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Light switch causes instant breaker trip (20 yr xp electrician couldn't solve)

Light switch causes instant breaker trip (20 yr xp electrician couldn't solve)

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  #1  
Old 02-19-18, 01:50 PM
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Light switch causes instant breaker trip (20 yr xp electrician couldn't solve)

Hello everyone, I'm new around here, especially to Home ACV, a few years or so ago we hired an electrician to check out a lighting issue, long story short we still have that lighting issue, and now i am finding myself in a position where i have the tools and some of the knowledge to get this done. Eventually I'd like to build my own home.

I am not new to dealing with electric stuff (For example so i have I have installed an alarm system into my car) so at the very least I have my basic safety knowledge gathered, and the tools (multi-meter etc)

I have tried to do as much research as possible before i resort to making a posting like this - but i am clearly on my last leg.

I have attached 3 images so you can get an idea of what i am dealing with - I will explain what i have done and what the results are.

Pardon my terminology in advanced.

I have 1 blue electric box with 3 CABLES going into it. TWO of the wires are 3-conductor cables. ONE is a 2-conductor cable. I used my multi-meter to test for hot voltage on all 3 black wire cables.

From left to right with all circuits ON

1 (2 wire-conductor cable)
This one looks like someone pigtailed off the black wire in order to power #2, they also pig tailed white in #1 and #2

BECAUSE OF THIS I PIGTAILED #3 WHITE INTO #1 and #2 aswell. This made no difference from what i could tell so i reverted that change. Only #1 and #2 are pigtailed, so please dont let that second photo mislead.

2 (3 Wire)
Black wire on this is not HOT at all. Yet this powers the room? - how could this happen? Bad Cable?

3 (3 Wire)
Black wire is hot. All wires functional?

The second picture with one switch connected is the "Working" Configuration of how this was - i took it apart and removed the other two switches.

This is the only LIGHT switch that works at the moment - which is a problem because one of these other ones should be powering the living room light ( I think it is the 2-conductor cable) because I have taken the liberty of taking that light down and reviewing the cabling and i found a 2-conductor cable going to the light fixture in the living room, the ground was not connected.

I have connected the 3 way light switch to the #3 Conductor and the result is INSTANT breaker trip.

With the #3 conductor disconnected, the breaker does not trip which leads me to believe it is a short.

I also have no idea what the dimmer switch was going to as it has never functioned.

The problem is - how do i go about further troubleshooting here? is my only option to jump inside the wall and see if i can find something wrong?
 
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  #2  
Old 02-19-18, 02:25 PM
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Welcome to the forums.

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In this labeled diagram. Check for power from white to black on cable A. 120v should be there.
Since that black wire of cable A was tailed.... it would stand to reason that this is your supply cable and should supply power to both switches. If cable A is indeed always live....there should be no other wires showing power. Check from each wire to the white of cable A. Let me know.

I see 2) three way devices here. That would mean each three wire cable is the line to the other switch. It would make sense that cable D is dead..... from black to white. You could temporarily connect cable A to D to see what happens.

It's going to be a light.... which is doubtful.... or other receptacles.
 
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Old 02-19-18, 03:19 PM
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HI Pj, thanks for your reply and warm welcome - hopefully this information clears stuff up a bit.

In this labeled diagram. Check for power from white to black on cable A. 120v should be there.
- From white to black on cable A 120v is there.

Since that black wire of cable A was tailed.... it would stand to reason that this is your supply cable and should supply power to both switches. If cable A is indeed always live....there should be no other wires showing power. Check from each wire to the white of cable A. Let me know.
- Okay i believe you're right here, it looks like i have two supply cables A and C. one circuit breaker controls each one so two total that i am turning off while troubleshooting.

I see 2) three way devices here. That would mean each three wire cable is the line to the other switch. It would make sense that cable D is dead..... from black to white. You could temporarily connect cable A to D to see what happens.

It's going to be a light.... which is doubtful.... or other receptacles.
- Okay now this is where i start to lose you . I temporarily connected A and B together ( white, black grnd) and the ROOM light lit up. - This tells me cable B as suspected is for the ROOM?

- Cable C is still hot 120v, not dead i have not connected them together with anything else yet

- I also tested the 2 conductor cable at the light fixture ( white black gnd) and received 0v

-Cable D is ground? i believe thats dead.
 
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Old 02-19-18, 04:28 PM
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Ok... I see now that is a three gang box. Does the switch for the light on cable D belong in the third position and is it a three way or single pole switch ?

