Light Wiring Diagrams

Multiway switching and switches – UK and US terminology

If you are searching online for 2 way switches/switching and 3 way stitches/switching the results can be very confusing to the layman depending on wether you land on a US or UK website. This is because the terminology used is very different.

This site follows UK usage. So for the benefit UK visitors searching online and American visitors to this site, hopefully the following will help to clarify:

Switches

2 way switch (UK) 3 way switch (US)

Fig 1: 2 way switch (UK) 3 way switch (US)


UK
– So, this (Fig 1) is what we call a 2 way switch: when you switch it one ‘way’ (on or position 1) the COM terminal is connected to the L1 terminal. When you switch it the other ‘way’ (off or position 2) the COM terminal connects to the L2 terminal.

If you are describing this switch to an electrician or electrical supplier you should refer to it as a 1 gang 2 way light switch and they will know exactly what you mean (see gangs and ways).

US – Strangely, our friends across the pond refer to this switch as a 3 way switch because it has 3 terminals.

Generic – if you asked someone in the field of electronics, they would probably describe this switch as a Single-pole, Double-Throw (SPDT) switch, to my mind a more useful description as this means the same in UK and US. A good electrician would understand this terminology but they, historically, rarely use it.

Intermediate or crossover switch (UK) 4 way switch (US)

Fig 2: Intermediate or crossover switch (UK) 4 way switch (US)


UK
– so, this (Fig 2) is what we call an intermediate switch, so called because it is used ‘in between’ two x 2 way switches to achieve 3 way switching (clarified below under multiway switching). Sometimes called a crossover switch for obvious reasons.

If you are describing this switch to an electrician or electrical supplier you should refer to it as a 1 gang intermediate light switch and they will know exactly what you mean.

US – in America they refer to this switch as a 4 way switch because it has 4 terminals.

GenericDouble-pole, Double Throw (DPDT) switch.

Multiway switching

Now we understand the different terminology used for the actual switches it is easy to appreciate why different switching arrangements are referred to using different terminology also.

Scenario 1: we have 1 light that can be turned on and off from two different light switches:-

UK – we would call this 2 way switching. Why? well a layman probably uses this terminology because 2 switches are used, whereas an electrician because two 2 way switches are used to achieve this. Either way, we are both referring to the same thing.

US – This would be referred to as 3 way switching because its uses what they would refer to a two 3 way switches.

Scenario 2: we have 1 light that can be turned on and off from three different light switches:-

UK – we would call this 3 way switching, well a layman certainly would (because of the three switches) and an electrician would assume this is what is meant but may also refer to it as 2 way plus intermediate switching.

US – This would be referred to as 4 way switching because it utilises what they refer to as a 4 way switch (what we in the UK call an intermediate or crossover).


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GANGS and their WAYS explained

No this is not a post about some dodgy Ross Kemp program:) Here we will attempt to clarify a subject that causes much confusion amongst  you budding D.I.Y. types…

Single gang 2 way, Triple gang 1 way, 2 gang 1 way, bla-d-bla-de-bla. So what the f**K does it all mean? Panic not my friends, it’s actually quite simple (although you wouldn’t think it if you have been reading many of the popular D.I.Y blogs).

Forget about the ‘WAYS’ first concentrate on the ‘GANGS’

So, just think of a gang as a single switch, simple as. If your light switch has one ‘switch button’ on it then it’s a single (or 1) gang switch. If it has two ‘switch buttons’ on it then it’s a double (or 2) gang switch. etc. etc.

single gang switch face

single gang switch

Double gang swith face plate

Double gang switch

Triple gang switch face

Triple gang switch

Glad we got that sorted?

‘GANGS’ are easy, so what of their ‘WAYS’

Well, as far as light switches (or gangs) are concerned, they can only be one of two things; a one way switch or a two way switch, end of.

One way light switch mechanism

One way light switch mechanism

A one way switch has two terminals, its the simplest of switch arrangements. it’s either on or off, thats all it does. When it’s ‘ON’ the COM terminal is connected to the L1 terminal (let there be light!). When it’s ‘OFF’ the COM terminal is connected to nothing and (the switch is open) no current flows through the switch.

 

 

 

Two way light switch mechanism

Two way light switch mechanism

A two way switch has three terminals its a little more complicated (any useful) than it’s one way cousin. When it’s ‘ON’ (position 1) the COM terminal is connected to the L1 terminal. But when it’s ‘OFF’ (position 2) the current is diverted from the L1 to the L2 terminal. This is what we use in circuits when we want to be able to switch a single light on and off from two different switches (see the two way switching lighting diagrams).

So, by way of a little revision

single gang switch face

single gang switch face

If we have a switch with one “switch button’ (1 gang) it can have a switch mechanism that is either one or two ‘WAYS’ so we have two possible options;

1/ A single GANG one WAY switch or

2/ A single gang two WAY switch

 

 

Double gang switch face plate

Double gang swich face plate

If we have a switch with two “switch buttons’ (2 gangs) it can have a switch mechanism that is either one or two ‘WAYS’ so we have two possible options;

1/ A Double GANG one WAY switch or

2/ A Double gang two WAY switch

And so on and so forth, Simples, you get the picture (I hope), I’m of to bed…

 


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Single gang 1 way light switch

There are two terminals in a one way light switch. When the switch is on, both terminals are connected together.

