Frequently Asked Questions
Below are questions and answers. Click on a question to view the related answer.
What is the time delay on a time delayed (“S” Type) RCD?
The minimum tripping time at IΔn is 130 ms – For full time / current criteria refer to BS 7671 Appendix 3 Table 3A. For further details on the application of time delay RCDs refer to Technical Publication No 08 - page 3
Can I adjust the sensitivity of an RCD to prevent nuisance tripping?
No – For safety reasons the standards for RCCBs (BSEN 61008-1) and RCBOs (BSEN 61009-1), do not allow adjustable settings* on products that are designed for resetting by non-electrical persons. For issues related to nuisance tripping refer to Technical Publication No 19 – page 2
*CBRs with IΔn > 30 mA (BSEN60947-2 Apx B) can have adjustable settings – see Doepke DFL8 X versions.
How often do I have to test your RCCBs?
Regular operation of the test button increases the operating life of the RCD. The interval between operating the test button depends on the environment and the application e.g. 3 – 6 months may be appropriate between tests for domestic installations. For higher risk installations covered by the Electricity at Work Regulations more frequent testing may be required to meet legal obligations e.g. Construction sites, daily testing of RCDs used in fixed equipment and for Portable equipment the RCD must be tested prior to each use – See IET Guidance Note 7 - 4.1.
Can I fit somebody else’s devices into your boards?
If it is a pre-configured board, assembled by Doepke with Doepke devices – No. If it is an empty enclosure, you are responsible for testing to the appropriate part of BSEN 61439 – See BS7671 536.4.203.
Can you use Type AC RCDs in the UK?
Type AC RCDs can be used on permanently connected equipment that cannot produce residual currents with DC components or high frequency components e.g., resistive heating loads - See BS7671 531.3.3. For further details on the application of different types of RCDs refer to Technical Publication No 05
Can I use a DFS 4 EV RCCB for application areas other than in charging stations for electric vehicles?
The DFS 4 A EV is designed specifically for use in Mode 3 charging stations for electric vehicles. For other applications requiring an RCCB with a 6 mA DC detection and switching feature – use DFS4 BSK MI or BNK MI
What are the differences between Type A and Type F RCCBs / RCDs?
Type A detect AC residual currents and pulsing DC residual currents at 50 Hz. Type F can detect residual currents with mixed frequency components (10 Hz < 1 kHz) generated in 50 Hz supplies feeding single phase frequency convertors used in modern appliances such as washing machines. For further details on Type F see Technical Publication No 20
Our house is supplied via overhead lines and our RCD trips during thunderstorms. Is there a remedy for this?
Short-time delayed RCCBs Type KV can help solve this problem. They have non-response lag time of 10 ms and are more resistant to surge currents < 3 kA. This feature is available on 30 mA devices.
What type of RCD is required for an induction hob?
Due to their design, induction hobs can generate smooth DC residual currents or residual currents with frequencies not equal to 50 Hz. Contact the hob manufacturer for advice: Designs that produce smooth DC < 10 mA and frequencies < 1kHz; DFS2 30 mA Type F may be suitable. For smooth DC > 10 mA and frequencies > 1kHz; DFS2 30 mA- BNK.
How do I test a Type B RCD?
The prerequisite is a test instrument that is calibrated correctly for testing Type B RCDs. This includes AC residual currents, Pulsed DC residual currents and smooth DC residual current. For details on tripping currents and times refer to the tables on page 6 of our Technical Publication No 19.
My Doepke RCCB tripped and now I cannot switch it on. What am I doing wrong?
The operating lever for DFS 2 and DFS 4 series is fitted with a reset function. The lever position indicates whether the RCCB has tripped due to a fault (Centre position) or been switched off by hand (zero position). To switch on, the lever must always be moved to the zero position first, before attempting to switch it back on.
Is the Doepke AFDD arc-fault detection device available as a 3+N variant?
No - BS 7671 only refers to their use in single phase domestic or similar installations. Two-pole AFDDs are recommended here because the number of electrical devices without protective conductors has grown rapidly in recent years. With these devices, the risk of undetected arc faults, and hence the risk of fire, is far greater. AFDD devices should be selected to detect serial and parallel arc faults.
Are the supply direction and polarity important when connecting a Doepke AFDD?
Yes, AFDDs from Doepke must have the incoming supply connected to the lower terminals. The neutral conductor position can be left or right.