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Old 06-19-2013, 02:39 PM   #1
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3 way as transfer switch?


I was wondering if using a 3 way as a transfer switch was: 1. Possible 2. Safe 3. Up to code.

I've read forums but they all refer to switching between the home circuit and a genarator. My situation is a little unique. I'm trying to switch between two hot lines for outdoor lights.

Here is the setup: (in progress)
I have a separate breaker for each yard and am working on the back. There is a 14-2 from the breaker to a GFCI. From there a 14-2 goes to a photocell. From the photocell a 14-3 wire is used throughout the rest of the line. The black powers the photocell and continues as an always live circuit. The red from the photocell is only live at night. The white is similar to the black - connects to photocell and keeps on going. Photocell is not grounded. Ground wire just passes through the box and is used as normal after that.

So, I want to have a couple switches to power some lights outside. What I want is a fast way to change the incoming line to the switch from "always live" to/from "live at night". Basically in day to day use I want the always live option, but if I'm away for a week I may want the "on at night" option so they operate as security lights. Yes I can always just open the box and move wires around but that's too much work for me

The only problem people mention with the generator example is the switching of the neutrals. Its the same nuetral for each hot wire as it is, so I was wondering if there were any other issues to look out for.

In case my setup sounds weird, what I did in the front yard was break off the tabs on the outlets and connected the top outlet to red and bottom outlet to black. Give me outlets for Christmas lights etc at night while also giving me outlets for things like lawnmowers etc during the day.
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Old 06-19-2013, 02:50 PM   #2
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3 way as transfer switch?


Since you are not involving a generator a lot of the restrctions are not the same or required.

How do you plan to connect the lights to the 2 hots; one constant and one switched? If connected to both the red and black, the circuit will backfeed onto the other hot.
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Old 06-19-2013, 03:02 PM   #3
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3 way as transfer switch?


Basically I want the 3 way to switch between black and red in (hot) and feed that as the line for the switch.

The switch for the lights will come after that and operate normally. If I drew a diagram of the wiring from the light switch on you'd think it was just another circuit.

So at night, if the transfer switch has the line selected as red then the light switches wont have power during the day, and turning those on/off during the day would have no effect since they have no power. This way I can leave those switches "on" and they will only be on at night.

I plan on using a blue wire throughout from light switch to fixture so if me or someone else comes in later its easy to know what's what btw. This is kind of necessary since what I'm doing isn't "end of line". ( the red/black.Etc will still pass through these boxes so the rest of the circuit can operate separately from these switches)

I also read the red/black may be "connected" for a split second when the switch is thrown. Is this true?
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Old 06-19-2013, 03:05 PM   #4
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3 way as transfer switch?


Btw I'm no expert on 3-ways, I'm just assuming this is possible based on what I think I know about how they work.
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Old 06-19-2013, 03:13 PM   #5
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3 way as transfer switch?


NFI on the code question, but..

as long as both "hots" come from the same phase, its relatively safe; However, 3-way switches were not made for this sort of thing, and WILL connect all 3 lines, when thrown.
Even if they are on the same phase, different voltage levels in the lines will cause a small arc in the switch every time you throw it.
Needless to say, 2 hots from different phases, will cause more than a small arc :P

V/r,
Mike
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Old 06-19-2013, 03:21 PM   #6
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3 way as transfer switch?


If you wired the lights off the common of the 3 way you could switch between power sources. The 2 different hots would connect to the traveler screws.
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Old 06-19-2013, 03:33 PM   #7
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3 way as transfer switch?


Quote:
Originally Posted by Jim Port View Post
If you wired the lights off the common of the 3 way you could switch between power sources. The 2 different hots would connect to the traveler screws.
Will this cause an arc? Would that possibly damage the photocell?
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Old 06-19-2013, 03:41 PM   #8
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3 way as transfer switch?


Quote:
Originally Posted by Conjur View Post
NFI on the code question, but..

as long as both "hots" come from the same phase, its relatively safe; However, 3-way switches were not made for this sort of thing, and WILL connect all 3 lines, when thrown.
Even if they are on the same phase, different voltage levels in the lines will cause a small arc in the switch every time you throw it.
Needless to say, 2 hots from different phases, will cause more than a small arc :P

V/r,
Mike

Thanks for giving me the term for what I'm doing. ("Phase"). will make describing what I'm doing way easier in the future!
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Old 06-19-2013, 03:50 PM   #9
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3 way as transfer switch?


The three way does not connect both at the same time. The operation is make - break - make.

There will be no more arc than a normal switch.
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Old 06-19-2013, 04:12 PM   #10
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3 way as transfer switch?


Any comment on code? I generally dont get permits but either build to code or make it easy to change to code should I either sell or get a visit from the county :P
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Old 06-19-2013, 05:29 PM   #11
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3 way as transfer switch?


I am not seeing any code issues with your proposal. The standard wiring codes would apply re box fill, cable type etc.
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Old 06-20-2013, 07:55 AM   #12
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3 way as transfer switch?


Quote:
Originally Posted by The Derek View Post
I'm trying to switch between two hot lines for outdoor lights.

You can use the 3-way as a single pole double throw switch. In the diagram below, up powers the light and down powers the receptacle.

no grounds shown for ease of drawing.
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Old 06-20-2013, 07:58 AM   #13
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3 way as transfer switch?


Or if devices are in separate locations
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Old 06-20-2013, 09:54 AM   #14
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3 way as transfer switch?


Quote:
Originally Posted by The Derek View Post
...
So, I want to have a couple switches to power some lights outside. What I want is a fast way to change the incoming line to the switch from "always live" to/from "live at night". Basically in day to day use I want the always live option, but if I'm away for a week I may want the "on at night" option so they operate as security lights. Yes I can always just open the box and move wires around but that's too much work for me
...
Can you accomplish what you want by wiring the photocell and a single-pole switch in parallel on the same line? The single-pole switch would act as a manual-on override for the photocell.
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Old 06-20-2013, 11:58 PM   #15
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3 way as transfer switch?


Are you thinking of doing something like this?
This will work. It works better if the photocell acts more like a switch then a resistor.
3 way as transfer switch?-untitled.png
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Last edited by goosebarry; 06-21-2013 at 12:00 AM.
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