T059_F: Water Sensed
Status
This is a critical fault experienced by the furnace. The furnace will not operate in gas heat modes but all other modes(e.g. cooling) should function if a call is present. However, if drain is completely blocked in common drain, condensation from the cooling coil in an up-flow configuration with a vent stand pipe above the sensor, water can back up into the secondary heat exchanger and eventually leak internally or get into inducer housing.
Description
The control looks for resistance from pin(s) 1 and/or 2 of connector P4 to chassis ground to determine water sensor flooding in the collector box. When water floods the sensor, the resistance from the sensor terminals to chassis ground decreases significantly. This notifies the control that the collector box is flooded.
Note: The condition must be present continuously for at least ten seconds before the IFC will declare the fault.
Expected Operation
If the furnace is in the middle of a heat cycle when the fault occurs, the control will immediately shut off the gas valves, proceed to post-purge and blower off delay. No gas heating operation will proceed and fault "T059_F Water Sensed" will be declared. Once the condition is no longer present and the blower off delay is complete, the control will resume normal operation.
Cause
1. A blocked condensate drain or the drain trap has become blocked and cannot allow condensate water to flow properly.
2. Wiring to the sensors has been damaged and exposed wiring is touching the furnace sheet metal.
3. Water sensor has been removed from the collector box with wires still attached and the metal probe is touching the sheet metal portion of the furnace.
4. A blocked drain in the main drain after the furnace and evaporator coil could cause water to back up into the furnace even in cooling mode in an up-flow arrangement. Even though this will not shut the cooling down, water will eventually leak inside the furnace.
5. Incorrect furnace model data parameters.
6. Faulty furnace control board.
Solution
1. Remove/Repair drain blockage.
2. Replace/Repair wiring between IFC and both sensors.
3. Return sensor(s) to proper location in the collector box.
4. Clear drain all the way to its termination. Make sure furnace condensate piping is correct with vent tee and the vent tee is NOT used to manage evaporator coil condensate.
5. Use Bluetooth Contractor App to reprogram furnace model data.
6. Replace furnace control board.
It is recommended to use separate drains for furnace and evaporator coils. If a common drain is used, vent tee for furnace should be well above any consolidation of drain lines.
