Old house in USA: Odd electrical wiring?....

Our old farmhouse was built in 1915 and electrified at some point after that.  Poking around behind the plaster and lathe over the years has revealed a combination of upgraded wiring and some still the old 2-wire with cloth covering.  I recently bought one of those nifty pen-sized tools that can detect the hot wire of 120V AC by plugging the plastic blade into the the two non-ground outlet slots--the device has a steady beeping when you are on the hot wire and no beeping when on the other wire.  Using this device, all outbuildings on the property (all new since the 1990s) test out as they should.  The ground floor of the house also tests out fine.  But the second floor outlets all test as thought both wires are hot.... ??  Any ideas here of what they were trying to accomplish?  I've never had any problems running appliances or computers from these outlets, but I'm hoping to replace some of these with GFCI outlets.  Thanks!

Do you have a volt meter? If both wires are hot I'd suspect it was accidentally wired up as 220V, and since most things are also 220V rated for Europe you wouldn't notice anything wrong.

I second Peter's motion for an actual voltmeter. This provides facts rather than hints.

Also note that I have found some non-contact voltage sensors to be extra sensitive to the point of uselessness. A small amount of induced voltage from the hot wire makes them go crazy (AC systems do this). And yet a quality voltmeter indicates all is exactly as it should be. I finally settled on a Klein non-contact tester after Gardner/Bender and Canadian Tire brands demonstrated they were absolute garbage. My 2c.

Douglas Alpenstock wrote:I second Peter's motion for an actual voltmeter. This provides facts rather than hints.

Also note that I have found some non-contact voltage sensors to be extra sensitive to the point of uselessness. A small amount of induced voltage from the hot wire makes them go crazy (AC systems do this). And yet a quality voltmeter indicates all is exactly as it should be. I finally settled on a Klein non-contact tester after Gardner/Bender and Canadian Tire brands demonstrated they were absolute garbage. My 2c.

So my tester is an Innova from NAPA auto and I can't vouch for the quality.  But the plot continues!.....  I set the voltmeter for VAC (capable of max 600V) and plugged in one lead.  When I plugged in the other lead to the other plug slot, it tripped the breaker on the circuit.  At least this allowed me to see what breaker it was on....and that the breaker is functional!  The circuit appears to be a standard 120V/15A, but I'm mystified as to why the breaker tripped and why the non-contact probe clearly sees some difference between this circuit and other more modern circuits on the property.  One puzzling thing as well is that the breaker that was tripped (labeled "kitchen lights") is immediately adjacent to a 120V breaker (20A) that is unassigned.....it's the only unassigned breaker in the bunch.  Tomorrow I will see if flipping that breaker off also turns off this same circuit.  ( I also want to see that/if my multimeter reads a 'proper' 120VAC circuit elsewhere on the property correctly.)  From my limited working with 220V, you can use a double-slot breaker as manufactured for 220V needs, but can you also just use 2 breakers next to each other to provide 220V if wired correctly?  Certainly, the differences in the amperage of the 2 adjacent breakers is not exactly inspiring confidence, but again the different wiring jobs in that box raise the eyebrows.....and I can't yet say if they are being deployed as a 220VAC breaker unit. Come to think of it, when we moved in it was all regular screw-in fuses, so we've had that breaker box installed professionally probably 25 - 30 years ago.  Hmmmm....  

I was kind of hoping I had 220V on the second floor so I could move my wife's cosmetics by the vanity lights in the bathroom aside to make room for my welder!....

.....Anyway, much thanks for the responses and I hope to update soon.

So it turns out that I should not be allowed to use a voltmeter past my bedtime...... ;-)

(..."can we have an eye-roll please!".....lol...)       Yeah, I had the setting right on the meter....just needed to have the wire leads in the right sockets on on the meter for it to work properly.  Hopefully, I haven't irreparably damaged the continuity testing side of the meter with that stunt... sheesh!  

