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Old 09-03-2023, 07:24 PM   #1
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Off Topic: Electrical question

I only want to do a very simple project of replacing a bathroom fan switch with a timer switch. I turned off the breaker to the bathroom lights (2 wall lights on one switch) and adjacent fan switch. Both switches are now inoperative (no power). However, when I put the Klein tool on the switches, both are still hot. I turned off the nearby GFCI outlet and it is now cold but the switches are still hot. The current setup is:

Left switch - lights - top screw black wire, bottom screw black wire (does the light switch feed the fan switch?). No ground wire. (Is this OK?)

Right switch - fan - top screw black wire, bottom screw white wire. No ground wire. (OK?)

There are no other switches or outlets connected to these switches, but there is quite a nest of wires behind them in the box.

So, it is safe to take the switch out even though it reads as "hot"? Or what else should I try?

This is a 1985 house and generally quite well wired up.

Thanks!!

PS: Sorry the straight up photos come in as 90 degrees off.
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Old 09-03-2023, 09:17 PM   #2
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Answers

Quote:
Originally Posted by MNtraveler View Post
I only want to do a very simple project of replacing a bathroom fan switch with a timer switch. I turned off the breaker to the bathroom lights (2 wall lights on one switch) and adjacent fan switch. Both switches are not inoperative (no power). However, when I put the Klein tool on the switches, both are still hot. I turned off the nearby GFCI outlet and it is now cold but the switches are still hot.
...
So, it is safe to take the switch out even though it reads as "hot"? Or what else should I try?
Not safe. See the procedure that follows.

What is this "Klein tool?" One of those "magic" devices that signals when you just get near a hot wire? What does it do when there are two circuits in the same box? Give a misleading reading of hot, even if one of the two circuits is off?

Do you have a real voltmeter? Even one of those neon lamps with two test leads?

I think you may be turning off the wrong breaker. Or maybe each of the switches is on a different circuit breaker. Try this experiment:
  • Turn on both switches--both lights on.
  • Turn a breaker off.
  • Check lights.
  • If both lights still on, turn breaker back on
  • If one light is off, you have found the breaker for that one light.
  • If both lights are off, you have found the breaker for both lights.
  • Repeat until you have found the breaker(s) for both lights.
The GFCI outlet is irrelevant.

Quote:
Originally Posted by MNtraveler View Post
The current setup is:

Left switch - lights - top screw black wire, bottom screw black wire (does the light switch feed the fan switch?). No ground wire. (Is this OK?)

Right switch - fan - top screw black wire, bottom screw white wire. No ground wire. (OK?)

There are no other switches or outlets connected to these switches, but there is quite a nest of wires behind them in the box.
There are TWO ways to wire in this situation:
  1. Power comes into the switch box, then goes to the load (light or fan) box.
  2. Power comes into the load (light or fan) box, then goes to the switch box.
In case 1, both wires will be black.
In case 2, the black is the "always hot" wire, direct from the breaker. The white wire is the "switched hot" wire. (This is a consequence of the fact that cable comes with one white and one black wire--you can't get it with two black wires. Electricians are SUPPOSED to mark the white wire with black marker or black tape, but often don't.)
See my drawing, below. Left switch is Case 1. Right switch is Case 2.

(You will observe that because they don't have a black wire running from one switch to the other, it is very likely that the two switches are on different breakers.)

It seems to me that you have two loads on different circuits, one wired in Case 1 style, and one in Case 2 style. This would not be unusual if the fan also has a light. The idea is that if a breaker opens, you will still have one of the two lights available.
Quote:
Originally Posted by MNtraveler View Post
Left switch - lights - top screw black wire, bottom screw black wire (does the light switch feed the fan switch?). No ground wire. (Is this OK?)

Right switch - fan - top screw black wire, bottom screw white wire. No ground wire. (OK?)
Not unusual or unsafe to have no ground wire connected to a switch. If you have a metal box, the ground wire may be connected to the box. There's no place to attach ground wires to switches.
Quote:
Originally Posted by MNtraveler View Post
PS: Sorry the straight up photos come in as 90 degrees off.
See the red line in my signature.
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Old 09-03-2023, 09:21 PM   #3
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My lights and fan are 12V. turning off the 120v outlet will not turn off the power to lights and fan. DR
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Old 09-03-2023, 09:33 PM   #4
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House!

Quote:
Originally Posted by dangerranger View Post
My lights and fan are 12V. turning off the 120v outlet will not turn off the power to lights and fan. DR
This is is house, not his trailer.
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Old 09-03-2023, 10:03 PM   #5
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Quote:
Originally Posted by Larry-NC View Post
This is is house, not his trailer.
Correct. Off topic, 120V house wiring. Thx.
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Old 09-03-2023, 10:24 PM   #6
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Quote:
Originally Posted by Larry-NC View Post
Not safe. See the procedure that follows.

