Pumpdown Control - Emerson Vilter Vission 20/20 Operation And Service Manual

Section 6 • Compressor Control

Pumpdown Control

For use of compressor control screen - page 4, see
Cool Compression Control in Section 25.
The Pumpdown Control defi nes a method of "pump-
ing" down a chiller, which is to draw off refrigerant
from the chiller. This feature can be enabled or disabled
from this page, see Figure 6-7. Compressor Control
Screen - Pumpdown/Pulldown Control. If Pumpdown is
enabled, this feature will only function when the com-
pressor is running in local Auto Mode and Control Mode
Confi gured is Suction Pressure.
If Pumpdown Feature is enabled, then;
• The Auto-cycle functionality is ignored. Pumpdown
mode will cause the compressor to cycle off via the
Pumpdown Stop Pressure setpoint. Normally, the
Pumpdown Stop Pressure setpoint will be set lower
than the Auto-cycle Stop setpoint. Therefore, as the
suction pressure is pulled down, the compressor is
Figure 6-7. Compressor Control Screen - Pumpdown/Pulldown Control
6 – 6
NOTE
Vission 20/20 • Operation and Service Manual •Vilter/Emerson • 35391SC 1.9
prevented from shutting down prematurely via the
Auto-cycle Stop setpoint by automatically ignoring
the Auto-cycle feature.
• The compressor will be placed into "Stop" mode af-
ter the suction pressure is equal to, or goes below the
Pumpdown Stop Pressure.
Pumpdown:
• This checkbox enables the Pumpdown feature. If
this box is unchecked, Pumpdown setpoints are ig-
nored and the user is not allowed to edit Pumpdown
setpoints.
Stop Pressure:
• This setpoint defi nes the suction pressure value at
which the compressor will cycle off. Normally, this
setpoint is set below the Suction Pressure Auto-cycle
Stop Pressure setpoint.
Stop Delay:
• This setpoint delays the compressor from stopping
when the suction pressure is equal to or less than the