So all house circuits tested (except the bona fide 220V appliance outlets) test out at 126VAC....close enough to 120.  I have not yet determined what circuit the extra breaker is on, nor do I know the basis for the double hot wire phenomenon in the upstairs sockets.  We will be having an electrician come out soon anyway to work on the well pump circuit....probably at that time will have them check on these wonky wirings in the upstairs of the house.  But at least now that I know which breaker controls the upstairs, I can install a 3 prong GFCI outlet that will be easier to work with regarding the many 3 prong plugs awaiting use.  Thanks again for comments and help!

only work with 240V in Australia.
I am surprised you mention using two 120v breakers instead of a single 240V breaker!
That seems like a chance of  something going wrong in the future.

John Weiland wrote: Hopefully, I haven't irreparably damaged the continuity testing side of the meter with that stunt...

So all house circuits tested (except the bona fide 220V appliance outlets) test out at 126VAC....close enough to 120.  I have not yet determined what circuit the extra breaker is on, nor do I know the basis for the double hot wire phenomenon in the upstairs sockets.  We will be having an electrician come out soon anyway to work on the well pump circuit....probably at that time will have them check on these wonky wirings in the upstairs of the house.  But at least now that I know which breaker controls the upstairs, I can install a 3 prong GFCI outlet that will be easier to work with regarding the many 3 prong plugs awaiting use.  Thanks again for comments and help!

If your meter still works, it wasn't cooked. There is a certain amount of whoops-I-goof-up engineered into good meters. I would just test the continuity function to see if it still works.

I had a century old farmhouse with many generations of wiring, from knob and tube onward, with live fuse panels and the works. There was also a lot of "cowboy wiring" from somebody who thought if they could wire lights on a car trailer they were journeyman electricians. I isolated the scary stuff as fast as I could -- the house was insulated with dead-dry chips from planed lumber, the finest kindling on Earth!

It's absolutely worth having a journeyman electrician look this over. Also I'm not sure a GFCI is the right tool for this job. At my old place, I actually installed an AFCI -- arc fault circuit interrupter -- in the panel, for the supply to the dodgy circuits. Not cheap, but a house fire has enormous costs in many ways more than money.

Luck!

The old circuits were often wired with the white wire as the hot side, and thus switched on the neutral side. This will often get you strange readings on a voltage sniffer.

I think someone has converted the downstairs to black wire as the hot side, but not upstairs. It was switched in the code about 1960 or so because under some conditions you can get stray voltage on both wires , and this more homeowners getting shocked.

There is nothing to be alarmed about just yet, but if upgrading the upstairs maybe budget for a swap.

Older homes had knob and tube wiring.

If any of this existed in my home I would want it replaced.  

https://en.wikipedia.org/wiki/Knob-and-tube_wiring

Anne Miller wrote:Older homes had knob and tube wiring.

If any of this existed in my home I would want it replaced.  

https://en.wikipedia.org/wiki/Knob-and-tube_wiring

There have been MANY types of wiring over the years with each replacing the other typically every twenty years.

None of it really matters, it just depends. Like Tube and Knot, although well known, is only but one type of old wiring. I was referring to the wiring that had a cotton sheath on it that is almost more dangerous than tube and knot. Why? Because it was treated with arsenic to kill rats and mice that nibbled on the wires. It can get you really sick working with that type of wiring. It was also the type that was typically had switched neutral conductors.

Tube and Knot, if been in place for many years and still energized, is fine to use. If it has not burnt after 70 years it probably won't and was wired right. The conductors are far apart so it is fine. The problem with tube and knot had to deal with water leaks. If you have this, YOU CAN NOT HAVE A WATER LEAK as that will cause fires. In older homes with board construction, hard pipes prone to winter freeezing, etc, it was a more common problem.

My house, at 70 years old has every type of wiring, from tube and knot, to a form of armored cable, to clothed sheathed wiring, to new wiring. It just gets confusing because the old wiring was abandoned and replaced with new wiring each time. It looks worse than it is.

But I work in an old electrical industry. We have some substations that have Bakelite, granite, and even wood insulators. We are talking 1920's and the place provides 34,000 volt electricity, 24/7/365. Some substations have been upgraded, but you would be shocked to see (pun intended) on what is out there powering the grid for a steady 100 plus years. Just because it is not new, does not mean it is bad and does not work.