Onwords Smart Solutions, Technical Guide

KNX Wiring:
Site Wiring Essentials

The exact conduit, cable, and panel requirements your site needs for KNX. A reference for architects, electricians, and homeowners.

🚨 Must be done before plastering⚡ 2-wire bus cable only✅ No WiFi dependency, wired bus protocol

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🚨

KNX Wiring CANNOT Be Done After Plastering

Once your walls are plastered, adding KNX means cutting open walls, re-routing conduit pipes, and replastering, weeks of civil work and significant extra cost.
You have ONE window. Don't miss it.

Step 0, Know Your Materials

The KNX Cable & Conduit You Need

🔌

KNX Bus Cable

The main cable

→YCYM 2×2×0.8mm, the standard KNX twisted-pair bus cable
→Just 2 wires carry both data AND power (29V DC from panel)
→Max segment length: 700m per line
→NOT regular electrical wire, must be KNX-certified bus cable

🔩

Conduit Pipes

Goes inside walls

→25mm ISI PVC conduit, run inside walls during construction
→Keep separate from electrical conduit, minimum 30cm gap from 230V wiring
→Every switch point needs a 60mm flush-mount box in the wall
→Panel location needs a 600×400mm DB enclosure space

✅ DO

• Use YCYM 2×2×0.8 certified KNX cable

• Keep KNX conduit separate from power lines

• Run conduit to every switch, sensor & actuator point

• Leave 30cm extra cable at each endpoint

• Label every conduit end before plastering

❌ DON'T

• Don't use regular electrical wire for KNX

• Don't run KNX and 230V in the same conduit

• Don't plaster before pulling cables through

• Don't use less than 25mm conduit diameter

• Don't make sharp 90° bends in conduit

Construction Sequence

Wiring Phase by Phase

Share this with your site engineer. Every phase has non-negotiable tasks.

Design & Layout Planning

Before construction starts

Onwords visits your site and creates a complete KNX wiring map. Every switch location, sensor position, actuator placement, and panel location is marked on the floor plan.

BUILDER MUST PROVIDE:

✓ Approved floor plan (soft copy)

✓ Confirmed room layout

✓ Panel/DB room location

✓ False ceiling height decisions

Conduit Embedding, During Slab & Wall Work

⚡ Critical window

PVC conduit pipes are embedded inside walls and slabs as brickwork / RCC work happens. This is the only chance to route conduits without civil demolition later.

WHAT THE MASON/BUILDER DOES:

① Embed 25mm PVC conduit in walls as brickwork rises

② Fix 60mm flush boxes at every switch location marked by Onwords

③ Run conduit from each box back to the KNX panel DB room (star or daisy-chain)

④ Ensure conduit runs at least 30cm away from power wiring

⑤ At ceiling level, embed conduit for ceiling-mounted sensors and light actuators

Critical, Route All Load Wires to the KNX Rack

Must follow

In a KNX system, switches on the wall do NOT directly connect to lights or fans. Instead, all load wires (light wires, fan wires, AC wires, curtain motor wires) from every room must be routed back to that floor's centralized KNX rack / distribution board where the actuators live. The actuators receive commands from the KNX bus and switch the loads on/off.

KEY RULE FOR ELECTRICIAN:

✗ DO NOT wire lights/fans directly to wall switches, this is NOT a conventional wiring system

✓ Route every load wire (light, fan, AC, curtain motor) from the fixture back to that floor's centralized KNX rack

✓ Each floor should have its own KNX rack / DB board where actuators terminate and switch all loads

✓ Wall switches only carry KNX bus signal (29V DC), they send commands, not power

✓ Label every load wire at both ends, fixture name + room + floor

✓ Keep 230V load wiring and KNX bus cable in separate conduits (min 30cm gap)

Pull KNX Bus Cable Through Conduit

🔴 Last chance before plastering

After conduit is in place but before walls are plastered, the site electrician pulls KNX bus cable through every conduit run following the Onwords wiring plan. This is the final critical step, once plaster goes on, no cable can be added without demolition.

SITE ELECTRICIAN FOLLOWS THE ONWORDS PLAN:

① Pull YCYM bus cable through every conduit from panel to each endpoint as per wiring plan

② Leave 30–40cm loop at each flush box for connection later

③ Label each cable end with room name

④ Terminate all cables at the panel end in the DB room

⑤ Onwords verifies, once signed off, plastering can proceed ✅

Device & Panel Installation

After finishing

After plastering and painting is done, Onwords installs KNX actuators, touch panels, sensors, and sets up the main distribution board.

All actuators live in the panel. Switches and sensors mount in the flush boxes on walls. Touch panels are surface-mounted. Everything gets a unique KNX address on the bus.

Programming & Handover

✅ Done!

Onwords programs the system using ETS (KNX Engineering Tool Software), button functions, lighting scenes, AC schedules, and automation logic. Tested room-by-room before handover.

ETS ProgrammingScene SetupApp IntegrationRoom-by-Room Test

Sample Layout

3BHK Wiring Floor Plan

Where conduits go in a typical 3-bedroom home. Every coloured line = one KNX bus cable run.

Lighting line

HVAC/AC line

Security/access line

Switch/sensor point

Actuator/panel point

4–6

conduit runs per bedroom

8–12

runs in living/common areas

1–2

security line per floor

panel DB room required

For Your Site Engineer

Site Execution Checklist

Print this and give to your civil contractor.

BEFORE BRICKWORK

☐ Obtain KNX wiring layout drawing from Onwords

☐ Mark all switch/sensor/actuator box locations on walls

☐ Identify KNX panel location (DB room with 600×400mm space)

DURING BRICKWORK & SLAB

☐ Embed 25mm ISI PVC conduit as marked in drawing

☐ Fix 60mm flush-mount boxes at each switch/sensor point

☐ Embed conduit in ceiling slab for ceiling-mounted devices

☐ Ensure KNX conduit is ≥30cm from all 230V power conduit

☐ Do NOT share conduit with electrical wiring under any circumstance

☐ Run all conduits back to panel/DB room location

BEFORE PLASTERING, CALL ONWORDS ☎️

☐ Onwords team visits to verify all conduit runs are correct

☐ Site electrician pulls KNX bus cable through all conduits as per Onwords plan

☐ All cable ends are looped out at flush boxes

☐ Onwords gives written clearance to proceed with plastering

AFTER FINISHING WORK

☐ Provide power outlet near KNX panel location (230V)

☐ Provide power outlet at each touch panel location

☐ Ensure flush box openings are clean and undamaged

☐ Onwords installs devices and programs the full system

Related Guides

KNX Smart Home

Why KNX is the gold standard for villa automation

Villa Project Guide

End-to-end KNX automation for large residences

Site Preparation Guide

Detailed execution plan for your construction team

Get a Quote

Tell us about your project and get a custom estimate

📐

Ready to Plan
Your KNX Wiring?

Reach out before brickwork starts. We'll visit your site, create the wiring plan, and coordinate with your architect and electrician. No charge for planning.

WhatsApp Now 📞 Kavin, +91 70103 64097

Kavin, Site Engineer, Onwords Smart Solutions

Coimbatore · Chennai · Bengaluru

KNX Wiring:Site Wiring Essentials