Honeywell Home C7835A1009 Discharge Air Temperature Sensor

Application

The C7835A1009 Discharge Air Temperature Sensor (DATS) is a duct-mounted temperature probe designed for capacity control of heating and cooling equipment. It is exclusively used with Resideo networked zoning systems.

When mounted in the supply air duct, the DATS measures the delivered air temperature. It automatically shuts off heating or cooling when the delivered air temperature exceeds or falls below predefined normal operating limits. These heating and cooling limits are adjustable in the field.

The DATS also compares the discharge air temperature to the room temperature. If a significant difference (out of tolerance) is detected, it issues a heating or cooling alert. Under normal operating conditions, the heat and cool indicator lights remain off. The COM (communication) light blinks periodically to indicate activity on the Enviracom bus.

When a limit setting is reached, the heating or cooling cycle is interrupted. The system call for heating or cooling remains active, and conditioned air continues to be supplied to the calling zones. Heating or cooling resumes once the delivered air temperature returns to a level ten degrees below the heating limit or ten degrees above the cooling limit. This ten-degree differential ensures adequate minimum off-time to prevent equipment damage.

Note: For 50 Hz power applications, Jumper W1 must be cut.

The sensor's placement is critical. It should not be positioned in direct line-of-sight of the heat exchanger or cooling coil to prevent premature activation. It should also be located upstream of any bypass damper, if present. Refer to Figure 1 for sensor dimensions.

The DATS requires a three-wire connection, typically using standard 18-22 gauge thermostat wire.

Figure 1: C7835A dimensions. The sensor housing is approximately 4-1/8 inches (102 mm) long, 3-7/8 inches (77 mm) wide, and 1-1/4 inches (25 mm) deep, with mounting holes on the back.

Installation Instructions

When Installing this Product...

1. Read these instructions thoroughly. Failure to comply may result in product damage or hazardous conditions.
2. Verify that the product's ratings are suitable for your specific application by checking the instructions and product labels.
3. Installation should only be performed by a trained and experienced service technician.
4. After installation, use these instructions to verify proper product operation.

IMPORTANT: Placement Considerations

Do not install the DATS probe in a duct section immediately adjacent to the heat exchanger or strip heat elements, as this can lead to inaccurate temperature readings.

1. Locate the DATS on the supply air trunk. The ideal position is between the bypass damper and the evaporator coil and/or heat exchanger. If a bypass damper is not installed, position the DATS between the zone dampers and the evaporator coil and/or heat exchanger. Refer to Figure 2 for mounting location guidance.

Figure 2: DATS mounting location. The diagram illustrates a duct system showing the placement of a bypass damper, zone dampers, evaporator coil, heat exchanger, and blower. The sensor should be placed in the supply trunk in the area indicated, between the bypass damper and the coil/exchanger. It explicitly warns against placing the sensor in the area near the heat exchanger.

2. Drill a 5/16-inch (approx. 8 mm) hole in the duct at the chosen sensor location.
3. Ensure the shoulder washer is inserted into the hole and fits snugly, as shown in Figure 3.

Figure 3: Shoulder washer inserted on DATS. This shows the sensor housing with a shoulder washer fitted into the duct hole.

3. Remove the cover from the DATS case. Insert the sensor probe into the hole drilled in the previous step.
4. Secure the DATS to the duct wall using the two mounting holes on the back of the case and the supplied screws.
5. Connect the three DATS terminals (labeled 1, 2, and 3) using standard thermostat wire to the appropriate Enviracom bus terminals. Upon connection, the red heating and green cooling indicator lights should illuminate briefly. Refer to Figure 4 for wiring details.

Figure 4: DATS wiring to Enviracom™ bus. This diagram shows the DATS sensor with its terminals connected to an Enviracom bus.

6. Set the MAX Temp dial on the DATS to the desired high-limit temperature. This setting can range from 110°F to 160°F (43°C to 71°C). Note that markings between the numbered lines are approximate. The cooling low limit is adjustable between 40°F (4°C) and 48°F (9°C), depending on the jumper position.
7. Reattach the cover to the DATS case.

Troubleshooting

Table 1. LED Operation

^aHeating or cooling system alerts can be cleared by cycling power, switching modes from heat to cool or vice versa, or automatically when the equipment begins to operate correctly.

To verify the DATS is reading the correct temperature, consult Table 2 for resistance readings corresponding to specific temperatures. For an accurate resistance measurement, disconnect the sensor probe's P1 connector from the circuit board and measure the resistance across the two sensor wires.

Table 2. DATS Resistance Cross Reference

^aTo obtain a correct resistance measurement, be sure the sensor probe is disconnected from the circuit board.

For technical support, call 1-800-828-8367. To download Zoning literature, visit www.resideo.com.

Resideo Technologies, Inc. 1985 Douglas Drive North, Golden Valley, MN 55422. ©2020 Resideo Technologies, Inc. All rights reserved. The Honeywell Home trademark is used under license from Honeywell International, Inc.