Since the Trane Company has a policy of continuous product improvement, it reserves the right to change specificationsand designs without notice. The installation and servicing equipment referred to into this booklet should be done by qual-ified experienced technicians.

GENERALSERVICE RTAA-SB -18BULLETIN

Library Service LiteratureProduct Section RefrigerationProduct Rotary Liquid ChillersModel RTAALiterature General Service BulletinSequence 18Date July 1998File No. SV-RF-RLC-RTAA-SB-18-0798Supersedes

Literature Change History:Original Service Bulletin: RTAA-SB-18

Subject: RTAA 100 Ton Compressor Lip Seal Failures

Introduction:

We have experienced infant failures of the lip seal on the 100 ton compressors built after U97A****. The failure does not affect the reliability of the compressor but it will affect the compressor’s ability to unload properly. This problem can be masked by high head pressure diagnostics, low oil flow diagnostics or frequent cycling of the compressor.

Discussion:

The 70 to 100 ton compressors are unloaded via internal porting in the compressor. The lip seal is used to isolate a cavity behind the bearings that is ported to suction. This creates a path from the unload solenoid to suction which relieves the pressure from behind the piston. If the lip seal develops a leak, internal port-ing is not large enough to vent the additional discharge gas back to suction. As the bearing cavity increases in pressure, the piston can no longer unload.

The lip seal can not be replaced in the field but the porting of the unload solenoid can be routed externally with out any adverse affect on the compressor. Do not re-route the porting of the unload solenoid until all other components used in unloading the compressor have been verified as operational. To determine if the lip seal is leaking, follow the steps under “Corrective Action” , prior to re-routing the unload sole-noid.

Units Affected:

The infant failures of the lip seal could affect any 100 ton compressor on the RTAA 130-400 units built after U97A****.

RTAA-SB-18 2

Corrective Action:

Read through all of the steps prior to starting the procedure. Additional information from other bulle-tins is necessary.

I) Check-out ProceduresBelow are the steps to determine the cause of the unloading problem. These steps must be completed before attempting a solenoid re-route.

NOTE: The re-route will NOT resolve all unloading problems. It is only intended to be used when a leak-ing lip seal exists.

1. Cycle the unit off line.

WARNINGSome procedures must be completed with power applied. Be certain to follow proper electrical practices to avoid shock or electrocution.

2. Attach an amp meter to the one of the main leads to the compressor.

3. Monitor and record the actual RLA at start-up.4. Determine if the compressor is starting loaded.

NOTE: The high head pressure from starting loaded increases the pressure drop across the oil line which could be enough to generate a low oil flow diagnos-tic. Starting loaded can also cause pressures to rise quick enough to open relief valves and or trip the unit on high pressure diagnostic.

5. If the compressor appears to have trouble unloading, refer to RTAA-SB-4 to troubleshoot the solenoids, microprocessor triacs and the pis-ton.

6. Before logging the measurements in RTAA-SB-4, one additional pressure must be read that is not included in RTAA-SB-4. This is the bearing cavity measurement.

7. To measure the bearing cavity pressure, a

shrader valve must be added to the top of the compressor.

8. To add the schrader valve, isolate the compres-sor by closing the suction service valve, dis-charge service valve and the oil line angle valve. Manually energize the master solenoid. Relieve the pressure from the backseat port of the suction service valve.

9. Remove the plug from the on top of the com-pressor, adjacent to the unload solenoid. Refer to Figure 2.

NOTE: At times, it is difficult to determine the exact cause of the loading problems. The only way to verify that the problem is NOT associated with the solenoids is to insert block-offs (shim stock) under both the unload solenoid and the load solenoid and verify the pressure in the piston cavity. The shims can be added under the solenoids while the compressor is isolated. If the shims are added, the compressor will need to be manually loaded and unloaded with a gauge set for the remainder of the test.

10. Perform and log the results of RTAA-SB-4 including the additional bearing cavity readings for each step. Compare the results to Table 1 to help determine what has failed.

NOTE: As the bearing cavity pressure rises above piston pressure, the compressor will begin to load when the unload solenoid is pulsed. If the lip seal leak is severe enough, the unload solenoid will no longer hold in reverse, causing the compressor to go fully loaded continuously.

