If the programmable limit is set below 100% of full load current, this control feature can be used for “demand limiting”. This is important when demand limiting is critical due to power requirements or limitations in the building (See also Section 1.10).

For the first 60 seconds of operation, the unloading control is disabled. After this time, if motor current exceeds the programmed limit, the SYS X CURR LIMITING message will appear on the display and a 1 second unload pulse will be sent to the slide valve of the affected compressor every 5 seconds, until the motor current drops below the programmed limit. The message will be removed and additional loading will take place when motor current drops below 90% of the programmed threshold.

Typically, this setpoint should be set at 100% for maximum motor protection. Programming for 100% is recommended. When programming values below 100%, the use of a leading “0” is required, e.g. 085%.

To program the High Motor Current Unload, key in the required setting and press the Enter key to store the value into memory and scroll to the next display.

 

Anti-Recycle Time

 

 

 

 

A N T

I R E C Y C L E T I M E R

 

 

= 6

0 0 S E C S

 

 

 

 

 

The Anti-Recycle Timer controls the minimum time between starts for each compressor. This is the time available for the heat build-up caused by inrush current at start to be dissipated before the next start. Insufficient cooling time between starts can cause heat build-up and motor damage. A fast compressor start response is needed in some applications and not in others. Al- though the minimum setting allowed on this timer will avoid excessive heat build up, adjusting the timer for the longest period acceptable in each application will reduce cycling and maximize motor life. 600 seconds is recommended.

The micro will accept a range of programmable values between 300 - 600 seconds.

To program the Anti-Recycle Time, key in the required setting and press the Enter key to store the value into memory and scroll to the next display.

FORM 201.19-NM1 (204)

S U C T I O N S U P E R H E A T

S E T P O I N T = 1 2 . 0 º F

The EEV superheat setpoint is programmable. The setpoint can be programmed for 9.0ºF (5.0ºC) to 15ºF (8.3ºC) with 12.0ºF (6.6ºC) as the default.

Local/Remote Communications

L O C A L / R E M O T E M O D E

L O C A L

The panel can be programmed for “Local” or “Remote” communications. “Local” mode allows monitoring only through the RS-485 port. “Remote,” allows an external device such as an ISN or Remote Control Center to change setpoints and programming points, as well as monitoring chiller parameters.

The keys are used to change from Local to Remote. The ENTER Key must be pressed to save the selection in memory.

Imperial/SI Units Display

D I S P L A Y U N I T S

I M P E R I A L

This allows the operator to select messages to display Imperial Units (PSIG, °F, etc.) or SI (Scientific Interna- tional, Bars, °C, etc.).

The keys are used to change from Imperial to SI units. The ENTER Key must be pressed to save the selection in memory.

Automatic/Manual “Lead/Lag”

L E A D / L A G C O N T R O L A U T O M A T I C

The chiller may be selected for manual lead/lag or auto- matic lead/lag. In some cases the operator may want to manually select the system that is desired to be the lead system. In most cases, automatic lead/lag is selected to allow the micro to attempt to balance run time between the system. Details of manual and automatic lead / lag operation are outlined in Section 1.21.

The keys are used to change from Automatic to Manual lead/lag. The ENTER key must be pressed to save the selection in memory.

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York YCAS0130 manual Local/Remote Communications, Imperial/SI Units Display, Automatic/Manual Lead/Lag, 169