# How to connect a Double Pole Switch?

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• posted on October 9, 2007, 2:16 pm
I am changing my light switches around the house from old fashion rusty ones to new ones. Yesterday I took off one of those switches and I realized that is a Double-Pole Switch and what is does is basically turning two lights in my hallway on and off. I went to home depot to get a new switch but they didn't have it so I decided to put the old one back but I can't remember how those wires were connected. I have two pairs of wires (black and white). On one pair (Pair A) my tester shows they are both Hot (both black and white wires). When I check it with Voltmeter, only Black one shows Hot (it's 110v). The other one (white) doesn't show anything. The other pair (Pair B) doesn't show anything.
Also there is another Switch for switching the same light as the end of hallway (Three-way Switch). I believe the other pair of wires (Pair B) is connected to Three-Way switch.
If I connect a light ball to Hot Wire from Pair A and one from the Pair B, light ball goes On. If I switch the three-way switch and do the same thing with another wire from Pair B, light ball goes On too. Something like this?:
H o o-------------o \\o-----N o o-------------o A B
If I check voltage of Hot wire from Pair A with another Hot from another switch box I will get 220v. I have no idea why I should have two phases inside my house (they should be all 110v).
Thanks,
Homer
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<%-name%>
• posted on October 9, 2007, 2:29 pm
How many switches are for this same light?
There is a "double pole switch" and then there is a "four way switch"
These are different.
If there are 3 or more switches for the same thing, then probably a four way switch. Below is a diagram.
4 way... http://www.selfhelpandmore.com/switchoutlet/4way /
Double pole... (See A DOUBLE KNIFE SWITCH) http://www.robomo.com/electronics/electronics/electronics106.html
"Homer" wrote in message

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<%-name%>
• posted on October 9, 2007, 2:29 pm
How many switches are for this same light?
There is a "double pole switch" and then there is a "four way switch"
These are different.
If there are 3 or more switches for the same thing, then probably a four way switch. Below is a diagram.
4 way... http://www.selfhelpandmore.com/switchoutlet/4way /
Double pole... (See A DOUBLE KNIFE SWITCH) http://www.robomo.com/electronics/electronics/electronics106.html
"Homer" wrote in message

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<%-name%>
• posted on October 9, 2007, 2:54 pm

Two Switches.
This switch is Double-Pole. On its back it says Two Input and Two Output (It's two single switches in one box).
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<%-name%>
• posted on October 9, 2007, 3:05 pm

So there are actualy two separate switch levers? How many screw terminals total?
Can you post a photo of the switch somewhere?
--
Regards,
Doug Miller (alphageek at milmac dot com)
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<%-name%>
• posted on October 9, 2007, 3:17 pm
On Oct 9, 11:05 am, snipped-for-privacy@milmac.com (Doug Miller) wrote:

What I have is a DPST (Four Screws, Two marked as Input, Two as Output).
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<%-name%>
• posted on October 9, 2007, 3:47 pm
"Homer" wrote in message

The only time I would use a double pole switch is with 240 volts. Like a range or hot water heater would use. But I would not need to place a switch on these. Of course there are saws and shop equipment which are 240 volts and it would be normal to place a switch going to the outlets for these.
So I'm trying to figure out why a double pole switch would be installed to switch a 120 V light?
Note you can use a continuity tester to be sure the switch is actually a double pole and not a 4 way. That might help.
Double pole = Off, neither input connects to either output.
4 way = Flipped either way (no off/on marking), one input connects to one output, flip switch and connects to other output.
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<%-name%>
• posted on October 9, 2007, 3:53 pm
P.S. Keep in mind if old house, people remodel these. There may have at one time been 3 switches controlling the light. Then remodel and they just tied wires together and hid in wall.
Or homeowner handiwork. No telling what they may have done!
Or at one time there may have been a large load which required two separate circuits on one switch. Then later remodeled and made the switch control a light instead????
All sorts of possibilities...
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<%-name%>
• posted on October 9, 2007, 3:55 pm

Tested already. It's Double Pole. Two screws marked as Inputs and two as Outputs. Inputs are not connected to each other or outputs if I flip the switch off. If I flip it On, one Input is connected to one Output and another Input is connected to the other Output.
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<%-name%>
• posted on October 9, 2007, 4:01 pm

Pretty hard to see how that could have ever functioned as a three-way switch.
I can believe that this one functions as a master switch: - if it's off, the lights are off regardless of the position of the other switch - it it's on, the lights are controlled by the other switch
--
Regards,
Doug Miller (alphageek at milmac dot com)
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<%-name%>
• posted on October 9, 2007, 6:31 pm
On Tue, 9 Oct 2007 08:47:14 -0700, "Bill"

Controlling lights on 2 different circuits?

