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Discussion Starter #1 (Edited)
Hi all,

thanks in advance for reading. I am a weekend DIY’er (usually takes me doing something twice to get it right) and am comfortable with simple electrical wiring/safety.

I would like to add a timer switch to an existing 4 way switch, configuration has two 3-way switches and one 4-way that is physically located between the two 3-way switches.

from what I’ve found online there could be a number of ways that the line and load are wired into the switch, but I didn’t build the house, so I don’t know directly how things are wired.

heres what I do know:
1) the ”leftmost” 3-way switch is in a single box with only one 3-strand wire entering the box: with the switch removed and power on, this box has power to the black wire.

View attachment 631211

2) 4-way switch in a crowded box in the middle:
View attachment 631212


3) 3-way switch on the “right“. This box has two other switches, but all three insulated wires to the 3-way switch in question originate from a single 3-strand cable entering the box.

View attachment 631213

this doesn’t match up with an old chat (from 2014] was discussing (that one of the 3-way switches needs to have both the line and load from the same box). Does this mean I cannot replace one of the three way switches with the timer switch?

Is this setup amenable to swapping out the 4-way switch with one of the 3-ways and putting the timer switch in the position currently occupied by the “hot” 3-way switch?
 

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A "Handy Husband"
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You can replace either of the 3 ways with a 3 way timer as long as it does not require a neutral. If you timer requires a neutral you are SOL.


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Discussion Starter #3
Is there a way for me to put the timer switch in the “right” side box (with two other switches) and piggyback the neutral into one of the other switches?

fwiw I have tried this, installing the timer in the right side switch, and wiring the neutral wire from the timer to a bundled group of white wires.

In this config, the timer switch works, gets power and can switch the light on/off. But if I flip one of the other switches in the circuit it will cut power (reversibly) to the timer.
 

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From your description this is what you have for wiring. The power and fixture connections are at the four way.


4waypw2ndfd2nd.jpg
 

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Discussion Starter #5
Thanks JoeD. So does that mean I’m SOL? I read somewhere that one option would be to swap out the 4way switch with one of the 3way switches, and then add the timer in the vacated 3way switch position, is that an option here?
 

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A "Handy Husband"
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Thanks JoeD. So does that mean I’m SOL? I read somewhere that one option would be to swap out the 4way switch with one of the 3way switches, and then add the timer in the vacated 3way switch position, is that an option here?
To make that swap you would need 4 conductors and you have 3.

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You're not allowed to poach neutral from another unrelated cable. Neutral has to come from one of the cables involved in this lamp.

I don't understand what you're trying to accomplish. How is the timer supposed to interact with the 3-way switches? Will the timer turn the light on for X minutes no matter the position of the 3-ways?

If someone starts the timer for 10 minutes and the light is now lit, and someone throws a 3-way switch 4 minutes in, what should happen? Should the light turn off immediately; if so, when the timer runs out 6 minutes later should the light turn back on? Or should the 3-way switch throw be ignored because the timer has control, in which case when the timer expires what should happen? Should it remain off or should it go to whatever the 3-ways say?

What if someone throws the light on with a 3-way, and then 1 minute later someone sets the timer for 20 minutes? Should the light turn off immediately, remain off for 20 minutes then what - turn back on or stay off?

See, it gets really complicated really fast.

Can you clarify exactly what "action" you want to happen?
 

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Discussion Starter #8
Thanks for your reply. The switches currently control an outside light, I wanted to have it turn on automatically at dusk, off at dawn. If I can add a timer switch, I’d actually be ok with the other switches not working. The diagram indicates that the timer switch can be used with an existing 3 way, so I presume that the timer switch “knows” enough to not flip the switch if it is already in the desired state? (eg if I installed it in a 3 way, and had already turned on the light at 5pm, when sunset happens later, the timer wouldn’t turn the light off?)

Is there a way to leave out one of the existing switches? I can do without one of the existing 3 way switch. Maybe convert the “middle” 4 way to a 3 way? If this is a possibility, which 3 way can I exclude from the circuit, and how do I tell?
 

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Any one of the existing three ways can be eliminated by disconnected the three wire cable going to it in the four way box.
 

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Discussion Starter #10 (Edited)
thanks joed. The instructions for the timer switch (Honeywell pls750c) indicate that the timer switch should be connected to the light, and the line should be jumped across the other 3-way switch:

631318


I have diagrammed the current 4 way switch below, <EDIT> after detaching both black wires from the two three-line cables going to the 4-way switch, the one on the right side of the diagram (marked “HOT”) was hot when power is on (checking only from the “HOT” wire to the bundle it was previously wired to. (actually the middle switch was still energized/working with the “HOT” wire detached, does that mean another wire brings in power eg the red one at the bottom?)

so does it matter which current 3-way I exclude, and where I place the timer switch (in the other 3-way position, or in the current 4-way position)?

for clarity, the middle switch is for a separate light, and the left switch does not appear to currently switch anything (outlet?)

631321


thank you
 

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Thanks for your reply. The switches currently control an outside light, I wanted to have it turn on automatically at dusk, off at dawn. If I can add a timer switch, I’d actually be ok with the other switches not working.
That's IT!!?? That's easy! They make things called day-night sensors. They come in all sorts of packages - some screw into an Edison base and give an Edison base you screw the bulb into. Some mount on junction box covers. Some go in knockouts. Some plug in and provide a socket. You name it. Any package you want.

They look at ambient light level, and automatically turn lights on when dark and off when light. They are dog-simple, just a photocell. Some of them have a computer and timer that notes high and low light levels over the last 24 hours to calibrate when they should turn on - I had one in a very dark porch, that was on in broad daylight because it was so dim in there -- until 24 hours elapsed and it realized what day/night light levels were in that location. Then it worked properly. And this was a $8 Walmart cheapie!

Then you just bypass all the switches and send always-hot to the outside light. Done!
 

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Discussion Starter #12
Any one of the existing three ways can be eliminated by disconnected the three wire cable going to it in the four way box.
joed, thanks a lot for your help! Was able to swap out the 4-way for a 3-way and install the timer switch at the other 3 way, working as intended.
 
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