Typically, these terminals will be marked COM and L1 (sometimes L1 and L2). Although, technically, it doesn’t matter which way round you connect the wires, it is best to stick to convention and connect the permanemt live (from the supply) to COM and the switched live (to the lamp) to L1.

This is the most common type of switch, and is used where a light is controlled from a single switch (although you will often see a two way switch used, with one terminal left unused).

single gang switch face

single gang switch face

Single gang one way light switch

Single gang one way light switch

Switch mechanism

One way light switch mechanism

One way light switch mechanism

This is fairly obvious, but when the switch is ‘on’ the COM and L1 terminals are connected together. When ‘off’ they are not.


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2 gang 2 way light switch

This switch arrangement is basically two two way switches on a single face plate.

Some brands of light switch may have slightly different labeling on the terminals (such as C L1 L2 or even L1 L2 and L3).

Double gang swith face plate

Double gang switch face plate

Double gang two way light switch

Fig 2: Double gang two way light switch

Switch mechanism

Two way light switch mechanism

Fig 3: Two way light switch mechanism

Each of the gangs (or switches) above in Fig 2 (of which there are two) work like this (Fig 3): In position 1 (when the switch is down or ‘on’), COM and L1 are connected together (just like the one way switch). In position 2 (when the switch is up or ‘off’), COM and L2 are connected together.

There are no connections between the two gangs in Fig 2. Each gang is a single discreet switch.

Just to be different:)

The terminals on your switch may be a little different to those shown above but rest assured they function just as described above but the terminal pins are in different positions. You may see the following:

double gang two way light switch terminal variation 1

double gang two way light switch terminal variation 1

double gang two way light switch 3

double gang two way light switch terminal variation 2


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3 gang 1 way light switch

This format of light switch has three discreet switches on a single face plate. Basically this is three Single gang 1 way switches on a single face plate.

The only place you would use such a beast is if you had three lights (or sets of lights) in a single room each controlled by one of the single switches. This arrangement is not common, you are most likely to find a 3 gang 2 way switch used (this will do the same job but you will have spare L2 terminals on each gang that you would not need to use).

Triple gang switch face

Triple gang switch face

Triple gang one way light switch

Fig 2: Triple gang one way light switch

Switch mechanism

One way light switch mechanism

One way light switch mechanism

Each of the gangs (or switches) above in Fig 2 (of which there are three) work like this: when the switch is ‘on’ the COM and L1 terminals are connected together. When ‘off’ the COM is connected to nothing.

There are no connections between the two gangs in Fig 2. Each gang is a single discreet switch.


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3 gang 2 way light switch

This format of light switch has three discreet switches on a single face plate. Basically this is three Single gang 2 way switches on a single face plate.

Triple gang switch face

Triple gang switch face

Triple gang 2 way light switch

Fig 2: Triple gang 2 way light switch

Switch mechanism

Two way light switch mechanism

Fig 3: Two way light switch mechanism

Each of the gangs (or switches) above in Fig 2 (of which there are three) work like this (Fig 3): In position 1 (when the switch is down or ‘on’), COM and L1 are connected together (just like the one way switch). In position 2 (when the switch is up or ‘off’), COM and L2 are connected together.

There are no connections between the three gangs in Fig 2. Each gang is a single discreet switch.


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1 gang intermediate light switch

The intermediate light switch is used where three or more switches control one light and used in conjunction with two two way light switches to achieve this

single gang switch face

single gang switch face

Single gang intermediate light switch

Single gang intermediate light switch

Light switch mechanism

Intermediate light switch mechanism

Intermediate light switch mechanism

There are four terminals, usually L1, L1 and L2, L2. In one position, L1 and L2 are connected in pairs. In the other position, alternate pairs are connected.


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2 gang intermediate light switch

The intermediate light switch is used where three or more switches control one light and used in conjunction with two two way light switches to achieve this. It is effectively two single gang intermediate switches on one face plate.

Double gang swith face plate

Double gang switch face plate

Double gang intermediate light switch

Fig 2: Double gang intermediate light switch

Light switch mechanism

Intermediate light switch mechanism

Fig 3: Intermediate light switch mechanism

Each of the gangs (or switches) above in Fig 2 (of which there are two) work like this (Fig 3): There are four terminals, usually L1, L1 and L2, L2. In one position, L1 and L2 are connected in pairs. In the other position, alternate pairs are connected.


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3 gang intermediate light switch

The 3 gang intermediate light switch is used where three or more switches control one light and used in conjunction with two two way light switches to achieve this. It is effectively three single gang intermediate switches on one face plate.

Triple gang switch face

Triple gang switch face

Triple gang intermediate light switch

Fig 2: Triple gang intermediate light switch

Switch mechanism

Intermediate light switch mechanism

Fig 3: Intermediate light switch mechanism

Each of the gangs (or switches) above in Fig 2 (of which there are three) work like this (Fig 3): There are four terminals, usually L1, L1 and L2, L2. In one position, L1 and L2 are connected in pairs. In the other position, alternate pairs are connected.


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