11. If it is determined that the lip seal is leaking. Fol-low the “Unload Solenoid Porting Re-route” pro-cedures.

3 RTAA-SB-18

Table 2: Possible Causes to Loading Problem

Possible ProblemRecorded

MeasurementEnergize Load

SolenoidEnergize Unload

SolenoidDe-energize both load and unload solenoids

Operating properly Piston Pressure increase decrease remain constant

Amp Draw increase decrease remain constant

Bearing Cavity Pressure

gradually increase to no more than 30 psi above suction pressure

gradually increase to no more than 30 psi above suction pressure

gradually increase to no more than 30 psi above suction pressure

Stuck piston Piston Pressure increase decrease remain constant

Amp Draw remain constant remain constant remain constant

Bearing Cavity Pressure

gradually increase to no more than 30 psi above suction pressure

gradually increase to no more than 30 psi above suction pressure

gradually increase to no more than 30 psi above suction pressure

Leaking load sole-noid or leaking piston

Piston Pressure increase increase increase

Amp Draw increase increase increase

NOTE: Leaking piston can only be confirmed by blocking off the sole-noids and re-checking the pressures.

Bearing Cavity Pressure

gradually increase to no more than 30 psi above suction pressure

gradually decrease to approx. 30 psi above suction pressure

gradually increase to no more than 30 psi above suction pressure

Leaking unload sole-noid

Piston Pressure remain constant or decrease

decrease decrease

Amp Draw remain constant or decrease

decrease decrease

Bearing Cavity Pressure

gradually increase to no more than 30 psi above suction pressure

gradually increase to no more than 30 psi above suction pressure

gradually increase to no more than 30 psi above suction pressure

Leaking Lip Seal Piston Pressure may load properly if <70% RLA

increase or remain constant - particularly at >70% RLA

increase - particularly at >70% RLA

Amp Draw may increase cor-rectly <70% RLA

increase or remain constant - particularly at >70% RLA

increase - particularly at >70% RLA

Bearing Cavity Pressure

Gradually increase to approx. dis-charge pressure

Gradually increase to approx. discharge pres-sure

Gradually increase to approx. discharge pres-sure

RTAA-SB-18 4

II) Unload Solenoid Porting Re-RouteWhen the lip seal develops a leak, the compressor is no longer able to unload through the internal port-ing. To unload the compressor without any adverse affects, follow the steps below:1. Cycle the unit off line.2. Disconnect all power.3. Close the discharge service valve, oil line angle

valve and the suction service valve.4. Manually energize the master solenoid.5. Evacuate the compressor through the backseat

port on the suction service valve.6. Remove the load and unload solenoids.7. Replace the small brass pill filters if installed

under the solenoids on the compressor. The lat-est design of compressor will have one pill filter under each solenoid.

Note: The pill filters are intended to filter out start-up debris. All compressors will operate successfully without the filters. If damage occurs to the filter, remove it from the compressor entirely and proceed with step 8.

8. Partially assembly the re-route block prior to installing on the compressor. Lay the first pair of gaskets over the ports on top of the re-route block. Refer to Figure 1.

9. Mount the solenoids on top of the re-route block using the M6x1-55 mm screws.

Figure 1. Top of Re-route Block

Note: Gaskets need to be installed on both sides of the re-route block, between the solenoids and the block and the block and the compressor.

10. Install the gaskets between the compressor and the re-route block and secure by torquing the M6X1-55 mm screws to 10 ft-lbs.

11. Thread in the 1/4” FL x 1/8” NPT connector to the side port on the block using a thin film of Fel-Pro Tight #51604 or other appropriate thread sealant. Refer to Figure 2.

12. Remove the 1/4” pipe plug from the bottom of the rotor housing. Refer to Figure 2.

13. Route a 1/4” copper line from the block over to the suction port on the bottom of the compressor.

Figure 2.Installed Re-route Block

Note: To avoid line breakage, run the copper line as close to the compressor as possible without securing the line with brackets.

Parts Information:

One re-route kit, KIT 06282, is required for each affected 100 ton compressor. Contact your local Trane Parts Center to obtain the parts.

Production Changes

Investigation of the problem is currently underway.

Unload Load