Electrical/Wiring question

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MustISO

Lifer
Oct 9, 1999
11,927
12
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I have two 3-way light switches that control one light. I want to replace one of them with a dimmer. The instructions say that the dimmer can be installed as single-pole or 3-way.

The switch I want to replace has a ground (on a screw), a BLACK wire in the hole labeled common, a BLACK wire in one of the holes at the top of the switch and a RED wire in a hole at the top of the switch (across from the BLACK wire).

If I don't care about using the other light switch, can I wire this dimmer as a sinlge pole, and if so, how would I do that?

The dimmer has a black wire, ground wire and a red wire.
 
Number1

Number1

Diamond Member
Feb 24, 2006
7,881
549
126
Disengage the circuit breaker before you do anything.

Take the blacks wire labelled common in the hole and hook it up to the black wire on the dimmer switch. Take the second wire from the dimmer (red) and connect it to the ground connection on the junction box.

Call the fire department

Flip the circuit breaker back on.

If the circuit immidiatly turns itself off, flip the breaker back on IMMIDIATLY AND HOLD FIRMLY IN PLACE. The breaker may feel hot to the touch. See a.

If nothing out of the ordinary is going on, go back to the dimmer location and change the position on the dimer switch untill you see or smell smoke. Spark may be flying at this point. See a.

a. Do not be afraid, the fire department is already on its way.


Enjoy.

 
Number1

Number1

Diamond Member
Feb 24, 2006
7,881
549
126
On a more serious note, disconnect and remove the second old switch and connect the common wire to one of the 2 top wires of the old switch.

At the spot where you want the dimmer, connect the red wire on the dimmer to the black wire marked common on the old switch. Take the black wire on the dimmer and connect to one of the 2 top wires on the old switch.
Turn on the circuit breaker and test, if it does not work, use the other one of the 2 wires on top of the old switch.

This should work now.

 
mobobuff

mobobuff

Lifer
Apr 5, 2004
11,099
1
81
There should be 4 terminals on the dimmer switch. Two on one side, one on the other and a ground. The black wire going into the COM (Common) terminal of the switch that's already in there should go to the COM terminal of the dimmer (usually the top terminal, the other black wire goes to the terminal below it on the same side). The red wire connects to the single terminal on the opposite side. The ground should be connected as usual.

If the dimmer only has 3 terminals, it's a single pole switch. In that case wire both black wires coming into the wall box to the two terminals, cap the red wire, and connect the ground. Since you don't see a white (neutral) wire in the wall box where you want to put the dimmer, this means that that switch is "past" the light in the wire run, so it goes FIRST SWITCH > LIGHT > SECOND SWITCH. The black wire NOT connected to the COM terminal of the current switch will now be your neutral. You say the dimmer has a red wire, black wire, and ground wire. So your neutral should go to red, COM to black, and ground is normal. If you have to wire it this way, you'll have to leave the first switch on all the time (unless you remove the first switch completely, cap the two black wires together, and cap off the other end of the red wire (make sure you still have a ground connection)).

I'm pretty tired and my wiring knowledge is a bit rusty so you might want to wait for a confirmation.
 
mobobuff

mobobuff

Lifer
Apr 5, 2004
11,099
1
81
Your current setup should look like this. Use that for reference when trying to decipher my first post.
 
Number1

Number1

Diamond Member
Feb 24, 2006
7,881
549
126
Originally posted by: Analog
Wire it as a 3-way dimmer. There should be instructions with it on how its done.
Click to expand...

His dimmer has a ground and 2 wires. How is he going to wire it as a 3 way dimmer?

cool looking diagram!.
 
U

us3rnotfound

Diamond Member
Jun 7, 2003
5,334
3
81
Originally posted by: Number1
Disengage the circuit breaker before you do anything.

Take the blacks wire labelled common in the hole and hook it up to the black wire on the dimmer switch. Take the second wire from the dimmer (red) and connect it to the ground connection on the junction box.

Call the fire department

Flip the circuit breaker back on.

If the circuit immidiatly turns itself off, flip the breaker back on IMMIDIATLY AND HOLD FIRMLY IN PLACE. The breaker may feel hot to the touch. See a.

If nothing out of the ordinary is going on, go back to the dimmer location and change the position on the dimer switch untill you see or smell smoke. Spark may be flying at this point. See a.

a. Do not be afraid, the fire department is already on its way.


Enjoy.
Click to expand...

