Filling the Pumped Circuit-R-134a

Checklist for Liebert XDP Startup

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; 41kPa; 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 21 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

3.1Filling the Pumped Circuit—R-134a

1.Connect a charging manifold to the service port of the receiver outlet valve.

2.Purge the hoses.

3.Calculate the amount of R-134a refrigerant needed to charge the system, using the values in Tables 6, 7, 8 and 9; for assistance, refer to 3.1.1 - Calculating Refrigerant Charge— Example. The section includes a worksheet to calculate system refrigerant charge requirements.

4.Weigh in the calculated charge.

5.After adding the calculated charge, allow the system to sit 15 to 30 minutes to reach equilibrium. Observe the refrigerant level through the sight glasses of the receiver. The level should be above the second sight glass at a minimum when the Liebert XDP is off.

6.If the refrigerant level is improper, the charge must be adjusted.

If the level is too high or too low, recalculate the required charge and reduce or increase the amount as needed to reach the proper level.

NOTE

All lengths in Tables 7, 8 and 9 are actual pipe lengths, not equivalent pipe lengths.

NOTE

System refrigerant volume calculations derived from Tables 6, 7, 8 and 9 are based on a fully loaded system. Additional charge may be required for lightly loaded systems.