SmartGlass wiring conduit placement through a Hennur partition: why surface-mounted beats in-wall when retrofit dimming breaks the tint uniformity

A 2800mm-wide office partition in Hennur, fitted with switchable glass, will show a visible tint gradient if the dimming relay is wired through in-wall conduit that splits the glass panel vertically. The gradient appears within weeks of handover—not a defect in the glass, but a consequence of uneven electrical load distribution across the PDLC film. Surface-mounted conduit, routed along the partition frame edge and dropped to the relay housing below slab, eliminates the problem entirely. The wiring path matters more than the wire gauge.

Why in-wall conduit creates tint uniformity loss

SmartGlass partitions—whether conference rooms that disappear or bespoke office dividers—rely on a continuous electrical field across the PDLC film. That field is generated by a single relay module, typically mounted in a service void or electrical cabinet adjacent to the partition. The power lines from relay to glass must distribute evenly across the film width.

In-wall conduit routing creates a physical interruption in the partition stud line. If the conduit passes through the centre of a 2800mm panel, the electrical load splits: the left half of the film draws current from the relay via a longer path through the left bus bar; the right half draws from the right bus bar via a longer, unequal path. The film responds by activating unevenly. In Bangalore's monsoon season (June–September), when humidity sits at 70–85% and Cauvery water TDS runs 200–300 ppm, the differential activation becomes visible as a faint vertical stripe where the conduit runs behind the glass. It persists even at full opacity.

The electrical load distribution problem

PDLC film is not a simple on-off device. It is a suspension of liquid-crystal particles in a polymer matrix. When voltage is applied, the particles align and become transparent. When voltage drops, they scatter light and turn opaque. If the voltage gradient across the film width is uneven, the particle alignment is uneven. A 2–3% variation in applied voltage between the left and right edges of a 2800mm panel is enough to produce a visible tint difference under daylight.

In-wall conduit creates this gradient because it forces the relay to sit off-centre relative to the glass. The nearest edge of the glass receives current before the far edge. The delay is microseconds, but the film is sensitive to it. Surface-mounted conduit, by contrast, allows the relay to sit directly below the partition, equidistant from both edges of the glass. Current reaches both bus bars simultaneously.

Retrofit dimming: why the electrical path governs the spec

Retrofit installations—where SmartGlass is added to an existing partition—present a tighter constraint than new-build. The partition studs, MEP routes, and slab voids are already set. You cannot relocate the relay to the geometric centre of the glass without breaking the existing electrical cabinet layout or running new conduit through occupied spaces.

The solution is not to force the conduit in-wall. Instead, spec the relay to sit in the service void immediately below the partition base, with conduit routed surface-mounted along the frame perimeter. This adds 1–1.5 metres of visible conduit, but it solves the electrical problem and preserves tint uniformity.

Measuring the conduit route before you spec

Before you issue shop drawings, measure the partition length and the relay location. If the relay is more than 400mm off-centre from the partition midpoint, surface-mount the conduit. If the partition is longer than 3200mm, surface-mount regardless of relay position. The cost of conduit and the visual impact of a 25mm-diameter PVC or stainless-steel tube along the frame is lower than the cost of a retrofit tint correction or a re-spec of the PDLC film after handover.

Joint tolerance at the conduit entry point into the relay housing should be held to ±2mm. If the entry angle is steeper than 15 degrees from horizontal, the conduit will create stress on the relay terminal block and increase the risk of a loose connection, which will show as flickering or uneven dimming.

Surface-mounted conduit: the frame and finish options

Surface-mounted conduit on a glass partition is not invisible, but it can be integrated into the frame design. If the partition is frameless, the conduit runs along the top and bottom edges of the glass, clipped to a 25mm aluminium channel that also serves as a cable tray. If the partition has a frame, the conduit is routed within or adjacent to the frame profile.

Aluminium vs. stainless-steel conduit

In Bangalore, both materials perform well. Aluminium is lighter and easier to bend on-site if the partition has a non-standard geometry. Stainless steel is more durable in high-traffic areas (Whitefield tech-campus office parks, for example) and looks cleaner in minimalist interiors. Joint tolerance at conduit couplings is ±1mm; over-tightening the coupling nut will deform the conduit wall and create a pinch point that can damage the wiring insulation.

