Introduction
Vaillant has recently confirmed important changes to the electrical protection requirements for its domestic heat pumps, including the aroTHERM Plus range. These changes directly affect any installation under our MCS Partnership Program.
Standard Type A or F RCDs can no longer be used because they do not reliably protect against the high-frequency and smooth DC leakage currents that inverter-driven heat pumps produce.
Vaillant now requires the use of a Type B RCD/RCBO with the following specification:
- Minimum detection capability up to 20 kHz
- Minimum trip threshold of 150 mA above 1 kHz
This requirement is mandatory for all new installations and is a condition of Vaillant’s warranty.
What This Means For Us
- Type B RCD/RCBO is required on all Vaillant heat pumps
- Vaillant recommends the Hager B-HP series, which meets their new technical specification
- Other brands may be acceptable if they meet identical Type B criteria
- If a Type B cannot be accommodated in the existing consumer unit, you must plan to install a sub-board dedicated to the heat pump circuit
Implementation Checklist
- Update all circuit designs and quotes to specify Type B RCD/RCBO protection
- Plan for dedicated heat pump sub-boards where existing space is insufficient
- Use dedicated circuits sized correctly with appropriate MCBs (typically 30 A–50 A)
- Brief all electricians, apprentices, and subcontractors on the new standard
- Document this change in your method statements and technical packs
Technical Background
Modern inverter-driven heat pumps produce a complex mixture of AC, DC, and high-frequency leakage currents. Type A or F RCDs cannot detect smooth DC residual faults or high-frequency currents reliably, risking “blinding” of the protection device.
Type B RCDs are designed to:
- Detect smooth DC residual currents
- Detect high-frequency residual currents up to at least 20 kHz
- Maintain correct operation and safe disconnection
This is also consistent with the 18th Edition Wiring Regulations (BS 7671), which requires protection devices to handle any DC components generated by inverter equipment.
Further Support
You can download Vaillant’s detailed bulletin here:
Download Vaillant Type B RCD Bulletin (PDF)
Quick Highlights
- Vaillant requires Type B RCD/RCBOs immediately
- Minimum 20 kHz frequency rating, 150 mA trip above 1 kHz
- Hager B-HP series is recommended
- Standard Type A or F devices no longer meet warranty conditions
- Plan for a sub-board if consumer unit space is limited
- Applies to all new installs and any remedial work
