User manual

Operation

3.2.3 Chilled Water Control

The chilled water control valve is adjusted proportionally as the temperature control varies the

requirement for cooling from 0% to 100%. A three-point actuator or motorized ball valve is used for

chilled water cooling, as well as free-cooling hot water or heating.

The three-point actuator is driven through two digital outputs: Open and Close. The control

determines the valve position by timing how long the open or closed signals have been active based on

the valve travel time set in the Service menu / Setup submenu. To determine the initial position of the

valve, the unit must perform a 3P Reset. The 3P Reset closes the valve for a time of 110% of the 3P

Actuator run time. This calibrates the valve with the controller and ensures that it is closed. A 3P

Reset is also performed if the fan is switched off for any reason (timer off, unit off, etc.). Once the reset

is performed.

The three-point actuator can be configured to utilize the pre-wired feedback signal provided from the

factory. Enabling the feedback signal is required when supply air control is being used with the 3P

valve to increase the valve’s position accuracy. Enabling the feedback signal will eliminate the need to

drive the valve closed after a loss of power or Unit Off command, decreasing the unit’s restart time.

Authorized Emerson personnel should use the following steps to enable the feedback signal:

1. The feedback on the control valve uses Analog Input 1.

2. Nothing can be connected to Analog Input 1 P11 pins 1 through 4.

3. Control board DIP switch SW2 Switch 1 must be ON, Switch 2 must be OFF.

Figure 18 DIP switch locations on Liebert iCOM control board

4. P68 must have a jumper placed between the top and bottom two pins on the left side and one

placed between the top and bottom pins on the right side, the two middle pins should be left

unconnected.

5. Go to Service/Diagnostics Service Menu and find S379. Set this option to Feedback and note that

S380 will go to Yes and S381 will go to Ongoing. If Feedback is already selected then go to line

S380 and manually select Yes. This means that the Liebert iCOM is doing auto calibration on the

valve using the feedback now available through the potentiometer. Wait for S381 to say Idle and

then the process is complete.