Understanding a switch wiring mistake.

[gromit]

I'm lost on a switch wiring issue. Details are below.
I decided to upgrade a bathroom exhaust fan toggle switch to a digital timer switch. The fan has both a light and fan, but each has a dedicated switch. The old fan switch had a load, line and ground attached. The new switch requires use of a neutral white wire. Four white wires were connected with a wire nut in the box so I probably made a mistake when I randomly chose one to use. With a meter the hot wire showed 120v when connected to the white wire that I chose to use. When I tried the wired up switch nothing happened and I double checked connections. Having messed with it enough for today, I reattached the old toggle switch and just put a wire nut over the white wire I had chosen, instead of reconnecting it to the 3 other white wires. The result was that the fan and light both worked, but the lavatory lights no longer worked. After reattaching the white to the other 3 whites that were originally grouped together all is ok.
Part of my problem is I didn't think the white wires were being used. Please enlighten me on what is going on with the white wires. I'd also like to know if my using one of the other white wires would resolve the original problem with digital timer switch. Thanks.

 

[Jerry1]

I cant quite picture your layout, but if I saw a wire nut with four wires in it, I would try to run one into the nut, not take one out to use. For example, if the new switch has a neutral (white wire), I’d try to add it to the wire nut, not take a wire out of the wire nut and connect it to the new switch.

 

[RobbieB]

The white wires are the neutrals, they are always connected. The hot (black) wire is switched. Line goes to black, load to fan. Never seen a switch with a ground attached.

 

[Just_Steve]

I like this site, helps me visualize.

https://www.do-it-yourself-help.com/ceiling-fan-wiring-diagrams.html

 

[Animorph]

Don't forget to turn off the electric circuit at the circuit breaker panel before working on the switchbox. (Mandatory warning.)

Yeah, all the neutrals (white wires) going out of the switchbox are connected to one neutral coming into the switchbox (from the electrical panel). Those are all necessary connections. You should see a similar bunch of black wires doing the same thing. Except the internal black wires go to the switches, while the "load" wires leave the switchbox and go to the fixtures.

Just add a short white wire of the same type to that bunch of white wires (undo the wire nut, add the new wire, redo the wire nut), and connect the other end of the short wire to the new switch's neutral connection. The GE smart switches usually come with a short white wire just for this. The old load and line wires from the old switch then go to the same load and line connections on the new switch.

The old switch did not require any power to operate, so it gets by with just interrupting the "line" side of the circuit mechanically. A smart switch or electronic timer switch requires power to operate, which has to come from a line wire and a neutral wire. That provides permanent power to the switch. Then it can control the load wire supplying line voltage (or not) to your fixtures. The neutral wires provide the return path from your fixtures back to the electric company.

 

[OldShooter]

... Part of my problem is I didn't think the white wires were being used.Please enlighten me on what is going on with the white wires. ...

An electrically powered household device needs two wires to operate. One we'll call "hot" and one we'll call "neutral." The "hot" typically has black or red insulation and the "neutral" always has while insulation. In addition there may be a connection to a safety ground, which will be bare copper or have green insulation.

The four white wires you found consisted of one wire coming from the panel and three wires going to devices. Through pure blind luck the one wire you chose to use was the one from the panel. By disconnecting the other three, you disconnected the other devices. One was the light. The others may have been outlets, maybe even in another room. As you found, all four wires need to stay connected together or stuff stops working.

The black wires work more or less the same way except that when a device is switched, like the light or the fan, the switch is added to the "hot" circuit and interrupts the electricity being carried on a black wire.

What you should do next is to buy and read a wonderful little book called "Wiring Simplified" (https://www.amazon.com/Wiring-Simplified-Based-National-Electrical/dp/099790531X) IIRC Home Depot also stocks it. Probably Lowes too. Read your way into it until you start to understand the situation you report here.

(There is an exception to this color coding for circuits that have two switches but we won't get into that here. There is also a wrinkle called "ground fault interruption" for bathrooms but that is out of scope here too. Wiring Simplified will explain all this.)

 

[RetiredGypsy]

I find Sparky Channel an excellent source for working through wiring.

 

[gromit]

Thanks everyone for the info. I can connect white from the switch timer to the existing grouping. Disconnecting the white from the other white wires explains why the lavatory lights wouldn't work. Since I moved here a year ago, I've messed with 3 switches and I haven't seen a white neutral connected to the toggle switches, just load, line and a ground wire. Because of that I incorrectly assumed that nothing on the circuit would be using a white neutral.