Bathroom fan controller - installation

After designing and building the first prototype for the automatic bathroom Fan controller, was time to install it in the bathroom.

Here few notes about what I did.

Basically the bathFan goes to replace the original manual switch that bring power to the  fan.

The first thing to do was to open the box containing the switch and verify :

• to have available in the box both neutral and phase (the bathFan project need to be powered)
• to see how the connection are made

There are many ways to rewire the circuit, I opted for this solution :

• use the original switch to power the new circuit. In this way if something goes wrong or for maintenance/experiments (see below) I can cut off power to the new circuit.
• use just 3 new wires to connect the circuit to the power and fan
• install a new box to contain the new circuit (power supply + bathFan)

Box installation

After verify to have everything I need in the original box (neutral/phase/etc.) I decided to place the new box above the original box but more centered in order to have a good spot where to measure the humidity of the bathroom but not too high to don't be able to reach the pushbutton to manually activate the fan.

Checking with a stud finder and another tool to "see" behind the wall, I spotted an area with no studs and free from other wires/obstacles.

Of course I did use a electric box for drywall only, i.e. with no need to be attached to a stud.

The mechanical part of the project doesn't require a box attached to a stud to guarantee stability.

Before

After

The last picture shows the installed box already wired, let see more details.

Wiring

As said before I choose to wire only 3 wires.

• Neutral
• Phase (coming from the original switch)
• Fan wire

Of course the idea was to use standard colored wires and because the need for more flexibility I didn't use the extra rigid cable usually containing the wires for ground/neutral/phase.

So I went to buy 3 small roll of high insulated stranded THHN 14 gauge wire, like this one. 

But of course my luck was lost with the colors !

I did want to buy black (phase), white (neutral) and red (fan) but no black available.

So I did buy :

• 25 ft white (for the neutral)
  Connect to the neutral wires of the original box
• 25 ft red (for the phase)
  Connect to the original switch 
• 25 ft green (for the fan)
  Connect to the red wire in the original box bringing power to the fan

These were the only colors available and didn't want to wait more looking online.

So the wiring is NOT a code, but I'll leave a message in the box explaining the colors.

Installation

So after installing the box and wiring it, it was time to install the prototype.

To do so I used a quick wire connector (like the one in the photo) but with only 3 terminals, attached to the new 3 wires in the new box.

On the other side of the connector I did wire the 4 wires going to the circuit, i.e. :

• neutral for the power supply
• phase for the power supply
• relay contact (connected to the phase)
• relay contact (connected to the fan wire)

After verifying everything was working, I did put everything together.

This is the first prototype installed, now I have to run tests to see what I have to improve/fix and then start to work to prepare the final circuit, reprinting a new wall plate and painting it with the same wall color.
Also the circuit will be a little bit different, already have a new PCB with some enhancements.

Let's start some tests