Issue:
Suction Temperature Sensor Failure
Resolution:
| SUCTION TEMP SENSOR FAILURE (CKT-1/CKT-2) |
- This diagnostic occurs when there is not a valid signal on the suction temperature sensor input on the SCM (1U49) used on 20 through 30 ton units or the MCM (1U49) used on 40 through 60 ton units.
- The sensor has to be in the range of 55° F to 209° F (approximately 500,000 to 700 ohms).
- These sensors would only exist on units with the Superheat/Subcooling option installed and are located on the suction line of each refrigeration circuit.
- This is an information-only diagnostic and will clear automatically when the module measures a valid resistance.
- This diagnostic will not affect the operation of the unit.
Here are the steps for Intellipak Air-Cooled Chiller
Step #1 Wiring Error
- Verify the wiring between the Suction Temperature Sensor and the SCM or MCM (1U49).
- Refer to unit schematics for wire numbers and connections.
- If the wiring checks good, proceed to the next step.
Step #2 Sensor Checkout
- Disconnect the sensor wires from the SCM/MCM (1U49).
- Check the resistance reading of the sensor and wiring at the plug connector.
- Compare the resistance reading to the above chart.
- If the values are not correct, double check for wire errors.
- Replace sensor if none are found.
- If the values are correct, proceed to the next step.
| TEMPERATURE (F) | RESISTANCE (kW) | TEMPERATURE (F) | RESISTANCE (kW) |
| -40 | 346.1 | 71 | 11.60 |
| -30 | 241.7 | 72 | 11.31 |
| -20 | 170.1 | 73 | 11.03 |
| -10 | 121.4 | 74 | 10.76 |
| -5 | 103.0 | 75 | 10.50 |
| 0 | 87.56 | 76 | 10.25 |
| 5 | 74.65 | 77 | 10.00 |
| 10 | 63.80 | 78 | 9.76 |
| 15 | 54.66 | 79 | 6.53 |
| 20 | 46.94 | 80 | 9.30 |
| 25 | 40.40 | 85 | 8.25 |
| 30 | 34.85 | 90 | 7.33 |
| 35 | 30.18 | 100 | 5.82 |
| 40 | 26.22 | 105 | 5.21 |
| 45 | 22.85 | 110 | 4.66 |
| 50 | 19.96 | 120 | 3.76 |
| 55 | 17.47 | 130 | 3.05 |
| 60 | 15.33 | 140 | 2.50 |
| 65 | 13.49 | 150 | 2.05 |
| 66 | 13.15 | 160 | 1.69 |
| 67 | 12.82 | 170 | 1.40 |
| 68 | 12.50 | 180 | 1.17 |
| 69 | 12.19 | 190 | 0.985 |
| 70 | 11.89 | 200 | 0.830 |
Step #3 SCM/MCM Checkout
- Connect a known resistance in the valid range to the Suction Temperature Sensor input to the SCM/MCM (1U49) directly.
- Using the Human Interface (1U65) check the status of the appropriate Suction Temperature Sensor.
- If the diagnostic clears and the correct temperature is displayed, recheck wiring and sensor.
- If the Human Interface does not display the correct value with the resistor connected to the board, replace the SCM/MCM (1U49).
Facts:
- Intellipak Air-Cooled Chiller 20-60
Document Identifier: DOC-74395
WARNING:
Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.