Questions about wiring light and fan together in bathroom

Factual Questions
1

My daughter refuses to use the fan in her windowless bathroom when she takes a bath or a shower. No matter how much we explain, plead, or yell and scream. When we punish her for it, she’ll use it for a few days, then decide we aren’t paying attention and stop again. She won’t admit it, but I suspect it’s because she likes to watch videos on her phone when she’s in the bathtub, and doesn’t like the noise of the fan.

So, I’ve decided the solution to this problem is to wire the light and the fan together in one switch, removing her choice in the matter. I’m no stranger to tools, but I’m not a handyman, either. I’ve done some online research, and I think I’ve got the process down on how to achieve this, it looks fairly simple and straight-forward. What I’m iffy on is making sure I’m using the correct parts. Because, you know, burning down the house would suck.

It’s a double light switch, so I’m gonna pigtail the light and fan together, and buy a cover that’s half blank. I’m good there. My problem is, I can’t figure out if her bathroom is wired for 15 or 20 amps. My online meanderings have told me that code states that bathrooms are supposed to have a dedicated 20-amp circuit, but I don’t think that’s the case here. My condo was built in the mid ‘70s, and we bought it three years ago. I have no idea what the history of electrical work is on the place. The breaker box does not list bathrooms; just the major appliances, and several 15-amp circuits labeled “lighting.” The only outlet in her bathroom is a normal one, not GFCI, if that helps.

So, my questions:

From my online research, it appears that it is ok to use a 20-amp light switch, even if the circuit is 15 amps. Therefore, my conclusion is that I should install a 20-amp switch, since I am unsure about the circuit. Does this seem sound?

If I pull the whole light switch apart and discover that the wiring is 14-gauge, that will solve the mystery of the circuit, I suppose. I’m hoping not to have to do that, though, until I’m going to be replacing the parts. So, supposing this turns out to be the case, and I’m putting in a 20-amp switch, is it ok to use 12-gauge wire for the pigtail? Meaning, joining the existing 14-gauge wires for the light and the fan, then running a short 12-gauge wire into the switch? I’ve tried to Google this, but all the hits I get describe the opposite: existing 12-gauge wire with a 14-gauge pigtail, which I understand is a big no-no.

Or do I need to just suck it up and pull the whole thing apart, and go from there?

Thanks!

2

I’ll let the experts answer your specific questions, but I’d just point out that if she’s as recalcitrant as you describe, she may decide there’s nothing wrong with taking a bath in the dark. Makes it even easier to see the phone.

3

You can do just a little “pulling apart”. Shut off the power, pull the switch away from the wall, and eyeball the wire. If it is the thickness of a dime, it’s 14 gauge (and 15 amp); if a nickel, 12 gauge (and 20 amp).

Wait until an electrician comes along and backs me up before taking this as gospel. :slight_smile:

Also, there are combo light/fan units available. Might be a little more work, but something to consider.
mmm

4

Use whichever switch you want. If you really want to be sure, use the 20amp switch, but you’re not going to be drawing anywhere near that much power just to turn on a light and fan.

Look at it this way, if the bathroom is wired for 20amps and you use a 15 amp switch, you’re fine since it’s never going to see that many amps. If it’s wired for 15 and you use 20, you’re fine since it’s oversized.

When talking about what something is wired for, it’s really about the size wires inside the walls, less so about the receptacles and switches.

The problem is that is you install a 20amp outlet on a 20 amp breaker plug in a 20 amp load, you run the risk of starting a fire if the wires are rated for 15 amps. The fire, mind you, would be due to the wires overheating and the insulation catching fire or the now bare copper arcing to something.
On the other hand, plugging a 15 amp load into a 15amp outlet with a 15 amp breaker is totally safe if the wires are oversized.

TL;DR, either switch is fine.
ETA: Just go look at the breaker (or fuse) that’ll give you a very good idea as to what’s going on.
ETA2: Be really careful, bathrooms tend to have more than one circuit on them. The possibility of turning off the breaker for the lights/fans and still having another live line coming in or a shared neutral is very real. Get a neon voltage tester, learn how to use it and test each and every wire before you touch it.

5

Good to know, thank you. But I said in the OP that the breaker box doesn’t tell me anything. I’ve got a voltage tester, that part is covered.

What about mixing the wiring? Is it ok to use 12-gauge for the pigtail if the wiring in the walls turns out to be 14-gauge?

I guess I need to just pull the damn switch apart… :o

6

The breaker itself will tell you the amperage. Start flicking the unknown ones till you find the correct one. And while you’re at it write down or sticker the others along the way.

7

Oh… right. :smack:

8

A typical bathroom fan is less than 1 amp. A 100W light bulb is 0.9 amps at 120V. You are more than OK with a 15-amp breaker and 14 gauge wire.

9

It’s a easy job if you know how, but how you present yourself it may be better to hire a electrician or enlist a family member who knows this.

