Emerson Liebert Economizer Solutions User Manual

If pe doesn't change, me will reach 30% after another minute. This continues until me reaches 100%, 

which is the maximum.
If pe changes, me will also be changed with the same value. For example: pe is 20%, me is 40%. When 

pe changes to 15%, me will change to 35%.

If the controller is unstable or shows too many damper repositions (see the Liebert iCOM’s Wellness 

menu, page 9 of 9; refer to Figure 15), the automatically adjusted controller values may not be best 

suited for this installation. Tuning the controller settings could help achieve better results.
Controller tuning involves the selection of the best values of setpoint (S102), proportional band 

(S104), integration time (S105) and (if enabled) the supply air limit setpoint (S125). This is often a 

subjective procedure and is certainly site dependent.
In most cases, unstable control (dampers constantly repositioning) is caused by too low of proportional 

band setting (S104) combined with an active supply limit control (the supply air temperature is close 

to or below the low limit S125).
A simple improvement may be to decrease the supply limit setpoint (S125).
If this is not successful/feasible/desired, follow these steps:
1. Set Autoset Enable (S107) to No.
2. Set Control Type (S103) to PI.
3. Set Supply Limit Temp Value (S125) a few degrees higher than the current return air 

temperature to have it active (if S125 is used).

4. Set Integration Time (S105) to 0; this will enable incrementing only the proportional band.
5. Set Temperature Proportional Band (S104) to 6°F and observe the response of the controlled 

dampers. Allow the control to stabilize.

6. Add 2°F to S104 setting and observe the response of the controlled dampers. Allow the control to 

stabilize.

7. Repeat Step 5 until the dampers operate as expected and the temperature is fairly stable on any 

value of temperature.

8. If the actual temperature remains too high above the set point, set Integration Time (S105) to 

4 minutes and observe the response of the controlled dampers. Allow the control to stabilize.

9. Increase (S105) in 1-minute steps until acceptable settings are achieved.
10. If the control operation is stable but sluggish, the proportional band can be reduced (10-15% of the 

current value) to allow faster reaction.

11. Set Supply Limit Temp Value (S125) back to the original setting.