ZST-ACC-TA
ZCS Azzurro ZST-ACC-TA current transformer with a 16 mm internal diameter, for single-phase storage systems and for the zero-export function on ZCS Azzurro hybrid and retrofit inverters.
It clips around the live conductor alone, without breaking the circuit. Single-phase systems need one CT; three-phase systems need three. For larger cables, 24 mm and 36 mm versions are available.
The ZCS Azzurro ZST-ACC-TA is the split-core current sensor that lets ZCS Azzurro inverters read the current drawn by the installation and regulate energy flow accordingly. It is the component that enables intelligent self-consumption on storage systems and the export limitation function on installations that must not feed energy back to the grid.
What the CT does
The sensor clips around the live conductor and measures the current passing through it by induction, without cutting or breaking the cable. The inverter receives this reading and knows at any moment how much energy the installation is drawing.
Two practical functions follow. On storage systems, the inverter decides whether to charge the battery, feed the loads or export to the grid. In zero-export mode, the inverter produces only the energy actually being consumed: the typical configuration for micro installations, sites without an export agreement and systems awaiting grid connection.
Which diameter you need: 16, 24 or 36 mm
This is the check to make before ordering. The ZST-ACC-TA has a 16 mm internal aperture, adequate for most cable sizes used in single-phase residential work. If the live conductor to be clamped has a larger outside diameter, the sensor will not close and you need the larger ZST-ACC-TA-24 (24 mm) or ZST-ACC-TA-36 (36 mm) versions.
Be careful to measure the overall outside diameter of the insulated cable, not the copper cross-section: a 16 mm² cable with insulation can comfortably exceed 16 mm of physical bulk.
How many CTs are needed
- Single-phase system: one sensor, on the live conductor
- Three-phase system: three sensors, one per phase
- Three-phase HYD hybrids use dedicated larger CTs (ZST-ACC-TA3PH200 and ZST-ACC-TA3PH600)
ZST-ACC-TA technical specifications
| Type | Split-core current transformer |
| Internal diameter | 16 mm |
| Application | Single-phase storage, zero export, hybrid and retrofit inverters |
| Installation | Clips onto the live conductor only, without breaking the circuit |
| Quantity required | 1 single-phase, 3 three-phase |
| Larger versions | ZST-ACC-TA-24 (24 mm), ZST-ACC-TA-36 (36 mm) |
| Weight | 0.5 kg |
Installation notes
- The CT goes downstream of the utility meter, so it reads the total consumption of the installation
- Clamp only the live conductor: including the neutral cancels the reading
- Observe the direction marked on the sensor body, otherwise import and export are reversed
- Verify the values read by the inverter with a known load switched on once installation is complete
Frequently asked questions
How do I know whether 16 mm is enough?
Measure the outside diameter of the insulated live conductor at the point where the sensor will sit, not the copper cross-section in mm². If it exceeds 16 mm the CT will not close and you need the ZST-ACC-TA-24 or ZST-ACC-TA-36 version.
Do I have to cut the cable to install it?
No. The sensor has a split core and clips around the cable already in place, without cutting or stripping it. This is still work on a live electrical installation and must be carried out by qualified personnel after isolating the circuit.
How many sensors does a three-phase system need?
Three, one per phase. With a single CT the inverter would read the consumption of one phase and attribute it to the whole installation, badly distorting self-consumption or zero-export regulation.
What is the difference between the CT and the ZSM-METER?
The CT is only the current sensor, wired directly to the inverter on systems designed for it. The meter is a complete DIN-rail energy counter with display and RS485 communication that processes and transmits the measurement. Check your inverter documentation to see which is specified: they are not interchangeable.
Can I use it with a non-ZCS inverter?
The ZST-ACC-TA is sized and calibrated for ZCS Azzurro inverters designed to use it. On other brands the transformation ratio and the parameters expected at the input may differ, so the reading would not be reliable.