Where should the grid CT clamp go on a solar or battery install?
Short answer
Clamp the grid CT on a single conductor of the incoming meter tail, usually the line, between the meter and everything else, with the arrow pointing as the manufacturer specifies (commonly toward the house or away from the grid). Every import and export must pass through it, so no circuits or other generation may connect upstream unless deliberately planned.
Last checked 24 September 2026 · 1 source
In more detail
- Check the arrow direction against the manual; a reversed CT shows import as export and breaks limitation and self-consumption.
- Only one conductor through the clamp (not the whole tail pair).
- Loads wired upstream of the CT (e.g. some EV chargers) are invisible to the battery - sometimes deliberate to stop the battery discharging into a car.
- MIS 3012 cl.3.5.21: treat CTs and wiring as LV Band II unless SELV is confirmed; cl.3.5.22 secure against accidental removal.
- Direction and placement conventions are manufacturer-specific; verify in the inverter manual.
The facts, dated
- 01CTs and CT wiring treated as LV (Band II) unless manufacturer confirms SELV/PELV — cl.3.5.21
standard · UK · checked 24 September 2026 · MCS
What we saw in the field
[QA review 2026-09-24] P-12 AGREES partly (corrected): 'pointing towards the house' is right only for brands that specify it; Fox ESS specifies towards the grid. | Earlier notes: Plug-in field install: DIN-rail meter with CT on the line conductor pointing towards the house - agrees. Customer 2: some chargers wired upstream of the battery so it does not drain into the car - addition.
Sources
Last checked: 24 September 2026