11 kW & 22 kW Wallbox Cable Guide: Cross-Section, Wiring & RCD Explained
The installation of an 11 kW or 22 kW Wallbox requires the correct supply cable, appropriate cable cross-section, and a suitable residual current device. In this comprehensive guide, we explain step by step which cables are suitable for permanent installation, how to correctly calculate the cross-section, and when a Type B RCD is necessary.
Whether for a new build, retrofit, or extension – here you will find all the important information for a standards-compliant and future-proof installation. Learn more about wiring for electric vehicles in our basic guide.
11 kW vs. 22 kW Wallbox – What does it mean for the cabling?
The power of the Wallbox determines the current, circuit breaker size, and required cable cross-section:
| Wallbox Power | Circuit Breaker | Phases | Minimum Cross-Section | Recommended Cross-Section |
|---|---|---|---|---|
| 11 kW | 3 × 16 A | 3-phase (400 V) | 2.5 mm² | 5 × 6 mm² |
| 22 kW | 3 × 32 A | 3-phase (400 V) | 4–6 mm² | 5 × 10 mm² (for longer distances 5 × 16 mm²) |
Which cable is suitable for which installation method?
1. Outdoor & Underground Installation → NYY-J Underground Cable
The NYY-J underground cable is the best choice for outdoor or underground supply lines. It is extremely robust, moisture-resistant, and UV-stable.
- NYY-J 5×6 mm² per metre – ideal for most 11 kW Wallboxes
- NYY-J 5×10 mm² per metre – recommended for 22 kW and longer runs
- NYY-J 5×16 mm² per metre – for maximum future-proofing
For very long distances (> 70–100 m), the more economical NAYY-J aluminium underground cable (e.g. 5×25 mm²) is a great option.
2. Indoor Installation / Concealed → NYM-J Sheathed Cable
In garages or dry indoor areas, NYM-J sheathed cable (5×6 mm² or 5×10 mm²) is the right choice.
3. Flexible Wiring in Distribution Boards → H07V-K Single Core Cable
Inside distribution boards or control cabinets, flexible H07V-K single core cables are used:
Cable Cross-Section Calculator Table – Taking Length into Account
The recommended cross-sections are based on a maximum voltage drop of approx. 3 %. For longer distances, simply choose the next larger size.
| Cable Length | 11 kW (3×16 A) | 22 kW (3×32 A) |
|---|---|---|
| up to 30 m | 5×6 mm² | 5×10 mm² |
| 30–60 m | 5×6 mm² | 5×10 mm² |
| 60–100 m | 5×10 mm² | 5×16 mm² |
| > 100 m | 5×16 mm² or NAYY-J Aluminium | 5×16 mm² or larger |
RCD Protection: When is a Type B RCD really necessary?
Every Wallbox requires a 30 mA residual current device (RCD).
- Modern Wallboxes with built-in 6 mA DC fault current detection → Type A RCD is sufficient.
- Wallboxes without DC detection or older models → Type B RCD (all-current sensitive) is mandatory.
- A Type B RCD offers the highest level of safety and works with all Wallboxes.
You can find suitable Type B RCDs in our RCD / FI Switch category.
Step-by-Step: How to Install the Supply Cable Correctly
- Planning: Determine power, cable length, installation method, and protection
- Material selection: Suitable cable (NYY-J / NYM-J / H07V-K) + accessories (cable trunking, enclosure, warning tape, sand)
- Installation: Observe minimum depths, use sand bed and warning tape
- Protection: MCB + RCD (Type A or B)
- Notification to the grid operator (§ 14a EnWG)
- Inspection by a qualified electrician
Frequently Asked Questions (FAQ)
Which cable for an 11 kW Wallbox?
We recommend NYY-J 5×6 mm² for underground installation or NYM-J 5×6 mm² indoors. For very short runs, 5×2.5 mm² is theoretically sufficient, but 5×6 mm² is the practical and future-proof choice.
Is 5×6 mm² also enough for 22 kW?
Yes, for cable lengths up to approx. 70 m. For longer distances or lower losses, use 5×10 mm² or 5×16 mm².
Do I need a Type B RCD?
Only if the Wallbox does not have integrated DC fault current detection (≥ 6 mA). Most modern models work fine with a Type A RCD. However, Type B always provides the highest safety.
Can I install the supply cable myself?
No. The actual installation may only be carried out by a registered qualified electrician. You can, however, do the planning and material selection yourself.
What additional accessories are needed?
Cable trunking, IP65 enclosures, main isolator, warning tape, sand, cable clips, and possibly empty conduits.
Is aluminium underground cable (NAYY-J) suitable for Wallboxes?
Yes – especially for very long distances, NAYY-J 5×25 mm² or larger is a cost-effective and technically perfect alternative to copper.
Conclusion
With the right combination of NYY-J underground cable, H07V-K single core cable, and the appropriate RCD, you create a safe, standards-compliant, and durable Wallbox supply line. All required products are available in high quality and from just 1 metre at our shop.
Do you have questions about your specific situation? Feel free to contact us or consult your local qualified electrician – we are happy to help with material selection.