Figure 4.1 - Adjustable Sensor End Support: Diagram of the Adjustable Sensor End Support. It shows the sensor tubing passing through a strain relief bushing and a sensor plate/gasket assembly on the opposite side of the duct from the sensor junction box.

Wiring to the Main Unit Carel Controller

For wiring of the sensor, refer to the following instructions:

1. Remove the cover of the sensor junction box by rotating the cover counterclockwise. Refer to Figure 4.2.
2. Remove the bottom knockout on the junction box. Install the wiring strain relief bushing included in the kit.
3. Connect the two red wires from the sensor to the terminal blocks included in the junction box.
4. Route the control wire (minimum 24AWG twisted pair shielded cable) between the sensor and the controller through the bushing and wire to the terminal block in the junction box per the wiring diagram on the unit.
5. Reinstall the sensor junction box cover, rotating it clockwise.
6. Wire the control wiring to the main unit controller per the wiring diagram on the unit.

Figure 4.2 - Sensor Junction Box Wiring: Diagram illustrating sensor junction box wiring. It shows the inside of the junction box with terminal blocks and wiring connections.

Duct Sensor Resistance Values

The Dwyer fixed and adjustable length sensors all include temperature sensing. See Table 4.1 for the resistance values at various temperatures.