Hi friendly people,
As you may be aware, I'm a plumber, so quite possibly what I am seeing is correct, though it seems a bit odd to my untrained eyes. Hoping someone might be able to explain a few things to me as I need a bit of reassurance regarding RCD ratings.
I'm currently at a relative's house in Portugal. The person I am staying with bought the house about 5 years ago and has had various work done by the most competent tradesmen they could find as the house had been uninhabited for decades and was in a poor state of repair. This is not the Algarve, but a very rural area where quite a lot of the houses are derelict. The house itself is scruffy, but the owner is happy so long as it is reasonably watertight and safe and she can work on her garden. The electrics have been upgraded and rewired in part, with some of the existing circuits connected to the new consumer units. In general, the wiring I have come across looks to have been carried out without much pride, but seems decent enough and I have seen far far worse.
The mains cutout has a 25A REC/DNO/electricity board current limiter which covers the entire property. One small consumer unit upstairs, and one downstairs. This seems quite a nice way of doing it. Each consumer unit has a 40A rated RCD with an IΔn of 300mA (not sure if it's an RCBO or an RCD, but that's an irrelevance here) protecting C curve MCBs. One floor has a Triton electric shower which has been derated to allow it to work without overloading the dedicated circuit (installed by a local electrician).
If I understand it correctly, the overhead wires are providing Ph and N, so it is either a TNCS or TT system. There is an earth rod just inside the basement, but how effective that is since it hasn't rained for months and the 10m deep well adjacent to the house ran dry yesterday is anyones's guess. I'm wondering whether that 300mA rating is (as I understand it) the earth leakage current that would trip the RCD, and, if so, why 300mA seems to be typical in Portugal (the posh house of the neighbour's has the same rating of RCD) when a fatal shock can be far less.
I'm left wondering if the only purpose the RCD serves here is to allow the mains to disconnect when a leak to an earthed metal casing is insufficient to trip the (C-curve) RCD due to dry ground conditions, and not to protect from direct contact at all.
Am I misunderstanding what the IΔn means, am I missing something country-specific, or could this be a lazy way of avoiding nuisance tripping? Bit of a concern when there are electric submersible well pumps in use and an electric shower! Do I need to insist that my relative find another electrician for a local second opinion (not ideal as local workmen don't really like talking to women customers) or is it just me not quite understanding what is going on?
Thank you for reading this and for any light you might be able to throw on the subject.
As you may be aware, I'm a plumber, so quite possibly what I am seeing is correct, though it seems a bit odd to my untrained eyes. Hoping someone might be able to explain a few things to me as I need a bit of reassurance regarding RCD ratings.
I'm currently at a relative's house in Portugal. The person I am staying with bought the house about 5 years ago and has had various work done by the most competent tradesmen they could find as the house had been uninhabited for decades and was in a poor state of repair. This is not the Algarve, but a very rural area where quite a lot of the houses are derelict. The house itself is scruffy, but the owner is happy so long as it is reasonably watertight and safe and she can work on her garden. The electrics have been upgraded and rewired in part, with some of the existing circuits connected to the new consumer units. In general, the wiring I have come across looks to have been carried out without much pride, but seems decent enough and I have seen far far worse.
The mains cutout has a 25A REC/DNO/electricity board current limiter which covers the entire property. One small consumer unit upstairs, and one downstairs. This seems quite a nice way of doing it. Each consumer unit has a 40A rated RCD with an IΔn of 300mA (not sure if it's an RCBO or an RCD, but that's an irrelevance here) protecting C curve MCBs. One floor has a Triton electric shower which has been derated to allow it to work without overloading the dedicated circuit (installed by a local electrician).
If I understand it correctly, the overhead wires are providing Ph and N, so it is either a TNCS or TT system. There is an earth rod just inside the basement, but how effective that is since it hasn't rained for months and the 10m deep well adjacent to the house ran dry yesterday is anyones's guess. I'm wondering whether that 300mA rating is (as I understand it) the earth leakage current that would trip the RCD, and, if so, why 300mA seems to be typical in Portugal (the posh house of the neighbour's has the same rating of RCD) when a fatal shock can be far less.
I'm left wondering if the only purpose the RCD serves here is to allow the mains to disconnect when a leak to an earthed metal casing is insufficient to trip the (C-curve) RCD due to dry ground conditions, and not to protect from direct contact at all.
Am I misunderstanding what the IΔn means, am I missing something country-specific, or could this be a lazy way of avoiding nuisance tripping? Bit of a concern when there are electric submersible well pumps in use and an electric shower! Do I need to insist that my relative find another electrician for a local second opinion (not ideal as local workmen don't really like talking to women customers) or is it just me not quite understanding what is going on?
Thank you for reading this and for any light you might be able to throw on the subject.
