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Checklist for Liebert XDC Startup
35
The Liebert XDC system is now ready to be turned ON.
1. Turn On all fans of the Liebert XD cooling modules.
2. Turn the Liebert XDC On via user interface (I/O button). Allow the system to attempt to start for
at least 2 minutes.
If the Liebert XDC pump cannot maintain flow and continues to switch over due to starting diffi-
culties, proceed to Step 4 and refer to the troubleshooting section of the Liebert XDC user man-
ual.
3. If constant flow is established, wait until the Liebert XDC has been operating 10-15 minutes, then
verify that the refrigerant level in the receiver sight glass is between the second and third level
(see Figure 31). Add or remove charge as indicated by sight glass level.
4. Check pressure differential functionality:
The Liebert XDC system should be On. If it is Off:
a. Turn On the Liebert XD cooling module fans
b. Turn the Liebert XDC On via user interface (I/O button).
If there is no “Loss of Flow” alarm present—This suggests that there is flow. Test the
pressure differential by closing the ball valve on either the suction line or discharge line to
stop the flow.
This should prompt an alarm for “loss of flow on P1.” This alarm confirms that the switch has
opened on low pressure (below 6 psi; 41 kPa; 0.41 bars).
If there is a “Loss of Flow” alarm present—This suggests that there is no flow. Verify
that this is correctly annunciated by looking at the sight glass in the receiver. If a true no-flow
condition exists, the level will not move.
However, if there is flow, but the differential reading is faulty, the level will slowly
drop, indicating flow, while the loss of flow alarm is annunciated.
Check the pressure differential physically by making sure that the electrical connections are
properly connected. Then check the pressure differential electrically by making sure that the
unit has 24VAC across it.
Figure 31 System R-134a liquid level
Operation above sight glass #3 can
make the system operate erratically
and reduce cooling capacity - Reduce
charge to recommended level.
Recommended operating level
Acceptable operating level
Operation below sight glass #1 may
cause loss of flow or cooling. Add
charge to reach recommended level.
For lightly loaded systems,
the recommended operating
level is sight glass #2.
Sight Glasses 1, 2 & 3