K&T Troubleshooting plan of attack

[RLyons]

So I'm sure every residential service guys favorite call is when there is K&T involved. Homeowner who I trust as I've done work for him previously said breaker tripped in the middle of the night. He noticed when he had no light getting up to go to the bathroom. Circuit goes from panel piped up to attic along with an additional K&T circuit for the upstairs of this 2 story flat. I believe the circuit then drops down to the first floor feeding devices located on the inside walls of the first floor. First thought is being a dead short is pinched fixture wire on twisty switch sconce fixtures, nope. Pulled out some fixture switches and they are all dead ends, outlet boxes are ungrounded obviously and slim chance of hot and neutral touching but I looked anyway. No work or renovations done recently. So there is no divide and conquer when it comes to K&T or is there? Can I just cut a hole in the middle of the ceiling and divide the circuit and go from there? I figure a half rewire is cheaper than a whole. Yes I know I should just rewire the place but this 67 year old guy just went back to work to put his kid in private school cause kid was getting bullied bad in the city school. Why am I unable to space my posts by hitting the return key :rant:

 

[electricalist]

Im not sure if in general k & t is wired the same, I was in a nice open attic .
The hot ran from fixture to fixture and the neutral went down to the switch and then back up to the attic,,, so im only guessing when i say from a hole you may find the hot but the neutral could be somewhere different.
If i was going to make a hole it would be justifiable like if i make this hole i can get a new circuit to point A.
Keep us posted k&t is cool in a creepy way.

 

[jaylectricity]

A dangerous thing to do would be to try blowing the circuit clear by resetting the breaker over and over until it finally held and then see what is and isn't working. You would know that this is futile if you notice the arc is happening at the breaker. So I definitely wouldn't try that.

 

[ActionDave]

So I'm sure every residential service guys favorite call is when there is K&T involved. Homeowner who I trust as I've done work for him previously said breaker tripped in the middle of the night. He noticed when he had no light getting up to go to the bathroom. Circuit goes from panel piped up to attic along with an additional K&T circuit for the upstairs of this 2 story flat. I believe the circuit then drops down to the first floor feeding devices located on the inside walls of the first floor. First thought is being a dead short is pinched fixture wire on twisty switch sconce fixtures, nope. Pulled out some fixture switches and they are all dead ends, outlet boxes are ungrounded obviously and slim chance of hot and neutral touching but I looked anyway. No work or renovations done recently. So there is no divide and conquer when it comes to K&T or is there?

Sure. K&T has some slight peculiarities, but it's still wiring.

Can I just cut a hole in the middle of the ceiling and divide the circuit and go from there?

Heavens no. Not yet anyway. How often has the breaker been tripping? Did you or the owner turn the breaker back on?

I figure a half rewire is cheaper than a whole. Yes I know I should just rewire the place but this 67 year old guy just went back to work to put his kid in private school cause kid was getting bullied bad in the city school.

The less old K&T has been messed with the less it is a worry. It's kinda like an old truck, most of the bad ones break down or get wrecked. The ones that are still on the road survived for a reason.

Why am I unable to space my posts by hitting the return key :rant:

Go into your General Settings on your profile page and scroll to the bottom where it says Message Editor Interface and try a different one, see if that helps.

 

[al hildenbrand]

K&T has some slight peculiarities, but it's still wiring.

The less old K&T has been messed with the less it is a worry. It's kinda like an old truck, most of the bad ones break down or get wrecked. The ones that are still on the road survived for a reason.

Pithy, and an accurate analogy. I like it!

It sounds like the OP situation has the hallmarks of a real honest to gosh challenging troubleshoot. These are the best test of one's skills.

1. Is the K&T added after original construction, or was it roughed in as part of the original construction? This will help you make generalizations about its routing in relationship to other conductive metallic systems such as metal piping or ducting.
2. What are the grounded systems in the house? If the dwelling is wood framing, plaster and lathe, wood exterior, and it hasn't been significantly altered over the decades, these are likely to be only gas, plumbing and heating runs. The incidental or deliberate grounding of these is part of the troubleshooting landscape.
3. Since the OP has already spent some time exploring openings with no success, the mapping of the affected branch circuit should be considered. It is a rare original K&T circuit that is still pristine, most have extensions. In early K&T extensions, armored cable was commonly used, and the armor did not have to be grounded. When examining openings, make note of whether the K&T conductors enter the boxes through individual nonmetallic loom sleeves or enter at a locknut fitting, which may be either armored cable or rigid metal conduit. Pay attention to the presence of the armored cable and test for grounding. The armored cable was routinely fished in and could be simply laying in contact with the grounded systems in #2 above.
4. Original K&T circuits get trimmed back, in dwellings that have a history of electrical upgrades, and, being lightly loaded, the K&T gets spliced, at a junction box, together with other wiring methods. Historically, K&T provided "smoke-less illumination" which was the "high tech" wonder of the late 1800s and early 1900s. Historically, there were VERY few receptacle outlets in the really early stuff. So pay attention to the load connected to any, and all, of the receptacles of the complete branch circuit. A plugged in load may well be the fault.
5. Unplug every thing, and take all the light bulbs out. If smoke detection is extended off the K&T, disconnect it. You should be able to "float" the neutral and energized conductors. Find the feed end of the K&T and disconnect both the neutral and hot conductors. With all load removed, there should be no continuity between each other and between each to ground.

