Mitsubishi VFD Pump PID & Sleep Mode Configuration: Stable Pressure Control
For submersible water pumps with motor power ratings from 0.75 to 15 kW, Mitsubishi FR-D700 and FR-E700 variable frequency drives serve as the industrial standard for long-term reliability. These drives regulate motor speed by analyzing feedback from a pressure transmitter. At our Kiev warehouse, we frequently assemble pre-configured control panels based on these Japanese drives for water supply systems in private houses, cottages, and farms. This automated system prevents water hammer in the piping, protects pipe connections from leaks, and reduces electricity consumption by 35–45%. Stable pump station operation without constant start-stop cycles is performed by the integrated PID controller and sleep algorithm.
Connecting a 4-20mA Pressure Transmitter to Mitsubishi VFDs
A 2-wire pressure transmitter with a 4-20mA signal is used to obtain the feedback signal. This current signal has high noise immunity, permitting cable runs up to 100 meters from the frequency inverter. Our engineering team recommends using a shielded twisted pair cable to minimize electromagnetic interference.
Electrical connection diagram for the transmitter on FR-D700 and FR-E700 drives:
- Positive Transmitter Terminal (+): Connect to terminal PC (+24 VDC output from the drive).
- Negative Signal Terminal (-): Connect to the analog input terminal 4 (4-20mA current input).
- Cable Shield: Clamp the shield under the metal EMC grounding plate or connect to terminal 5 (analog common).
A highly important step for commissioning: on Mitsubishi drives, the current input (terminal 4) is disabled by default. To activate current signal processing, the AU control signal (Terminal 4 input selection) must be turned ON.
- If your model has a physical AU terminal on the terminal block, simply install a jumper wire between terminal AU and terminal SD (digital signal common).
- If the physical AU terminal is absent (which is common on smaller FR-D700 models), assign this function to an unused digital input. For example, set parameter Pr. 180 (RL terminal function selection) or Pr. 181 (RM terminal function selection) to "43" (AU signal). Then install a jumper wire between that terminal (RL or RM) and terminal SD.
PID Controller Settings (Pr. 128 to Pr. 133) for FR-D700 and FR-E700
The integrated PID loop automatically regulates the motor speed to keep the water pressure constant. All PID parameters on Mitsubishi drives are configured through a dedicated parameter group. Our technical team has prepared a reference table based on successful field installations.
| Parameter | Function Name | Factory Default | Recommended Pump Value | Practical Application Details |
|---|---|---|---|---|
| Pr. 128 | PID Action Selection | 0 | 20 | Enables the PID controller. Setting 20 selects terminal 4 (4-20mA feedback) and direct action (pressure maintenance). |
| Pr. 129 | Proportional Band | 100% | 150% | Acts inversely to proportional gain. Increasing this value (e.g., to 150-180%) stabilizes the system and prevents pressure oscillation. |
| Pr. 130 | Integral Time | 1.0 s | 2.5 s | Time to eliminate static error. The default 1.0 s is often too dynamic for water pumps. Setting it to 2.5–3.0 s provides smooth operation. |
| Pr. 133 | PID Action Setpoint | 0.0% | Application dependent (e.g., 40.0%) | Target pressure preset as a percentage of the sensor full scale. For a 10 bar transmitter, 40.0% represents a target of 4.0 bar. |
In our experience, if the piping has a long run, the proportional band Pr. 129 should be increased to 200% to damp pressure swings during sudden valve opening. If the pump reaction is too slow and pressure drops heavily before the regulator responds, decrease Pr. 129 to 120% and set the integral time Pr. 130 to 2.0 seconds.
Configuring Sleep and Wake-up Modes (Pr. 575, Pr. 576, Pr. 577)
The sleep algorithm stops the pump when water consumption drops to zero. When all taps are closed, the motor speed decreases. Running the motor continuously at minimum speed must be avoided: the water inside the pump chamber will heat up and boil, destroying diffusers and shaft seals.
