Tutorial: How 3-way and 4-way switch circuits work
Controlling a light with two or more switches
This page describes how to use 3-way and 4-way switches to control lights from
two or more locations. This is the first of several related pages explaining
how to control lights with multiple switches. Click
here for an overview of all these pages.
Link to Sager
A light or lights can be controlled by more than one switch. The usual practice
in home construction is to use 3-way switches. "3-way" is the electrician's
designation for a single pole double throw (SPDT) switch.
A 3-way switch is shown below. Slide your mouse over it to see it change state
(requires Javascript enabled):
Here is a typical circuit in its four possible states.:
The switches must create a complete circuit for current to flow and the bulb
to light. When both switches are up, the circuit is complete (top right). When
both switches are down, the circuit is complete (bottom right). If one switch
is up and one is down, the current reaches a dead end, no current flows and
the bulb is off (top left and bottom left).
Note that the above color scheme does NOT reflect wire color. It is functional
coloring intended to illustrate the voltage state of each wire segment.
- Red indicates a hot wire (120 volts ac).
- Green indicates a neutral wire at ground potential.
- Blue indicates
a wire that is floating. "Floating" here means isolated from hot
and neutral by switches and/or light bulbs.
For choosing wire color for your circuit, see later in this page..
Controlling a light with three or more switches
For
more than two switches, one or more 4-way switches are added between the 3-way
switches. A 4-way switch has two positions. In the first position, the contacts
are connected straight through, so that the switch has no effect. In position
two, the switch cross connects the contacts on the left with the contacts on
the right, in an "X" connection. Slide your mouse over the image to
see the switch change state (if you have Javascript enabled in your browser).
To view an animation showing how this works in a complete circuit, see How
4-way switches work -- an animation. This one-minute animation is the
clearest illustration of the function of three- and four-way switch function.
(Don't worry about file size -- it should download in seconds even via a modem.)
Below is one example of a four-switch light circuit. This circuit also shows
rough-in boxes, wire nuts, and proper color code.
If you want to learn more, please visit our website triple light switch.
Note that the light can be placed anywhere in the return wire, shown above
as white. It may be as shown at the end of the run, but it may be between any
pair of switch boxes (as shown in a later figure), or even between the panel
and the first switch box. You can use as many 4-way switches as you like.
Color coding
For the official word, consult the National Electric code. Here I will try
to describe a bit of what the color coding is about, and how wires should be
colored in lighting circuits (and why).
Common practice in wiring a multiswitch circuit is to use two-conductor (black
and white) cable from panel to the first switch, and then three-conductor (black,
red, white) cable between pairs of switches. White denotes neutral, a current
carrying wire that is bonded to ground in the circuit breaker panel. Black and
red are used for "hot" conductors 120 volts with respect to ground.
The previous figure shows a circuit that follows this convention.
The NEC allows certain exceptions to this in lighting circuits, so that standard
two-conductor (black and white) and three-conductor (black, red, and white)
can be used, and used efficiently. In particular, it is often convenient and
efficient to place a light between two switches or between the panel and the
first switch. In such cases, it is convenient and permissable to bring 120 volts
to a switch via a white wire.
If you place a light in such a location, please be aware of the confusion that
can occur from this wire color. In the above picture, white is always neutral,
while black or red may be hot. If the light is located between the middle two
switches, then the white wire leading from the light to a switch is, in fact,
sometimes hot. To avoid confusion and to conform to code, use a black marker
to mark any "hot" white wire feeding a switch. Such color coding is
shown in the following example:
Other variations
Here are another couple of variations of 3- and 4-way switch circuits. All
the 4-way switches are optional. If you only need two switches, leave out
both the 4-way switches. You can also add as many 4-way switches as you like
in place of any one shown in the circuits that follow.
Here is an example of a light in the middle of the run. Notice the pattern
is very similar, but the color code is a little trickier. Two of the white wires
must be remarked black where the feed the switches.
