YORK YMC2 — LEAVING CHILLED LIQUID - LOW TEMPERATURE

The control center shows LEAVING CHILLED LIQUID - LOW TEMPERATURE. The manuals print the message only in this wording. It is classified with the cycling shutdown messages, and the manuals list it among the events that initiate a soft shutdown while the chiller is running.

The Leaving Chilled Liquid Temperature has decreased to the programmed Shutdown Temperature Setpoint, the low limit defined for the leaving chilled liquid. If the chiller is running when this occurs, a soft shutdown is performed. During a soft shutdown the drive speed is ramped to 0 Hz and the chiller then transitions to coastdown. The chiller is not left down: it restarts automatically at the programmed Restart Temperature Setpoint (see reset below).

• The Leaving Chilled Liquid Temperature fell to the programmed Shutdown Temperature Setpoint — the offset below the leaving chilled liquid temperature setpoint that establishes the minimum allowed temperature for the leaving chilled liquid and prevents over-cooling of the building.
• The shutdown offset in effect can change automatically so the leaving chilled liquid temperature never goes below the minimum allowed value (36°F for water, 34°F for water with Smart Freeze enabled, 6°F for brine). A shutdown can therefore occur at a higher temperature than the programmed offset alone suggests.

1. On the evaporator screen of the control center, read the Temperature Setpoints - Shutdown display: it shows the leaving chilled liquid temperature at which the chiller shuts down on this cycling shutdown, calculated automatically from the temperature setpoint minus the shutdown offset and limited to the chiller minimum.
2. Read the Effective Offset display, which shows the present value of the leaving chilled liquid temperature shutdown offset in effect, limited by the chiller minimum temperature.
3. Read the Temperature Setpoints - Restart display — the leaving chilled liquid temperature at which the chiller will restart after this shutdown — together with its restart offset.
4. If the chiller tripped at a temperature above the programmed shutdown value, check whether the Leaving Chilled Liquid Temperature setpoint was increased within the last 10 minutes: the shutdown threshold is held at 36.0°F (water), 34.0°F (Smart Freeze) or 6.0°F (brine) for the next 10 minutes after such an increase, and only then becomes the programmed setpoint value.

• Leaving Chilled Liquid Temperature Cycling Offset - Shutdown (OPERATOR access): defines the shutdown temperature as an offset below the Leaving Chilled Liquid Temperature setpoint, programmable over a range of 1°F to 64°F below the setpoint.
• Minimum cutout: 36°F for water, 34°F for water with Smart Freeze enabled, 6°F for brine. Smart Freeze is switched Off/On at SERVICE access and is only available if the chiller is not in Brine mode.
• Hold after a setpoint change: anytime the Leaving Chilled Liquid Temperature setpoint is increased, the shutdown threshold is 36.0°F (water) or 6.0°F (brine) — 34.0°F with Smart Freeze enabled — for the next 10 minutes; after 10 minutes have elapsed, the shutdown threshold becomes the programmed setpoint value.
• Leaving Chilled Liquid Temperature Cycling Offset - Restart (OPERATOR access): defines the restart temperature as an offset above the setpoint, programmable over a range of 0°F to 80°F above the setpoint, to a maximum restart value of 80°F. The chiller automatically restarts when this temperature is reached; delaying the restart until the cooling load has increased is a way to reduce chiller cycling.
• Related displays: Temperature Setpoints - Restart shows the restart temperature with its offset; Effective Offset shows the shutdown offset in effect; the shutdown temperature itself is calculated from the temperature setpoint minus the shutdown offset setpoint.
• Heat pump operation in heating mode: the heating-mode shutdown temperature defaults to the leaving condenser liquid temperature setpoint minus 60°F, its low limit is the higher of the leaving condenser liquid temperature setpoint minus 86°F or the cooling-mode shutdown temperature, and the heat pump restarts when the leaving chilled liquid temperature exceeds the shutdown temperature by 5°F.

The manual gives no operator reset for this fault — it is a cycling shutdown, so the unit comes back on its own. The chiller will automatically restart when the temperature increases to the programmed Restart Temperature Setpoint. That restart temperature is programmed as an offset above the Leaving Chilled Liquid Temperature setpoint, so the restart can be delayed until the cooling load has increased, which the manual notes is a way to reduce chiller cycling.