:roll:
 
B

BigJ

Lifer
Nov 18, 2001
21,330
1
81
Originally posted by: mobobuff
If the dimmer only has 3 terminals, it's a single pole switch. In that case wire both black wires coming into the wall box to the two terminals, cap the red wire, and connect the ground.

If you have to wire it this way, you'll have to leave the first switch on all the time (unless you remove the first switch completely, cap the two black wires together, and cap off the other end of the red wire (make sure you still have a ground connection)).
Click to expand...

This is fine. Just to clarify, cap the red wire that is coming into the box, not the red wire on the dimmer.

Since you don't see a white (neutral) wire in the wall box where you want to put the dimmer, this means that that switch is "past" the light in the wire run, so it goes FIRST SWITCH > LIGHT > SECOND SWITCH.The black wire NOT connected to the COM terminal of the current switch will now be your neutral. You say the dimmer has a red wire, black wire, and ground wire. So your neutral should go to red, COM to black, and ground is normal.

I'm pretty tired and my wiring knowledge is a bit rusty so you might want to wait for a confirmation.
Click to expand...

This is where I lost you. Where did a neutral come into play? The black COM is going to be the wire hooked up to the other switch, and the other black is going to be the load line for the light. The non-traveler black is supplying power, it is not a neutral.

Incandescent light switches in residential applications almost never have neutral lines hooked up to them. On top of that, you don't use a black wire as a neutral, end of conversation. Even if it is a white wire marked as a hot with black electrical tape (and you remove the black electrical tape), it's still not hooked up to neutral system and will not function as one.

To expand on what mobobuff said to completely override the other switch and just have the dimmer control the light:

With the first switch (the one you're not replacing). Take the line Black (the one that's not the black traveler) and hook it up to just the black COM (black traveler).

Then on the switch you're replacing, hook up the black COM line to the black wire, and hook up the other black wire to your red wire, which is going out to the light.

What you're essentially doing is just completely ignoring the first switch (it will not have any power going to it, and will not have any switching) and just having a straight wire run to your new switch.

 
B

BigJ

Lifer
Nov 18, 2001
21,330
1
81
BTW OP, are you sure there isn't a sticker covering a screw terminal on your dimmer or a fourth screw terminal? What brand/model # is the dimmer?
 
mobobuff

mobobuff

Lifer
Apr 5, 2004
11,099
1
81
Originally posted by: BigJ
Originally posted by: mobobuff
If the dimmer only has 3 terminals, it's a single pole switch. In that case wire both black wires coming into the wall box to the two terminals, cap the red wire, and connect the ground.
Click to expand...

This is fine. Just to clarify, cap the red wire that is coming into the box, not the red wire on the dimmer.

Since you don't see a white (neutral) wire in the wall box where you want to put the dimmer, this means that that switch is "past" the light in the wire run, so it goes FIRST SWITCH > LIGHT > SECOND SWITCH.The black wire NOT connected to the COM terminal of the current switch will now be your neutral. You say the dimmer has a red wire, black wire, and ground wire. So your neutral should go to red, COM to black, and ground is normal. If you have to wire it this way, you'll have to leave the first switch on all the time (unless you remove the first switch completely, cap the two black wires together, and cap off the other end of the red wire (make sure you still have a ground connection)).

I'm pretty tired and my wiring knowledge is a bit rusty so you might want to wait for a confirmation.
Click to expand...

This is where I lost you. Where did a neutral come into play? The black COM is going to be the wire hooked up to the other switch, and the other black is going to be the load line for the light. The non-traveler black is supplying power, it is not a neutral.

Incandescent light switches in residential applications almost never have neutral lines hooked up to them. On top of that, you don't use a black wire as a neutral, end of conversation. Even if it is a white wire marked as a hot with black electrical tape, it's still not hooked up to neutral system and will not function as one.

To expand on what mobobuff said to completely override the other switch and just have the dimmer control the light:

With the first switch (the one you're not replacing). Take the line Black (the one that's not the black traveler) and hook it up to just the black COM (black traveler).

Then on the switch you're replacing, hook up the black COM line to the black wire, and hook up the other black wire to your red wire, which is going out to the light.

What you're essentially doing is just completely ignoring the first switch (it will not have any power going to it, and will not have any switching) and just having a straight wire run to your new switch.
Click to expand...

Yes, you are correct. Like I said, tired and rusty. But it still works :)
 
B

bctbct

Diamond Member
Dec 22, 2005
4,868
1
0
Originally posted by: AlienCraft


As far as I'm concerned, 4-ways don't exist ;)
Click to expand...
Try telling my Mom that. :laugh: She's running them all over the damn place.
[/quote]


:Q
 
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