EV charging

EV charger tripping RCD

Warning Do not attempt any electrical or gas work yourself. Always use a qualified, MCS-certified, or Gas Safe registered professional for repairs.

What you’re seeing (symptoms)

As soon as you plug your car in, or a few minutes after charging starts, the power to the charger (or sometimes the whole house) goes out. You find a switch flipped “down” in your fuse box.

What’s normal vs not normal

Normal:

  • The charger taking a few seconds to “handshake” with the car before the loud “thunk” of the relay closing.

Not normal:

  • The RCD tripping as soon as the cable is inserted.
  • The RCD tripping only when it rains.
  • The RCD or the fuse box feeling hot to the touch.

Likely causes (ranked)

  1. DC Leakage: EVs can naturally “leak” a tiny amount of DC current; if the charger’s protection isn’t high enough, it trips the RCD.
  2. Nuisance Tripping: The RCD in your fuse box is a “Type AC” or “Type A” when the charger requires a more specialized “Type B” or built-in 6mA DC protection.
  3. Damaged Cable: A nick or cut in the charging cable allowing moisture in.
  4. Overload: Charging the car at 7kW while the shower and oven are on is exceeding your house’s main fuse limit (though smart chargers should prevent this).
  5. Moisture in the unit: Rain getting into the charger casing due to a failed seal.

Quick checks you can do safely

  • Check the charging cable for any visible damage or kinks.
  • Try a different charging cable if you have a “socketed” charger.
  • Check if the trip happens only when other big appliances (like the kettle) are on.

When to call an installer

  • Immediately if you smell burning or see smoke from the charger or fuse box.
  • If the RCD trips every time you try to charge.
  • If the charger casing is damaged or loose on the wall.

Questions to ask your installer

  • “Does this charger have built-in 6mA DC leakage protection?”
  • “Is the RCD in the consumer unit the correct ‘Type’ for this charger?”
  • “Is the load-balancing sensor (CT clamp) working correctly?”

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FAQs

Can I just flip the switch back up? You can try once. If it trips again, do not force it. There is a fault that needs investigating by an electrician.

Why does it happen when it’s wet? Water is a conductor. If there is a tiny entry point in the charger or the cable, the water can create a “path to earth,” which the RCD correctly identifies as a danger and cuts the power.

What is ‘Load Balancing’? It’s a feature where the charger “listens” to how much power the rest of your house is using and slows down the car charging to prevent blowing your main house fuse.

Is it my car or the charger? It’s usually the charger or the installation, but you can test this by trying to charge your car at a public charger. If it works there, the fault is likely at home.

What is a ‘Type B’ RCD? It’s a high-spec safety switch designed to handle both AC and DC faults. They are expensive but often necessary for EV installations.

Written by NetZeroNow | Last updated on 2026-03-02