EV charger safety advice
Why Type AC RCDs Should Not Be Used With EV Chargers
A home EV charger is not the same as a normal socket circuit. Electric vehicles and charging equipment can create DC leakage currents, and the wrong type of RCD may not operate correctly when you need it most.
What is a Type AC RCD?
A Type AC RCD is an older style of RCD designed to detect standard alternating current faults. The problem is that many modern electrical appliances, including EV chargers, can produce fault currents that are not purely AC.
EV charging equipment can produce pulsating DC or smooth DC leakage current. If a Type AC RCD is exposed to DC current, it can become less reliable or even fail to trip correctly. This is why Type AC RCDs are not suitable for EV charger circuits.
Why this matters
The RCD is there to disconnect the supply quickly if a dangerous fault occurs. If the wrong type of RCD is fitted, the protection may not work as intended.
For EV chargers, the correct solution is normally one of the following:
- A Type A RCD or RCBO where the EV charger has suitable built-in 6mA DC leakage protection.
- A Type B RCD where the charger does not provide the required DC fault protection.
- A dedicated EV circuit designed and tested specifically for the charger being installed.
Common RCD symbols
You can usually identify the type of RCD or RCBO by looking for the symbol printed on the device. These are the common symbols you may see:
Type AC
AC only. Not suitable for EV charger circuits.
Type A
Detects AC and pulsating DC. Commonly used where the charger has built-in 6mA DC protection.
Type A-EV
Designed for EV charging with additional DC leakage protection.
Type B
Detects AC, pulsating DC and smooth DC fault current.
What happens when there are two RCDs in line?
Another common issue is having an RCD on the main consumer unit and another RCD on the garage board feeding the EV charger.
This can cause problems because both RCDs may see the same fault. If they are both 30mA RCDs, either one could trip. That means a fault on the charger could trip the main board instead of just the garage circuit.
This is poor design because it can lead to nuisance tripping, loss of power to other circuits, and confusion when trying to reset the system. In some cases, the upstream RCD may also be the wrong type, such as Type AC, which makes the issue more serious.
Best rectification
The best repair is usually to remove the EV charger from the existing shared RCD arrangement and install a properly designed dedicated EV supply.
This may involve:
- Installing a dedicated EV RCBO of the correct type.
- Confirming whether the charger has built-in 6mA DC leakage protection.
- Removing any unsuitable Type AC RCD protection from the EV supply path.
- Ensuring the garage supply and charger circuit are correctly protected.
- Testing the installation properly and issuing the correct certification.
In many homes, the neatest solution is a correctly selected Type A EV RCBO at the main consumer unit, provided the charger has suitable built-in DC leakage protection. If it does not, a Type B RCD solution may be required.
Why use DSG Electrical Services?
EV charger faults and RCD issues should not be guessed at. The circuit needs to be assessed properly, including the existing consumer unit, garage board, earthing arrangement, cable route, charger instructions and test results.
At DSG Electrical Services, you deal directly with Darren. I provide clear advice, safe workmanship and proper testing across Hastings, St Leonards, Bexhill, Eastbourne and surrounding areas.
I will not just swap parts and hope for the best. I will identify why the installation is wrong, explain the safest rectification, complete the work neatly and provide the correct certification.
Worried about your EV charger installation?
If your EV charger is protected by a Type AC RCD, trips the garage board, trips the main board, or you are unsure whether it has been installed correctly, get it checked before relying on it.
