Humidity sensing bathroom fan with light: need wiring help

[vavet]

I’ve got it narrowed down to 2 replacement fans. The wiring diagram for one of them confuses me.
this is an existing installation. I don’t have the expertise to pull wires through walls which is what I really need to install this. I have a single 14/2 romex feeding this fan

im interested in having the humidity sensing feature trigger the fan when it reaches a threshold. I also want the ability to turn it on manually by removing power for 1 second and then reapplying power. My point is I don’t want to just hardwire it and bypass the wall switch. If I can make the light work when the fan comes on, that’s a nice feature, but it’s not needed. The bathroom has other lights.
I think if I connect the switched black wire to the brown and gray wires, that would make the fan work as intended with the humidity sensor being able to activate it or the wall switch. Right?

 

[fitter30]

Wiring diagram option 1
Right now have 2 wire with ground from light switch to fan?
2 function control need neutral white, red controls light, black for fan and ground
The way the RH control is drawn
Looks like low RH would bring the fan on not the light
High RH would bring the fan on if the optional wire is tied to the light.
Showing if brown and grey were wired to wall switch fan and optional grey wasn't wired to light fan would run all the time.

 

[mm08822]

Wiring diagram option 1
Two function control is using the ground wire and not the white neutral that makes the two function work.
Right now have 2 wire with ground from light switch to fan?
2 function control need neutral white, red controls light, black for fan and ground
The way the RH control is drawn
Looks like low RH would bring the fan on not the light
High RH would bring the fan on if the optional wire is tied to the light.
Showing if brown and grey were wired to wall switch fan and optional grey wasn't wired to light fan would run all the time.

No it's not. Clearly the housings are grounded and no further use of the ground wire is shown in either diagram.

 

[walta]

The first question is the current light wired like circuit A or B in my photos?

 

[chinboys]

The unit wants a 4-conductor Romex to feed power from your switch area.
Two hots (110V), neutral, and ground.

The two hot conductors (red and black) are to energize the humidity sensor for automated fan start\stop and to manually start\stop the fan.
The white line or neutral is for the current to return on.
The ground line is for current not returning on the white line to return on.

Since you have a three conductor Romex, I suggest you use the black hot to provide power to the manual start\stop of the fan.
And to tap the light circuit to the same manual start\stop of the fan.

 

[walta]

One or two wireless switches like the one in the photo could do what you want.

If it were me, I think I would tear out the drywall and run the wires. Drywall is cheap patching it is not that hard and the room needs new paint anyway.

Amazon.com

Walta