Troubleshooting in a old house

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Birddawg

Member
Location
Ann Arbor, MI
Occupation
Electrical Engineer
I was called out to a family members old house to identify and fix a short circuit. The house was built in the 1920s and the original nob and tube wiring was still in use. Years ago the electrical service was upgraded and then it was upgraded again. So there was nob and tube wiring, old romex without a ground wire and modern romex such as 14-2 with ground and 14-3 with ground. There was a dead short on the original lighting circuit. This circuit left the circuit breaker panel in the basement in old romex which traveled above a hard ceiling in the basement so we could not tell where it went. The circuit feeds all of the ceiling lights on the main floor, lights and receptacles in two bedrooms upstairs and the light at the head of the stairs. All of the lights were controlled by single-pole switches except the light at the head of the stairs. That light had two three-way switches.


My brother-in-law George and myself went to work. We took every switch out of their boxes and every light fixture down looking for the short. We disconnected each lighting fixture to eliminate the possibility that the short might be in one of the fixtures. It was clear that the original light fixtures were not mounted from boxes and that boxes were added later. Every ceiling box had just two wires coming in so the original connections on the nob-and-tube wiring were made on the wiring itself, not in boxes. I have seen this before in old houses that I have helped remodel. It was standard that the connections were soldered and then wrapped with rubber tape and then friction tape. They didn’t have plastic tape in those days.

All of the switches were in single-gang boxes except for two. There was a two-gang box for the kitchen light that had two switches. The wiring for the kitchen light was original and had two original wires coming into the box which connected to the switch. The other switch had modern wiring for the porch light which worked. It was on a different circuit. There was a three-gang box in the dining room next to the front door with all original wiring coming into the box. One hot wire that had some THHN connected to it and this fed all three switches. Then there was one wire for the dining room light, one for the covered front porch light and one for the outer porch light. None of the switch boxes were grounded nor were there any neutral wires in any of the boxes as far as we could tell. All wires were black. It was clear that the wire connections were made behind the plaster walls.

I had taken the hot wire off of the circuit breaker in the basement and connected it to a lamp socket and then connected a wire from the circuit breaker to the other terminal on the socket. After I screwed in a regular incandescent lamp into the socket and switched the circuit breaker on, the lamp came on full brightness which indicated a dead short. I turned the circuit breaker off and disconnected the white wire from the old romex from the neutral bar and turned the circuit breaker back on. The lamp did not come on which indicated that the hot wire for this branch circuit was shorted to the white wire of the same circuit. Then I reversed the process and with the white neutral wire reconnected, the lamp came on with the circuit breaker on. We left the power on and had another person watch the lamp waiting to see the lamp to go off. George and I inspected all of the boxes on the circuit. The lamp never went off. Please do not point out to me that by some definitions, a two wire branch circuit does not have a neutral. I am using white and neutral to refer to the circuit wire that was connected to the neutral bar.

Please do not criticize me for breaking safety rules. I could write a list of the rules that I broke. I recommend that these procedures not be followed.

I found the short. I want to ask for recommendations for the next step for the sake of discussion. What would be your recommendations?
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
Couple of things...
Electrical Engineer. Then you should know it is Knob and Tube.
also the wiring wasn’t upgraded, it was added to.
as an Electrical Engineer you shouldn’t have to ask what to do next after you have found the short.


kudos though for the lamp troubleshooting...
 

al hildenbrand

Senior Member
Location
Minnesota
Occupation
Electrical Contractor, Electrical Consultant, Electrical Engineer
You've had a somewhat unusual opportunity to exam key places on the branch circuit conductors where common insulation aging tends to occur. Critters, heat, ozone and humidity are the primary agents that degrade the condition of early 1900s synthetic rubber insulation. What have you observed?
 

kwired

Electron manager
Location
NE Nebraska
I was called out to a family members old house to identify and fix a short circuit. The house was built in the 1920s and the original nob and tube wiring was still in use. Years ago the electrical service was upgraded and then it was upgraded again. So there was nob and tube wiring, old romex without a ground wire and modern romex such as 14-2 with ground and 14-3 with ground. There was a dead short on the original lighting circuit. This circuit left the circuit breaker panel in the basement in old romex which traveled above a hard ceiling in the basement so we could not tell where it went. The circuit feeds all of the ceiling lights on the main floor, lights and receptacles in two bedrooms upstairs and the light at the head of the stairs. All of the lights were controlled by single-pole switches except the light at the head of the stairs. That light had two three-way switches.


