What the earth leakage unit is telling you
An earth leakage unit, also called a residual current device (RCD), compares the current flowing out on the live conductor with the current returning on the neutral. If they differ by more than its setting, some current is going elsewhere, usually to earth, and the unit trips. Units set at 10mA or 30mA are the high-sensitivity types used to protect people, according to Sparks Electrical News's guide to earth leakage testing. Less sensitive settings, such as 100mA or 300mA, protect equipment and installations rather than people.
The test button injects a small imbalance to check that the mechanism trips. Sparks suggests testing domestic units somewhere between monthly and quarterly. It also notes that earth leakage tests are a legal part of the CoC and of any replacement.
A solar installation changes what the unit sees. There is now a second source of power, new wiring between the board and the inverter, often a separate essential board, and electronics that behave differently from the appliances the original board was designed around. Each is a possible source of an imbalance.
Safe checks you can do yourself
None of these involve opening the DB board, an isolator box or the inverter. Stop if anything is hot, smells burnt, crackles, or shows scorch marks, and call your installer.
- Note exactly when it trips. At the start of load-shedding? When the grid returns? After rain? When a particular appliance switches on, such as the geyser, washing machine or pool pump? At night, when the inverter switches from solar to battery? Write down the date and time. This pattern is the most useful thing you can give an electrician.
- Note which unit tripped. After a solar install there may be more than one earth leakage unit: one in the main board and one on the essential board. Tell the installer which one.
- Check the inverter app or screen for fault codes. Inverters monitor leakage themselves. Solis inverters, for example, show "Ileak-PRO" alarms when they detect residual current, according to Solis's RCD application note. Sunsynk's manual lists leakage current and PV insulation faults, and suggests checking the panel and inverter cables. Screenshot any code with the time it appeared.
- Unplug, don't just switch off. With the earth leakage unit reset, unplug everything on the affected circuits, then plug appliances back in one at a time, leaving each running for a while. Unplugging matters because many wall sockets only switch the live, so an appliance with a fault on its neutral side can still cause a trip while switched off at the wall. If the trip returns when one appliance goes back in, stop using it until it has been checked.
- Look at outdoor equipment from the outside. Check outdoor isolator boxes, the PV combiner box, outdoor sockets and garden lights for cracked covers, missing glands, open lids, signs of water inside a clear cover, or chewed cables. Don't open them, especially when wet.
- Call the installer. A new installation should be under the installer's workmanship warranty. Give them your notes, the fault codes and which unit tripped.
If the unit won't reset at all with everything unplugged, leave it off and call an electrician. That points to a fault in the fixed wiring or the installation, not an appliance.
What the timing tells you
| When it trips | Likely area | Who fixes it |
|---|
| When the inverter switches to battery, or back to the grid | Neutral-earth arrangement on the backup output, or the earth leakage unit's type, rating or position | Installer or registered electrician |
| When one appliance is used | That appliance, or the circuit it is on | Appliance repairer, or an electrician for the circuit |
| During or after rain | Moisture in outdoor isolators, sockets, lights or cable joints | Electrician |
| Randomly, more often since the install | Accumulated leakage on one unit, a shared neutral between circuits, or a damaged cable | Installer or registered electrician |
| Only on the essential board | Wiring of the essential board or the inverter's backup output | Installer |
This table is a starting point for the conversation, not a diagnosis. An electrician confirms the cause with insulation and earth leakage tests.
Likely causes after a solar install
The neutral-earth arrangement on the inverter's backup output
On the grid, your supply authority provides the link between neutral and earth. When a hybrid inverter runs during an outage, it disconnects from the grid, so its backup output needs its own neutral-earth reference. When the grid returns, that arrangement has to work with the grid's. If it is wrong, the earth leakage unit can see current returning by the wrong path and trip, often exactly at the moment of switchover.
Manufacturers handle this differently:
- Deye's manual for its SUN-7.6K and 8K single-phase hybrids says that in the off-grid state, "the N line needs to be connected to the earth", through an external relay on some hardware versions and a built-in one on others.
- Sunsynk's 3.6/5kW single-phase manual (v41, July 2024) includes a note headed "Only for South Africa". It recommends a permanent neutral-earth bond on the load output, in an external box clearly marked as such, and says the supply to the inverter's grid port "needs to be taken from the mains before the main RCD to prevent RCD from tripping".
