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I replaced an old AC fan with light with a new DC fan (from the company Modern Forms) and wired it up to the old wall control and it set it up just to turn on/off the unit (obviously doesn't "control" the fan/light beyond just giving it power).

I am now trying to replace the old wall control with the proprietary Modern Forms wall control but the instructions don't cover my wiring situation.

The Modern Forms wall control works over bluetooth and only needs power; it doesn't have to be connected to the fan itself.

In the wall I've got a single 3-wire romex cable: white, black, red, and ground. White is hot (tested with multimeter), the others are not.

In the ceiling I've got two 2-wire romex cables; previously 1 was used for fan power and the other for the light's power. Makes sense. One of the cables's white wire is not used.

I can't inspect how the 3-wire ultimately gets split into 2 2-wires without an attic crawl, and I'm not quite ready for that level of effort just yet :-)

I know I can wire the wall's white (hot) directly to the wall's black/red and the fan will get power, but I can't make out how to wire the wall control, as there isn't a separate neutral and "to fan" wire that the instructions call for.

I know I can (but obviously must not... unless I want to kill someone or burn my house down) wire the wall's white (hot) together with the wall's black/red AND the control's black, and then the control's white directly to the walls ground (😱). The control's red (which is supposed to go to the wall's "to fan") would be left unused. This does work, as I briefly tested it.

My actual question: what is the correct and safe way to wire the fan to the control?

Please let me know in the comments if I need to test more wires or if you have more questions new more pictures or a better diagram.

New wall control instructions: wall control instructions

Old control's wiring (wall's white wire was connected to the control's black): old control's wiring

Wiring diagram:

diagram

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  • Is/was there any black marking on that white wire that is hot? If so, that's a switch loop bringing power down from the ceiling to be switched at the wall.
    – FreeMan
    Commented Oct 6, 2022 at 18:05
  • The black or red marking on the hot white is rarely seen in the wild, IME. It's in the proper illustrations. At some point it got into code, but evidently both electricians and inspectors continued to not actually do it or write it up as a violation, in large numbers.
    – Ecnerwal
    Commented Oct 7, 2022 at 0:13
  • Never hurts to ask, @Ecnerwal. I never knew about this requirement, but then, fortunately, I never ran any switch loops in my rewiring of my house.
    – FreeMan
    Commented Oct 7, 2022 at 14:10

2 Answers 2

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an attic crawl, and I'm not quite ready for that level of effort just yet

Well, get ready for it, because that's the only way to sort this out given what you have.

You need neutral to the switch, which means you have to find where the switch white gets connected to always-hot, and change it to neutral. While you are up there, you'll connect switch black to always-hot, and switch red is probably (almost certainly) already connected to one of the two cables going to the fan location - if not, make it so.

You should end up with one cable from the mystery location in the attic to the fan location unused - just cap off all the wires in that cable. The other cable to the fan location should have its black connected to switch red, and its white connected to neutral.

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  • Thanks, I'm happy to at least get confirmation that the current wiring setup was insufficient. Commented Oct 6, 2022 at 17:41
  • I voted you down for bad advice suggesting having to work in the attic. That is not needed, since the switch loop is no longer needed the wires from it can be used to bring neutral to the wall outlet from the ceiling box.
    – Traveler
    Commented Oct 7, 2022 at 0:04
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    The only place you can connect neutral to the switch box (without causing a gigantic code violation) is in the attic on the described wiring. The white and red from the wall box are "somewhere in the attic" NOT in the accessible fan box.
    – Ecnerwal
    Commented Oct 7, 2022 at 0:09
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    You really don't read the questions, do you? The controller being installed at the switch location needs neutral. And code since 2011 requires it, but that's not relevant here.
    – Ecnerwal
    Commented Oct 7, 2022 at 0:15
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    Bingo. You really don't want to do that. You really do need to visit the attic, unless you want to rip the ceiling open and repair it rather than visit the attic (some attics, I'd do that instead.) Remember, stuff gets into code mostly because people have died from it not being in code. It can seem arbitrary, but it's not.
    – Ecnerwal
    Commented Oct 7, 2022 at 1:17
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Your old fan could Not have worked without neutral, so it is there in the ceiling box.

The colors might be confusing.

Disconnect the current wiring to individual wires. In the ceiling there is wire nut connecting the Hot black and going to the wall. There it is switched and goes back to the celling as hot, most probably as white or red that would connect to the fan.

You do not need that (called switch loop) anymore, since you are switching wirelessly.

Connect the white (neutral) to the white (or red) going to the wall box. Now you will have neutral in the wall box and in the celing.

Use your multimeter and find out which one has 120 volt to the ground.

That would be your HOT.

Now measure between that hot and other wires to find 120 to identify the neutral in the ceiling box. Use the white that goes to the wall box from the ceiling and that is now your neutral.

Still not going to the attic.

Here is simple wiring

Old

old

New

new

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  • So, you don't understand switch loops, which are stunningly common in anything built before NEC2011 applied to the area. No neutral to the switch location yet neutral at the fan/light is normal for switch loops. As is always-hot white, which they have already measured.
    – Ecnerwal
    Commented Oct 6, 2022 at 18:34
  • @Ecnerwal in that case the Neutral is already in the ceiling box. Problem solved. Neutrals are newer switched. This has noting to do with switch loop.
    – Traveler
    Commented Oct 6, 2022 at 18:39
  • Has everything to do with a switch loop since they now need neutral at the switch.
    – Ecnerwal
    Commented Oct 6, 2022 at 19:50
  • @Ecnerwal Since the switch loop is no longer needed, use that wire as neutral
    – Traveler
    Commented Oct 6, 2022 at 20:07

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