The six existing 36 W lights were all working, but the stairwell still felt dark.
When we walked through this older four-story commercial building in South Korea, the problem became clear. Light was concentrated around the existing fixtures, while the stair corners and intermediate landings remained in shadow.
The building owner did not want a major renovation. His priorities were simple: make the stairwell brighter, complete the work quickly, and keep the cost as low as practical.
Rather than removing six working fixtures, we kept them and added six smaller LED lights where the existing light could not reach. This commercial stairwell lighting upgrade was completed by two electricians in approximately four hours using the existing lighting circuit and surface-mounted conduit.
The Problem Was Light Distribution, Not Just Wattage
Each area depended on a single light source. The fixtures provided basic illumination, but noticeable shadows remained around the stair corners, intermediate landings, and the spaces in front of tenant entrances.
Installing higher-wattage replacements in the same positions might have increased the brightness immediately around each fixture, but it would not necessarily have removed the shadows created by the original layout. In this building, adding light from a second direction was more useful than simply increasing wattage at the same points.
Adding LED Fixtures to the Existing Lighting Circuit
The six original fixtures were rated at 36 W each, giving an existing connected load of 216 W. A directly matching replacement was not readily available, so we selected smaller LED fixtures as supplementary light sources rather than replacing equipment that was still serviceable.
Three new lights were installed at intermediate stair landings, and three were installed in front of tenant entrances. All six new fixtures were connected in parallel with the existing lighting and operate at the same time. No additional switch, timer, or sensor control was required.
Before reusing the circuit, we checked the 20 A protective device, the 2.5 mm² conductors, the existing connected load, and the insulation condition. Because each new LED fixture was rated below 36 W, the combined nameplate load of all 12 fixtures remained below 432 W. For this particular circuit, the available capacity was sufficient for the additional lighting.
Why We Chose a Surface Wiring Installation Method
The walls were solid concrete, and fast completion was the owner's highest priority. Concealing a new cable route would have required cutting or opening the finished wall and then repairing the surface. That would have added time, dust, cost, and disruption inside the occupied building.
We therefore installed 16 mm flame-retardant corrugated conduit visibly along the accessible indoor concrete surface. For this field condition, surface wiring allowed us to create a new branch route without major demolition and left the conduit accessible for visual inspection.
At the original fixture locations, extension steel junction boxes provided additional space for the incoming conductors, original fixture leads, and new branch conductors. New 44 mm steel junction boxes were installed at the supplementary fixture locations.
.jpg "44 mm Steel Junction Box for Additional LED Light")
The Difficult Part: Keeping Flexible Conduit Straight
Connecting the fixtures was straightforward. The most demanding part was keeping the flexible conduit straight and consistent on the exposed concrete surface.
Corrugated conduit naturally bends and can appear uneven when its supports are too far apart. We used 16 mm half saddles at approximately 500 mm intervals and fastened them to the concrete with a concrete fastening tool. Additional support was provided where the conduit changed direction.
The close saddle spacing controlled the conduit’s natural curvature, prevented visible sagging, and produced a cleaner exposed route. This small installation detail made a significant difference to the finished appearance.
Insulation Resistance Testing Before Re-Energizing
After completing the branch wiring and fixture connections, we tested the circuit before restoring normal operation. Because the LED drivers remained connected, we intentionally selected a 250 V DC test voltage to reduce the risk of stressing the connected electronic components.
The measured insulation resistance exceeded 100 MΩ. After checking the test result and completed connections, the breaker was switched on and all 12 fixtures were operated together as intended.
Test voltage should be selected according to the connected equipment, applicable local requirements, and the test instrument manufacturer's instructions. It should not be copied from this field case without evaluating the actual circuit.
.png "250 V DC Insulation Resistance Test Above 500 MΩ")
Final Result: More Light From More Directions
No before-and-after illuminance measurements were taken, so this project does not claim a measured lux improvement. The visual change, however, was clear.
Increasing the number of light sources from six to 12 allowed the staircase to receive light from more directions. The overall stairwell appeared brighter, and the shadows around the corners were noticeably reduced.
The completed work was photographed and sent to the building owner, who was not present when the installation was finished. Two electricians completed the upgrade in approximately four hours without replacing the six serviceable fixtures or opening the concrete walls.
When This Surface Wiring Method Should Not Be Used
This was a practical solution for this building, but it should not be copied without first assessing the existing installation. A different approach is required when:
- the existing conductors are excessively aged, damaged, or deteriorated;
- the insulation resistance is unsatisfactory or an insulation fault remains unresolved;
- the existing circuit does not have sufficient capacity for the additional load;
- the conduit route would pass through an inaccessible concealed ceiling space; or
- the exposed conduit would be vulnerable to mechanical damage or unsuitable for the surrounding environment.
If the existing wiring is deteriorated or the insulation test result is poor, the wiring should be replaced or the fault should be located and corrected before additional lighting is connected.
Field Takeaway
The most effective lighting upgrade is not always the one with the highest wattage or the newest fixtures.
In this stairwell, the original lights were still usable. The better solution was to identify where their light did not reach and place smaller supplementary fixtures in those areas.
By checking the existing circuit, reusing serviceable equipment, targeting the shadowed locations, and choosing a surface wiring installation method suited to the accessible concrete walls, we improved the stairwell lighting with limited demolition, cost, and downtime.
Electric Korea
Korean Electrical Construction · Field Experience · Safety · Technical Education
Website: electrickorea.co.kr
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