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

A Hennur-based residence, 2800 sq ft, three-bedroom. The architect specified in-wall conduit for SmartGlass dimming wiring through a load-bearing partition between the master suite and dressing room. The structural engineer's drawing showed a 200mm reinforced concrete beam at 1.2m height, directly in the path. The site team called us on day 14 of the fit. This coordination note is the result.

The in-wall conduit problem: why it fails on retrofit partitions

Retrofit SmartGlass dimming—whether our Privato bathroom privacy glass, Studio conference partitions, or Notte blackout panels—requires a 4-core power and control cable run from the relay unit (typically mounted at the electrical panel or at a dedicated wall outlet) to the glass panel itself. The cable carries 230V supply, neutral, earth, and a low-voltage control signal. Architects, trained to conceal electrical runs, often specify in-wall conduit as the default.

On load-bearing partitions in Bangalore—especially in the post-tech-corridor housing stock around Hennur, Kalyan Nagar, and Whitefield—structural engineers place reinforced concrete beams at partition mid-span to carry floor loads. These beams sit at heights between 1m and 1.5m, precisely where in-wall conduit would run horizontally. Drilling or chasing through a reinforced beam is not permitted under the building code and voids the structural warranty. The site team then faces a choice: reroute the conduit above or below the beam (adding length and cost), or switch to surface-mounted.

Surface-mounted conduit: the specification that works

Surface-mounted conduit—typically 16mm PVC or aluminium—is not a compromise. It is the correct specification when in-wall routing is structurally blocked. The conduit sits flush against the partition face, held by saddle clips at 400mm centres, and runs from the relay unit to the glass panel. On a finished plasterboard partition, it is visible, but it is also cleanly finished, serviceable, and requires no structural work.

The conduit itself carries the 4-core cable (2.5mm² or 4mm² depending on cable run length and voltage drop—check the relay datasheet for your specific SmartGlass unit). The cable terminates in a weatherproof junction box mounted directly on the glass frame, or feeds into the control module embedded in the frame itself. At the relay end, the cable enters a standard IP54 or IP65 enclosure, depending on the room's moisture profile.

Routing logic: the 1.5m water-line clearance rule

In a Bangalore bathroom or kitchen, water lines (both supply and waste) often run horizontally through the same partition. A common error is to route the SmartGlass conduit parallel to water lines at close proximity. Condensation, minor leaks, and the hard water TDS (~200–300 ppm in Cauvery-fed properties) can corrode the conduit and degrade the cable insulation over time. Specify a minimum 1.5m horizontal separation between the SmartGlass conduit and any water line. If the partition is narrow (less than 3m), route the conduit on the opposite face of the partition, or run it vertically above the water line by at least 0.5m.

On a site in Indiranagar, we routed a Privato dimming conduit up and over a waste stack by running it 0.3m above the partition head, then down the adjacent wall to the relay enclosure at skirting level. The extra 1.2m of cable cost less than the risk of future water damage and the service call that would follow.

Relay placement: wall-mounted vs. panel-mounted

The relay unit is the decision point. If you specify a wall-mounted relay (typically 150mm × 100mm × 80mm, installed at 1.5m height on a standard outlet plate), the conduit run is direct: from the relay, along the partition face, to the glass panel. If the panel is on the same wall as the relay, the run is under 2m. If the panel is on the opposite side of the partition (a common scenario in master-suite dressing rooms), the conduit must wrap around the partition edge or cross through a dedicated chase.

An alternative is to specify a panel-mounted relay, integrated into the frame of the SmartGlass unit itself. This eliminates the long conduit run and simplifies the wiring to a single 230V supply cable from the nearest outlet to the frame. The trade-off is that the relay sits inside the frame, making future firmware updates or relay replacement more involved—you must remove the glass panel or access the frame cavity. For retrofit work in occupied homes, wall-mounted relays are safer.

Why dimming delay is not a fault—it is the wiring route

A common complaint on site: the dimming response is sluggish. The user taps the wall switch, and the glass takes 0.8–1.2 seconds to begin transitioning from clear to frosted. The architect suspects a faulty control module. In most cases, the delay is the wiring route.

A long conduit run—say, 8m from the relay at the panel to a corner partition in a Jayanagar apartment—introduces capacitive load on the low-voltage control signal. The 4-core cable, sheathed in PVC, acts as a distributed capacitor. The control signal (typically 5V or 12V DC, modulated at 10–20 kHz) experiences a phase shift and amplitude loss as it travels the length of the cable. The SmartGlass control module interprets this as a slower signal rise time and extends the switching window to ensure the command is registered. The result is perceptible lag.