But perhaps have a heart to heart talk and come up with a solution, perhaps install a quieter fan, perhaps a smartswitch that will tur on for a set time after she has left the room.

10

Perhaps if you just replaced the fan with a low sone model? Mine is whisper quiet.

11

Yes, that will be absolutely fine. You can always use larger wire, it’s using smaller wire that has a potential to be problematic. And mixing different gauge wires won’t be a problem, the wires don’t care.
If you hooked up an amp meter to this switch, you’re going to see something 1 or 2 amps (less if the light is LED), maybe a little more or a little less, but nowhere near 15 or 20.
The 20 amp circuit you’re reading about, is usually meant for an outlet in the bathroom. Blow dryers, curling irons etc, start to get up over 15 amps. If you have an outlet in there somewhere, it’s likely on it’s own circuit.

12

Another, possibly easier option, if you have access to the fan wiring: Connect the hot leads from the fan and light together, the neutral leads from the fan and light, and connect those to one of the hot and neutral wires coming from the wall. Cap off the other hot and neutral and you’ve accomplished the same thing. Now one switch will control both the fan and light and the other won’t do anything.

If you’ve never done this before, this way will be a lot easier than trying to monkey around shoving all those wires, plus the ones you added back into a switch box.

ETA: this is assuming the fan ad light area single unit, if not, disregard this since it would then require doing some rewiring.

13

The old practice was to just power the bathroom with any handy branch circuit. I’m not sure when this changed but my 1967 house that was the case. Presumably too many people popped circuit breakers running a space-heater in the bedroom and then plugging in a hair dryer in the bathroom. Codes now require the separate 20 amp circuit for at least the receptacle. My preference is to still tap bathroom lights off a nearby branch circuit so the lights don’t go out if the bathroom GFCI receptacle trips.

Generally you only use 20 amp switches if you know you’re going to control more than 15 amps of lights, regardless of the branch circuit rating. A vent fan and any reasonable number of bathroom lights, even incandescent lights, isn’t going to be close. There’s nothing wrong with it but 12 gauge wire is noticeably harder to work with so I wouldn’t use a 12 gauge pigtail on a 15 amp circuit unless that’s the only scrap of wire I had handy.

As far as the taking a shower in the dark comment, they do make vent fans that run automatically based on humidity. I installed one because my bathroom had no fan and I didn’t initially want to mess with the tile wall for installing a separate switch.

I have no comments on the parenting aspects, except to note that one of my nieces went through a phase where she wouldn’t disrobe before showering and then dumped all her wet clothes on the floor and left them there after changing into dry ones. Her parents could never get a straight answer as to why.

I would also suggest replacing the bathroom receptacle with a GFCI.

14

I pulled the plate off, and I can see the wires. I was thinking I’d have to pull the actual switches out to get to the wiring, which is why I was reluctant. Anyway, they look rather thick. I used a sewing tape measure, and they appear to be just under 1/8 inch in diameter. But according to a couple of charts I looked up, that would be 8 or 9 gauge. Are the charts not counting the insulation?

The lights and fan are separate fixtures; the lights are in the wall above the mirror, and the fan is in the ceiling (of course).

I wouldn’t put it past my daughter to just bathe in the dark. But I think she’ll tire of it after a few times, once she feels like she’s made her point and “won.” I did look into the humidity sensing fans earlier today. I like that idea better, but I’m not about to try installing a fan myself, and money is tight enough right now that I can’t really justify the expense of the fan and hiring someone to install it. The wife and daughter are gone for the weekend, you see, and I was hoping to get this done and “surprise” my daughter when they get home. :smiley: But maybe I’ll give it some more thought and wait a couple of months until I can afford to do this right.

15

Wire gauge does not count insulation, just the bare copper, and before the 1980s insulation wasn’t as good as modern stuff so they compensated by making it thicker.

16

Wouldn’t ear buds also solve the problem?

17

Am I the only one who is nervous at the thought of playing with your phone while taking a bath?
mmm

18

What makes you nervous about that? Are you more worried about electrocution or killing your phone by dropping it in the tub?

Neither should bother you much, IMHO. My iPhone XS is rated IP68 (30 minutes under 2 meters of water) and even the years-old iPhone 7 is rated IP67 (30 minutes under 1 meter of water).

19

Have your wife upstairs on the phone when you do this. Much easier to label everything if she’s up there calling out what room/outlets you just turned off so you don’t need to constantly run up & down the stairs.
Another option, if you want to spend some $ is my gf has a combo light/fan/bluetooth speaker; that would get your daughter to use it. :wink:

20

I’m having trouble understanding the problem. My family rarely uses the bathroom fan.

It’s never caused any mold problems.

You can wire the fan and light together. Constantly turning it on/off will shorten the life of the fan.

It may shorten bulb life too. There’s going to be a current surge as the fan motor starts. Those spikes may be a problem for the bulbs.