Short answer: a Type B RCD is the device that still works when the residual current contains smooth DC. An electric vehicle charger can put that kind of current on the earth conductor through its rectifier, and a Type A device cannot measure it. If the charge point already contains a 6 mA DC detector to IEC 62955, a Type A RCD is often accepted for the final circuit. If it does not, specify Type B. The charger data sheet and the wiring rule for the installation country both have to line up before you order.
Key facts
- RCD types describe which shape of residual current the device can detect, not how fast it trips. The base standards are IEC 61008-1 for RCCBs and IEC 61009-1 for RCBOs; Type F and Type B are defined in IEC 62423.
- A Type AC device sees alternating residual current only. Type A adds pulsating DC. Type B adds smooth DC, which is the form produced by a rectifier front end.
- A DC component above a few milliamps can saturate the summing current transformer inside an AC or A device. The device does not fail visibly — it simply stops responding, which is the dangerous outcome.
- IEC 62955 defines a residual direct current detecting device (RDC-DD) with a 6 mA DC threshold, built into charging equipment.
- IEC 60364-7-722 covers the electrical installation for electric vehicle charging. National rules sit on top of it and are not identical.
The four RCD types and the current each one detects
| Type | Alternating residual current | Pulsating DC | Smooth DC | Where it is normally used |
|---|---|---|---|---|
| AC | Yes | No | No | General socket circuits with no electronics on the load side |
| A | Yes | Yes | No | Circuits with switch-mode supplies, LED drivers, most household electronics |
| F | Yes | Yes | No | Single-phase drives and appliances that mix frequencies, and circuits exposed to surge currents |
| B | Yes | Yes | Yes | Three-phase drives, PV inverters, and charging equipment without its own DC detection |
Why an EV charger is a DC problem
An AC charge point supplies AC to the vehicle, and the rectifier that turns it into battery current sits inside the car. A fault in that rectifier can push a smooth DC component back onto the protective earth. The vehicle is a moving object with a cable that gets driven over and plugged in wet.
The fault current path is the reason the device type matters more here than on a domestic socket circuit. On a socket circuit, a Type A device covers the switch-mode supplies you are likely to find. On a charge point, the source of the DC is the load itself, and the load is replaced every time a different car plugs in. You cannot control what rectifier arrives in the driveway.
Portable in-cable control boxes usually contain DC detection because the standard for that product class asks for it. Wallboxes vary. Some integrate a 6 mA DC detector and state it on the data sheet; some rely on the installer to provide Type B protection upstream; some state Type A is sufficient because of the detector, with a footnote about local rules. That footnote is where projects go wrong.
Three charging arrangements and what each needs
| Arrangement | What produces the DC | Usual protective device | What to verify before ordering |
|---|---|---|---|
| Mode 2, portable in-cable box | Vehicle rectifier, box may include DC detection | Type A where the box declares 6 mA DC detection, otherwise Type B | The declaration in the box manual and the socket circuit’s existing protection |
| Mode 3 wallbox without DC detection | Vehicle rectifier | Type B, 30 mA, 4-pole or 1P+N depending on the supply | Whether the manufacturer expects the device in the board or in the wallbox |
| Mode 3 wallbox with integrated RDC-DD | Vehicle rectifier, detected internally | Type A, 30 mA, subject to the national rule | That the RDC-DD is to IEC 62955 and the wiring rule accepts it |
| Mode 4, DC charger | The charger itself | Type B on the AC supply side | Isolation arrangement and the charger’s own earth fault monitoring |
The regulation that changed the answer in some markets
Regulation is moving in one direction. Australia is the clearest published example: the Electrical Regulatory Authorities Council advised that from 1 May 2023 Type AC RCDs may no longer be installed, leaving Type A, B or F as the permitted types. In the EESS framework an RCD or RCBO is a Level 3 risk product, which means registration by a responsible supplier in Australia or New Zealand and the RCM mark before it can be supplied.
