Service manual

6 – 8

Vission 20/20 • Operation and Service Manual •Vilter/Emerson • 35391SC 1.9

Auto Cycle Differential:

• This setpoint deﬁ nes the offset pressure values for

Auto Cycle Start Pressure and Stop Pressure from the

Suction Pressure setpoint. Auto Cycle Start Pressure

setpoint will be Suction Pressure setpoint increment-

ed by this setpoint pressure value, while Auto Cycle

Stop Pressure value will be Suction Pressure setpoint

decremented by this setpoint pressure value.

When Pulldown feature is enabled, Pumpdown checkbox

is automatically grayed out. Similarly when Pumpdown

feature is enabled, Pulldown checkbox is automatically

grayed out and hence, the user will not be able to op-

erate Pulldown feature. This is done to keep Pulldown &

Pumpdown features mutually exclusive.

Control Mode

This drop down box gives the operator the ability to

change the type of control mode such as suction pres-

sure control or process temperature control. The

operator can also switch from setpoint 1 and setpoint 2

for each control method. What is available in this drop-

down box is dependent on the number and type of con-

trol selected in the conﬁ guration screen, see Figure 6-8.

Compress Control Screen - Misc 1 (Control Mode).

Stop Load and Force Unload

The stop load and force unload feature’s primary pur-

pose is to attempt to prevent the compressor from

tripping off due to particular instrument reading. For

example, if the suction pressure drops too low, the com-

pressor will trip off for safety reasons. However, the stop

load & force unload algorithm recognizes a potential trip

and either stops the compressor from loading up or even

unloads the compressor to prevent the trip.

Stop load:

• When this value is reached, the capacity slide will not

Section 6 • Compressor Control

Figure 6-8. Compressor Control Screen - Misc. 1 (Control Mode)