Fault 22 Tz_EmergStop_Fault Sunsynk and Deye: Emergency Stop Wiring Fix

Key Takeaways

• Fault 22—reported as Tz_EmergStop_Fault (or Tx_EmergStop_Fault) on Sunsynk Classic, Acure, Elite, and Deye hybrid inverters—signals that the inverter's emergency shutdown circuit has engaged.
• When this condition triggers, the front red Fault LED illuminates, the internal contactors disengage, and the unit completely ceases power production.
• On newly commissioned installations, Fault 22 is almost universally caused by an installer wiring error: landing the secondary black and white CT coil cables into the P6 Emergency Shutdown connector instead of the P2 CT strip connector.
• Because the secondary coil of a current transformer has very low winding impedance, connecting it across the P6 emergency terminals short-circuits the shutdown sensing loop, forcing an immediate F22 shutdown.
• Correcting the fault requires moving the CT cables to pins 3 and 4 of connector P2, verifying that P6 is correctly configured or jumpered, and performing a controlled power restart.

How the Emergency Stop Circuit Operates

Modern hybrid inverters designed for South African residential and light commercial applications incorporate physical emergency stop safety inputs. These interfaces allow an external emergency push-button switch (frequently mounted outside a plant room or battery enclosure) to instantly de-energize the inverter.

The manufacturer's technical support bulletin explains the fault symptom:

"When the Fault LED is lit and the Acure shows Fault 22 Tx_EmergStop_Fault the Inverter is reporting that its Emergency Stop / Emergency Shutdown feature has been activated."

Under normal operation, the emergency stop input monitors an external contact. If the circuit state changes—either opened or shorted depending on hardware design—the inverter's central processor immediately disables the high-frequency gate drive signals to the inverter bridge and drops the AC output relays within milliseconds.

The Most Common Installation Mistake: The P2 vs P6 Trap

While Fault 22 can theoretically indicate a depressed emergency mushroom button, in the vast majority of newly commissioned South African solar systems, the root cause is terminal confusion during physical installation.

Inside the lower wiring compartment of the inverter, several green multi-pin pluggable terminal strips sit in close proximity on the control printed circuit board (PCB):

• Connector P2: Houses external current transformer (CT) sensor inputs, external meter communication, and auxiliary control lines.
• Connector P6: Houses the dedicated Emergency Shutdown / Rapid Shutdown terminals.

The technical support documentation highlights this common installation trap:

"If the secondary black and white CT Coil Cables (or CAT-6 extension) have been inserted into the P6 Emergency Shutdown Connectors + and – (as per below in the Red Box) then the Acure will be Shutdown by the short circuit connection of the CT Secondary Coil and it will show F22 Fault."

Because many installers extend CT coil wiring across long distances using twisted-pair CAT-5 or CAT-6 network cable, the fine conductors look identical to external signaling lines. Landing these wires into P6 shorts the emergency loop, triggering an immediate and permanent F22 fault.

Step-by-Step Resolution Workflow

Follow this procedure to verify and correct terminal assignments:

Step 1: Isolate the Inverter

Before working inside the lower wiring compartment, perform safe electrical isolation:

1. Switch off the main AC grid supply breaker in the home distribution board.
2. Turn off the backup load output circuit breaker.
3. Switch off the external DC solar array isolator switch.
4. Switch off the battery DC disconnect switch or battery BMS breaker.
5. Wait five minutes for internal DC link capacitors to discharge safely.

Step 2: Identify Connector P2 (The Correct CT Terminal)

Examine the printed circuit board markings carefully:

• The manufacturer states: "The correct connections for the CT are 3,4 of Strip Connector P2 (as per above in the Green Box) and Installers must be observant to ensure the correct connectors are used for their correct function."
• Confirm the silkscreen markings: "Below is an image of P2 clearly showing CT 3,4 to the left in white lettering on PCB."
• Strip connector P2 is located on the control board with clear white text indicating CT 3,4. Land the white and black secondary CT coil wires into pins 3 and 4 of connector P2.

Step 3: Inspect Connector P6 (Emergency Shutdown)

Examine the adjacent connector block:

• The manufacturer notes: "P6 is also shown for further clarity with 3,4 clearly marked as + and -"
• If you do not have an external emergency shutdown button installed, connector P6 should not have CT coil wires inserted. Ensure that pins 3 and 4 on P6 are not shorted by stray copper strands.

Step 4: Verify CT Wire Polarity on Connector P2

When inserting the CT wires into P2:

• Pin 3: Connect the positive (usually white) CT signal conductor.
• Pin 4: Connect the negative (usually black) CT return conductor.
• Verify that conductor insulation is stripped cleanly and that screw clamping terminals grip the bare copper firmly without pinching outer insulation.

Step 5: Execute a Clean System Restart

Once wiring is confirmed:

1. Reinstall the lower access cover and secure all fastening screws.
2. Turn on the battery DC isolator switch and allow the battery BMS to boot up.
3. Switch on the inverter power switch; verify that the screen illuminates and boots without the red Fault LED.
4. Switch on the AC grid breaker and DC solar array isolator.
5. Check the System Alarms screen on the touchscreen to ensure Fault 22 has completely cleared from the active fault queue.

Review our companion guide on /za/guides/fixes/sunsynk-fault-codes-explained for complete reference tables covering all operational warning and error codes.

Connecting a Genuine External Emergency Stop Button

If your site requires a genuine physical emergency stop button (common in commercial installations, school microgrids, and healthcare facilities under South African SANS standards):

For sizing considerations on commercial and residential installations, consult our comprehensive buying guides for /za/guides/buying/5kw-hybrid-inverter-buying-guide-south-africa and /za/guides/buying/8kw-hybrid-inverter-buying-guide-south-africa.

Conclusion: Checking Terminals Before Replacing Hardware

Fault 22 Tz_EmergStop_Fault can cause panic for installers who suspect internal hardware destruction. However, the solution is almost always straightforward:

• Never land CT coil cables into connector P6.
• Connect external CT sensor conductors strictly to pins 3 and 4 of connector P2.
• Always inspect PCB white silkscreen lettering before terminating control cables.
• Perform a full power-cycle restart after correcting control wiring.