YORK YMC2 — WARNING - CONDENSER OR VGD SENSOR FAILURE

The panel shows WARNING - CONDENSER OR VGD SENSOR FAILURE. This is a warning, not a protective shutdown: the fault table classifies it as a Manual Reset Warning with Shutdown Type None, and Running is an allowed state, so the chiller keeps operating while the message stands. It stays on the display until the two transducer outputs are back within the acceptable range of each other and the warning is manually reset.

This message is a plausibility check between two pressure sensors. The Stall Pressure Transducer (the discharge pressure) and the Condenser Pressure Transducer measure essentially the same pressure, so both outputs should stay within the specified tolerance of each other. The feature exists to verify the operation of these two transducers. When the difference between their outputs exceeds the set threshold for 3 continuous minutes while the chiller is running, the control raises this warning. While the message is displayed, the Variable Geometry Diffuser (VGD) is driven to the full open position and held there until the warning is manually cleared; when cleared, the VGD returns to normal operation.

• The difference between the Discharge Pressure Transducer output and the Condenser Pressure Transducer output exceeded 21 psid for 3 continuous minutes while the chiller was running. One manual of the set prints the same threshold as 0.28 VDC between the Stall (discharge) Pressure Transducer output and the Condenser Pressure Transducer output.
• In fault-table terms: the warning sets when the difference between the Condenser Pressure and the Discharge Pressure is > 21 PSID or < -21 PSID.
• A software note applies: it was discovered that this warning was not always being set when the set condition was satisfied; in software V11 it was corrected so that it sets whenever the set condition is satisfied.

1. Identify the two signals involved: the Stall Pressure Transducer output, which is the discharge pressure, and the Condenser Pressure Transducer output. Both measure essentially the same pressure.
2. Compare the two outputs. The warning stands while their difference remains outside the acceptable range; the manuals expect both outputs to be within the specified tolerance of each other.
3. Note the VGD while the message stands: it is driven to the full open position and held there until the warning is manually cleared.
4. Before attempting a reset, make sure the two transducer outputs are back within the acceptable range of each other — the message can only be cleared once that condition is met.

• Trip Time: 3 minutes of continuous condition while the chiller is running.
• Set condition: difference between the Condenser Pressure and the Discharge Pressure > 21 PSID or < -21 PSID (also printed as 0.28 VDC between the transducer outputs).
• Bypass Time: None.
• Enable: Always; Clear/Disable: Never.
• Allowed States: Running; Shutdown Type: None.
• Event Type: Manual Reset Warning.

This message must be manually cleared. It remains displayed until two things are true: the transducer outputs are within the acceptable range of each other, and the WARNING RESET button is pressed in SERVICE access level. The release logic alone is not enough — the warning releases when the set condition is no longer true, but as a Manual Reset Warning it still waits for the manual reset. Only when the warning is cleared does the VGD return to normal operation. It will be displayed until the transducer outputs are within the acceptable range of each other and the WARNING RESET button in SERVICE access level.