That would indicate either wire D is not neutral or the box is not grounded.
In any case you’ve done a great job and there’s not much more you can do. So button it up and enjoy yourself.
BTW Although I have an electrical background but I would have had to go through the same steps as you did and arrive at the same conclusion so don’t feel bad as you are learning.
John
This house has no ground 
Built in 1956 and updated from time to time. The previous owner installed GFI outlets everywhere to pass inspection. Although I updated the panel to 200A when I bought the house, I had no idea what was behind the plaster walls!
So I have learned that my house is wired with 2-wire Romex without a ground.
I will finish up with my new Inovellis and be thankful for that! I will not go into the garage where the previous owner disconnected one end of the 3-way switch there for some reason. I won’t. I won’t…well, maybe next weekend…
Thanks again!
Oops, guess I need a bit more help. With the Inovelli dimmer switch it looks like I don’t have 3-way any longer…unless the toggle switch is on, the dimmer doesn’t have power.
On the old dimmer switch I noticed that the wires destined for Line and Traveler were wired together? If I remove the C wire (traveler) I get the same result even when its disconnected. Should it also go into the Line screw on the Inovelli?
If I have the toggle switch flipped where the Inovelli gets power, the dimmer works to a point…so I guess the LED lights aren’t pulling enough and I’ll need to get a bypass or have an electrician run neutrals?
The issue with non-neutral and some low power LEDs is the LEDs never go off, there will always be a faint glow.
If you are seeing something else then let us know.
I’ll need to get a bypass or have an electrician run neutrals?
What would be great if the other end of the D wire can be found and determine if it could be a neutral. Actually it SHOULD be a neutral but it is what it is.
Is this an Inovelli Red or Black dimmer. The part number in your topic would suggest Black but just to be sure.
John
Its a black dimmer. When I toggle the power on the switch and get power to the Inovelli, I can turn the lights on…when I brighten them to a certain point, the Inovelli dimmer flashes red and the lights flash on/off.
So in summary, you removed the old rotary Lutron dimmer (which worked fine?)
Replace it with an Inovelli Black wired essentially the same way and not the inovelli is not working correctly.
Unfortunately I’ve not run into this issue, however the forum has a person with a similar issue here.
If you change the position of the dumb switch does it work the same?
Is it easy for you to change the LED bulbs (just for a test) the best would be some old incandescent bulbs.
John
Yes, the old dimmer worked. The only difference on the old dimmer is that both black wires went to the same location on the dimmer switch.
I was wrong on the description of the lights…when I raise the dimmer up to full, the lights flicker/blink and after a few seconds of this, the Inovelli LED cycles through the colors (red green blue) and then powers off.
This is with the traveler wire disconnected or connected. Its like that wire isn’t doing anything.
I’m not sure what you mean by changing the position (of the dumb switch). Do you mean swapping the location of the two switches?
Yes, the old dimmer worked. The only difference on the old dimmer is that both black wires went to the same location on the dimmer switch.
By this do you mean both black wires went into the same slot on the old dimmers? If so, remember the 2 wires going into the same slot doesn’t matter as they separate once inside the housing.
No, I meant to actually flip the switch. Then see what happens. With the traveler disconnected the light should go off.
Yes, when I flip the switch, the Inovelli switch goes dark and the lights go off. When I flip the switch again, the Inovelli switch illuminates and the lights stay off until I use the Inovelli dimmer to turn them on.
That is not what is expected. Can you make a quick chart of the house light and DImmer LED
for each combination
dimmer 3-way
on down
etc
Don’t take this the wrong way, but both of you are jumping down rabbit holes. IMO, the box with the old dimmer DOES NOT have a constant hot. As I mentioned before, you have to find the source of the constant hot and start with that. I’m guessing that either the other box or the light has the constant hot.
The reason that the dimmer comes on when when you throw the other switch is because it’s sending the hot over a traveler, which is probably wired to the line terminal on the Inovelli.
OP, you have to find the location of where hot comes into the run. I don’t think that is the box you are trying to put the switch in. IMO, BOTH of those 2-wires are being used in lieu of a 3-wire. That’s why the one white wire isn’t connected to anything.
Don’t take this the wrong way,
Never, it is always helpful to have another set of eyes on a problem 
I’m willing to rethink the wiring, especially since it’s not a typical configuration.
OP, you have to find the location of where hot comes into the run. I don’t think that is the box you are trying to put the switch in. IMO, BOTH of those 2-wires are being used in lieu of a 3-wire. That’s why the one white wire isn’t connected to anything.
I agree it would be nice but I’m of the mind there is both these boxes are missing either hot or neutral.
I think wires A and E are either:
In either case we are missing one of the two wires we would like to have.
Okay, breaker off. I have an old Micronta 22-212 in ohms mode, and the meter doesn’t budge a bit. The meter is working because I can touch two places on the box itself and it registers.
I should have asked to perform the same measurement on the G wire. If that is neutral and power is coming in on wire E then we could be in luck.
John
I think you may be correct, as I’ve been thinking the same thing. That means power is going to the light first, which AFAIK means the Inovelli won’t work. You’d have to use another brand that only requires one traveler so you can steal the other to route the hot to the primary box.
There is still hope the unconnected wire in the other box is a neutral…lets hope.
John
My money is on that is the other end of the unconnected white in the dimmer box. It’s not conventional, but if you don’t have 3-wire Romex, you can use two 2-wires. You only need three conductors, so the 4th one is unused.
Lets hope your right
So I need to test to see if I get anything on the ohm meter on the “G” wire (white wire in the dumb switch box)?
Yes when measuring from the white wire to the metal box.
Also something has been bothering me. Can you tell if the incoming cables are Romex (plastic jacket) or BX/MX which have a metal spiral jacket ?
It would be a shame if the white wire(s) were actually neutral but the box isn’t grounded.
John
Okay, sorry for the delay–it got dark and noone here to hold the flashlight!
The “G” wire, white solo doesn’t register a thing (power off, ohm mode, touching the white and the side of the electrical box).
I cannot see beyond the electrical box, all that I can see is a bunch of paper wrapper around the two wires. I have two sets of those as mentioned, each with a black and white rubber/plastic copper wire.
Its tough to see, especially when your not familiar with the hardware.
To summarize:
You’ve found the wiring between the two switches consists of travelers but no Hot or Neutral
Each box has a white wire that one would assume is Neutral but measurement to the metal box are “opens” and not able to verify the white are neutrals.
You said earlier “…So I have learned that my house is wired with 2-wire Romex without a ground…”
By looking in the box you were not able to see whether the cable is Romex or metal.
It would be great if D and or G were neutrals as then the Inovelli will work fine.
I’m likely being over conservative here but I don’t want to take a step unless we are sure of the situation.
I would suggest:
With your trusty Micronta 22-212 measure AC voltage between:
A and D = ______
E and G = ______
If one or both readings is ~120V then we are 90% sure the white(s) are neutral.
John
Green, clamp for Romex (plastic jacket)
Red, clamp for metal jacket cable
