Well I tried searching for a good messagboard on electrical help/handyman and came up with not much. Nothing that could help me here anyway, so I decided to post this here. I know very little about this stuff, but I think I can handle this.
Easy question:
I am trying to replace a regular up/down light switch in my bathroom(house built '66) with a light dimmer switch. I saw a tv show that showed how to do it and it looked soooooo easy, of course they were replacing a brand new switch with a brand new switch.
Problem: the old light switch, when pulled out, has a black wire coming from the back/top and a red wire coming from the back/bottom. That’s it-2 wires.
The new one I want to replace it with has a black wire from the back/right side and a black wire from the back/left along with a green wire coming out to, the ground, this much I know.
There is also a double outlet right next to the switch. It has a red and white coming out of it, the red meeting with the red from the switch I want to replace, and with 2 blacks from outside the box.
There are also 3 white wires coming out of 3 holes at the top of the little metal box that hold the outlet & switch, which are joined with the white from the outlet.
Question: Where do I put the green/ground from the new switch? There is no screw to attach it to that I’ve heard might be the answer. I can’t just let it sit there. Attach it to the metal box? Hook it to the nuetral/white?
If it has all metal conduit throughout the house, you can ground it to the box. Hardware stores sell little green grounding wires, with either a screw or a clip to attach to the box. An easy way to determine if this would be a good ground would be to take a voltage tester. Attach/touch the black probe to the box and touch it to each of the wires in there. If one of them gives you voltage (that would be the hot one) then you should be able to use the metal box as a ground.
Just let it sit there. Tape the end. There’s not much else you can do. You’re installing new stuff in an old application, so ideally you would give up $3500 or so to upgrade your service, but that isn’t likely.
BTW; switches do, once in a while, come apart inside and “live” the strap. Rare but possible, imo.
Peace,
mangeorge
Warning: while the above is mostly true, reading full line voltage from hot to ground does not necessarily mean the ground is good, as it cannot indicate the current-carrying capacity of the ground connection. You may have a fairly high-resistance path to ground, which may not be adequate for safety purposes. Best to contact a qualified electrician who can determine if the ground is good.
You need to call an electrician if you don’t know what to do from this point. The two main wires are both hot and ground in alternating fashion, reflecting the alternating current that runs your household appliances. The third wire replaces what in old houses was and is the third hole the round one in a standard electrical outlet. This is a preferred ground. The idea is that if you if you unwittingly join yourself into the circuit or create a short, that ground is the least resistant and will stop you from frying yourself too badly.
In old lights they didn’t bother the third wire and assumed that it was safe enough, or else they did it back at a junction box. In modern appliances and lights this third wire represents an improvement over the old system called a “ground fault interrupt.”
If you are unwise you may simply omit this wire from your set up and everything will likely be just fine. On the other hand, if you’ve done something wrong or there is a fault in the wiring your new switch may burn the house down or fry you to death if you touch it with a sweaty hand.
To do things properly your ground fault interrupt needs to go to a good ground, or to a Ground fault interrupt circuit breaker.
IANA an electrician and any errors here or my own, but the basic gist is correct.
Leave it out and everything will likely be fine. Then again you may fry.
try this
The green wire (relatively new requirement) on the switch is there to ground the mounting strap, not the device powered thru the switch. If you have no ground, you have no GFCI.
Connecting the green as Joey P suggests probably won’t hurt.
I should have mentioned to be SURE the power is off.
Yea, i turned the power off, and know red & black are supposed to be hot. I installed a motion detector outdoor light once, and have learned a bit from a book.
Mangeorge, the link expired.
Since there is no green wire currently attached, does that mean there is no ground now??
To fry or not to fry…since this is a bathroom and there’s water flying around, I think I’ll play it safe.
If so, then I would install a GFCI outlet next to the switch. They’re only about $8 or so. You’ll also need to purchase a new cover plate that can accommodate 1 switch and GFCI outlet.
There are two GFCI “line” terminals: “line hot” and “line neutral.” The GFCI’s “line hot” terminal should connect to a black wire that is always hot, while the GFCI’s “line neutral” terminal should connect to a white neutral wire. Just like a regular old outlet.
There are two GFCI “load” terminals: “load hot” and “load neutral.” The GFCI’s “load hot” terminal should connect to one side of the switch, while the GFCI’s “load neutral” terminal should connect to one side of the lamp (the lamp’s “neutral”).
The other side of the switch should connect to the other side of the lamp.
Using the above configuration, the outlet, switch, and lamp will be GFCI protected.
So, what Joey said in his first post should work for you.