--
77 days until the winter solstice celebration

Mark Lloyd
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<%-name%>
• posted on October 9, 2007, 4:20 pm

What you're describing doesn't conflict with your having a 4-way switch. In fact, seeing the connections labeled as "Input" and "Output" argues very strongly for your switch being a 4-way switch.
See about getting a ohm meter or a continuity checker. If you can't do this, just use a flashlight bulb, a couple of batteries, and some tape and wire.
Test the switch you have using the continuity checker. Assuming it's a 4-way switch you should see the following behaivor.
Switch set one way Input 1 connected to Output 1 Input 2 connected to Output 2
Flipping the switch you'll get Input 1 connected to Output 2 Input 2 connected to Output 1
If upon testing the switch you determine that it is a 4-way switch, then take a look at http://www.selfhelpandmore.com/switchoutlet/4way/ and see if it helps you understand how a 4-way switch is connected and helps you with your problem.
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<%-name%>
• posted on October 9, 2007, 5:19 pm
On Oct 9, 12:20 pm, snipped-for-privacy@smof.fiawol.org (John Cochran) wrote:

Thanks John. I will test it when I get home. From what you've described, it maybe 4-way. This is what I tested:
Switch set one way Input 1 connected to Output 1 Input 2 connected to Output 2
Flipping the switch you'll get Input 1 is not connected to Output 1 Input 2 is not connected to Output 2
If it's a 4-way, how can I replacing it with 3-way switch? Assuming we only have two switches now.
Homer
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<%-name%>
• posted on October 9, 2007, 6:33 pm
Homer wrote:

Ah, but after "flipping" the switch:
Is input 1 connected to output 2, and input 2 connected to output 1?
If so, it IS a "four way" switch and COULD have functioned fine with the hot wire from Pair 1 connected to just ONE of the two inputs and the two wires from Pair 2 to the two outputs. Nothing needs to be connected to the other input, you could cap off the other wire from Pair one.
Interestingly, if the other wire of Pair 1 IS a nuetral, things would still work fine even if it WAS connected to the other input of the four way switch. (Disbelievers, I suggest you sketch it out before igniting your flames...<G>)

Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat \'57 EE)
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<%-name%>
• posted on October 10, 2007, 12:22 pm
Another possibility is that the switch *should* be a 4 way switch, but someone replaced it in the past with the wrong switch (double pole).
The key to this would be how the light switches operated *before* the switch was removed from the wall.
A proper 3-way, 4-way, 3-way operating switch setup would allow any switch to turn on/off the light no matter what position any other switch was flipped to at a given time.
However if someone incorrectly replaced the 4 way switch with a double pole switch, then when that switch was flipped to off, the other 3 way switch(s) would not be able to turn on the light.
Again, all sorts of possibilities with this situation...
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<%-name%>
• posted on October 10, 2007, 12:57 pm

True -- but the OP said there's only *one* other switch controlling the lights.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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<%-name%>
• posted on October 10, 2007, 1:08 pm
On Oct 10, 8:57 am, snipped-for-privacy@milmac.com (Doug Miller) wrote:

Actually I bought this house recently and have replaced ALL old switches with new ones already. This one was the last one and didn't expect to get into complication.
Homer
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<%-name%>
• posted on October 10, 2007, 2:31 pm

OK, fine -- but there is only one other switch controlling these lights, right? And there was only one other switch before you started replacing switches, too, right? (You didn't replace a switch, and suddenly wind up with only two switches controlling these lights when there were three before, right?)
--
Regards,
Doug Miller (alphageek at milmac dot com)
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<%-name%>
• posted on October 10, 2007, 4:04 pm
wrote:

Keep in mind this is a house and it could have been remodeled in the past. So at one time there may have been three switches controlling the light.
Or if it had an builder like myself, I might have had an eye for the future and may have designed things for a future addition which would at that time include a third switch.
(Anything is possible in a house and especially if an unqualified handyman has been at work!)
Anyway if it is a double pole switch and it is 240 V, then you would probably have one romex being the "in" and the other romex being the "out". One wire would be going to the main panel, the other to the lights.
Or it if is 120 V and for some reason the hot and neutral are both switched, then again you would probably have one romex being the "in" and the other romex being the "out". One wire would be going to the main panel, the other to the lights.
Or if it is a 4 way wiring design and should have been a 4 way switch, then you would also probably have one romex being the "in" and the other romex being the "out". One wire would be going to one switch, the other wire to the the other switch.
If it is one double pole switch controlling two separate lights on two separate circuits (unlikely and I don't know why anyone would do this?), then one wire might switch the hot for one light and the other wire might switch the hot for the other light.
If it is knob and tube, then no telling unless you trace out the wires or do a bit of experimenting. Leave the experimenting to an electrician.
P.S. If you get an electrician and find out the answer to this riddle, please let us know what he says...
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<%-name%>
• posted on October 9, 2007, 3:02 pm

There are several types of double-pole switches. How many screw terminals does yours have?

You've probably figured this out already... but next time, sketch out which wires are connected to which poles on the switch before you disconnect anything.

Voltmeter is probably correct.

As expected.

Is there only *one* other switch (two total) controlling the same light?

Probably -- does flipping that switch change the voltage readings on either wire in Pair B?

Do you mean light *bulb* ??

What happens when you flip the 3-way switch? Does it go off?

What happens when you flip the 3-way switch again? Does it go off?

It better *not* be -- switches should *never* be placed on the neutral side of a circuit.

Why are you doing that? What do you expect to measure?

That is incorrect -- nearly all North American homes have 240V service. There are two separate hot legs, each at a potential of 120V with respect to neutral, and at a potential of 240V with respect to each other. You're measuring from one hot leg to the other, and seeing exactly what you should see when you do that -- but why are you doing that?
--
Regards,
Doug Miller (alphageek at milmac dot com)