At the incoming supply. The clamp goes around the main supply conductor where electricity enters the property — on a meter tail or the incoming cable at the consumer unit — because that is the one point every load in the house passes. Fitted there by a licensed electrician, it reports the whole home’s draw to the managed setup, which trims charging before the house limit is reached. Anywhere else, it measures only part of the picture and the readings mislead.
Key Takeaways
- The CT clamp belongs around the incoming supply conductor at the consumer unit — the one point that sees the whole house.
- On the charger’s own cable it measures only the charger, which defeats its purpose.
- Fitting, direction and the house limit are set by a licensed electrician at installation.
- Wrong-place clamps show up as odd charging behaviour; report the symptoms, do not open the consumer unit.
Why the Location Decides What the Reading Means
A CT clamp (current transformer) senses the current in the conductor it surrounds — nothing more. It cannot know what it is wrapped around. So position is the design decision, and the right one follows from the question being asked: how much is the whole house drawing right now?
| Clamp position | What it actually measures | Result for load management |
|---|---|---|
| Around the incoming supply conductor at the consumer unit | Every load in the property, charger included | The designed arrangement — the house limit is watched truthfully |
| Around the charger’s own circuit cable | Only the charger | The cooker, heating and everything else stay invisible |
| Around one sub-circuit or a single phase’s tail | That circuit, or part of the house | Partial readings — the setup trims too late, too early, or not at all |
That is why the clamp sits at the supply entry, not at the charger: the charger is what gets controlled, not what needs watching. What the reading then does — slowing and restoring the session — is covered in our article on whether load balancing increases charging speed.
Who Fits It, and What Is Set at the Same Visit
The clamp lives on mains conductors inside the consumer unit, so fitting is a licensed electrician’s task, done to the sensor maker’s instructions; no fitting steps are given here. At the same visit the installer sets the house limit, confirms the clamp’s direction against a known load, and checks the charger responds as the house gets busy and quiet again. If the supply, panel or charger changes later, both are worth revisiting — tell your installer.
Symptoms That Say the Clamp Is in the Wrong Place
A misplaced or reversed clamp announces itself in behaviour. These are symptoms to report to your installer — not faults to open the consumer unit and fix:
- Charging slows when the house is idle — the setup reacts to a load that is not there, or reads its own session as house load.
- Charging runs unchecked at the busy hour — the clamp is not seeing the loads it exists to watch.
- The app reading does not move when a large appliance switches on or off.
- Readings that look impossible — negative draw, or a house total below the charger’s own session.
What the Charger Itself Does — and Does Not — State
The division of labour, plainly: no EVDANCE charger listing includes a CT clamp or states a built-in house-limit sensor. The sensing hardware belongs to the installation design, chosen by the installer for the house. What EVDANCE chargers state is their own side: the EV-ACS4005T sets its charge current at 16, 24, 32 or 40 A (9.6 kW, NEMA 14-50P, IP66) — a ceiling on its own draw, not a measurement of the house — and the EV-ACT5006T is a wall charger of up to 48 A, hard-wired or NEMA 14-50P, IP65/IP66. If a managed setup is part of your plan, confirm the sensor arrangement with your installer in writing before ordering. See the residential charging range.
Frequently Asked Questions
Can the clamp go on the charger’s cable in the garage instead?
It would fit, but it would only measure the charger itself. The oven, the heating and a second car — the loads the limit exists for — would never appear in the reading, so there would be nothing true to manage.
Can I move or refit a clamp myself?
No. It sits on live mains conductors inside the consumer unit. If the behaviour above suggests a placement problem, note the symptoms and call the installer who fitted it.
Does every EV charger installation need a CT clamp?
No. Clamps belong to managed setups, typically where the supply is tight. A straightforward installation on a supply with spare capacity usually has none, and the charger simply runs at its set rate.
Related Reading
- Will an EV Charger Work Without a CT Clamp?
- Does Load Balancing Increase EV Charging Speed?
- What Is Dynamic Load Balancing, and Why Does Your Wallbox Home Charger Need It?
- Do You Need a Smart Meter for an EV Charger?