To enable sleep mode on Mitsubishi drives, configure three primary parameters:
- Pr. 575 (Output frequency detection time / Sleep delay): Set to 5.0 s. The VFD waits 5 seconds after the frequency falls below the sleep threshold before stopping the motor to ensure that demand has completely stopped. This prevents cycling from brief drops in usage.
- Pr. 576 (Output frequency detection level / Sleep frequency): This is the speed at which the pump runs against closed valves without producing useful flow. Typically this threshold is between 33.0 and 36.0 Hz. To determine it during commissioning, close all valves, check the current frequency on the drive display, and set Pr. 576 to 0.5–1.0 Hz above that value (e.g., 35.0 Hz).
- Pr. 577 (PID sleep cancellation level / Wake-up deviation): Defines the pressure drop that wakes up the drive, entered as a percentage of the target pressure. In our experience, a practical choice is 10.0% to 15.0%. For example, with a 3.0 bar setpoint and a 10% deviation, the drive restarts the motor when pressure drops to 2.7 bar.
Dry-Run Protection via Digital Input Terminals (MRS / RL / RM / RH)
Running a pump dry causes rapid wear of slide bearings and plastic components. We highly recommend installing a dry-run sensor (level electrodes, a low-pressure switch, or a float switch) in the well or storage tank.
Based on our engineering experience, you can connect this sensor to digital inputs on FR-D700 and FR-E700 series in two ways:
- Emergency Stop via Terminal MRS (Hardware output shutoff): Connect the dry-run switch contacts between terminals MRS (Output stop) and SD. On Mitsubishi drives, shorting MRS to SD immediately cuts off the output voltage, letting the motor coast to a stop. This simple setup requires no parameter modification.
- Fault Lockout via Terminals RH / RM / RL: For a setup that displays a fault code and locks out operation until manual reset after water levels restore, use the external fault function THR (External thermal relay). Set parameter Pr. 181 (RM terminal function selection) to "7" (THR signal). Connect a normally closed (NC) float switch contact between terminals RM and SD. When water is present, the contact is closed and the drive runs. If water runs out, the contact opens. The drive immediately stops the motor and locks out, displaying fault code E.OHT. To restart, press the RESET key on the panel or cycle the power after water level is restored.
Expansion Tank Sizing and Air Pre-Charge Rules (2-24 Liters)
Constant-pressure VFD systems do not require large 100-liter or 200-liter pressure tanks. Large volumes make the system sluggish and delay the PID response. However, running the system without a tank is prohibited.
Rules for expansion membrane tank preparation:
- Volume: We recommend a small membrane expansion vessel of 8 to 24 liters. It compensates for micro-leaks (such as dripping valves or check valve leakage), protecting the pump from rapid cycling and constant wake-ups.
- Pre-charge Pressure: The air pressure in the empty tank must be 60-70% of the target system water pressure. If the target pressure is set to 3.0 bar, pre-charge the air bladder to 1.8–2.1 bar. Always measure air pressure when there is no water pressure in the system.
- Maintenance: Check the pre-charge pressure with a manual gauge every 6 months. Running without air in the tank will cause the VFD to cycle the motor on and off every 1–2 seconds, which quickly damages the drive inverter stage and motor windings.
Summary and Recommendations
A properly configured Mitsubishi variable frequency drive turns a standard borehole pump into a constant-pressure water station. The main task is to set the sleep frequency (parameter Pr. 576) and install a small expansion tank of 8-24 liters with the correct air pre-charge pressure. Check out our catalog to see the available Frequency Inverters for different power ratings. For specialized pumping applications, visit our section on frequency inverters for pumps. Our engineering team will help you calculate the parameters and provide free wiring advice. We also recommend reading our guide on the Mitsubishi Electric VFDs to review general brand details. Additionally, step-by-step guides are available for other VFD series, such as the Schneider Altivar pump PID setup guide, the ABB VFD pump PID guide, and the INVT VFD pump PID and sleep guide. For a comparison of different drive manufacturers, please consult the Siemens vs Mitsubishi VFD comparison.