The practical point: if your earth leakage trips at switchover, ask the installer to check the neutral-earth arrangement against the manual for your exact inverter model and the wiring code. This is design and wiring work, not something to adjust yourself. Our hybrid inverter explainer covers how the switchover works.
The wrong type or rating of earth leakage unit
Earth leakage units come in types, defined in IEC 60755, according to a Schneider Electric explainer on RCD types:
- Type AC detects sinusoidal residual current at mains frequency. These are general-purpose units in many countries.
- Type A also detects pulsating DC residual current from electronic loads with rectifiers, and tolerates a small amount of smooth DC (up to 6mA).
- Types F and B handle more complex waveforms, such as those from variable-speed drives in some heat pumps, pumps and EV chargers.
Inverter manufacturers specify what they expect, and they don't all say the same thing:
- Solis says its inverters are designed so they cannot feed DC residual current into the grid, and recommends an external Type A unit. For its single-phase S6-EH1P(3-10)K-L hybrids, the recommended rating is 100mA, according to the application note (updated 13 October 2026).
- Deye says its inverter has a built-in leakage current detection circuit, and that if an external leakage device is connected, "its operating current must be equal to 300 mA or higher, otherwise inverter may not work properly". Its wiring diagram shows a 300mA unit on the grid side as recommended.
- Sunsynk's single-phase manual carries the same 300mA warning for a device connected to the inverter, while an appendix recommends Type A, 30mA earth leakage protection on the circuits connected to the inverter.
These are not contradictions to resolve at home. They show why the installer has to read the manual for your model and design the protection for each part of the installation: the feed to the inverter, the essential board and the non-essential board. A 30mA unit placed where the manufacturer expects a less sensitive one can trip as soon as the inverter operates normally. The wrong type can fail to detect a fault it should catch. Both are reasons for a qualified review, not a quick swap.
Leakage from appliances adding up
Every appliance leaks a little current to earth, and electronic equipment more so. An ageing geyser element, a washing machine, a fridge compressor or an outdoor pump can leak enough on its own to trip a 30mA unit. After a solar install, the problem can be new for another reason: circuits that used to be spread across the board may now all sit on one essential-board earth leakage unit, so their small leakages add up on a single device.
The unplugging test above finds a single faulty appliance. If no single appliance is to blame but tripping is frequent, ask the installer whether too many circuits share one earth leakage unit.
A shared or crossed neutral
An earth leakage unit only balances if every circuit's live and neutral both pass through it. When circuits are moved onto a new essential board, a neutral can end up connected to the wrong board's neutral bar. The unit then sees the live current go out without its matching return, and trips, sometimes only when a particular combination of loads is on. This is a wiring fault for the installer to find and fix.
Moisture and damaged cables
Water in an outdoor socket, light fitting, cable joint or AC isolator box gives current a path to earth. If tripping follows rain, that is the first suspect. Cables can also be damaged during an installation, crushed under a roof sheet, nicked by a screw or chewed by rodents.
Faults on the panels' DC side tend to show up differently. They often appear as an insulation or leakage fault code on the inverter, rather than as a tripped earth leakage unit in the board. Sunsynk's manual, for example, lists a low PV insulation resistance fault and suggests checking the panel connections and earth bond cable, or a faulty panel with an earth short. Either way, water in outdoor electrical enclosures needs an electrician, and you should not open them yourself. Our guide to hail, lightning and surges covers weather damage to the wider system.
What must be done by a registered electrician
Anything beyond observing, unplugging and looking from the outside is electrical installation work. That includes:
- opening the DB board, the essential board, isolator boxes or the inverter's wiring compartment;
- replacing or changing an earth leakage unit, including swapping its type or rating;
- changing the neutral-earth arrangement on the inverter's output;
- moving circuits between boards or separating shared neutrals;
- insulation resistance and earth leakage testing to find the fault.
Under the Electrical Installation Regulations, 2009, a registered person must exercise general control over electrical installation work. Regulation 7 requires a CoC for at least any addition or alteration to an installation that already has one. Changing protection devices is an alteration. The Department of Employment and Labour's November 2025 notice says a CoC may only be issued after the inspections and tests needed to confirm compliance with SANS 10142-1. Sunsynk's manual says the same at the commissioning stage: before switching on, the installer must have completed the earth bond, RCD and earth leakage tests.
So the first call for a new installation is the installer. Ask them to return, test, fix the cause and update the CoC if the work changes the installation. Our electrical CoC guide explains what that paperwork should cover.