You had three switches there.... I don't believe you mentioned all of them.
Cable A is power to 2 switches.
Cable B is the ROOM lights.
Cable C is on a different circuit so it does not connect to A or B.
 
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Old 02-19-18, 06:57 PM
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Ok... I see now that is a three gang box.

You had three switches there.... I don't believe you mentioned all of them.
Cable A is power to 2 switches.
Cable B is the ROOM lights.
Cable C is on a different circuit so it does not connect to A or B.
I might've skipped over that detail accidentally - but yes it is a 3 switch box.

Does the switch for the light on cable D belong in the third position and is it a three way or single pole switch ?
I am unsure of this - I believe they were moved around before i got my hands on it. I specifically remember using the dimmer switch to control ROOM - However now a single pole is controlling the room.

The other two switches = One Single Pole switch and One Three way switch

I looked on the other side of my house where i expected the other connection of the three way switch to be and it appears it was fully connected but no current flowing through that three way either.

To recap - I have One Dimmer, One single pole, One three way

If i put the single pole onto Cable C the breaker immediately falls.

If i put the three way On Cable C the breaker will immediately fail AFTER i turn the switch on.

From what i know so far - I want to move the dimmer to cable B now and figure out What functions Cable A and cable C serve.

This is an old home i guess ? Two of the other rooms in the house have switches that control ONE outlet Receptacle port - this was clearly for lighting purposes as there are not any overhead lights except for that one room (CABLE B)
 
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Old 02-19-18, 07:14 PM
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You've discussed the room light. What are the other two switches suppose to control.

Cable A is a 120v supply.
Cable B goes to room light. It probably connects to the other 3 way switch. You connected A white to B white. A black to B black and the light worked. If you flip the other three way switch the light will probably go out. If it does... try connecting A black to B red and see if it comes back on.

Cable C is on a different circuit. It should not be connected to A or B. Only the grounds will be combined. Try this..... connect just the red and black together of cable C. What happens ? Can you determine which color is hot.... red or black ?

So far we have no idea what D feeds.
 
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Old 02-20-18, 06:16 AM
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Have you determined which of the 3 wire cables is going to the other 3 way switch, what is the wiring configuration at the light fixture?
Geo
 
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Old 02-20-18, 10:51 PM
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You've discussed the room light. What are the other two switches suppose to control.
Okay i think further clarification is needed - I do not fully understand the paths of the cables, that is what i am trying to identify first.

D should be C - C should be D - There are only 3 cables going into the gang box. (Review pics that will be attached, i could be wrong)

Cable A = 2-conductor cable Controls?? = black is hot - White is neutral - ground connected together with ABC
Cable B = 3-conductor cable Controls ROOM = nothing on this wire is hot. Black, White, Red, Gnd wires. - This is piggyd onto A
Cable C = 3-conductor cable Controls?? = Black is hot - white is neutral - ground connected together with ABC - Separate Circuit

Light Fixture
One Cable = 2-conductor cable = nothing on this wire is hot - has white black gnd

One of these should control the LIVING ROOM LIGHT The other should control ROOM light. the third??? i have no idea - maybe something heating related?

I noticed above the gang box was what i believe to be an electric thermometer that was receiving power at the time.
After looking at the circuits I've shutdown more than half the Circuit Breakers on the panel because this apartment no longer has any electric heating, it is gas powered. I have no use at all for this - yet.


Cable A is a 120v supply.
Cable B goes to room light. It probably connects to the other 3 way switch. You connected A white to B white. A black to B black and the light worked. If you flip the other three way switch the light will probably go out. If it does... try connecting A black to B red and see if it comes back on.
Okay so starting off i would like to say that other 3 way switch (Across the living room is where its located) is completely cold - I think at this point i know its NOT associated with the living room - i will most likely cover it up since there's no use for it, nor do i know what its use was for since i wasn't able to get a history.



Cable C is on a different circuit. It should not be connected to A or B. Only the grounds will be combined. Try this..... connect just the red and black together of cable C. What happens ? Can you determine which color is hot.... red or black ?
Grounds have been combined - Connecting Red and black together of Cable C - Nothing Happens. Absolutely nothing. I tried seeing if this provided power at the light fixture but unfortunately not..

Also while using my multi-meter on cable C i noticed if i test from white to black for some reason black does not show as hot. Testing from ground to black shows that it is indeed hot.

Hopefully the two attached pictures will help in some way, i appreciate your efforts.
 
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Old 02-21-18, 11:38 AM
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How many wires are in the other box with the lone 3 way ?
Geo
 
 

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