What is this "Klein tool?" One of those "magic" devices that signals when you just get near a hot wire? What does it do when there are two circuits in the same box? Give a misleading reading of hot, even if one of the two circuits is off?
*** The Klein tool is a non-contact voltage tester. I don't know that it gives any misleading readings as normally when a breaker is off the most you get is a very slow beep representing background energy from something else in the wall.

Quote:
Do you have a real voltmeter? Even one of those neon lamps with two test leads?
*** Yes, I can pursue using that. However, there is no visible ground wire.

Quote:
I think you may be turning off the wrong breaker. Or maybe each of the switches is on a different circuit breaker. Try this experiment:
  • Turn on both switches--both lights on.
  • Turn a breaker off.
  • Check lights.
  • If both lights still on, turn breaker back on
  • If one light is off, you have found the breaker for that one light.
  • If both lights are off, you have found the breaker for both lights.
  • Repeat until you have found the breaker(s) for both lights.
*** The breaker is correct because when the breaker is off nether the lights nor the fan have power. The two light fixtures are wired to the one switch (left). The fan is on the other switch (right). (There was a typo in my original post saying the switches are "not inoperative" (makes no sense) which I corrected to say, after the breaker is thrown, they are "now inoperative" (no power).)

Quote:
The GFCI outlet is irrelevant.
*** I killed that circuit in case it was sending its power line through that box as it is immediately adjacent to the switches. It didn't matter.


Quote:
There are TWO ways to wire in this situation:
  1. Power comes into the switch box, then goes to the load (light or fan) box.
  2. Power comes into the load (light or fan) box, then goes to the switch box.
** There is only one "box" (plastic) with two switches, one is lights (2 fixtures on one switch), the other is the ceiling vent fan. But I gather that is called two boxes.


Quote:
In case 1, both wires will be black.
In case 2, the black is the "always hot" wire, direct from the breaker. The white wire is the "switched hot" wire. (This is a consequence of the fact that cable comes with one white and one black wire--you can't get it with two black wires. Electricians are SUPPOSED to mark the white wire with black marker or black tape, but often don't.)
See my drawing, below. Left switch is Case 1. Right switch is Case 2.
** The light switch has black on both terminals. The fan has black on top, white on the bottom. So I gather that is Case 1. However the light switch has no white wire that I can see, only two black wires.

Quote:
(You will observe that because they don't have a black wire running from one switch to the other, it is very likely that the two switches are on different breakers.)

It seems to me that you have two loads on different circuits, one wired in Case 1 style, and one in Case 2 style. This would not be unusual if the fan also has a light. The idea is that if a breaker opens, you will still have one of the two lights available.
*** I think there might be a black wire from the switch to the fan switch, but I haven't pulled them out to see yet. They are both on the same breaker as the one breaker turns off both the lights and fan power. There is no light in the fan.

Quote:
Not unusual or unsafe to have no ground wire connected to a switch. If you have a metal box, the ground wire may be connected to the box. There's no place to attach ground wires to switches.
*** Thanks. The box is plastic. Each switch appears to have a green ground terminal, visible in one of the photos. The screw is extended in each case and not connected to anything.

Quote:
See the red line in my signature.
*** Good to know. Many thanks!
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Old 09-04-2023, 08:56 AM   #7
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More...

Quote:
Originally Posted by MNtraveler View Post
*** The Klein tool is a non-contact voltage tester. I don't know that it gives any misleading readings as normally when a breaker is off the most you get is a very slow beep representing background energy from something else in the wall.
My thought was that if the box was served from two circuit breakers and you were turning off one at a time, that the tool would always alert.
Quote:
Originally Posted by MNtraveler View Post
*** Yes, I can pursue using that. However, there is no visible ground wire.
You don't want to measure voltage to ground (although you can do it in a pinch). You want to measure voltage from hot (black--sometimes red, blue, or other non-white color) to neutral (always white). If this box is wired as Case 1, there will always be neutrals tied together, maybe stuffed at the back. Usually you can force a voltmeter probe into the wire nut without disconnecting anything.

