APNT-54 - Installing Fibaro Dimmers with Neutral

IMPORTANT - Read this first!

This guide relates to the ORIGINAL Fibaro Universal Dimmer.

Do NOT follow this guide if you are installing the Fibaro Universal Dimmer 2.

You can cause damage to the device, your lighting circuit and your lights if you ignore this warning!

For assistance in installing your Fibaro Universal Dimmer 2 devices, please refer to this guide.

This application note shows how to install a Fibaro Dimmer module into a light circuit that has neutral available.

Most of the time the Fibaro Dimmers are installed at the light switch using a 2-wire system (non-neutral).
However, it is also common to install them near the light fitting in the ceiling space - at which point you will be able to also use the neutral cable.

Note: To simplify these diagrams, we have not shown the earth cables - but all circuits MUST have the earth cable correctly installed.

Standard Lighting Circuit

Standard Lighting CircuitFigure 1: A standard lighting system.

A 2-core + earth cable (brown, blue & bare earth) carries the Live, Neutral and Earth to the light fitting and then 'loops' to the next light in the circuit. A 2-core cable carries the Live and Switched Live to the switch - this enables the switch to control the light fitting.

This type of lighting system uses 'Toggle' (latching) switches. These latch in position - for instance when you press the switch to On, the switch physically stays in the On position. These are the standard light switches you'll find already fitted in your home.

Installing the Fibaro Dimmer

We can simply install the Fibaro Dimmer module into the lighting circuit as shown in Figure 2. Installing the dimmer in this position will require access to the ceiling or floor space.

Installing a Fibaro dimmer near light fittingFigure 2: Installing the Fibaro Dimmer into the main lighting circuit near the light fitting.

Alternative Installation

If you have a 3-wire system, where Neutral is available at the switch, then the dimmer can be installed into the switch back box.

Standard 3-wire Lighting Circuit wiring

3-wire lighting circuit with Fibaro Dimmer Installed

Figure 3: Standard 3-wire lighting circuit (neutral at the switch)

Figure 4: Lighting circuit (3-wire) with Fibaro Dimmer installed

Fibaro Dimmer Connections

The Fibaro Dimmer has six terminals to connect it to the electrical wiring, this application note uses five of them:

Fibaro Dimmer Connections

  • L – Live
  • N – Neutral (this is connected to O in 2-wire installations)
  • O – Output – connected to light or load
  • Sx – power supply to switch (internally connected to L)
  • S2 – connection to Switch 2
  • S1 – connection to Switch 1

Fibaro Dimmer Parameter Setting:

The following parameters need to be set:

  • 14 - 1 - enables the dimmer to work with a toggle switch (default is 0 for a momentary switch)
  • 17 - 1 - enables the dimmers S2 switch to also control the dimmer (default 0)


All electrical circuits MUST be correctly Earthed.

All cables used in lighting circuits contain a bare Earth wire - this typically has a green/yellow sleeve when it is wired to the switch or backbox. The Earth is a very important part of the electrical system and all switches, appliances and lights must be correctly earthed.

For simplicity we do not show the earth wire in these drawings or explanations as it plays no active role in the day-to-day workings of your light circuits, it is there for your protection in case of emergency.



Installing the Fibaro Dimmer modules involve working with 240V mains wiring. If you are not comfortable doing this you should consult a qualified electrician. This application note is provided as a guide, all work is are carried out at your own risk. Vesternet do not accept any responsibility or liability.

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