Mitsubishi FR-A800 Fault E.SAF Safety Circuit Fault

Getting the E.SAF error on your Mitsubishi FR-A800 drive? Learn what causes the safety circuit to trip, how to check S1/S2 terminals, and the correct switch positions to clear the fault.

 

The Mitsubishi FR-A800 series is equipped with a high-integrity safety circuit designed to protect personnel and machinery. If your drive stops and displays the E.SAF fault code, the inverter has shut off its output because it has detected an open circuit or a discrepancy in its safety monitoring loop.

Think of E.SAF as a hardwired "No-Go" signal. Even if you send a start command via the keypad or PLC, the drive will refuse to move the motor until the safety loop is satisfied. Here is how to diagnose and fix the source of the E.SAF alarm.

What Triggers the E.SAF Fault?

The FR-A800 uses dual-channel safety inputs (terminals S1 and S2) to comply with international safety standards. The fault triggers when the drive senses that the connection to these terminals is broken. The cause depends on whether you are actually using an external safety system or not.

Scenario 1: You ARE Using the Safety Stop Function

If your machine is wired to an Emergency Stop button or a Safety Relay Module, the drive is acting on a real command to stop.

• Broken Continuity: Check the wiring between terminals S1 and SIC or S2 and SIC. If either wire is loose, broken, or has high resistance, E.SAF will trigger.
• Safety Relay Failure: Verify that your upstream safety relay is healthy and not in a faulted state. If the relay doesn't send the 24V signal to the drive, the drive cannot run.
• Signal Mismatch: The drive expects both S1 and S2 to change state at nearly the same time. If one channel stays "high" while the other goes "low," the drive detects a safety circuit failure.

Scenario 2: You ARE NOT Using the Safety Stop Function

In many basic applications, the safety function isn't used. In this case, the drive ships from the factory with shorting wires (jumpers) installed. If these have been bumped or removed, the drive will trip.

• Check the Jumpers: Look at the control terminal block. There must be a physical jumper wire connecting S1 to PC and S2 to PC.
• Loose Terminals: Ensure the screws holding these jumpers are tight. Vibration in the electrical cabinet is a common cause for these small wires to slip out.

Internal Hardware: Switch Settings (SW3 and SW4)

Inside the FR-A800, near the control terminals, there are small DIP switches used for manufacturer settings. If these have been accidentally moved, the drive will throw an E.SAF error regardless of your wiring.

• Check Switch Positions: Locate switches SW3 and SW4 on the control circuit board.
• The Fix: Ensure both switches are set to their initial position (OFF). If they were changed during commissioning or maintenance, toggle them back and cycle the power to the drive.

Step-by-Step Resolution Guide

1. Visual Check: Inspect the control terminal block. Are the S1, S2, and PC jumpers present? If using a safety relay, are the wires firmly seated?
2. Multimeter Test: Measure the voltage at terminals S1 and S2 relative to SIC (or PC). You should see a steady 24V DC signal if the safety circuit is healthy.
3. Switch Inspection: Open the drive cover and verify that SW3 and SW4 are in the OFF position.
4. Reset: Once the wiring or switches are corrected, press the [STOP/RESET] button on the keypad. The E.SAF error should clear, and the drive should return to "Ready" status.

Summary Checklist

Component	Desired State
Terminals S1 / S2	Must have 24V signal (from PC or Safety Relay).
Jumper Wires	Firmly installed across S1-PC and S2-PC (if no safety relay).
Internal SW3 / SW4	Must be in the OFF position.
Safety Relay	Must be reset and showing "Healthy" LEDs.