The fix is not to replace the control module. The fix is to reduce the cable run by repositioning the relay closer to the glass panel, or to upgrade the cable gauge (from 2.5mm² to 4mm² or 6mm²) to lower the line impedance. We specify 4mm² cable as standard on any run over 5m. On a 10m+ run (a single-story home in Sarjapur Road with a dimmed partition at the far end of the living room), we use 6mm² and shield the control pair with a foil wrap to reject electromagnetic noise from the home's other circuits.

Conduit material: PVC vs. aluminium, and Bangalore's monsoon humidity

PVC conduit is cheaper and sufficient for interior-only partitions. Aluminium conduit is specified when the partition is near an external wall, a balcony, or a window—anywhere monsoon humidity (June through September) can reach the conduit surface. Bangalore's monsoon brings sustained 80–90% relative humidity. PVC absorbs moisture and can swell, pinching the cable. Aluminium expands minimally and sheds condensation. On a Whitefield apartment with a SmartGlass partition adjacent to a large north-facing window, we specified aluminium conduit and sealed all entry and exit points with silicone, not foam.

Conduit clips (saddles) must also be chosen for durability. Mild-steel clips will rust in the monsoon humidity. Specify stainless-steel or nylon saddles. The cost difference is 40–60 rupees per clip; the difference in longevity is five to ten years.

Shop drawing and site handover: what to specify

Before the fit, provide the site with a 1:50 plan showing the relay location, the conduit route (marked in a distinct colour), the water-line positions, and the glass panel frame outline. Include a 1:20 elevation at the partition, showing the conduit clip spacing, the junction box height, and the distance from the partition head. Specify the cable gauge, the conduit diameter (16mm for 4-core, 20mm if bundled with other services), and the relay enclosure IP rating.

At handover, the site electrician should verify that the conduit is securely clipped at 400mm centres, that there are no pinch points where the cable enters the junction box, and that the relay enclosure is earthed and bonded to the partition's metal frame (if any). Test the dimming response at the wall switch—it should begin within 0.3 seconds of a button press. If the lag exceeds 1 second, check the cable gauge and the relay's signal input voltage (should be within ±10% of the specified 5V or 12V).

Questions we get asked

Can we run the SmartGlass conduit inside the same partition as the water lines, just spaced vertically?

Not recommended. Partition cavities in Bangalore homes are often damp during the monsoon, and any water-line micro-leak will eventually reach the conduit. Specify the conduit on the opposite face of the partition, or route it on a separate wall entirely. The cost of rerouting during fit is far less than the cost of a failed control module and a service call during the monsoon.

What if the architect wants the relay hidden inside a wall cavity?

Possible, but only if the cavity is dry and accessible for future maintenance. The relay must be mounted in a weatherproof enclosure (IP54 minimum, IP65 preferred) and the conduit entry point must be sealed with a grommet and silicone. You lose the ability to manually reset the relay or update its firmware without opening the wall. For retrofit work, we advise against it. Specify a surface-mounted relay in a discrete location—a utility corner, a pantry wall, or a dedicated electrical closet.

Does the conduit need to be earthed or bonded?

The cable inside the conduit carries an earth conductor (the third core), which is bonded to the relay enclosure and to the glass frame's metal frame. The conduit itself (if aluminium) should be bonded to the relay enclosure earth terminal with a 6mm² copper wire, to ensure a low-impedance return path in case of a fault. PVC conduit does not require bonding. Check your local electrical code; Bangalore's adoption of IS 1885-1 (Indian Standard for electrical installations) requires earth bonding on all metal conduits carrying power cables.

What happens if we need to move the glass panel later? Can we reuse the conduit?

Yes. The conduit is a permanent installation; the cable inside is replaceable. If the panel is relocated to a different partition, the old conduit can be capped at both ends and left in place, or carefully removed and reused if the new run is similar in length. We recommend capping and leaving in place—removal risks damage to the partition finish. The new conduit run should be specified and installed to the same standard as the original.

Our site has a very tight timeline. Can we run the conduit after the glass is fitted?

Only if the conduit is surface-mounted and the partition finish (plaster, paint, or cladding) is complete. If you route the conduit before the partition is finished, you risk damage during plaster application and sanding. Coordinate with the site manager: finish the partition, fit the glass panel, then route and clip the conduit. This adds 1–2 days to the schedule but ensures a clean finish and no rework.

For a detailed specification of your SmartGlass partition, conduit routing, and relay placement, talk to the atelier. We provide shop drawings and site coordination notes at no charge for active projects in Bangalore.