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I have installed a shunt-type surge protector (SPD) after the main switch, but before the RCCB. A separate earth wire (with separate grounding) was used for the SPD.

Sometimes during heavy (indirect) lightning, the RCCB trips.

Does this mean the SPD is not installed correctly, or can the RCCB still trip (on indirect lightening) even when the SPD is installed correctly?

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  • \$\begingroup\$ Indirect lightning can affect the RCB outfeed live-neutral balance and cause it to trip especially on long runs of cable. An SPD won't stop this sort of tripping. \$\endgroup\$
    – Andy aka
    Commented Jan 28, 2023 at 17:03
  • \$\begingroup\$ There's enough wiring inside a house/building to act as antenna. Surge protectors are best placed very close to the device you're intending to protect. \$\endgroup\$
    – glen_geek
    Commented Jan 28, 2023 at 20:07

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If there is earth leakage in your system.

For example an RCCB rated 100 mA, nominal voltage 240 Vac.

Since R=240V/100mA = 2.4kΩ, this is the minimum resistance at 240V before your 100mA RCCB could trip. If your resistance drops below 2.4kΩ; (for example 2.3kΩ;), since I=V/R this current passing through RCCB is 104 mA, already exceeding, and voila it trips the RCCB. This is the situation if it trips without lightning.

In the same way if voltage is coming from lightning, it could be 40 kV, while your resistance is only 300kΩ. I=40kV/300kΩ; I=133 mA, which already can cause your RCCB to trip.

My suggestion is to check any leakage that could possibly less than 400kΩ. Normally, ensure your insulation resistance is more than 1MΩ

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  • \$\begingroup\$ but isn't SPD expected to avoid having 40kV at RCCB (by grounding the surge) ? are you saying SPD's response time is longer than a RCCB's ? \$\endgroup\$
    – asan123K
    Commented Jan 29, 2023 at 18:46
  • \$\begingroup\$ i think your SPD installation was correct. as long as you wire it up parallel with your load after the Main Breaker. SPD is faster and normally no more nuisance tripping after installing SPD. Provided your SPD short circuit during the transient overvoltage. Before installing the SPD itself can you confirm there is no leakage in your system. Example the voltage increase no yet reach the SPD zone of protection. \$\endgroup\$
    – Epe
    Commented Feb 16, 2023 at 9:02
  • \$\begingroup\$ SPD is installed just before the RCCB. so I don't understand what you mean by "Example the voltage increase no yet reach the SPD zone of protection". \$\endgroup\$
    – asan123K
    Commented Mar 5, 2023 at 11:59
  • \$\begingroup\$ could you please clarify. \$\endgroup\$
    – asan123K
    Commented Mar 12, 2023 at 10:28
  • \$\begingroup\$ Epe, could you pls clarify \$\endgroup\$
    – asan123K
    Commented Jun 25, 2023 at 4:49

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