6-10T Eflex Precedent units with ReliaTel controls utilized a Mitsubishi Variable Frequency Drive (VFD) mounted in the filter section of the unit for the control of the variable speed Copeland compressor. The operation of this VFD along with the condenser fan are both controlled by the ReliaTel Variable Speed Module (VSM). The VSM communicates to the ReliaTel Refrigeration Module (RTRM) through the same MBUS link that the RTRM uses for all the boards in the unit.
In the ReliaTel logic, the variable speed compressor is always Compressor 3, regardless of the amount of installed compressors or unit tonnage.
Condenser fans on all Eflex units that utilize ReliaTel controls are ECM motors using a PWM signal. The speed of the condenser fan motor is directly related to the Outdoor Air Temperature (OAT) vs. the running compressor speed. Due to the operation of the condenser fan, no low ambient kit is necessary for low ambient operation and a low ambient kit should never be fitted to the unit.
The link below is an internal Elibrary link for the most current version of the Mitsubishi manual for Eflex products. This manual covers both ReliaTel and Symbio 700 controls.
Can't access the guide? Contact your local Trane Commercial Sales Office
How does the unit start, stop and control the VFD?
How does the unit start, stop and control the VFD?
When the RTRM determines there is a need for compressor cooling, the VSM will energize the Compressor On Relay (COR) which closes VFD J4-SD to VFD J4-STF (Start, Forward Rotation).
At the same time the VSM is starting the VFD, the VSM is also sending the start-up speed command to start ramping up the compressor. This command is passed from VSM J2-5 to VFD J1-2. This is a 0-10vdc control signal.
ReliaTel will modulate the compressor speed based on the cooling load required. On startup, shutdown and intervals throughout operation, ReliaTel will ramp the compressor to a fixed speed for 60-90 seconds (depends on where the unit is in operation, ie starting/stopping normal operation) to force oil back to the compressor. If the compressor goes into this oil recovery during normal operation, the compressor speed will return to it's last normal control speed and then begin modulating to maintain the load.
How does the condenser fan start?
How does the condenser fan start?
When the RTRM determines there is a need for compressor cooling, the VSM will begin sending the PWM (Pulse Width Modulation) signal to the fan motor. This signal alone is what starts the condenser fan motor, there is no relays or contactors involved. This signal can be measured at PPM-VSM using a voltmeter set to DC volts. The range for the condenser fan is ~2-17.5vdc.
Below is the speed chart for the condenser fan on 6-10T Eflex with ReliaTel controls:
| OAT Condition | VSPD Comp. Speed | 6 Ton | |||
| RPM | Cond Airflow | Duty Cycle | PWM Vdc | ||
| OAT>95°F | Min<Hz<Max | 1001 | 100% | 83% | ~14.525 |
| 45°F<OAT<90°F | <48Hz | 473 | 40% | 31% | ~5.425 |
| 50Hz<Hz<70Hz | 733 | 70% | 56% | ~9.8 | |
| >72Hz | 1001 | 100% | 83% | ~14.525 | |
| 25°F<OAT<40°F | Min<Hz<Max | 312 | 22% | 16% | ~2.8 |
| OAT<20°F | Min<Hz<Max | 312 | 22% | 16% | ~2.8 |
| 7.5 Ton | |||||
| OAT>95°F | Min<Hz<Max | 1111 | 100% | 92% | ~16.1 |
| 45°F<OAT<90°F | <48Hz | 465 | 40% | 31% | ~5.425 |
| 50Hz<Hz<70Hz | 790 | 70% | 61% | ~10.675 | |
| >72Hz | 1111 | 100% | 92% | ~16.1 | |
| 25°F<OAT<40°F | Min<Hz<Max | 300 | 22% | 15% | ~2.625 |
| OAT<20°F | Min<Hz<Max | 300 | 22% | 15% | ~2.625 |
| 8.5 Ton | |||||
| OAT>95°F | Min<Hz<Max | 1116 | 100% | 92% | ~16.1 |
| 45°F<OAT<90°F | <48Hz | 532 | 40% | 31% | ~5.425 |
| 50Hz<Hz<70Hz | 831 | 70% | 61% | ~10.675 | |
| >72Hz | 1130 | 100% | 92% | ~16.1 | |
| 25°F<OAT<40°F | Min<Hz<Max | 352 | 22% | 15% | ~2.625 |
| OAT<20°F | Min<Hz<Max | 352 | 22% | 15% | ~2.625 |
| 10 Ton | |||||
| OAT>95°F | Min<Hz<Max | 1130 | 100% | 94% | ~16.45 |
| 45°F<OAT<90°F | <48Hz | 532 | 40% | 37% | ~6.475 |
| 50Hz<Hz<70Hz | 831 | 70% | 65% | ~11.375 | |
| >72Hz | 1130 | 100% | 100% | ~16.45 | |
| 25°F<OAT<40°F | Min<Hz<Max | 352 | 22% | 20% | ~3.5 |
| OAT<20°F | Min<Hz<Max | 352 | 22% | 20% | ~3.5 |
PWM Vdc values are estimates, actual voltage may vary based on the unit entering voltage and meter accuracy.
