YORK YMC2 — UPS - INVERTER LOW BATTERY VOLTAGE

The panel shows UPS - INVERTER LOW BATTERY VOLTAGE in exactly this wording; the manual lists no other variant of the message. It belongs to the safety shutdown messages of the YMC2, and the manual treats it as a safety fault rather than an advisory notice.

The control has seen all of the following hold at the same time for 5 continuous seconds: Battery Voltage Faults is Enabled, the Control Voltage digital input is low — which the manual reads as line power being lost — and the Battery Voltage is below the Inverter Low Battery Voltage Threshold. Read together, the message means that the chiller is without line power and the battery voltage has fallen below the inverter low battery threshold. The manual defines this safety fault entirely through these conditions and adds no further interpretation.

• Line power is lost: the Control Voltage digital input is low, which the manual states indicates that line power is lost.
• The Battery Voltage is below the Inverter Low Battery Voltage Threshold, which is 11.0 V by default.
• Battery Voltage Faults is Enabled — the fault monitoring must be active, and the message cannot set while it is Disabled.
• All of the above must hold continuously for 5 seconds before the fault sets.
• During a battery health test the same threshold serves as the pass/fail level: if the Battery Voltage drops below the Inverter Low Battery Voltage Threshold during the test, the test fails and ends, and the manual considers the battery evaluation good when this fault is not set by the end of the 60 second test.

1. Establish whether the chiller has lost line power. A low Control Voltage digital input is what the manual reads as lost line power; if line power is present, this condition of the fault is not met.
2. Read the Battery Voltage and compare it with the Inverter Low Battery Voltage Threshold (default 11.0 V). The fault requires the battery voltage to sit below this threshold.
3. Check the state of Battery Voltage Faults in the control. It must be Enabled for the fault to set, and setting it to Disabled releases an active fault.
4. For the release condition, compare the Battery Voltage with the Line Low Battery Voltage Threshold: the fault releases once the Battery Voltage is greater than the Line Low Battery Voltage Threshold + 0.1 V. The manual notes the set and release thresholds are intended to be different, so the fault will not clear exactly at the set threshold.
5. If the message appeared during a battery health test, apply the manual's test criterion: the Battery Voltage dropping below the Inverter Low Battery Voltage Threshold is what fails the test and ends it.

• Inverter Low Battery Voltage Threshold — default 11.0 V; the manual identifies this value as the UPS - Inverter Low Battery Voltage fault threshold.
• Set condition — the set conditions must hold for 5 continuous seconds.
• Release level — Battery Voltage > Line Low Battery Voltage Threshold + 0.1 V.
• Battery Voltage Faults — the Enabled/Disabled function that gates the fault; Disabled both prevents setting and releases the fault.
• Battery health test — the battery evaluation is considered good when this fault is not set by the end of the 60 second test.

The manual describes no separate reset action for this safety fault; it releases on its own. It is released when any of the following becomes true: Battery Voltage Faults is Disabled, or the Battery Voltage rises above the Line Low Battery Voltage Threshold + 0.1 V. Note the thresholds for set and release are intended to be different — so, apart from disabling Battery Voltage Faults, release depends on the battery voltage reaching the release level rather than simply leaving the set threshold.