How should a diesel or petrol generator interlock with a home hybrid solar system in South Africa?

Answer first: Put changeover / ATS, generator make/model, earthing and who trains the household on the quote — ATS / changeover · diesel vs battery · dual-supply labels.

Safe patterns

• Break-before-make changeover between grid and generator, with the hybrid in the OEM-supported topology.
• OEM generator input (often with current limits) charging batteries while solar is offline.
• Clear labelling so a locum electrician does not invent a third path at 21:00.

Unsafe patterns

• Backfeeding the DB through a stove plug.
• Two sources tied without interlock.
• Floating neutrals that trip RCDs or shock.
• Undersized earth spikes for a floating generator frame.

Sizing notes

Generators hate hard surge loads (borehole, compressor, some heat pumps). Battery hybrids often start those loads more cleanly; the generator then replenishes the battery at a steady kW — borehole · Stage 6 · runtime tool.

Fuel maths belongs on the brief

Hours of Stage × litres/hour × rand/litre quickly exceeds battery wear for many suburban homes. Keep the generator for deep storms and long Stage stacks, not every 2-hour slot — fuel cost desk.

CoC and estate rules

Estates may limit generator hours and noise. CoC must reflect the dual-supply arrangement — CoC · sectional title · holiday home.

Commissioning tests

1. Grid → island → generator → grid sequences.
2. RCD / earth continuity checks.
3. Battery charge-from-generator proof with voltage/Hz logged.
4. Household training: who may start it, where fuel is stored.

Desk closing

Interlock is a safety line item, not an accessory — get quotes · check a quote · red flags.

Installer questions to send today

• Show me the setting / document / photo that proves this works on my DB.
• Price the labour and any refile risk as separate lines.
• Put the OEM manual page reference on the as-built.
• Train a household member and leave the password escrow note.

Related desk links

Read a quote · Choose installer · Red flags · Costs & savings · FAQ.

Worked homeowner checklist

1. Photograph the relevant breaker, CT, inlet or portal screen today.
2. File the screenshot with the CoC and SSEG pack.
3. Ask two installers the same question and compare written answers.
4. Refuse verbal-only assurances on compliance settings.

Why hybrids + generators still make sense in SA

Batteries cover most Stage 2–4 evenings; generators cover multi-day storms, deep Stage stacks and rural feeders where solar resource is weak for a week. The interlock is what keeps that pairing legal and safe — fuel vs battery · Stage 4 · Stage 6.

OEM generator modes to ask about

• Voltage and frequency windows the hybrid will accept.
• Maximum charge current from generator into the battery.
• Whether PV can operate in parallel with generator on that model.
• Warm-up and cool-down timers to protect the engine.
• Dry-contact or ATS start signals if automated.

Earthing and neutral topology

Floating portable generators, MEN links and RCD behaviour interact badly when improvised. Your electrician must draw the neutral/earth scheme for grid, island and generator states on the single-line — earthing · labels · CoC.

Noise, estates and neighbours

Body corporates and estates often cap generator hours and dB levels. Factor acoustic placement and exhaust direction before you buy a 10 kVA unit that can only run at 05:00 — sectional title · holiday home.

Fuel logistics checklist

1. Stable storage (legal volumes, ventilated).
2. Stabiliser plan for petrol units that sit for months.
3. Runtime maths at 50% load, not brochure 25%.
4. Who refuels during a multi-day outage.

Quote lines that must appear

Changeover/ATS hardware, inlet socket, earth upgrade, OEM generator-mode commissioning, household training and a test tank of fuel. “Client supplies generator” without interlock design is how unsafe DIY starts — red flags · read a quote.

After commissioning

Run a full grid→island→generator→grid drill twice a year. Log voltage, Hz and battery charge current. Replace transfer gear that arcs or hesitates — monitoring · load shedding hub.

South African primary documents to keep nearby

Metro SSEG guidelines, NRS 097 inverter listings, OEM manuals, and your CoC are the primary sources. Desk pages here translate those into homeowner checklists — they do not replace them. When a figure on a quote disagrees with the live metro schedule, the metro wins.

How this page should change your next email

Forward the checklist sections to your installer and ask for written replies against each bullet. Vague “we handle that” answers are why handover packs fail at sale or inspection time. Serious firms answer with model numbers, photo proofs and document names.

Numbers to write on one page before you pay a deposit

• Relevant kW / kWh / limit values named on the quote.
• Who commissions and who signs the CoC.
• Which photos will exist on handover day.
• Which municipal or OEM form will be filed.
• What happens if approval lags (zero-export / export-limit plan).

Related: choose installer · install timeline · FAQ · contact.

Worked Stage evening script

1. Hybrid islands essentials on battery at Stage start.
2. If SoC hits your reserve floor, ATS starts or you manually start the generator.
3. Hybrid charges from generator within OEM current limits.
4. When grid returns, break-before-make back to utility; generator cools down.

Practise that script in daylight once. The first time should not be during Stage 6 rain — load shedding · essentials · runtime tool.

Document fuel burn from that drill so your diesel-vs-battery spreadsheet uses your machine, not a brochure — fuel desk.

Desk cross-links worth opening next

Read a quote · CoC · SSEG need · zero-export · ATS · selling · costs & savings · batteries.

Educational ranges only — confirm live metro, Eskom and OEM documents the week you sign. Brands named here come with a checkable fact; they are not national rankings.

Insurance and disclosure

Schedule the generator and the hybrid together. Undeclared dual-supply arrangements complicate claims after a fire or surge — insurance · surge · claims.

Keep the ATS model, inlet rating and earth test results with the CoC so a claims assessor does not invent a story for you.

Handover sentence for the CoC pack

“Break-before-make ATS model [x], generator inlet [A], hybrid generator-mode enabled, earth test [value], household trained on [date].” File it with dual-supply label photos — labels · CoC · ATS.

Hybrid genset input vs changeover

Some hybrids accept a generator on a dedicated input with soft-start and anti-islanding logic; others need a break-before-make changeover so the genset never parallels the grid. Mixing the two stories is how ATS contacts weld and CoC inspectors fail dual-supply labelling — ATS / changeover · dual-supply labels · diesel vs battery.

Rand and tariff check

Before you resize hardware, open your latest municipal bill and the live metro tariff PDF. Fixed charges and TOU bands often move the payback more than a brochure kWh figure — fixed charges · monthly savings · export vs self-use · tariffs 2026 · metro tariffs · costs & savings.

Handover file

Keep CoC, dual-supply photos, export-limit screenshot, CT polarity photo, firmware version and guest monitoring login with the invoice — CoC · export limit · CT clamps · labels · guest monitoring · check a quote.

Lock the decision rule into the handover pack

Write one clear operating rule for this topic — what stays on, what stays off, which setting is correct, and who to call. Store it with the CoC and monitoring login. Households that rely on memory fail the first awkward Stage 4 evening.

Revisit the rule when you add loads or change tariff. Stale rules create expensive surprises on the next bill.

Quick questions

Portable vs standby — different interlock stories

A wheeled petrol set on an inlet still needs break-before-make and earth discipline. A fixed diesel with auto-ATS needs commissioning logs and estate noise rules. Do not copy a farm topology onto a complex suburban DB without redrawing the single-line — ATS · farm solar · earthing.