ELECTRIC KOREA · EK CONSTRUCTION #001
Adapting a German rotary switch to an existing Korean wall box and a new drywall partition
European rotary switches are increasingly used as design features in luxury homes, boutique hotels, cafés, and other carefully finished interiors. In South Korea, however, they remain uncommon—and the wall behind the switch is often built around a completely different mounting format.
This project involved a German THPG rotary switch, an existing Korean rectangular metal box, and a separate new drywall installation. The electrical connection was only part of the challenge. The more unusual work was creating a mechanically secure, accurately aligned mounting surface without unnecessarily reopening a wall whose painting had already been completed.
I have worked in South Korea’s electrical field since 2009. This article records the actual solution used on this site, including the parts that required field fitting. It is a project-specific retrofit, not a substitute for the manufacturer’s installation instructions or a universal method for every wall construction.
The core challenge
THPG’s flush-mounted system is designed around standard European boxes. The existing Korean box on this site was rectangular and approximately 50 × 100 mm, while the visible THPG cover was round. The retrofit therefore had to solve both structural support and wall finishing—not merely transfer the wires.
Two Different Installation Conditions
| Condition | Site constraint | Approach used |
|---|---|---|
| Case A: Existing wall | Korean rectangular metal box, approximately 50 × 100 mm | Create secure backing, mount the mechanism, then repair and repaint the visible opening |
| Case B: New drywall | No standard German flush-mounted box installed | Field-fit the actual mechanism, establish the centers with a laser, and drill approximately 57–58 mm openings |
Separating these two conditions is important. The modification around an existing rectangular box and the hole size used in a new drywall partition are not the same operation.
Case A: Retrofitting the Existing Korean Wall Box
The work began with a standard Korean three-way switch. After the circuit was safely isolated and the conductors verified, the original mechanism was removed so the box, wiring, and available mounting space could be inspected.
The box opening was much larger than the circular mounting area needed for the new mechanism, and the round decorative cover could not conceal the full rectangular opening by itself. Because the wall finish was already complete, fully opening and rebuilding the partition was undesirable.
Transferring the Three-Way Circuit
The existing common conductor and travelers were identified before being transferred to the appropriate THPG terminals. Similar switching functions do not mean terminal positions can be assumed: the circuit, conductor identification, switch diagram, ratings, and operation all have to be verified for the specific device.
Creating a Mechanically Secure Backing
Small wooden backing pieces were inserted behind the drywall to create a solid surface for the mechanism. A hot glue gun was used only as a temporary positioning aid—a tack that held each piece in the correct location while the final fasteners were installed.
Adhesive did not carry the switch load
The backing was mechanically secured with screws driven through the drywall. Those screws—not the hot glue—provided the final structural fixing. The switch mechanism was then screwed into the backing so repeated rotary operation and its associated torque were resisted by mechanical fasteners.
The internal spacing was adjusted to approximately 58 mm to accept the actual mechanism used on this project. This dimension describes the site-built support arrangement; it is not presented as a THPG wall-box specification.
Alignment, Trim, and Wall Repair
The mechanism was leveled before its mounting screws were tightened. The decorative ring and rotary knob were then installed. Because the original rectangular opening extended beyond the round cover, the exposed area was filled, sanded, and repainted as part of the wall-finishing work.
Case B: Three Switches in a New Drywall Partition
The second condition allowed the switch positions to be laid out before installation. A laser level established one vertical centerline, and the three centers were marked at approximately 100 mm center-to-center spacing.
The wider spacing was selected as a visual decision for this particular wall and its separate round covers. It must not be confused with the manufacturer’s standard system-cover geometry.
What the 54 mm and 57–58 mm Measurements Mean
A 54 mm opening proved slightly too small for the switch body used here and required additional trimming. Approximately 57–58 mm provided the most practical fit during this installation.
Field measurement—not an official THPG hole specification
The 57–58 mm dimension applies to the actual switch body and wall construction encountered on this project. THPG does not present it as a universal drywall cutout. Installers must verify the product variant, approved mounting method, wall construction, and required box before cutting.
Manufacturer Spacing vs. This Project
THPG states that centers must be exactly 71 mm apart when its system covers are installed. The manufacturer also recommends compatible flush or hollow-wall boxes and spacers for the intended system. The approximately 100 mm centers in this project were used with separate round covers as a site-specific design choice; they are not the standard spacing for a THPG multi-unit system cover.
| Dimension | Meaning | Status |
|---|---|---|
| 71 mm | Center spacing when using THPG system covers | Manufacturer instruction |
| Approx. 100 mm | Spacing selected for three separate covers on this wall | Project-specific design choice |
| Approx. 57–58 mm | Opening that fit the tested body in this drywall | Field observation, not a universal specification |
Electrical and Regulatory Limits
The switch operated correctly in this specific circuit after the conductor identification, device ratings, mounting, switching function, and final operation were checked. That result should not be interpreted as proof that every THPG product or installation method is automatically compatible with every Korean building.
Important safety limitation
Mains wiring, imported-device suitability, enclosure requirements, protective measures, and local regulatory compliance must be assessed for the actual project. This field record does not authorize direct drywall mounting where an approved box or another mounting method is required. Installation must be completed by appropriately qualified personnel with the supply isolated and verified.
Final Result
The completed work brought the appearance of a German rotary switch into a Korean interior, but the useful part of the project was hidden behind the cover: understanding the incompatible wall geometry, creating screw-fixed backing, distinguishing field measurements from manufacturer specifications, and restoring the finished surface.
The hot glue was never the structural solution. It simply made it possible to position the backing through a limited opening. The final stability came from mechanical fastening, careful alignment, and verification of the completed switch operation.
For a new project, using the manufacturer’s intended box and spacing from the design stage remains the cleaner approach. The retrofit shown here documents how one already-finished Korean site was handled when those provisions had not been made in advance.
Reference
Electric Korea · Document ID: EK Construction #001
Published: August 4, 2026 · Written by Foreman Hong
Korean Electrical Construction · Field Experience · Safety · Technical Education
Website: electrickorea.co.kr
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