By marking the wire as above, you are informing anyone working in the box later
that this is the wire that will deliver (occasionally) 120 volts to the switch.
This will enable the worker to properly wire replacement switches. (For circuits
with only two switches, just ignore the 4-way switches in the above figure.)
Here is one more variation, with the cable from the panel going directly to
the light box, which is in turn between some of the switches..
- More variations of 3-way (two switch) circuits.
- More variations of 4-way (three or more switch)
circuits.
Want more information on direct discharge type exhaust Fan? Feel free to contact us.
Related pages:
- 3-way switches and 4-way switches. This is
the main page of this collection.
- 4-way switches --
an animation. My clearest description of how three and four-way circuits
work
- 3-way switch variations. A collection
of several different arrangements of lights and two switches.
- What if you want to control more than one light? See Multiple
lights with multiple switches.
- Disconnected your switches and cannot figure out how to put them back? See
My 4-way switches don't
work or My 3-way switches
don't work.
D
Danuk
Hi,
I decided to turn my triple switch in the middle of the wall to a double and single switch by moving them apart. A TV is to be wall mounted between them.
When I opened the light switch there were more wires than I expected and I can't work out how to divide them so they work. I am tried to disconnect one item first and ensuring the rest still work, which I thought was a good way of working, but whenever I remove one part it all stops working.
The triple switch consists of (from left to right)
> bathroom light (2 spots and a standard bulb)
> bathroom extractor fan
> bedroom light (single light)
All are operated from this one single triple switch.
Opening the switch up, there are:
5 Black wires all joined together but not connected to the switch.
5 Earth wires all joined together but not connected to the switch.
From top, left to right on the switch:
L2 - Red Wire
L3 - Empty
L1 - 1 Red Wire
L2 - 1 Red Wire
L3 - Empty
L1 - 1 Grey Wire
L2 - 1 Red Wire
L3 - Empty
L1 - Red Wire
between the second set of wires above, L1 and L2 are connected with a short red wire, and then the L2 and the second L1 are connected with a short wire.
Any advice on how I should go about in determining what group of wires are for which item so that I can get to splitting these apart?
Also, anyone able to explain why the small wires are going between the L1's and L2's and if I have to do the same thing on my new switch?
T
The Ghost
Sounds like a lot of fun and games.
K
KEV 1 N
Any advice on how I should go about in determining what group of wires are for which item so that I can get to splitting these apart?
Don't touch it! Leave it alone! Please get an electrician to look at it, if you take it to bits you will not get it back together. You have been warned
telectrix
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if you post your location, sure one of us is close enough to sort this out without it costing an arm and a leg. or you could call Harry Potter.
HandySparks
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Are you keeping the existing switch position and adding a new one?
Gavin John Hyde
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I certainly wouldn't suggest anything without seeing it as its not unheard of for wiring to be done as the installer sees fit and only they understand. so the next person who comes along has no chance.
Best advice is get an electrician in who can inspect and do it for you.
Once had to sort out some wiring in a sports club changing rooms with live, neutral and earth all wired in red singles in conduit! made sorting it interesting, it was put in for free by a guy who played on one of the rugby teams who claimed he was an electrician.
K
KEV 1 N
I certainly wouldn't suggest anything without seeing it as its not unheard of for wiring to be done as the installer sees fit and only they understand. so the next person who comes along has no chance.
Best advice is get an electrician in who can inspect and do it for you.
Once had to sort out some wiring in a sports club changing rooms with live, neutral and earth all wired in red singles in conduit! made sorting it interesting, it was put in for free by a guy who played on one of the rugby teams who claimed he was an electrician.
What sort of electrician would only pinch red cable off the site to do a fiddle job?
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Risteard
telectrix
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well, we all know that rugby players are plumbers with their brains removed.
telectrix
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What sort of electrician would only pinch red cable off the site to do a fiddle job?
bloody obvious. it was before brown came in. DOH.
