What are CT clamps for home solar and hybrid metering in South Africa?

Answer first: On commissioning day, photograph each CT, its arrow direction, and the breaker it references. Those photos save hours when export-limit misbehaves — export limits · bi-directional meters · single vs three-phase.

What CTs are for

• Self-consumption control (solar follows loads).
• Export-limit / zero-export enforcement.
• Portal charts that separate import, export and solar.
• Sometimes generator or essential-board logic on advanced hybrids.

Install details that matter

1. Clamp the grid feed, not a random subcircuit.
2. Match CT ratio to the OEM manual.
3. Respect arrow / labelling toward the grid or load as specified.
4. Keep signal cables away from noisy DC runs where the OEM warns.
5. Record phase colours on three-phase boards.

Symptoms of a wrong CT

Portal shows export while the municipal meter shows import, export-limit never settles, or the battery charges from grid unexpectedly at noon. Fix with the installer — do not “guess flip” arrows — monitoring · grid charge.

Related reading: grid-charge & shedding hub.

CTs vs municipal meters vs prepaid tokens

Inverter CTs do not replace City Power / Cape Town / Eskom billing meters. Prepaid token behaviour after SSEG is a separate conversation — prepaid + solar · SSEG timelines.

Expansion and second inverters

When you add a second hybrid or move the DB, CTs often need redesign. Put that in the expansion path on day one — expand later · DB upgrade cost.

Desk closing

Demand CT photos in the as-built pack — get quotes · check a quote · CoC.

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.

Single-phase vs three-phase CT layouts

Single-phase homes usually need one correctly oriented CT on the main live. Three-phase hybrids typically need a matched set — one per phase — with phase rotation documented. Mixing CT brands or ratios without OEM approval is a common silent failure — single vs three-phase · NMD.

Where not to clamp

• On the inverter AC output only (misses house load from grid).
• On a geyser circuit you hoped to “prioritise” without OEM support.
• Downstream of a changeover that leaves the CT dark on generator — unless the OEM topology says so — generator interlock · ATS.

Cable distance and noise

Long CT extension runs next to DC strings can inject noise. Follow the OEM max length, shielding and ferrite notes. If the portal flickers between import and export every few seconds on a calm day, suspect signal integrity before you rewrite export limits.

Prepaid tokens and “phantom export”

Homeowners sometimes see inverter export charts while prepaid tokens still drain because the municipal meter path differs from the CT path. Believe the utility meter for money; use the CT path for control — then reconcile both with the installer — prepaid · token tips.

As-built minimums

1. Photo of each CT on the conductor with arrow visible.
2. Label sticky with phase colour and CT ratio.
3. Settings screenshot linking CT input to export-limit.
4. Torque / strain-relief note if required by OEM.
5. Replacement part number for the CT set.

Maintenance

After DB upgrades, EV charger adds or generator installs, re-verify CTs. A board swap that “kept the same wires” often rotates a phase or leaves a CT on the wrong feeder — DB upgrade · EV charger · inspection fails.

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 fault tree when charts look wrong

1. Compare inverter import/export to the municipal meter for the same hour.
2. Inspect CT arrows and phase colours against commissioning photos.
3. Check export-limit value has not drifted after a firmware update.
4. Confirm no temporary leads bypass the clamped conductor.
5. Only then retune self-use schedules or battery grids.

Most “my solar is broken” tickets after a DB change are CT tickets — DB upgrade · export limits · inspection fails.

Keep a spare OEM-approved CT set SKU on the as-built so a future electrician does not improvise with an HVAC clamp from the bakkie.

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.

EV chargers and CT priority myths

Some marketing claims a second CT will “always put the car on solar first.” Only OEM-supported load-management features do that reliably. Otherwise the wallbox is just another load the self-use algorithm may or may not catch — EV load management · charger cost · TOU / prepaid EV.

Photograph the charger feed and the grid CT together so future electricians see both.

Handover sentence for the CoC pack

“CTs photographed on phases L1/L2/L3 (or single live), arrows toward grid per OEM, ratio X:Y, export-limit proof test passed at 0 kW on [date].” That one sentence prevents half the callbacks we see after board changes — CoC · export limits · read a quote.

Commissioning photos that prevent month-one fights

Photograph CT orientation arrows, clamp position relative to the grid feed, and the inverter’s CT ratio setting before covers close. Wrong polarity makes “export” look like import and wrecks self-use automation. After firmware updates, re-verify — firmware updates · export limits.

Practical next steps this week

• Open the live metro SSEG/tariff PDF and tick what your quote already matches.
• Export one week of monitoring CSV so peaks and Stage windows are visible.
• Photograph the DB, labels and serials before any further work starts.
• Write three questions for the installer; do not accept shrug answers on CoC or export limits.

choose installer · read a quote · check a quote · get quotes · CoC.

How this ties to Stage and tariffs

Every hardware choice should survive your worst Stage cluster and your metro’s fixed charges. Self-use usually beats weak export credits — Stage strategy · fixed charges · export vs self-use · metro tariffs · tariffs 2026.

Quick questions

Smart meters and CT coexistence

Municipal AMI / bi-directional meters and inverter CTs measure different jobs. Never move a CT onto the municipal meter tails without the OEM and electrician agreeing — billing disputes follow — bi-directional meters · export limits.