Sunsynk & Deye Generator Auto-Start (ATS) Wiring & Troubleshooting Guide

Automating an auxiliary backup generator is a cornerstone of resilient solar microgrid engineering in South Africa. When extended utility load shedding overlaps with adverse weather, an automated standby generator ensures battery storage is never depleted past critical recovery thresholds.

Sunsynk and Deye hybrid inverters incorporate integrated programmable dry-contact relays specifically engineered to command an external Automatic Transfer Switch (ATS) or generator remote-start control panel. However, commissioning these circuits frequently poses challenges: generators failing to crank on low battery signals, relay contactors remaining open, or control loops refusing to close.

This technical engineering guide details the mechanical sizing rules, dry-contact wiring terminals (G-S and G-V), diagnostic continuity loop tests, and factory reset recovery procedures for Sunsynk and Deye generator auto-start circuits.

1. Electrical Sizing: The 2x Inverter Power Rule

A frequent mistake in residential and small commercial installations is pairing a hybrid inverter with an undersized standby generator.

```
[ Inverter Sizing Rule ]
Hybrid Inverter Rated AC Output: P_inv
Recommended Generator Sizing: 2x P_inv

Example: 5 kW Hybrid Inverter ──► 10 kVA Generator
Example: 8 kW Hybrid Inverter ──► 16 kVA Generator
Example: 12 kW Hybrid Inverter ──► 24 kVA Generator
```

As specified in official engineering recommendations:

When installing a generator we advise using a generator with twice the rated output of the inverter power to allow for batteries to be charged in conjunction with powering the loads.

Technical Rationale

• When a generator starts and synchronizes with the inverter, it must simultaneously supply active household consumption and deliver substantial DC charging current to replenish the depleted battery bank.
• If an installer pairs a 5kW generator with an 8kW inverter, the moment heavy domestic loads (such as borehole pumps or heating elements) cycle on while the battery is charging, the generator's mechanical governor is overwhelmed, causing rapid frequency and voltage collapse.
• Sizing the generator at roughly twice the inverter's continuous rating provides the mechanical rotational momentum required to handle load transients without stalling.

2. Hardware Wiring: The GS and GV Dry Contact Ports

The hybrid inverter triggers generator auto-start via a voltage-free dry-contact relay situated on its auxiliary communication terminal block:

```
+──────────────────────────────────────────────────────────────────────────+

+──────────────────────────────────────────────────────────────────────────+

+───────────────────────────+──────────────────────────────────────────────+

+───────────────────────────+──────────────────────────────────────────────+
```

As detailed in manufacturer installation instructions: to connect the auto-start you must use the connection pins on your inverter labelled g-s or g-start. (Note: On certain single-phase low-voltage inverter variants, this start trigger signal may instead operate on terminals labelled G-V or G-Valve).

Critical Installation Caveats

1. Auto / Standby Generator Selection: The auto-start feature cannot operate a purely manual pull-start or manual key-start generator. The generator must possess an electronic control module (e.g., Deep Sea Electronics, ComAp, or Smartgen) with its selector switch set to Auto or Standby.
2. Voltage-Free Signal: The G-S terminals are dry contacts (an electronic switch), not a 230V AC power source. Wiring mains voltage directly across these pins will destroy the inverter's internal relay board.

3. Diagnostic Testing & Troubleshooting Sequence

If the generator fails to initiate when the battery state of charge drops below the trigger threshold, follow this systematic diagnostic sequence:

```
[ Step 1: Manual Short-Circuit Loop Test on Trigger Leads ]
│
▼
[ Step 2: Inverter Setting Verification (Aux Load & Battery Menus) ]
│
▼
[ Step 3: Continuity Multimeter Test Across GS / GV Terminals ]
│
▼
[ Step 4: Factory Reset via Code 9999 to Clear Latched Firmware Relay ]
│
▼
[ Step 5: Cold Battery-Only Reboot to Re-engage Normal Operation ]
```

Step 1: The Loop Closure Verification

Before diagnosing inverter firmware, verify that the generator's remote-start circuitry is operational:

• Disconnect the two ATS trigger wires from the G-S pins on the inverter.
• Short the two stripped wire ends together using an insulated jumper.
• If the generator control panel is healthy, the generator should crank and start up smoothly within 15 to 30 seconds.
• If the generator fails to crank when the wires are shorted, the fault lies in the generator's starter battery, fuse, or control board settings.

Step 2: Triggering the Inverter Relay for Testing

To force the inverter to command a start:

• Access the Aux Load menu and locate the On Batt setting.
• Access the Battery Settings menu and locate the Gen Start setting.
• Set both parameters to a percentage value comfortably above the current state of charge of the batteries.
• As documented in service bulletins: these settings should close the lv relay on the gs / gv pins as the gen start trigger.
• With the trigger wires disconnected, test for continuity across the G-S terminal pins using the continuity beeper mode of a digital multimeter. The multimeter should confirm a short-circuit (closed contact).

4. Restoring Latched Relays: Factory Reset Code 9999

Occasionally, electrical noise, lightning surges, or firmware updates cause the inverter's internal auxiliary relay driver to latch in an unresponsive open state. When this occurs, clearing the microcontroller state requires a formal factory reset:

Factory Reset Execution

1. Navigate to the Basic Settings screen on the inverter LCD display.
2. Select the Reset tab and toggle the factory reset option to enable.
3. When the numerical security authorization prompt appears: enter code 9999 and the inverter will be set to factory defaults.
4. The internal alarm beeper will emit a continuous tone confirming that the parameters have been reset. (If desired, silence the alarm by selecting Beeper Off in basic settings).

Cold Reboot Sequence

1. Power cycle the inverter: turn off the physical rocker power button on the side of the chassis, isolate AC grid feeds, and isolate solar PV DC isolators.
2. Wait for the LCD touchscreen display to extinguish completely.
3. Reboot the inverter strictly from battery power alone.
4. Allow approximately four minutes for internal microprocessors to complete self-checks and observe that the green Normal LED illuminates.
5. Restore original grid and battery parameters. Re-test the G-S terminals with a multimeter—the relay will now close reliably in response to low battery commands.

Summary Checklist

• Generator capacity verified to provide roughly 2x inverter rating for simultaneous load and charging support.
  
• Generator control panel confirmed set to Auto or Standby mode.
  
• Two-wire start leads connected to voltage-free G-S (or G-V) terminal pins.
  
• Direct loop short-circuit test performed to verify generator starter operation.
  
• Relay continuity confirmed under low SOC trigger conditions.
  
• Factory reset code 9999 executed if internal relay driver fails to respond.