Gavin John Hyde
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bloody obvious. it was before brown came in. DOH.
Well this was just before Easter so the colours had changed a few years before then! No doubt it was something lying around and he thought that will do. This will make @telectrix smile, he was also the club plumber not that he was qualified mind, he did the toilets and showers which were always failing to work... In his eagerness to be useful he never considered if the work was anygood and as he was free nobody thought to ask if he was qualified!
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The connections sound straight forward, supply in and out with a live link across the switches and three feeds out. They all serve the bathroom so why would you separate them to fit a tv. How would a separate two gang and one gang make a difference surely the three gang is the same dimensions as a two gang?
telectrix
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The connections sound straight forward, supply in and out with a live link across the switches and three feeds out. They all serve the bathroom so why would you separate them to fit a tv. How would a separate two gang and one gang make a difference surely the three gang is the same dimensions as a two gang?
logical thinking after beer o'clock.I'm impressed.
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westward10
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Totally lost by what you are trying to achieve with this, I don't see the point of it at all.
telectrix
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K
KEV 1 N
Wonder if the OP will watch X factor on his new telly when he gets it on the wall between his two light switches?
E
einstein
grid switch? link the commons?
call a qualified electrician if in doubt
telectrix
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most wall mounted TVs have at lreast 2 " clearance behind them.plenty of room for a poxy light switch.
K
KEV 1 N
westward10
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Why would you separate a three gang for a single and double how does it make more space.
P
PEG
The OP's post is very well worded...could be a rat-in-a-tin
(Forgot you lot didn't grow up with me...long story short,pals dad had issues with an impromptu meeting of a dozen dog trainers,with dogs,gathering on a Sunday,parking everywhere,poo and litter,etc...We were young ,got down early,put a large rat in a Rover biscuit tin with holes,buried it in their training circle,just below the turf...
Absolutely hilarious consequences,took them 30 minutes to jack,dogs all needed throat lozenges ...)
HandySparks
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Why would you separate a three gang for a single and double how does it make more space.
I'm guessing that the OP wants the bathroom stuff near the bathroom, and the bedroom light switch near the bedroom door.
westward10
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I'm guessing that the OP wants the bathroom stuff near the bathroom, and the bedroom light switch near the bedroom door.
Ah yes at a quick glance I thought they all said bathroom.
Pete999
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i don't see the point of xfactor but millions watch it.
IMO the biggest load of Carp on TV to date, it has made millionaires out of no entities, I'm talking of the panel members.
P
PEG
Yeah,and that Bungle,off Rainbow,he's a dead loss now,hooked on spice...
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Devonchris
A
Andy78
Yeah,and that Bungle,off Rainbow,he's a dead loss now,hooked on spice...
You're not kidding
P
PEG
You're not kidding
Now THAT,has made me laugh.
Permission to use that image,as proof to my children,of the dangers of substance abuse...
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Andy78
A
Andy78
Now THAT,has made me laugh.
Permission to use that image,as proof to my children,of the dangers of substance abuse...
Fill your boots, it's not my image, lol.
That's the first Bungle before they realised that he was absolutely terrifying and softened his image...
Hi face at about the one minute mark
P
PEG
"See if you can find anything else with a pattern on it-and rub it...." said the man in an unconvincing bear suit...deary me...
Mr Saville must have took a look,and thought "Here's an employer and an industry,where i could probably hide for decades..."
I reckon the public safety films of that era,are the pinnacle. My two lads watch them in absolute disbelief...
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Andy78
D
Danuk
Thanks all - yes I splitting the switch so the bathroom light and fan would be near the ensuite door and the bedroom light near the bedroom door. Was planning on moving the bathroom one a foot to the left and the bedroom a foot to the right.
Once the TV is mounted it would be awkward to uses the switches as it would be dead centre of the TV.
Guess I best find an electrician. Thanks for taking the time to have a read though.
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westward10
westward10
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From what you described in #1 it is a straight forward job.
telectrix
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