Not sure ground was required in switch-only boxes in 1985. The concern was safety for plug-in appliances.
Quote:
Originally Posted by MNtraveler View Post
*** The breaker is correct because when the breaker is off neither the lights nor the fan have power. The two light fixtures are wired to the one switch (left). The fan is on the other switch (right). (There was a typo in my original post saying the switches are "not inoperative" (makes no sense) which I corrected to say, after the breaker is thrown, they are "now inoperative" (no power).)
Good that you are assured that both switches are not powered now.
Quote:
Originally Posted by MNtraveler View Post
*** I killed that circuit in case it was sending its power line through that box as it is immediately adjacent to the switches. It didn't matter.
Pretty sure that they are isolated. If you turn off the breaker that feeds that box and the breaker that feeds the two switches, maybe the Klein tool will cease to alert.
Quote:
Originally Posted by MNtraveler View Post
*** There is only one "box" (plastic) with two switches, one is lights (2 fixtures on one switch), the other is the ceiling vent fan. But I gather that is called two boxes.
No, just one box. I drew the Case 1/2 pictures separately to make it less confusing.
Quote:
Originally Posted by MNtraveler View Post
*** The light switch has black on both terminals. The fan has black on top, white on the bottom. So I gather that is Case 1. However the light switch has no white wire that I can see, only two black wires.
Possibly the fan is Case 1 and the light switch is Case 2. If you take my drawing and flip Case 2 left-to-right, you see that a single hot (black) wire from the breaker feeds both the Case 1 and Case 2 switches. In this case you would see both switches connected to the same black wire. When I do this, I add extra length to the black wire, strip 1/2" about 2-3 inches from the end, and wrap it around one switch terminal screw, then strip 1/2" at the end are wrap it around the second terminal screw.
Quote:
Originally Posted by MNtraveler View Post
*** I think there might be a black wire from the switch to the fan switch, but I haven't pulled them out to see yet. They are both on the same breaker as the one breaker turns off both the lights and fan power.
Just what I said immediately above.
Quote:
Originally Posted by MNtraveler View Post
*** Thanks. The box is plastic. Each switch appears to have a green ground terminal, visible in one of the photos. The screw is extended in each case and not connected to anything.
I don't know the history. Pretty sure that grounding switch brackets was not required before then. Don't know if it is required in all jurisdictions now, or just the heavily-unionized ones.
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Old 09-04-2023, 09:41 AM   #8
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Thanks a lot, Larry-NC! I think I need to turn off more breakers until there are no powered circuits stuffed in the box.
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Old 09-04-2023, 10:12 AM   #9
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If you are unsure.... turn off all the breakers OR the Main
anyone complains... tell them to bite their butts!


Maybe time to update your labels in the breaker box too.
Two people on phones is so easy to do the updated labels



As Larry said ... those non contact voltage sensors can be a PITA in a confined spot


Once you know which switch you are changing .... it's fairly simple to swap it for a timer switch


Measuring with a multi meter is so much more accurate and you can do much more with one...
Highly recommend you get one and learn how to do the basics. Get one that can do AC/DC amps with a clamp. Mine has lasted 20years and is the most used electrical tool I got...



Also keep an eye out in the flea market for GOOD wire strippers , crimpers and insulated pliers cutters and screwdrivers.
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Old 09-04-2023, 11:24 AM   #10
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Originally Posted by Larry-NC View Post
I don't know the history. Pretty sure that grounding switch brackets was not required before then. Don't know if it is required in all jurisdictions now, or just the heavily-unionized ones.
Has been required since 1999 NEC.
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Old 09-04-2023, 12:16 PM   #11
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Go to the main breaker, usually at the top of the panel, but sometimes remotely mounted. Turn the main off.
Option 2 turn every breaker you can find off.

If that doesn't work we can dig deeper. Electronic voltage detectors can be quirky until you get to know them. Doesn't sound like you have time for that.
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Old 09-04-2023, 12:18 PM   #12
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Originally Posted by Larry-NC View Post
My thought was that if the box was served from two circuit breakers and you were turning off one at a time, that the tool would always alert.
Once I turned off the surround rooms’ light breakers, there was no power detected in the box and I was able to safely pull out the switches.

However the wind-up timer makes a horrible ticking sound like a 1950s kitchen timer, so it’s back to the store for a digital model. Didn’t mind the spring windup but that ticking would drive me crazy.

Now my next and hopefully final question: the fan switch did not have black and white wires (the white was stray paint). It has two black wires, and the electrician wrapped one with red tape. The fan timer has two identical black wires and the instructions do not say anything except to “connect to the wires” (so helpful!), so does it matter which is which?

By the way the voltmeter would not have detected current at these switches with the breaker off but the NCVT did detect power in the box so that was an extra measure of safety for me that a pro probably would not have needed.

Many thanks!
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Old 09-04-2023, 12:36 PM   #13
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Originally Posted by Aussieguy View Post
If you are unsure.... turn off all the breakers OR the Main
anyone complains... tell them to bite their butts!


