Short answer
With two-way switching you switch a light from two places, with two two-way switches and an extra conductor between them. From three places you put an intermediate switch in between, or you use an impulse relay with ordinary push buttons. The latter is often the neater solution for a stairwell or a long hallway.
Who this article is for Anyone who wants to understand what is behind their switches. Changing it is work for the installer.
From one place: the single-pole switch
The ordinary switch. Live in, switched live out to the light. Nothing special beyond that.
From two places: two-way switching
Two two-way switches, with two conductors between them: the so-called strappers. Whatever position one is in, you can always switch over with the other.
So what you need is an extra conductor between the two points. In an existing installation that is often exactly what is not there.
From three or more places
Then an intermediate switch goes between the two two-way switches. For each extra place another intermediate switch. That works fine, but needs conductors between the points every time.
The alternative: an impulse relay
A relay goes in the meter cupboard that switches over with every pulse. The switches become ordinary push buttons, all connected in parallel on one control wire.
For a stairwell or a long hallway the relay is usually the neater solution.
Advantages:
- adding an extra button means branching off a wire, not a new circuit
- you can put buttons anywhere, even in ten places
- central switch-off becomes possible, for example a button by the front door that turns everything off
- handy for a long hallway, a stairwell or a large living room
Disadvantage: the relay clicks audibly and takes up space in the consumer unit.
The classic fault
Two-way switching that sometimes works and sometimes does not is almost always a bad connection in one of the switches or in a box between them. In older installations it is the push-in terminals that no longer grip.
See also socket not working, because the cause is exactly the same.
During a renovation
Decide beforehand where you want to be able to switch. An extra switch point during the first fix is a matter of pulling an extra wire; afterwards it means chasing walls. See when the electrician comes.
From my own work
In a home in Beek the customer wanted to switch the hall light from the front door, the kitchen and the landing. There was not enough wire for intermediate switching. With an impulse relay in the meter cupboard and push buttons in all three places it was solved, and a fourth button could be added later without new cabling.
When to call an electrician
- You want to switch a light from several places
- There is not enough wire for classic switching
- The existing two-way switching behaves oddly: sometimes it works, sometimes not
With an impulse relay there is almost always a solution without chasing walls. Request a quote.
Frequently asked questions
What is the difference between a two-way and an intermediate switch?
With two two-way switches you control a light from two places. For each extra place an intermediate switch goes in between.
Can I add a third switch point without chasing walls?
Often yes, with an impulse relay in the meter cupboard and ordinary push buttons. Adding a button then means branching off a wire.
My two-way switching sometimes works and sometimes not, what is that?
Almost always a bad connection in one of the switches or in a box between them, often an old push-in terminal.
Further reading
Installing outdoor lighting: what goes on underground
The light is the fun part, the cable the most important. Lay an empty duct now and you can extend later without digging.
The light is not working: check it yourself in four steps
Nine times out of ten it is the bulb, the lampholder or the switch. The tenth time it is a connection, and then you call.
Dimming LEDs: why they flicker, buzz or do not switch off
Almost every LED dimming problem comes from a dimmer made for incandescent bulbs. A new dimmer solves it.
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