Conduit labelling and future maintenance

Label the conduit at both ends with the relay circuit number and the installed date. Use a waterproof label, not a marker. During monsoon season, condensation inside the conduit can form if the conduit is not sloped toward a drain point. A 2–3 degree downward slope from the glass to the relay housing is sufficient. If the partition is horizontal (a skylight or overhead panel, like our sky-rated PDLC overhead), ensure the conduit terminates in a sealed junction box with weep holes at the base.

Retrofit dimming: electrical coordination with the site MEP plan

Before you issue the partition shop drawing, request the as-built electrical and MEP plan from the contractor. Mark the location of the existing electrical cabinet, the slab void, and any live wiring routes. If the cabinet is on the opposite side of the partition from the relay location, you will need to drill the slab or route conduit through the partition base. Both options add cost and time. Plan for this in the project schedule.

The relay module itself occupies a 300mm-wide, 200mm-deep space. It must be mounted on a 25mm plywood backing plate, screwed to the partition stud or to a dedicated service frame. Do not mount it directly to the partition base slab; vibration from foot traffic will loosen the terminal block connections. If the relay is mounted in a service void, ensure the void has a 15mm inspection access cover. You will need to access the relay during commissioning and for future dimmer-switch calibration.

Commissioning: the uniformity test

After the conduit is fitted and the relay is connected, commission the glass by running a full dimming cycle (100% transparent to 100% opaque) at least three times. Observe the glass from a distance of 3 metres, perpendicular to the partition. If you see a vertical stripe or gradient, the electrical load is uneven. Do not hand over the project. Check the relay voltage output at the left and right bus bars using a digital multimeter. The voltage difference should be less than 0.5V. If the difference is greater, the conduit routing or the relay position is the issue, not the glass.

In a retrofit scenario, if you discover uneven tint after handover, the fix is to relocate the relay or to re-route the conduit. Neither option is quick or cheap. Specify the conduit route correctly before the partition is installed.

Questions we get asked

Can we run the dimming wiring through the same conduit as the power supply?

No. The dimming signal (typically 0–10V DC) must be shielded from the power supply (230V AC). Use two separate conduits, or use a single conduit with an internal divider rated for high-voltage separation. The cost of a divided conduit is 15–20% higher, but it eliminates the risk of signal noise and uneven dimming.

What gauge wire do we specify for the dimming signal?

Use 1.5mm² (14 AWG) shielded twisted-pair cable for dimming runs up to 50 metres. The gauge matters less than the shield and the twist. The shield must be grounded at the relay end only, not at the dimmer switch end. Grounding at both ends creates a ground loop and introduces 50Hz hum into the signal, which the relay interprets as a dimming command.

If the partition is in a high-humidity space (like a bathroom with switchable bathroom privacy glass), does the conduit routing change?

Yes. In high-humidity spaces, use stainless-steel conduit and ensure the conduit is sloped toward a weep point. Condensation inside the conduit will corrode aluminium and can damage the relay. If the bathroom is in a Bangalore high-rise (Indiranagar, Koramangala), the humidity during monsoon can reach 90%. Plan for this in the spec.

Can we use surface-mounted conduit on a partition that has a fabric or veneer finish?

No. Surface-mounted conduit will be visible through or behind any non-opaque finish. If the partition has a veneer or fabric, you must route the conduit in-wall or within the frame. If you choose in-wall routing, ensure the relay is positioned at the geometric centre of the glass width, and commission the glass carefully to detect any tint uniformity issues.

What is the typical lead time for a retrofit SmartGlass partition with surface-mounted conduit in Bangalore?

From shop drawing approval to site fit, 6–8 weeks. The conduit fabrication and the relay module assembly add 2–3 weeks. If the existing partition frame needs modification to accommodate the conduit clips, add another 1–2 weeks. Coordinate with the site MEP contractor early; they often control access to the slab voids.

Commissioning and handover

After the uniformity test passes, provide the client with a commissioning report that documents the relay voltage at full brightness and full opacity, the conduit route, and the location of the dimmer switch. Include a maintenance note: the relay module should be inspected annually for loose terminal-block connections, especially after the monsoon season. A loose connection will show as intermittent flickering or a failure to reach full opacity.

Talk to the atelier about your partition layout, the relay position, and the electrical coordination plan. We will review the site MEP plan and recommend the conduit route that preserves tint uniformity and meets the site constraints.