Impulse Relays

What's the difference between an impulse relay and a 2-way switch? 

A 2-way switch is used to switch a lighting circuit on or off from a maximum of 2 points in different locations. It can be flush-mounted or surface-mounted directly on the wall. The current supplying the bulbs passes through the 2 control points.

An impulse relay performs the same function as a two-way switch but controls more than 2 control points. It is installed in the electrical panel and can be single-pole or double-pole. The control circuit and the power circuit are completely separate. Push buttons replace the switches, i.e. the buttons return to their initial position after being operated. 

What are the advantages of an impulse relay compared with a two-way switch?

The impulse relay controls more than 2 control points

A two-way switch can only control 2 points. For example, a staircase that is switched on at the bottom and switched off at the top, and vice versa. If you have a long corridor with several doors, it is useful to switch on the light from each door and at each end of the corridor. You therefore have more than 2 control points, and in this case, the two-way switch is not suitable. You need to install an impulse relay which has no limits.

With an impulse relay, the electrical installation is evolutionary

With an impulse relay, you can increase the number of control buttons even after the electrical installation is complete. Do you want to add a fourth switch to your shop storage area? There is no issue with the impulse relay, but it is impossible with the two-way switch which is limited to 2 control points.

The different impulse relays

Single-pole impulse relays cut off only one phase of an electrical circuit, for example, to switch off all the lighting in a house using a single push-button. 

• A two-pole impulse relay that cuts both the phase and neutral of the lighting circuit for greater safety.
• This modular remote switch is installed on a DIN rail in the electrical panel of the house or shop. It is connected directly to the push-button controls that switch the lighting on or off. This is the most common type used by electricians today.
• Less commonly used is the flush-mounted remote switch, which is installed in a junction box located as close as possible to the lighting, unlike the modular remote switch located in the general electrical panel.

Impulse Relays from Schneider and Legrand are available from One-Elec

One-Elec distributes the two leading brands in the electrical sector, Schneider Electric impulse relay and Legrand impulse relay.

Acti9 and Resi9 impulse relays for Schneider Electric. Single-pole and double-pole, the range is extensive, with centrally controlled remote switches, changeover switches, quick-connect switches up to 32 A or switches with screw terminals. Standard or silent, One-Elec also offers a circuit-breaker + impulse relay combination. Less electrical wiring is needed in the panel, saving time and money on installation. Impulse relays from the CX3 range from Legrand. This range is compatible with the majority of single-phase electrical installations. Screw terminals are used for the connection terminals and are available in 16 A, for control voltages of 12, 24 or 230 V.

What's the difference between an impulse relay and a contactor?

An impulse relay is a bistable power relay, meaning that it can assume two possible stable states and switch from one state to the other by an external impulse. We can also refer to this device as a remote control switch. The contactor, on the other hand, needs to be held down to change its state.

How does an impulse relay or switch work?

Pressing one of the push buttons on the lighting circuit creates an electromagnetic pulse that powers the remote switch coil. This pulse then engages its mechanical contact, which provides the electrical contact until the next time a push-button is pressed.

Technically, when the remote switch coil is energised, the core is magnetised, making the normally closed contact open and the normally open contact closed. When the coil is de-energised, the electromagnetism disappears and the contact returns to its initial state under the action of the reaction spring.

What is the difference between a pulsed remote switch and an impulse relay?

They are the same thing. There is no difference between the two. An impulse relay, sometimes called an impulse switch or remote control switch can be either electromechanical or electronic but in all cases, the operating principle and uses of these devices are the same.

How quiet are remote impulse relays? 

While older models of impulse relays were particularly noisy, each time a light was switched on or off, the latest generation of models is designed to be "quieter". The fact remains, however, that each time the light is switched on or off, a very slight click can be heard. 

There are standard impulse relays on the market, but there are also silent ones, which, especially if they are installed in the night zone of a house, make no noise whatsoever.