ᐅ Preparation for Electrician: Insulation Resistance Testing

Dear forum community,

Something incredibly frustrating happened again. I could have cried…

While installing lights in our new build yesterday, something unusual occurred. Even though the circuit breaker was switched off, the upstream RCD (residual current device) tripped just as I was on my way to the breaker. This happened neither directly while drilling/screwing nor after turning the breaker back on. I can’t rule out that I may have hit a cable during installation. My main goal now is to check the safety of the cables running through the ceiling without having to open it up. From what I’ve read online, a smoldering fire is almost inevitable if I continue to use the (still functioning) cable…

I have already contacted three electricians and am now waiting for their responses. My question to you: Is it sensible to perform an insulation resistance test? Or would calling an electrician at this point be like using a sledgehammer to crack a nut? Has anyone had experience with this? Are there other options? Would the RCD trip again if there was an exposed cable before a dangerous situation occurs?

Thanks to everyone who contributes…

Best regards,
Björn

Hafenstraße schrieb:

contacted

Contacted? Are these larger companies? I only know electricians who go to their computers once a month, just to write invoices.
But anyway: with tradespeople, phone calls still matter, and that’s what I would do.

Maybe your drill is simply broken and tripped the RCD? Or perhaps another device is defective?
Sure, that might be a big coincidence, but it can’t be ruled out.
Have you tried resetting the RCD? Does it trip again immediately?

Exactly, I called a small local electrician directly after I couldn’t get any response from the larger companies with impressive websites. In the end, it is now assumed that I probably short-circuited the neutral to ground, while power was still flowing through another circuit breaker behind the same RCD. Especially since the lamp’s circuit breaker was switched off. That seems to be the most likely scenario. Since I’m already following the advice to drill into my ceilings with a “soft” concrete drill bit, to hopefully avoid any cables if needed, that seems to be the most probable case at the moment…

The RCD holds, and I see no signs of a damaged cable (I know that doesn’t necessarily mean much…). But I’m increasingly convinced that I was lucky. I will keep monitoring the wiring. Since only a very low load is running (an LED strip), this should be okay.

We have owned this house for only a week. I’m starting to go crazy…

Your concern about the RCD tripping has a different cause.
During your lamp installation, the protective earth conductor probably came into contact with the neutral. This can cause the RCD to trip even if the circuit breaker for that circuit is switched off.
So this is completely normal.

Always connect a terminal to the neutral wire (N) when working with lamps; otherwise, the same problem will occur again. This is completely normal and just as safe as your electrician explained.