Troubleshooting
Troubleshooting
Compressor VFD will not start
There a couple of common scenarios where ReliaTel will not start the compressor. This could be due to no actual load request, BAS control, unit is unoccupied and failures. Common failures will be discussed and described below
VSPD Compressor Drive Fault on BAS or TD5 Touchscreen
VSPD Compressor Drive Fault is a generic fault generated by the VSM module based on an alarm input from the VFD. This VSM input is monitored and if voltage is detected from the the VFD alarm point, the VSM treats this as a shutdown alarm and will stop all compressor and condenser fan operation. This is also a manual reset to clear.
Random Alarms for features the unit does not have or no/random compressor operation
6-10T Eflex is unique in how the unit is configured to know what size/tonnage the unit is. On the VSM, there are three inputs that can receive different 24vac inputs to tell the VSM/ReliaTel what the unit tonnage is. The difference is a configuration jumper in the wiring harness at the VSM and how the jumper is pinned out. It is crucial to the unit operation that this configuration is correct.
Multiple unit operational issues have been observed when this configuration jumper is missing:
- No indoor fan operation on MZVAV configured units
- No condenser fan operation
- High Pressure Trips
- Incorrect indoor fan operation
- Incorrect condenser fan operation
- Poor unit performance
This jumper and the matrix is available on the wiring diagram of the unit:
The configuration jumper is present on 6 - 8.5T units and the 10T unit has a specific harness with no config jumper. All configuration jumpers have wires 100CV(BK) & 100CZ(BK). The difference in the jumpers are the presence of 100CW(BK), 100CX(BK), 100CY(BK).
If the jumper is missing on a new unit and the unit is not 10T, the corresponding 100DB(BK), 100DC(BK), 100DE(BK) can be cut and isolated to simulate the jumper.
VFD Fault E.P24
E. P24 = 24 VDC power fault
E.P24 fault points to an issue with the 24vdc generated from the VFD PC terminal being shorted. Disconnect the VFD PC terminal to verify the alarm clears. If it does, check associated wiring for damage. If it does not clear, the could indicate a failed VFD, contact Trane LCU Tech Support.
VFD Fault E.OV1, 2, 3 or E.OC1, 2, 3
- E.OV1 = Regenerative overvoltage trip during acceleration
- E.OV2 =Regenerative overvoltage trip during constant speed
- E.OV3 = Regenerative overvoltage trip during deceleration or stop
- E.OC1 = Overcurrent trip during acceleration
- E.OC2 = Overcurrent trip during constant speed
- E.OC3 = Overcurrent trip during deceleration or stop
All of these alarms are similar and can be generated due to incorrect parameter adjustments, compressor wiring/connections, failing compressor, failing VFD.
At no time should the parameters of the VFD be changed away from factory settings and any parameter settings made should follow the guide based on the unit unit size and compressor model. Changes to the VFD parameters settings can cause compressor damage, unit damage and poor unit performance.
VFD Fault SA
SA = Safety Stop
The SA fault occurs when the safety inputs on the VFD are open. VFD J1-S1 & S2 receive 24vdc from VFD J1-PC through the High Pressure Cutout (HPC) & Temperature Discharge Limit (TDL) or Discharge Temperature Limit (DTL).
24vac is provided to from VFD J1-PC to the HPC then to the TDL then is spliced to two wires, one returns to VFD S1 and is jumped over to S2 and the other is the safety/compressor proving input to the VSM on J2-17.
VFD Low Voltage Wiring
The VFD utilizes connector bodies physically connected to the VFD to allow plugs to be connected at the factory to limit the amount of hand wiring required. In this article, there has been mention of the VFD terminals PC, SD, STF, ect terminals, the image below shows what this low voltage wiring should look like.