York 160.87-OM1, Operation And Maintenance Manual

Page: 191 / 268

Motor – High current limit
The Compressor Motor current is greater than or equal to the local or remote Current Limit
Setpoint. The Current Limit Setpoint is programmed over a range of 30 to 100% of the Chiller
Full Load Amps (FLA). When the motor current increases to the Inhibit Open threshold, the Pre-
Rotation Vanes are inhibited from further opening. This prevents a further current rise. If the
current continues to rise to the Start Close threshold, the Vanes begin closing until the current falls
to the Stop Close threshold. Automatic Vane operation is resumed and this message automatically
clears when the motor current decreases to the Allow Open threshold. The thresholds are different
for the various motor starter applications. To allow field calibration of the Solid State Starter (Mod
“A”) Logic Board or CM-2 Current Module, pressing the Pre-Rotation Vanes OPEN key in SERVICE
access level, starts a 10 minute timer during which the current limit thresholds are elevated. Refer
to table:
Table 197: Motor current thresholds
Motor current (%FLA)
Vane control
Electro- mechanical/ Solid State Starter VSD Service mode
On rise, inhibit open 100 100 107
On fall, allow open 98 98 106
On rise, start close 104 103 110
On fall, stop close 102 101 109
An example of current limit is as follows: If a Solid Sate Starter chiller FLA is 100 Amps, and the
Current Limit Setpoint is 50%, the following will occur:
• 50 Amps – inhibit vane open
• 52 Amps – vanes begin closing
• 51 Amps – vanes stop closing
• 49 Amps – allow automatic vane control
Load control mode - Access level required: Service
The Compressor Motor Variable Speed Drive has not yet reached full speed after having been
commanded to do so in Manual Speed Control mode. While this is displayed, the Pre-Rotation
Vanes are inhibited from further opening.
Start inhibit messages
Anti-Recycle XX min/Sec
The chiller is inhibited from starting because the 30 minute anti-recycle time has not yet elapsed.
Time remaining is displayed.
Vane Motor Switch Open
The chiller is inhibited from starting because the Pre-Rotation Vanes are not fully closed.
Motor – Current >15% FLA
This start inhibit is instantaneously set whenever the chiller is not running and a motor current
of greater than 15% FLA is detected. The oil pump is started as soon as this fault is detected. The
starting frequency for the Variable Speed Oil Pump is 45.0 Hz. The start inhibit is released when the
motor current decreases to greater than or equal to 15% FLA and the WARNING RESET button is
pressed. A full System Coastdown is performed when this fault is released.
191 YK-EP Style B Centrifugal Chiller