Sunsynk and Deye Inverted Load and Doubled Grid Load Reading Fix

Key Takeaways

• If phase rotation direction is correct but individual phase lines L1, L2, and L3 are swapped relative to their CT sensors, solar export registers as artificial load demand.
• Extending analogue CT cables with CAT-6 network wire can double the displayed load reading if solid color and striped color/white cores are mixed in parallel.
• Paralleling cores reduces secondary circuit resistance over runs exceeding 10-15 metres, but extensions longer than 15 metres should transition to external Modbus energy meters.
• The arrow on the Sunsynk CT clamp must point away from the grid and toward the inverter; reverse placement inverts power direction vectors.
• Adjacent current transformers from EV chargers or third-party energy monitors must be spaced at least 12 inches apart to prevent mutual magnetic induction.

Diagnostic Symptoms: Inverted & Doubled Telemetry

Accurate power measurement is the cornerstone of hybrid inverter operation. Sunsynk and Deye hybrid inverters rely on external current transformers (CT clamps) or digital power meters to regulate battery charging, enforce zero-export limitations, and display residential power flow.

When CT wiring geometry or phase alignment is compromised, two distinct telemetry anomalies frequently occur:

1. Load Climbs with Solar Export: As solar production ramps up and surplus energy flows outward toward the municipal grid, the displayed household consumption climbs in direct proportion rather than staying flat or declining.
2. Doubled Grid Load: The displayed grid load is consistently double the actual power measured by utility billing meters or handheld clamp instruments, distorting power flow calculations.

Both anomalies originate from physical wiring mistakes rather than internal microprocessor hardware failures.

Issue 1: Three-Phase Sequence Misordering (Export Increases Load)

In three-phase commercial and residential installations, the relationship between AC voltage phase rotation and current measurement is critical. If the rotational direction of the grid supply is completely inverted (anti-clockwise instead of clockwise), the inverter software trips an immediate fault code (such as W03 Grid Phase Error).

However, a more subtle defect occurs when the rotational direction is technically correct, but the individual phase assignments—L1, L2, and L3—are misordered between the AC grid terminal block and the respective CT sensor inputs.

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When this mismatch exists:

• The voltage wave for Phase 1 is paired with the current waveform of Phase 2 or Phase 3.
• The calculated vector dot-product reverses sign.
• Instead of registering outgoing current as solar export, the software computes the current as an active domestic load drawing power from the utility.

Structured Diagnostic Testing Procedure

To rectify phase sequence misordering, the field installer will require a clamp meter to read L1, L2 and L3 directly at the incoming distribution board.

Electrical Safety Caveat

Live Panel Working Hazard: Testing current and voltage across three-phase distribution busbars involves lethal AC potential. Only qualified, registered electrical personnel wearing certified personal protective equipment should open main panel covers and position clamp meter jaws around uninsulated conductors.

1. Eliminate Solar and Battery Variables:

• Isolate all rooftop PV strings by turning the rotary DC isolators to the OFF position.
• Access the inverter touchscreen and open Settings > System Mode.
• Set the battery target SOC in the active system timer to 100%. This commands the inverter to charge solely from the utility supply, ensuring that 100% of power is drawn directly from the grid and eliminating any masking from solar export.

2. Apply a Predictable Pure Resistive Load:

• Turn on a consistent, high-draw appliance on one phase (such as an electric kettle or resistive space heater).

3. Compare Physical Readings with Inverter Telemetry:

• Measure actual current draw on L1, L2, and L3 using the handheld clamp meter.
• Click the AC Load dial at the top right of the home screen on the inverter LCD display. This expands the live telemetry screen, showing individual phase current and power values for L1, L2, and L3.
• Check whether the displayed loads match closely to the clamp meter to determine how accurate they are.

4. Correct Phase Cable Order:

• If the load applied to physical conductor L1 appears under L2 or L3 on the touchscreen, de-energise the main AC supply.
• Swap the corresponding CT coil leads or re-terminate the incoming AC phase conductors until physical phase measurements match the digital telemetry channels point-for-point.

Issue 2: CAT-6 Double-Helix Core Induction (Doubled Load Reading)

A common installation challenge in South African properties is physical distance between the main electrical distribution board (where the utility meter sits) and the inverter mounting location (often an outbuilding or garage). Installers frequently extend the factory CT clamp cable using unshielded twisted pair (UTP) network cables, such as CAT-6.

When extended over long runs, multiple copper cores are often paralleled together to reduce overall loop resistance and ensure an accurate reading from the secondary winding of the CT coil, particularly when the extension length is greater than 10-15 metres.

However, improper core pairing within CAT-6 cabling creates a bizarre physical phenomenon where the load appears exactly double what is expected.

