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Challenges of RCD and Surge Protection with Smart Home Devices

Mudassar

With the rapid adoption of smart home devices and IoT loads, modern electrical installations are becoming increasingly complex. While BS 7671 (18th Edition) provides detailed requirements for RCD protection, surge protection, and earthing, many installers are reporting practical issues such as nuisance trips, unexpected load interactions, and challenges integrating these devices safely.

I’d like to open a discussion on:

  • Are current BS 7671 requirements sufficient to handle the growing number of smart devices?
  • What real-world challenges have you faced in protecting these installations while ensuring compliance?
  • Are there any best practices or workarounds for minimizing RCD trips and surge issues in smart-enabled homes?

I’m looking forward to hearing your experiences, insights, and recommendations from both domestic and commercial perspectives.

  • Having perhaps "more than the average" number of gadgets about the place, I can't say I've encountered any particular problems. Most small devices seem to have Class II power supplies, so there's no great issue with earth leakage currents (sorry, protective conductor currents) upsetting RCDs. SPDs are relatively new to my installation - but almost all will be upstream of RCDs - I'd guess people who like surge protected extension leads and the like might be more vulnerable.

    I do have RCBOs though - i.e. one 30mA RCD per final circuit, not shared across many final circuits as some still like to do.

       - Andy.

  • in reply to AJJewsbury

    Thanks, Andy that’s a great point about RCBOs helping isolate nuisance trips.

    I’m wondering, have you noticed any “always-on” smart devices, like Wi-Fi cameras or smart thermostats, that occasionally cause RCD tripping even on dedicated RCBO circuits? With so many devices constantly communicating with hubs or cloud services, it seems like the type of load might start challenging our protections.

    And on SPDs do you find upstream protection usually enough, or have you tried placing smaller SPDs closer to sensitive devices like NAS servers or AV hubs?

  • Mudassar said:
    handle the growing number of smart devices?

    What distinguishes a smart device from a not-so-smart one?

  • in reply to Mudassar

    Never had a nuisance trip - although the CCTV cameras are PoE rather than WiFi and the heating controls are likewise hard-wired (12V programmable thermostats in most rooms). The NAS etc is on a UPS which provides some incidental protection, but no other SPDs after the CU at the moment

      - Andy.

  • Can you clarify if you think these are true direct safety issues from 'faulty' modern electronic equipment, or implied 'unsafe' scenarios from nuisance tripping, or unsafe operations from nuisance operation/commands?

    From my perspective, one of the biggest accumulating 'nuisance' is the conflict between all the EMC RFI [electro-magnetic compatibility radio frequency interference] filters that are, by design, deliberately dumping leakage currents, from the Live circuit, into the Earth Circuit (notionally isolated at the MET main earth terminal) to such an extent that the RCB (residual current breaker) function operates. 

    Older folks may remember when the old IBM PCs had a power 'kettle lead' link through the PC to power the VDU (visual display unit). These failed retrospective EMC testing so the power leads for the PC and display became separated so that they were allowed twice the leakage currents, needed to filter the two unit's conducted EMC & RFI.

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