Maybe time to update your labels in the breaker box too.
Two people on phones is so easy to do the updated labels



As Larry said ... those non contact voltage sensors can be a PITA in a confined spot


Once you know which switch you are changing .... it's fairly simple to swap it for a timer switch


Measuring with a multi meter is so much more accurate and you can do much more with one...
Highly recommend you get one and learn how to do the basics. Get one that can do AC/DC amps with a clamp. Mine has lasted 20years and is the most used electrical tool I got...



Also keep an eye out in the flea market for GOOD wire strippers , crimpers and insulated pliers cutters and screwdrivers.
I turned off the surrounding room light breakers and then the box was cold. I have a multimeter that I use all the time for all RV work but I never do A/C work except simple stuff like replacing a switch or socket. The NCVT was a safety check that told me the box was still hot. I probably could have pulled out the switches with the breakers off since they had no power but the extra safety measure was good.

Thanks for your input!
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Old 09-04-2023, 03:18 PM   #14
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This is how the two switches are wired, one for the fan the other for the light.

Two black wires - one power, the other load side.
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Old 09-04-2023, 03:53 PM   #15
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Which is...

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Originally Posted by MNtraveler View Post
This is how the two switches are wired, one for the fan the other for the light.

Two black wires - one power, the other load side.
Which is Case 1.

Something I meant to ask earlier and never did.

This (original post) is a simple windup timer right. Two terminals. It just closes the switch when wound up and opens it when the timer expires. You don't need to know which wire is which. A mechanical switch doesn't care. We have these in the storage lockers we rent. Just remove the two wires from the old switch (with power off) and connect them to the new switch. Period.

But now that you've changed the problem to a digital timer, the problem has likely changed. These may have three wires: one for hot (black) in from breaker, one for hot (black) out to fan, and one for neutral (white) added to wire nut.
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Old 09-04-2023, 04:30 PM   #16
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Originally Posted by Larry-NC View Post
Which is Case 1.

Something I meant to ask earlier and never did.

This (original post) is a simple windup timer right. Two terminals. It just closes the switch when wound up and opens it when the timer expires. You don't need to know which wire is which. A mechanical switch doesn't care. We have these in the storage lockers we rent. Just remove the two wires from the old switch (with power off) and connect them to the new switch. Period.

But now that you've changed the problem to a digital timer, the problem has likely changed. These may have three wires: one for hot (black) in from breaker, one for hot (black) out to fan, and one for neutral (white) added to wire nut.
OK I understood Case 1 to be wired with white and black in the picture but I now see the white is really not "in" the switch, it is tied off with a wire nut in the box and is connected to the load. Only the black goes in and out of the switch itself. Got it.

I will see what the digital one looks like when I pick it up.

Thanks again!
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Old 09-04-2023, 04:33 PM   #17
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Right!

Quote:
Originally Posted by MNtraveler View Post
OK I understood Case 1 to be wired with white and black in the picture but I now see the white is really not "in" the switch, it is tied off with a wire nut in the box and is connected to the load. Only the black goes in and out of the switch itself. Got it.

I will see what the digital one looks like when I pick it up.

Thanks again!
Right. You never interrupt the neutral, just the hot side.
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Old 09-04-2023, 04:34 PM   #18
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Thanks

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Originally Posted by Mike134 View Post
Has been required since 1999 NEC.
Thanks for confirming that.
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Old 09-04-2023, 05:52 PM   #19
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I learned a lot from our workplace electrician
he had to do all the electrical work (as much as possible) without interrupting my workers

he showed me .... how to test fuses, work with 3 phase 440v...

must not have paid enough attention on the section on how to make sure the fuses were seated correctly......... on a hot3 phase panel
learnt real quick, don't hold onto the panel's door while inserting fuses.
sweaty hands or a missing probe cover sure gives you a nasty zap


A lot of his wisdom still is pertinent 30yrs later... most important of all
"treat everything as if it is live"
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Old 09-09-2023, 08:00 PM   #20
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Quote:
Originally Posted by Larry-NC View Post

This (original post) is a simple windup timer right. Two terminals. It just closes the switch when wound up and opens it when the timer expires. You don't need to know which wire is which. A mechanical switch doesn't care. We have these in the storage lockers we rent. Just remove the two wires from the old switch (with power off) and connect them to the new switch. Period.

But now that you've changed the problem to a digital timer, the problem has likely changed. These may have three wires: one for hot (black) in from breaker, one for hot (black) out to fan, and one for neutral (white) added to wire nut.
You were quite right - the digital timer actually has 4 wires: black, white, red and green. I was able to pull ALL the wires out of the box (quite a bunch, and quite stiff when wrapped in bunches) and with the help of the NCVT determined hot vs. load. Now the project is done. (Though I will put in more of these.)

Many thanks again for your help!
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