2

This has been a great site over the years, thank you. Now it’s my turn to post a question.

I did see some similar questions as mine; however, s/he used a different switch so I’m not sure if the answer is the same.

I have two lights operated by separate single pole switches. I’d like to replace them with dimmer switches. There’s not a lot of room in the box, so I found a switch that has two light dimmers on it (not a fan/light slider). It is Lider Electric LDDS-1P-WWP Dual LED dimmer switch singe pole… The box says singe; however, I assume it’s single. (The type-o on the box doesn’t add to confidence about the product.)

As you see in the picture of the dimmer back, there is one screw for the hot line (two backstabs in the back), two load screws, and of course ground.

As you see in the picture with the wires, each set has a black, white, and ground. They appear to go directly to the lights. If I follow the instructions and connect the white wires together, I still have one too many black wires, and no load wires.

I was going to try wiring it different ways, but thought I’d post the “what do I do?” question here. To be honest, it did try wiring it with one black (capped the other with a nut), and the two white wires. Both switches operated one light.

Also, I don’t know if this is related or maybe is a separate post: it’s regarding the dual toggle switch in the picture. With the power on and the toggles off, my non contact tester beeps up a storm when near the white wires and not the black wires. I would think it should be the other way around? When the toggles are on, both white and black beep up a storm.

(Note: I see the screw on the side of the box… is that at risk of arcing and be relocated?)

Thanks.

enter image description here enter image description here enter image description here enter image description here enter image description here enter image description here

9
  • 3
    You probably have a pre-NEC 2011 switch loop - if you took before pictures (with the wires that connected to the old switches still connected) that would clarify the situation considerably. If the white wires were connected to the old switches, (as the hooks imply) that's almost certainly what you had. The grounds are not properly connected here, either.
    – Ecnerwal
    Commented Mar 6 at 16:43
  • 1
    You have old switch loop. The whites are supposed to be hot(and marked black) while the blacks are switched hot. You need to find out if both lights are on the same single breaker. Someone else will be by on how to connect.
    – crip659
    Commented Mar 6 at 16:44
  • Thanks for the fast replies! @Ecnerwal: yes, the white and black wires were connected to the old switches. The white ones were on the brass screws. The grounds are attached to the switch.
    – SkierDude
    Commented Mar 6 at 17:12
  • The issue with the grounds is that the one loosely twisted around the other is NOT a suitable connection. The same configuration can be made properly with a "greenie" grounding wirenut that has a hole for the longer wire to pass out the end, which can then be tighted down to make a proper compression connection beween the shorter and longer wires.
    – Ecnerwal
    Commented Mar 6 at 17:15
  • @crip659: yes, they are on the same single breaker. This is in a room addition built in 2011 or so. The room is on the same breaker (3 receptacles, two lights). And, if the whites are supposed to be marked black, I can do that.
    – SkierDude
    Commented Mar 6 at 17:16

1 Answer 1

1

You can't turn a pair of switch loops into a double-switch (dimmer or otherwise) that only has one "line" connection. Why? Because in each cable the current needs to be balanced. In a switch loop that means "hot" (or "line") and "switched hot" (or "load") need to be in the same cable. That works fine for a single switch loop. But if you have two switch loops in separate cables then if you combine the "hot" wires onto one double-switch then there is no guarantee that each hot will have the same current as its matching switched hot. So that just doesn't work.

The alternatives are either to find a single-gang double-dimmer switch that has separate "hot" connections (I don't know if any are readily available) or, in your particular situation, a double-switch that includes a single switch and a 3-way switch with entirely separate connections.

As it turns out, combination 3-way/regular switches are available, such as this Leviton from Home Depot:

3-way/regular

Note that you can also use a double-3-way switch, as long as it has entirely separate connections for the two switches. That's because a 3-way switch works perfectly fine as a single switch if wired correctly.

13
  • 1
    Thanks. First part makes sense. Since there are two backstab holes in the back, I'm guessing that doesn't mean I can attach both hot lines into those and tighten with the screw. Regarding the 3-way switch for the other side of the box (not shown), only one of the switches needs to be a 3-way. I but I know the other one can be wired as a single.
    – SkierDude
    Commented Mar 6 at 21:58
  • Why would they sell a dual dimmer switch that operates two separate lights but with one hot line terminal if the issue could be unmatched current going to both?
    – SkierDude
    Commented Mar 6 at 22:04
  • 1
    Because (a) dual dimmers a relatively small market compared to general double switches (i.e., fewer uses), (b) old-style switch loops are gradually going away (none in new construction in most places for many years now), (c) if you are designing a new two-switches with lights setup today with neutral required everywhere, etc. using switch loops might actually use more wire than panel->2 switches->2 separate lights. Your setup is relatively unusual. Commented Mar 7 at 0:20
  • Coming back to this answer. It said “only one line connection”. However, there are two two spots for hot in the back. Can I use those?
    – SkierDude
    Commented Mar 7 at 3:05
  • 1
    Yes, from the picture and from the diagram in the installation manual, it looks like each of those holes (2 hot, 2 load 1, 2 load 2, 1 ground) can take a wire and that they are screw-to-clamp and not "back stab". But that doesn't solve the switch-loop problem. The reason for two "hot" wires is normally for one incoming (from the panel) and one going onward to the next switch or light or receptacle or whatever. Doesn't help here because of the balance each cable issue. Commented Mar 7 at 3:22

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.