McQuay WGS130AA: WGS140AW, Руководство по эксплуатации

Страница: 56 / 98

56 WGS 130A to 190A OM WGS-5
Starting
A compressor will start (stage up):
IF LWT is above the Active LWT Setpoint plus the Startup Delta-T SP AND no
compressors are running OR all running compressors are at full load
Stopping
A compressor will stop (stage down);
IF LWT is below the Active LWT Setpoint minus the Stop Delta-T SP AND other
compressors are running or not;
OR IF LWT is below the Active LWT Setpoint minus the Stop Delta-T SP AND all other
running compressor’s slide position is less than the light load stagedown setpoint.
Multiple Compressor Start/Stop Timing – Ice Mode
This section defines when a compressor is to start or stop when the chiller is operating in ice
mode.
Required Parameters

Startup Delta T setpoint.

Stage Up Delta T setpoint

LWT error (See definition under Compressor Capacity Control section.)
Starting
A compressor will start (stage up):
IF LWT is above the Active LWT Setpoint plus the Startup Delta-T SP AND no
compressors are running OR all running compressors are at full load.
Stopping
The compressor will stop.
IF LWT reaches the ICE LWT Setpoint
Compressor Capacity Control
Compressor capacity is determined by calculating a slide position target. Adjustment to the
slide target for normal running conditions occurs every 5 seconds. For loading a maximum
change of 1% is allowed, and for unloading a maximum change of 2% is allowed.
Required parameters

Count In Load Balance status for each compressor

Slide targets of all compressors

LWT error

LWT slope
LWT Error
LWT error compares the actual LWT to the active LWT setpoint. The equation is:
LWT error = LWT – active LWT setpoint
LWT Slope
LWT slope is calculated in the unit controller and sent to circuits via pLAN.
In the unit controller, this value is calculated such that the slope represents a time frame of
one minute.