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The Double-Helix Mechanism

CAT-6 network cables are manufactured with precise helical twists to reject external electromagnetic interference. Critically:

• The solid color core and its matching striped color/white core have opposite helix winding directions.
• If an installer connects multiple cores in parallel, solid color cores can be connected in parallel, and striped color/white cores can be connected in parallel.
• But mixing solid color cores with striped color/white cores in the same conductor leg causes electromagnetic induction interference.

Because the solid core and striped core spiral in opposite directions, the alternating current passing through the secondary loop interacts with the opposing helix geometry. The inverter sensing circuitry perceives this as two distinct, additive signals entering the CT coil pins, effectively doubling the displayed load measurement.

Standard Wiring Recovery

To restore true load metrics:

1. Strip back the CAT-6 extension terminations at both ends.
2. Dedicate one solid color core (e.g. solid blue) to the positive CT lead, or parallel exclusively with other solid cores (e.g. solid blue + solid orange).
3. Dedicate the matching striped core (e.g. blue/white) to the negative CT lead, or parallel exclusively with other striped cores (e.g. blue/white + orange/white).
4. Never cross-couple solid and striped strands into a single conductor bundle.

Distance Threshold: Analogue CT vs External Digital Meter

While core paralleling allows extending analogue CT leads across moderate distances, there is a strict operational limit:

The 15-Metre Rule: If the distance between the main electrical incomer and the hybrid inverter exceeds 15 metres, analogue CT extension is strongly discouraged. Beyond 15 metres, cable capacitance, radio frequency interference, and cumulative resistance degrade sensor accuracy.

When runs exceed 15 metres, installers should replace the analogue CT clamp with an external digital energy meter (such as an Eastron SDM series meter) communicating via RS485 Modbus RTU shielded serial communication. Digital data frames transmitted over RS485 remain completely impervious to the induction artifacts that plague extended analogue CT cables.

Physical CT Placement, Arrow Orientation & Clearances

In addition to core configuration, the physical location and spatial clearances of the CT sensor dictate measurement fidelity.

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Main Incomer Location

The CT clamp must always be installed on the main incoming live conductor of the property ahead of any Henley splitter blocks, changeover switches, or sub-distribution boards. This allows the inverter to monitor total household power draw as well as gross import and export before energy enters or leaves the premises.

Arrow Orientation

If using the standard CT clamp supplied with the Sunsynk inverter, observe the physical arrow molded into the plastic sensor housing:

• The arrow must point away from the utility grid and towards the inverter / main distribution board.
• If the clamp is snapped over the cable in reverse orientation, all power vectors flip: consumption reads as export, and export reads as load.

12-Inch Separation from Adjacent Sensors

In modern South African households equipped with EV chargers, backup generators, or solar diverters, multiple current sensors may be clamped along the same meter box panel.

If third-party CTs are installed nearby, they must be spaced at least 12 inches apart from each other along the cable run. Placing two CT clamps directly adjacent allows the magnetic core flux of one sensor to couple into the neighboring winding, distorting current calculations on both devices.

Cable Routing Prohibitions

• Never Coil Excess Cable: Excess CT wire must be trimmed to length or laid in wide, loose serpentines. Coiling excess CT cable forms an air-core inductor that amplifies harmonic noise.
• Maintain Physical Separation: Route CT signal wiring well away from high-voltage AC mains wiring, generator feeder conduits, and noisy motor cables.

Inverter Terminal Pinouts & Selling First Mode Settings

At the base of the Sunsynk inverter, the CT wiring terminates into a dedicated multi-pin connector block:

• Standard single-phase inverters use a removable grey connector strip.
• Consult the user manual to verify port assignments; standard single-phase models terminate the white CT lead into port 3 and the black CT lead into port 4.
• Ensure terminal screws clamp firmly onto the copper conductors without crushing insulation.

The "CT Connected" Setting in Selling First Mode

A software setting that frequently causes confusion occurs when the inverter is operated in Selling First mode (prioritising full battery export and maximum solar sale to the grid):

In Selling First mode, older firmware profiles defaulted to ignoring the external CT clamp, assuming that all generated power should discharge indiscriminately into the grid connection. In current Sunsynk Connect software:

• Ensure the CT Connected toggle option is explicitly enabled within the power flow configuration menu.
• If Selling First is active without the CT Connected option enabled, the system microprocessor bypasses all external CT measurements, leading the user to believe the sensor has failed.

Summary Diagnostic Checklist

By executing a structured three-phase clamp test, eliminating improper CAT-6 core pairing, respecting the 15-metre external meter limit, and observing 12 inches of sensor spacing, technicians can guarantee flawless power flow telemetry and eliminate doubled or inverted load readings.