I wouldnt worry about the resistance of the Ground as **QED** alluded. The reason being is that any ground is better than no ground, and in all my years of wiring I have never seen a ground in a home that read as a ground on the meter and turned out to be an unsafe situation. Just dont use the nuetral as the ground, turn off the circuit before wiring the switch, and try to get a good connection to the existing ground in the box. Or use one of the threaded holes in the back of the metal box for the 8-32 ground screw that comes with the grounding pig tail that you can get at the hardware store. These pigtails are just a solid peice (about 8" long) of green wire with one end wrapped around an 8-32 screw. Thread the screw into the back of the box and splice the other end to the green wire that comes out of the switch. If you don`t have a threaded hole in the back of the box then use the green ground wire that is on the outlet and wire nut the ground from the switch to the one that grounds the outlet. You will then have the outlet and the switch grounded to each other and also grounded to the box.
mangeorge a service upgrade should only cost around $1,000 or less. And it wouldn`t solve any internal wiring problems inside the walls.
Crafter_Man If you GFCI protect the switch and light (which is not required in the code) what happens if the switch is replaced at a later date with a dimmer? Or if a dimmer is installed on that load nuetral in the next room? If you dont know how the walls are wired, you may have nuisance tripping of that GFCI and lights or dimmers that wont work.
There are 3 neutrals coming in from 3 different holes from the top of the metal box, they all meet up with a neutral coming off the “2-outlet” housed in the same box. I’m pretty sure the switch is not connected in anyway with the neutrals-if my memory serves me right. The switch simply has two hot wires.
Even so, the nuetral that goes up with the hot from the switch may originate in that box. Does the switched wire from the switch go into the same raceway as one of the nuetrals?
*a raceway is any cable or conduit that carries the conductors.
The first question I asked was, “Is the neutral from the light also in the box?”, but I probably didn’t explain it clearly enough.
In order for this to work, there must be a “closed loop” as seen from the GFCI’s load terminals. In other words, there can’t be any external “neutral sharing” going on; all of the current on the GFCI’s “hot load” terminal must also show up on the GFCI’s “neutral load” terminal.
This should be easy enough to figure out if the OP is the least-bit experienced in electrical matters.
If one of those neutrals is connected directly to the light, then you could connect it to the GFCI’s “load neutral” terminal (as described in a previous post), and then the switch, GFCI, and light would all be ground-fault protected.
As I think about this more and more, your biggest problem is not the light switch/dimmer; there really isn’t much risk if it’s not grounded and/or protected from ground faults. Instead, your biggest problem is that you don’t have a GFCI outlet. So your #1 priority is to install one. Then, if it looks feasible & simple, go ahead and connect the light circuit (dimmer + light) to the GFCI load terminals as previously described.
Thats exactly it. I seem to recall when the dimmers didnt work properly they were on a different circuit but sharing a nuetral that was GFCI protected.
TBC, you just bought the wrong kind of switch is all. Some municipalities require an earth ground on switches, some don’t. It’s not a bad idea. The GFCI is a good idea, especially in a bathroom. In fact it’s required pretty much everywhere. If this switch and outlet is near the sink, you absoluteky need a GFCI.
So hire an electrician to connect the green wire as Joey suggests, to install the switch.
Or you can have him/her upgrade your service, including inside wiring as needed to meet code for remodel. It’ll cost you more than $1000 though. whuckfistle, I think, is talking about just the load center (commonly called a “service” or “breaker box”) on the outside of the house.
I don’t know if there’s “neutal sharing”. I do know the nuetral from the switch is joined in one of those yellow screw-on things with 3 other nuetrals that enter the box from 3 different holes. That’s it. They don’t touch light switch. Where they come from and where they go outside the box I don’t know.
2 hots join the switch and outlet. Then another hot leaves the switch.
I’ll have to go see what a GFCI box lookslike to figure out what you’re talking about, and if I’m capable of this. Hopefully I can figure it out then, or I’ll either table this until my cousins husband (an electrician) comes up for a wedding at the end of July and can do it/help, or just live with it the way it was originally.
I wish I knew more about this. thanks for our help, I did learn a lot though.
It’s this one, there are many more.
“The Complete Guide to Home Wiring: A Comprehensive Manual, from Basic Repairs to Advanced Projects (Black & Decker Home Improvement Library; U.S. edition) – by Black & Decker, The Editors of Creative Publishing international;”
That way, when your cousin-in-law comes, you can sound like you know what you’re talking about.
A GFCI simply measures any imbalance in the current flowing in the hot and back through it’s neutral. More current in the hot means some of it is going somewhere else (you?). That’s why they’re rated in mA.