Why you should never bypass an earth leakage unit
When an earth leakage unit trips repeatedly, someone may suggest bridging it out, removing it, or moving circuits off it "for now". Don't agree to it.
The earth leakage unit is the device that switches off the supply when current flows to earth through a person. Without it, a fault that would have caused a trip can instead leave a metal appliance case, a wet outdoor fitting or a damaged cable live. Eskom's fact sheet on selecting the right type of generator warns that people who switch off the earth leakage unit to get alternative power into the house leave their family without earth leakage protection, at high risk of electrocution. The same logic applies to an inverter installation.
There is a paperwork risk too. An installation with protection removed no longer matches its CoC and test report, which matters if you claim on insurance after a fire or sell the house. Our solar insurance guide covers what insurers ask about.
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Get your free quote →What to ask your installer
- Which earth leakage units protect the inverter feed, the essential board and the non-essential board, and what type and rating is each?
- Do those match the inverter manufacturer's requirements for my model?
- How is the neutral-earth connection on the backup output arranged, and does it follow the manual and the wiring code?
- Are all the essential circuits' neutrals on the essential board's neutral bar?
- How many circuits share each earth leakage unit?
- What did the insulation and earth leakage tests show?
- Is the call-out covered by your workmanship warranty, and will I get an updated CoC if you change anything?
If your original installer is no longer trading, a registered electrician can inspect and test the installation. If you are still choosing an installer for a new system, look for one who documents the protection design and testing at handover. Alumo supplies, installs, finances and warrants the systems it installs, so ask its advisor to show the protection devices, testing and CoC in the quote. Compare an installed, certified system for your home →
Frequently asked questions
Why does my earth leakage trip when load-shedding starts or the power comes back?
Tripping at the moment the inverter switches between grid and battery usually points to the neutral-earth arrangement on the inverter's backup output, or to the type, rating or position of the earth leakage unit protecting the inverter's circuits. Both are installation design questions. Note the times, check the inverter for fault codes and ask your installer to check against the manual for your model.
Can I replace the earth leakage unit myself with a less sensitive one?
No. Changing a protection device is electrical installation work that a registered person must do or control, and it is an alteration that needs a CoC. A less sensitive unit in the wrong place can also leave people unprotected. Let an electrician find the cause and choose the right device for each part of the installation.
Is it safe to keep resetting the earth leakage?
Resetting once to see whether it holds is reasonable. Repeated tripping means something is leaking current, so keep resetting to a minimum, unplug suspect appliances, and get the installation tested. If it won't reset with everything unplugged, leave it off and call an electrician.
Will my warranty cover the call-out?
For a recent installation, a wiring or protection fault is usually a workmanship issue for the installer. Check your workmanship warranty and handover pack. Our solar warranties guide explains the difference between product and workmanship warranties.
Is SolarGuide the installer?
No. SolarGuide is an independent referral partner. Alumo supplies, installs, finances and warrants the systems it installs. We help you compare options and get a free quote. We can't diagnose or repair an existing installation; for that, contact your installer or a registered electrician. All pricing is indicative and subject to a site assessment and credit approval.
Sources and review note
Checked on 21 October 2026. Earth leakage sensitivities, the test button and testing frequency are from Sparks Electrical News (9 December 2021). RCD types are from Schneider Electric's explainer (25 April 2019). Manufacturer requirements are from the Solis Application Note for External RCD Selection (modified 13 October 2026), the Deye SUN-7.6/8K-SG01LP1-EU user manual and the Sunsynk 3.6/5kW single-phase hybrid user manual v41 (19 July 2024, distributor-hosted copy). The earth leakage warning is from Eskom's fact sheet Selecting the right type of generator (February 2015). Legal requirements come from the Electrical Installation Regulations, 2009, regulations 5 and 7, read on Acts Online, and the Department of Employment and Labour's notice of 21 November 2025. We have not published figures on how often earth leakage trips after solar installations, or repair costs, because we found no reliable South African source. This guide helps you describe the problem and know who should fix it. It is not wiring or repair instruction, and it does not replace testing by a registered electrician who has seen your installation.
SolarGuide is an independent referral partner. We help you compare options and arrange a free quote — Alumo supplies, installs, finances and warrants the systems. Pricing is indicative, sourced from Alumo’s published catalogue, and subject to a site assessment and credit approval.