Where a market has taken that step, a Type AC device is not a budget option — it is a non-compliant one. In markets that have not, Type AC may still be legal on general circuits, but it is a poor choice for anything with a rectifier behind it. The safe reading of the trend is that Type A is the floor for new work and Type B is the answer wherever smooth DC can appear.
Specification checklist
- Read the charger data sheet and find the sentence about residual current detection. If it is absent, assume there is none.
- Decide the device form: RCBO if the circuit also needs overcurrent protection in one module, RCCB if an MCB already sits downstream.
- Fix the residual current rating. 30 mA is the usual figure for socket-outlet and vehicle-charging circuits; 100 mA and 300 mA belong to selective or fire-protection duties.
- Match the poles to the supply: 1P+N for a single-phase charge point, 3P+N for three-phase.
- Check the short-circuit coordination with the upstream device, because an RCD is not a short-circuit protective device.
- Confirm the certificate covers the exact ordering code, and confirm the mark the destination country requires.
What our own ranges cover, stated precisely
The residual current devices we publish data for are Type AC and Type A families: NB1L and NXBLE-63 RCBOs, NB2LE in 1P+N from 6 A to 40 A, and the NL1-63 RCCB range, where the published variants include AC, A and the F and SI versions intended for circuits with surge currents. Pole options in those families run from 1P+N through 4P, with residual current settings of 30, 100 and 300 mA depending on the code.
Where a project specification calls for Type B, the honest answer is that the ordering code and its test certificate decide what we can offer — we quote against the code and send the document for that code, not a family-level statement. HAZAM is an independent trading company: not a manufacturer, and not an appointed distributor for any brand. That is exactly why we would rather send you the certificate PDF for the code than a marketing line about the series.
What to send for a quotation
Charger model and its DC detection statement · single-phase or three-phase supply with voltage and frequency · device form wanted (RCBO or RCCB) · residual current setting · poles · destination country and the mark it requires · quantity. You get unit price, packing data and the certificate for the exact ordering code. Request a quotation.
FAQ
Q: Can I use a Type A RCD on an EV charger and stay compliant?
A: Often yes, when the charging equipment contains a 6 mA DC detector to IEC 62955 and the wiring rule for the country accepts that arrangement. Both conditions have to be documented. If either is missing, specify Type B.
Q: Is a Type B RCD the same as a Type B MCB trip curve?
A: No, and the collision of letters causes real ordering mistakes. The B on an MCB refers to the magnetic trip band, roughly three to five times rated current. The B on an RCD refers to the residual current forms it can detect. They are unrelated markings on different devices.
Q: Does one Type B device protect a whole group of charge points?
A: Only if the upstream device is rated for the total earth leakage of the group and the installation allows single-device protection for several final circuits. In practice each charge point gets its own, because a fault in one vehicle should not disconnect the others.
Q: Why does a Type B cost more?
A: It carries a second detection channel: it injects a small signal and watches for a DC shift, so it can see a residual current with no zero crossing at all. The price difference is in the electronics, not the contacts.
Q: What about 110–127 V supplies?
A: The device type logic does not change; the voltage and frequency rating does. A 60 Hz, 127 V charging circuit needs a device rated for that voltage and frequency, and the residual current setting stays at 30 mA. Send the grid details with the enquiry and the code follows.
Where to go next
If you are still choosing between the three device families, start with MCB vs RCCB vs RCBO. If the question is which residual current form your existing circuits need, read RCCB Type AC vs Type A. For board-level planning, see how to size a distribution board, and for the short-circuit side of the same board, 6 kA vs 10 kA breaking capacity. Grid data by country is in the voltage and frequency guide, and the plain-language answers to ordering questions are on the FAQ page.
Related: RCCB and RCBO range · MCB vs RCCB vs RCBO · RCCB Type AC vs Type A · How to size a distribution board · Voltage and frequency by country · How to verify genuine product