My brother-in-law George and myself went to work. We took every switch out of their boxes and every light fixture down looking for the short. We disconnected each lighting fixture to eliminate the possibility that the short might be in one of the fixtures. It was clear that the original light fixtures were not mounted from boxes and that boxes were added later. Every ceiling box had just two wires coming in so the original connections on the nob-and-tube wiring were made on the wiring itself, not in boxes. I have seen this before in old houses that I have helped remodel. It was standard that the connections were soldered and then wrapped with rubber tape and then friction tape. They didn’t have plastic tape in those days.

All of the switches were in single-gang boxes except for two. There was a two-gang box for the kitchen light that had two switches. The wiring for the kitchen light was original and had two original wires coming into the box which connected to the switch. The other switch had modern wiring for the porch light which worked. It was on a different circuit. There was a three-gang box in the dining room next to the front door with all original wiring coming into the box. One hot wire that had some THHN connected to it and this fed all three switches. Then there was one wire for the dining room light, one for the covered front porch light and one for the outer porch light. None of the switch boxes were grounded nor were there any neutral wires in any of the boxes as far as we could tell. All wires were black. It was clear that the wire connections were made behind the plaster walls.

I had taken the hot wire off of the circuit breaker in the basement and connected it to a lamp socket and then connected a wire from the circuit breaker to the other terminal on the socket. After I screwed in a regular incandescent lamp into the socket and switched the circuit breaker on, the lamp came on full brightness which indicated a dead short. I turned the circuit breaker off and disconnected the white wire from the old romex from the neutral bar and turned the circuit breaker back on. The lamp did not come on which indicated that the hot wire for this branch circuit was shorted to the white wire of the same circuit. Then I reversed the process and with the white neutral wire reconnected, the lamp came on with the circuit breaker on. We left the power on and had another person watch the lamp waiting to see the lamp to go off. George and I inspected all of the boxes on the circuit. The lamp never went off. Please do not point out to me that by some definitions, a two wire branch circuit does not have a neutral. I am using white and neutral to refer to the circuit wire that was connected to the neutral bar.

Please do not criticize me for breaking safety rules. I could write a list of the rules that I broke. I recommend that these procedures not be followed.

I found the short. I want to ask for recommendations for the next step for the sake of discussion. What would be your recommendations?
I see you concluded you have a short but don't see anything that indicates you know were it is so what exactly are you asking for? You said you inspected all the boxes in the circuit, did you open any connections during this process? if not I don't expect you probably would see the test lamp go out unless you moved conductors that had incidental contact away from one another during the process, you would have to physically open whatever short circuit path you do have to make that lamp go out or at least get dimmer.

Hint - anything that has changed recently is a good place to start looking.

Another hint - the three way switching setup for stairs would been somewhat common to see both circuit conductors run to each switch and the common terminals of switch run to the controlled light - reversing polarity at lamp if you operated both switches. Anyone ever replaces one of those switches and not get them connected correctly (for what it is) and you could easily have line to line fault in one of those switches. Won't be able to really tell this one without disconnecting the switch, especially if the switch happened to weld a contact during the fault.
 

tom baker

First Chief Moderator & NEC Expert
Staff member
Location
Bremerton, Washington
Occupation
Master Electrician
Sometimes the easy way is the hard way. I have never worked in an older home that has had electrical work done by homeowners that is correct.
Rewire, and just think of the time you would of saved on that long post.
 

480sparky

Senior Member
Location
Iowegia
Customer: I need an electrician.
Electrician: I'll be there tomorrow.
Customer: OK.

Next day:
Electrician: I found a short circuit... you need to have your house completely rewired. That'll be $18,500.
Customer: Get out... you're a rip-off artist.
 

Rdcowart

Senior Member
Location
North Carolina
Occupation
Electrical license Holder
A lot of times when I start seeing a lot of incorrect wiring mixed with knob and tube I stop and I will not touch the home until it is upgraded. one of my best customers bought a house that was built in 1883. Man I found every type of wire that has ever been made In that house. That was four months of pain can’t tell you how many drill bits I went through. But in the end his home will live on for years to come and that family is safer.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
In my opinion, the best way to completely rewire a house is for it to be gutted.

Odds are there are other deficiencies that can be best addressed that way, too.
 

Birddawg

Member
Location
Ann Arbor, MI
Occupation
Electrical Engineer
Thank you kwired, you knew what to look for. Nobody had told me that the light at the top of the stairs wasn’t working. When I finally found that out, I knew what to look for.

