YORK YMC2 — WARNING - EVAPORATOR - LOW PRESSURE LIMIT

The panel shows WARNING - EVAPORATOR - LOW PRESSURE LIMIT, in exactly this wording. The manual lists no other variant of this message. It appears in the group of warning messages for this chiller.

The evaporator pressure has decreased to the Warning threshold. While this condition is in effect, the chiller capacity control is in override to increase suction pressure — the control deliberately shifts capacity to bring the suction pressure back up. The condition ends on its own: when the evaporator pressure increases to the reset value, the message clears automatically and normal LCHLT capacity control is restored. No other response of the machine to this warning is described in the manual.

• The evaporator pressure has decreased to the Warning threshold — the manual gives no other cause for this message. Which numeric threshold that is depends on the refrigerant and on whether the application is Water cooling or Brine cooling (see the thresholds below).

The manual prints warning and reset thresholds in psig for each refrigerant, separately for Water cooling and Brine cooling applications. In Water cooling applications the values are fixed. In Brine applications the values are offsets above the programmable safety shutdown threshold (Safety setpoint), and that Safety threshold is determined by the brine solution at the YORK Factory — so the actual pressures are these offsets above the safety setpoint configured for the brine in the machine.

• R-134a — Water: warning 27.8 psig, reset 28.8 psig. Brine: warning 1.7 psig above Safety setpoint, reset 2.7 psig above Safety setpoint.
• R-513A — Water: warning 32.0 psig, reset 33.0 psig. Brine: warning 1.8 psig above Safety setpoint, reset 2.8 psig above Safety setpoint.
• R-1234ze — Water: warning 16.7 psig, reset 17.7 psig. Brine: warning 1.3 psig above Safety setpoint, reset 2.3 psig above Safety setpoint.
• R-515B — Water: warning 16.5 psig, reset 17.5 psig. Brine: warning 1.3 psig above Safety setpoint, reset 2.3 psig above Safety setpoint.

Recovery is automatic; the manual describes no manual clearing or acknowledgment step for this warning. This message automatically clears and normal LCHLT capacity control restored when the Evaporator pressure increases to the reset value. Once the evaporator pressure has risen to the reset threshold that matches the refrigerant and application listed above, the override ends and normal LCHLT capacity control resumes.