Some of the interesting shorts I have found have been the heat-aged-and-deteriorated metal chandelier reversed polarity lampholders that are shorting to gas-pipe-hanger grounding. Another was the K&T installed as part of the original construction of the building where a steam heat pipe was installed after the electricians, and the pipe was installed in contact with the K&T conductor (the pipe fitters didn't inform the electricians, the required "tube" protective sleeve was not installed, and, I found, 95 years later, the heat degradation of the insulation and its crumbling had resulted in a spot weld of the copper conductor to the steam pipe.)

The most common cause, though, is the cord and plug connected load, at a receptacle that is in an area that doesn't "seem" to be part of the area served by what one "thinks" is where the branch circuit should be.

 

[RLyons]

General setting changed...

Ahhh Return key back in action. :lol:


electricalist
I've done a good amount of reno's and wiring upgrades in this area and the K&T is usually the same. Wires run down center of house (front to back) and from them neutrals or hots are tapped off and goes directly to outlet, fixture or in some cases switch. Switches are always dead ends.

If I cut a hole across 2 bays cut this main line in half. If the fault is cleared I will junction the front of house in the ceiling and re-feed the remaining devices in the back of house. And if the fault remains I will junction the back of house and re-feed it as well as the devices in the front of the house.



jaylectricity
You can blow a fault clear?


ActionDave

It tripped in the middle of the night few days ago owner said he tried to reset it and it tripped immediately. I went there also tried to reset it and it tripped hard immediately.



al hildenbrand

Test my skills it has.
Now I'm curious as to the ohms readings I should be receiving from such a event and how I can use them to help me.

K&T was original and from what I was told by the boss the reason it starts in the attic is because that is where the service meter use to be located in these types of houses. It was after the service was relocated The K&T was junctioned and them piped to the basement then outside wall outlets were added to the house.

Wood framing, Plaster and wooden lathe, Wood siding original would only be an assumption.
I didn't see evidence of gas fixtures before K&T
Friday the 13th coal fired air boiler that was converted to steam system at some point. Pipes do not run in walls.

I see no add on's to the circuit and from what I can tell it looks like the bathroom was removed as that light still works.

I'll go back and kick the tires a little more...
Try #5

I appreciate all the feedback and can't tell you how valuable the input I received is and appreciate all your patience.
I should try and volunteer my weekends for a EC who specializes in resi service work to further hone my skills.

 

[electricalist]

It sounds like you got it under control.
I find K n T interesting.
I had to fix a light , the first time I got a chance to really see it ran..
I go in the attic looking for hoist to walk on and bend down ,,moving insulation and realize I'm in the middle of the circuit and shined my light only to realize the wires are bare from dry rot...I freaked out . I thought I was in a SAW movie.

 

[al hildenbrand]

. . .
I've done a good amount of reno's and wiring upgrades in this area and the K&T is usually the same. Wires run down center of house (front to back) and from them neutrals or hots are tapped off and goes directly to outlet, fixture or in some cases switch. Switches are always dead ends.
. . .
K&T was original and from what I was told by the boss the reason it starts in the attic is because that is where the service meter use to be located in these types of houses. It was after the service was relocated The K&T was junctioned and them piped to the basement then outside wall outlets were added to the house.

Wood framing, Plaster and wooden lathe, Wood siding original would only be an assumption.
I didn't see evidence of gas fixtures before K&T
Friday the 13th coal fired air boiler that was converted to steam system at some point. Pipes do not run in walls.

I see no add on's to the circuit and from what I can tell it looks like the bathroom was removed as that light still works.

I'll go back and kick the tires a little more...
Try #5. . .

1. Don't forget that it was the original K&T installer's choice as to whether the switches were inserted in the energized or the neutral conductor (if the K&T install is old enough. . .the "switched neutral" became non-Code around the Twenties.)
2. Isolate the K&T conductors at the old K&T service center in the attic. This may have been reduced to a simple J-box.
3. If the K&T was installed as part of the original construction of the building, it may be routed off-center of the bearing beam of the house.
4. If you have a through-the-wall-signal-tracer look for the signal to go off the expected K&T route onto grounded piping/duct systems, and THEN open the wall (ceiling) to find the fault.
5. The immediate blow-back of the breaker upon reset indicates a solid connection (obviously) and, even if you cut the K&T branch circuit in half, you'll still have to find this to clear it.
6. The fault could easily be on the supply side of the old K&T attic service location. . .shed the K&T here and re-set the breaker to see if the fault is on the new or old wiring.

 

[RLyons]

Update:

Got a call from the customer on Monday saying he thinks he may have found the problem.
He had a storage/work room in the basement where a battery charger was apparently plugged into the problem circuit.
Unplugged the charger and he reset the breaker and apparently the circuit is back to normal. In my defense the room was locked and I never questioned it which I should of on my first visit. I am curious how the charger worked initially then ended up shorting. I'm glad it all worked out but feel bad not finding it myself.

Thanks again for the replies and will use the listed information on any future K&T troubleshoots.