ELECTRIC KOREA · GROUNDING RETROFIT FIELD CASE
Installing a protective grounding conductor and electrode during the renovation of an older Korean building
During an electrical renovation in an older Korean building, I opened the third-floor distribution board and found a problem more important than the lighting and receptacle work I had originally come to do: no protective grounding conductor was present at this unit’s distribution board.
This field record follows the installation of a new grounding conductor from the third floor to the first-floor garden, a 1,000 mm ground rod, its connection to a verified nearby grounding electrode, and the final resistance measurement obtained from the interconnected installation.
What the 24.8 Ω Reading Means
Because the new electrode was connected to an existing nearby electrode before testing, 24.8 Ω is the measured result of the interconnected grounding installation under the site test arrangement—not the resistance of the new rod alone. The number is useful field data, but it does not by itself establish compliance.
Project at a Glance
The Problem I Found Inside the Distribution Board
I originally entered the site to carry out lighting and receptacle work. The building appeared to be roughly 30 years old, although its exact age could not be confirmed.
As soon as I opened the old distribution board, I found no protective grounding conductor connected to it. More precisely, there was no existing grounding connection for this unit that I could verify and rely on. This conclusion applies to the inspected unit and distribution board; it is not a claim that the entire building had no earthing system.
Why Missing Protective Grounding Gets My Attention
Years ago, I received an electric shock after touching the metal enclosure of electrical equipment that was not properly grounded. That experience changed the way I inspect old electrical installations.
During normal operation, a protective conductor may appear to do nothing. When insulation fails and a live conductor contacts exposed metal, however, the earthing arrangement and protective conductor help limit dangerous touch voltage and support automatic disconnection by the appropriate protective device.
Field Experience Behind the Decision
I have personally experienced an electric shock from an ungrounded metal enclosure. For that reason, I do not treat a missing protective conductor as a cosmetic defect. It requires a careful assessment of the earthing arrangement, protective devices, conductors, and the condition of the installation as a whole.
The Existing 5.5 mm² Feeder and 50 A MCCB
The existing main feeder was 5.5 mm², a conductor size often encountered in older Korean installations, and the existing main protective device was a 2P 50 A MCCB. For this particular renovation, I planned to replace it with a 2P 40 A device after assessing the existing installation.
A conductor size alone is not enough to determine ampacity. Cable type, insulation, installation method, ambient temperature, grouping, termination condition, protective-device characteristics, and other site conditions must be considered. This field decision should therefore not be read as a universal rule that every 5.5 mm² conductor requires a 40 A breaker.
Why I Installed GV 10 mm²
I selected GV 10 mm² after considering the protective-conductor route, mechanical protection, possible fault conditions, installation environment, and foreseeable future alterations. The route extended from the third floor down to the first-floor garden, so repeating the work later would involve considerably more labor than installing the selected conductor during the renovation.
The decision was not based on the idea that “bigger is always better,” nor was the grounding conductor sized as though it were a normal load-carrying conductor. The existing breaker ratings and planned loads provided context for future work, but they were not, by themselves, the sizing rule for the grounding conductor.
Installing and Connecting the Ground Rod
I routed the GV 10 mm² conductor from the third-floor distribution board to the first-floor garden and installed a 1,000 mm ground rod. Because the exact metallurgy of the rod was not independently verified for this article, it is described here simply as a ground rod rather than assumed to be solid copper.
An existing grounding electrode serving another unit was located nearby. Before interconnection, it was necessary to confirm that it was an actual grounding electrode and to consider its existing connections and the building’s earthing arrangement. The new electrode was then connected to that verified electrode instead of being left isolated.
The conductor was prepared and joined using a metal compression sleeve. After the mechanical connection was completed, green-and-yellow tape was applied to identify the protective conductor and cover the joint during the work.
Buried-Connection Limitation
Identification tape alone is not a substitute for a connector and corrosion/moisture protection suitable for direct soil exposure. A permanent buried connection must retain electrical continuity and mechanical strength while being protected against moisture, chemical attack, and electrochemical deterioration. The appropriate system depends on the connector, materials, soil conditions, and applicable requirements.
Interpreting the Final 24.8 Ω Measurement
After the new rod and the verified nearby electrode had been interconnected, the earth tester displayed 24.8 Ω. The photograph records the instrument result obtained at the site.
The article does not document enough information to reconstruct the full test method, auxiliary-electrode arrangement, or spacing. For that reason, the result should be presented as the actual site reading under the test arrangement used—not as a universally reproducible value.
More importantly, resistance alone does not determine whether an electrical installation is adequately protected. The result must be considered together with the earthing arrangement, protective-conductor continuity, RCD or other protective-device characteristics, required disconnection time, and applicable installation requirements.
Grounding does not replace an RCD, MCCB, correctly selected protective conductor, or sound wiring. Electric-shock protection depends on these elements operating together as a coordinated system.
Why the Photographs Show Work in Progress
The photographs do not show the final completed distribution board. At this stage, the main grounding conductor had been brought to the board, while the lighting and receptacle renovation—and the protective grounding of the individual branch circuits—remained in progress.
This distinction matters because an intermediate construction photograph should not be interpreted as the completed electrical installation.
Key Takeaways
- Inspected condition: no protective grounding conductor was present at the unit’s distribution board.
- Existing supply: 5.5 mm² feeder with a 2P 50 A MCCB; replacement with 2P 40 A was planned following the site assessment.
- New work: GV 10 mm² conductor routed from the third floor to a new 1,000 mm ground rod in the first-floor garden.
- Electrode arrangement: the new rod was interconnected with a verified nearby grounding electrode.
- Measured result: 24.8 Ω for the interconnected installation under the site test arrangement.
- Status: main grounding installed; branch-circuit renovation still in progress.
A Grounding Conductor Nobody May Ever Notice
Most occupants will probably never see the grounding conductor running from the third floor to the garden. If the installation continues to operate normally, they may never know it is there.
Electricians, however, cannot think only about normal operation. We also have to consider the moment when insulation fails and an exposed metal part becomes energized. I know what that contact can feel like because I have experienced an electric shock from an ungrounded metal enclosure myself.
I came to this building to work on lighting and receptacles. I did not expect to install the main elements of a grounding retrofit that day, but after opening the distribution board, I did not want to leave the verified defect exactly as I found it.
The completed protective-earthing system is intended to help limit touch voltage and allow the protective device to disconnect a fault before a person becomes part of the current path.
Technical scope: This article documents an actual field installation and the electrician’s judgment at this specific site. Requirements vary with the earthing arrangement, conductor installation, protective devices, fault conditions, test method, and applicable regulations.
Photo note: Some field photographs were edited only to obscure personally identifiable information. The electrical equipment, wiring, and installation conditions shown were not altered.
Electric Korea
Korean Electrical Construction · Field Experience · Safety · Technical Education
Website: electrickorea.co.kr
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