Years ago I used to stand in the driveway at my uncles house all look at the three wires that ran from the house to the garage overhead and wondered how the wiring worked. There was a receptacle in the garage that was always on, a single pole switch that controlled the lights in the garage, and a three-way switch in the garage and another one in the house that controlled the light on the front of the garage. As far as I knew, four wires were required, a hot, a neutral, and two wires that ran between the two three-way switches, yet it worked. Finally one day my uncle let me take a look. What I found was that both three-way switches had a hot and a neutral connected to the brass screws and the black screws had a wire that went to the light on the outside of the garage. So that light either had a hot and a neutral, two hots, or two neutrals depending on the position of the two three way switches.

This wiring configuration is against code rule 404.2 which states “Three-way and four-way switches shall be wired so that all switching is done only in the ungrounded circuit conductor.” When was this code rule introduced? My library of code books goes back to 1959 where Rule 380-2 has the same wording. Do any of you have older code books? This sure is a good rule and the words haven’t changed over all these cycles.

As soon as I found out that the light at the head of the stairs wasn’t working, I went to one of the three-way switches and removed the hot wire from one of the brass screws and the light in the basement went out. There was a dead short between the two brass screws of the three-way switch.

Another interesting thing about the wiring in this house is that there were actually two upstairs switches for the light at the top of the stairs, one was a three-way and the other was a four-way. These switches had modern wiring. The hot and the neutral were connected to two terminals on the four-way switch. Two wires were connected from the other two terminals on the four-way switch to the two brass terminals on the three-way switch. And the wire connected to the black screw on the three-way switch went to the light fixture. This indicated that the electrician that installed those upstairs switches knew about the way that these switches used to be wired and connected those two switches even though it is against code. I will not complain because I am going to replace the bad switch and walk away, no charge. What did I learn? Ask questions. Is there anything else that isn’t working.

Thanks for correcting my spelling, knob and tube. On my next post I will use the proper terminology, the grounded circuit conductor and the ungrounded circuit conductor instead of neutral and hot. Thanks again and stay home and be safe.
 
Last edited:

al hildenbrand

Senior Member
Location
Minnesota
Occupation
Electrical Contractor, Electrical Consultant, Electrical Engineer
Birddawg, Welcome to the Forum.

A lot of times when I start seeing a lot of incorrect wiring mixed with knob and tube . . .
There is nothing in the opening post that attests to incorrect, homeowner or DIY wiring.

Birddawg mostly describes his troubleshooting method (I. too, like the use of the in-circuit-lamp), but gives no observational info about the K & T (Knob and Tube) wiring method he has handled.

Birddawg, if you don't come back and toss a few crumbs into this thread, you'll just have an unresponsive thread that is an echo chamber of old favorite war stories.
 

480sparky

Senior Member
Location
Iowegia
.........This wiring configuration is against code rule 404.2 which states “Three-way and four-way switches shall be wired so that all switching is done only in the ungrounded circuit conductor.” When was this code rule introduced? My library of code books goes back to 1959 where Rule 380-2 has the same wording. Do any of you have older code books?.........

It started as Rule 19.a in the 1915.
 

al hildenbrand

Senior Member
Location
Minnesota
Occupation
Electrical Contractor, Electrical Consultant, Electrical Engineer
This wiring configuration is against code rule 404.2 which states “Three-way and four-way switches shall be wired so that all switching is done only in the ungrounded circuit conductor.” When was this code rule introduced? My library of code books goes back to 1959 where Rule 380-2 has the same wording. Do any of you have older code books?
If you google "Carter Threeway" you should quickly arrive at discussion and diagrams of this "polarity switching" switching method.

I don't have the exact date in mind, at the moment, but the permission for this Carter threeway disappeared in the 1920s when the lamp holder was required to be "polarized."
 

480sparky

Senior Member
Location
Iowegia
If you google "Carter Threeway" you should quickly arrive at discussion and diagrams of this "polarity switching" switching method.

I don't have the exact date in mind, at the moment, but the permission for this Carter threeway disappeared in the 1920s when the lamp holder was required to be "polarized."

Carter. Chicago, California, Farmer, Handyman, Illinois, Power Beyond, Homeowner, DIY, Hot-wired, Husband, Three-Wire-Hot, Switchback, and my personal favorite, Who-cares?-It works,-and there's-no-inspection!.
 

480sparky

Senior Member
Location
Iowegia
Calif3wayanim.gif
 
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