Gas Pump Checkout Procedure RTHD, RTHC

Issue:

• The Gas Pump is designed to return samples of the liquid refrigerant at the bottom of the evaporator, with the oil mixed in, to the compressor suction.  The mixture of refrigerant/oil at the bottom of the evaporator is typically 90% refrigerant, 10% oil.  When this is not occurring the gas pump circuit needs to be validated.

Resolution:

Gas Pump Checkout - Unit Off

1. Turn off chiller.
2. Close (front seat) the ¼” angle valve (49) downstream of the “cold” filter (48).
3. Back seat valve and Install gauge at (47). Re-open to read pressure.
4. Close the ¼" angle valve (11) on the condenser which supplies the Gas Pump.
5. Make sure the gas pump solenoid valves (22 & 23) are de energized.
6. Pressurize the line between the Gas Pump and the ¼" angle valve (47) upstream of the "cold" filter using POE oil taken from the oil sump at (7). If desired, refrigerant from the condenser can be used as well.
7. Pressurize the line to approximately 115 psi.
8. Monitor the pressure leak rate in the line. It's typical to see an immediate 5 psi drop in pressure, and then a slow drop thereafter. A normal leak rate is 10 psi in 5 minutes. A rapidly falling pressure may indicate a leaking check valve (24) but may also indicate a leaking solenoid valve (22). Further testing may be necessary to determine which component is leaking.
9. Before returning to service, make sure all valves and coils are returned to their normal positions.

Gas Pump Checkout - Unit On

• Important: At least a 50 psi differential must exist between the evaporator and condenser before performing this test.

1. Turn the compressor off and close the valve on the oil return line from the Gas Pump to the compressor (49).
2. Back seat valve and Install gauge at (47). Re-open to read pressure.
3. Allow the unit to start.
4. Allow the Gas Pump to enter and complete a "fill" cycle (valve 22 will energize).
5. Allow the Gas Pump to enter a “drain” cycle (valve 22 will deenergize and valve 23 will energize). During the drain cycle deenergize the fill solenoid. Unplug J4-1 and J4-2 from the Chiller Module (1U1). Verify that the correct coil is de-energized. Or remove the electric coil from the valve (to disable the valve) and place a screwdriver or bolt shaft through the coil center to prevent overheating of the coil.
6. Monitor the gauge pressure at angle valve (47). The pressure should build toward condensing pressure. At the completion of the drain cycle de-energize the drain solenoid. Unplug J6-1 and J6-2 from the Chiller Module (1U1). Verify that the correct coil is de-energized. Or remove the electric coil from the drain valve (23) to disable the valve and place a screwdriver or bolt shaft through the coil center to prevent overheating of the coil. If the pressure holds to within 10 psi in 5 minutes, the system is functioning normally.
7. If the pressure fails to hold near condensing pressure, there may be a solenoid valve (22) or a check valve (24) leakage.
8. If the pressure falls rapidly to or near suction, either the "fill" solenoid (22) or the check valve (24) is leaking by.
9. To determine if the check valve (24) is leaking by, place a temperature probe on each side of the check valve (24). Monitor the temperature differential across the check valve (24) during the time that the “drain” solenoid (23) is energized. If the check valve is leaking, the temperature differential will be very small because condensing gas will push into the evaporator. In a properly operating system, the temperature differential across the check valve (24) during the drain cycle will be about 2-4 degrees depending on operation conditions.
10. If step 8 shows that there is a leak, but step 9 indicates it is NOT related to the check valve (24), the problem most likely resides in the "fill" solenoid (22), and it should be replaced.
11. Before returning to service, make sure all valves and coils are returned to their normal positions.

Notes:

• If it is determined that the check valve (24) is leaking, it is recommended that the entire Gas Pump assembly be replaced because the check valve contains a teflon ball. Units with a Design Sequence of G0 and earlier have the check valve brazed in. It is very difficult to braze in without damaging the teflon ball. Design Sequence H0 changed this to a o-ring boss fitting and the check valve can be replaced independently.

Resources Available:

• Tech TV Video(s):
  • N/A
• Reference Literature:
  (Electronic copies can be pulled from e-library at Trane Residential (tranetechnologies.com))
  • IOM:
    • RTHC-IOM-1C
    • RTHD-SVX01*-EN
  • Service Bulletin:
    • RTHC-SVD01B-EN (Troubleshooting Guide)
    • RTHC-SB-1B (Component Locations)
    • RLC-SVD05A-EN (Troubleshooting Guide)
    • RTHD-SVB01*-EN1B (Component Locations)
• Other:
  • N/A

Other Question/Problem/Cause Statements:

• RTHC Refrigerant Gas Pump Diagnosis
• Refrigerant Gas Pump checkout procedure
• RTHD Gas Pump checkout procedure
• RTHD Refrigerant Gas Pump Diagnosis

Facts:

• RTHC (Pueblo)
• RTHD (Pueblo)