Emerson 3000 用户手册

The control utilizes an upper and lower pressure threshold with a 35psi (241kPa) deadband to reduce 

valve movement. If the liquid pressure is between the upper and lower threshold, the valve remains 

at the current position. If the liquid pressure exceeds the upper threshold the valve opens, and if the 

pressure falls below the lower threshold the valve closes. There are multiple adjustment bands to ease 

discharge pressure back into control range.

Both pressure thresholds can be shifted simultaneously over a 50psi (345kPa) range (the 35psi 

[241kPa] differential remains constant). The ball valve setpoint offset parameter in the Liebert 

iCOM

®

 Service menu can be adjusted from 0 to 50 PSI (345 kPa) to raise or lower the control band 

similar to the pressure adjustment on a water regulating valve. Changing the setpoint offset will 

adjust the pressure thresholds for both circuits. Units are factory-set at a 30psi (207 kPa) setpoint 

offset (30psi [207 kPa] above minimum). This results in a 220psiA (1517kPa) lower threshold and a 

255psiA (1758kPa) upper threshold pressure.

The setpoint offset is adjusted to the minimum value during startup, then changes to the set value 

once the compressor reaches normal operating pressures. Changes in fluid temperature could cause 

pressure changes that do not result in valve movement within the deadband. Fan cycling stats should 

be set to prevent continuous fluid temperature swings greater than 10

°

F (5.6

°

C).

The motorized ball valve is located in the condenser fluid return line. Three-way valves are piped in a 

mixing arrangement with the common port at the valve outlet.

The valve can be manually set by disconnecting AC power, depressing the manual override button on 

the valve actuator and adjusting the valve position with the handle. The motorized ball also can be 

controlled through the Liebert iCOM’s Service menu using manual mode to override the normal 

control.