Space limitations replacing switches with Z-Wave devices

I just bought two Z-wave dimmers from Leviton to replace two ‘manual’ switches in a standard electrical wall box (US standard stuff).

The connections are easy, but while the old switches just had two wires (black/hot and black/load), I now need to additionally connect white/neutral and ground to each switch. The old switches are thin (width) and shallow (depth). The new switches are fat and deep. There doesn’t appear to be enough space to put in the new switches even without the added clutter of the extra wires. The use of solid Copper wires (as opposed to stranded/flexible) makes things that much harder.

I realize this is not specific to ST, or Z-wave, but is a real practical issue for the general idea of installing smart devices in existing installations. Are there any tricks/tips you guys can share? I was wondering if there are ‘low profile’ switches, perhaps?

In this particular box, there’s a ‘source’ cable (Hot/Neutral/Ground), two ‘load’ cables, and an onward feed cable … so lots of thick wires screw-capped and folded into the back of the box. I suppose a deeper box may be a possibility, assuming there’s nothing behind the box that’s currently there? I don’t relish the thought of removing the existing box though - I think the are typically nailed/screwed to a stud, and I don’t want to deal with wall patching as I have textured walls …

You are entering a realm where you need an electrician to be sure of local codes and not the least safety. I would be concerned with just taking advice online with something like this if you aren’t an electrician. Just my 2 cents.


The most important thing is your technique when you “fold” the wires inside the box. Try to fill every bit of space back there before you screw the fixture down.

One thing you can do that will save you a tiny bit of space is to use a copper crimp instead of a wire-nut on the ground wires that are not insulated.

For the insulated wires, use the smallest wire-nuts that will do the job. An orange one will be smaller than a yellow one. You probably won’t need any red ones. But, be sure the wire-nut you select is rated for the gauge, type, and number of wires that you are twisting.

Another thing might be to get a “old work” box that is deeper than the one you have. If you can get the original box pulled out without damaging the drywall too much, the new box can be fitted into the same hole.

As a last resort, most electrical wires are 5 to 10 inches inside the box. You might shorten them a bit before twisting your wire nuts. Don’t make them too short or you might have to tear the wall out to replace them.

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As others have said, you may need to consult an electrician.

As far as the general issue, different models are of different depths, so you can check the specifications before you buy something new. Quite often the in wall micros, particularly the newest ones, like Qubino or Aeotec nano, Will take the least amount of room in the wall.

To address the issue with the specific box, you basically have two choices. You can replace the box with a deeper back box if your construction allows for that. Some people with A light box that can’t be made deeper may substitute a double gang box for single gang and use the extra width if the issue is wires that were running behind the switch. It just all comes down to the specific details of each box as to what solutions might work.

The other option that will work is to use a box extender which essentially puts a collar on top of the box so you get an extra half an inch or so of depth that way. These usually only cost a dollar or two, so go ahead and get one which is fire safety certified. Your local Home Depot or similar store should have quite a few choices. This is a common issue when people put in tile, for example, and they then need to lift the switch up above the tile, so they’re easy to find. :sunglasses:

Lots more discussion of all these options in the following thread (this is a clickable link)


Thank you!

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Thanks for the information! I will pay more attention next time to device dimensions before ordering. I like the idea of a ‘collar’ to gain 1/2 inch or so; that may just do it for me.

I’m also re-thinking my plan here; I currently have a 2-gang (2 switch) box, and was going to replace both switches with smart dimmers. But I really only need to replace one; if I do that, I still have some space behind the other (old) switch to accommodate wiring and nuts, etc. So I’ll try that.

With solid conductor #14 wire, it’s hard to unfold-refold the existing wiring, which is 90% of what I’m dealing with here. But I’m going to try. You also have to ‘predict’ where the folds are going to be needed since everything moves together in there, due to the fact that all the grounds are joined tightly and close to point of entry. I bought a ‘crimp collar’ to crimp the grounds, rather than using a ‘nut’ - good tip.

This is all a good learning experience! I love planning, researching, and finally buying and configuring all these gadgets from a technology perspective, but hate it when the issue comes down to old, tangled wiring! Oh well!


I’ve been looking at the Aeotec Nano Dimmer, and I like what I see - it uses existing switches as controllers (that is, existing switches now just signal to the Aeotec, they no longer interrupt the main load), and works with/without a neutral - so great flexibility. However - I also read that you must have a minimum load of 20W for ‘no neutral’ operation, and 10W for ‘neutral’ operation, so if you are controlling a single LED light (~9W) you have to install a bypass load, which is a pain (this is their article: How to wire a bypass to your Nano Dimmer load. : Aeotec Help Desk ).

Are there micro switches that don’t have a minimum load requirement, and what happens if you do fall below their load threshold?

All dimmer switches have a minimum load requirement, but it does vary, so you just need to check the specs. And in some cases you can change the bulbs that you’re using so you find a bulb that draws a little more current and puts you over the minimum.

As far as what happens when you’re below the load, that again varies from model to model, but none of it is pleasant. Either the bulb never goes off completely (sometimes called the “low glow” problem) or you get flickers or buzzing.

I know that seems counterintuitive, that a bulb with too low a draw would stay lit, but it’s just what happens with a dimmer.

If you just get a plain on/off switch instead of a dimmer, it shouldn’t have a minimum load.

Does this mean the switch is using power below that min load all the time? I.e. if I have something with a 10W min load it might be drawing 9W continuously and this requires a 10W min load so the bulb doesn’t light up

I’m sorry, I don’t understand the question. If you’re asking if the switch itself is drawing 9 W of power continuously, then no.

Yes, that’s what I was trying to ask.

Let’s say we have a light bulb that draws 9W max and we install a 10W bypass load and a dimmer switch. When OFF, no power is consumed (must be the case as no power is delivered to the light/bypass). When ON, and at max brightness, is 9W, 10W, or 19W consumed? And when ON at min brightness, is, say, 11W consumed (10W for the bypass and (roughly) 1W from the bulb)?

Actually, the network radio inside the dimmer switch is always consuming a very small amount of power, that’s what keeps the radio on and allows it to hear the next “on” command even when it appears to be off. “No power delivered to the Bulb” is not the same as “no power consumed” for this reason.

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When ‘on’ at 100% consumption is roughly 19w. When ‘off’ it is as JD mentions. In between, it is proportional, split between the lamp and the artificial load.

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