Knob and tube wiring is common in our area. Ideal used to make a contact pocket voltage tester (61-050), it is no longer available. I used it to identify the hot conductor.
Does anyone know of another method to find the hot conductor?

evad 73....

If you have a non-contact type voltage tester it would be a cinch to check which conductor is "hot" on K&T.

Top of my must-have tool list.

Bill

evad:

Showing my age now...long before the 'non-contact' age, internet, cell phones, cordless landlines, and a whole lot of stuff........

Locate a 'ground' somewhere within the building, or if that's not possible, a known neutral point. even if you have to go back to the service entrance. Connect a suitable length of #12 stranded THHN or equal to said point & stretch it out to the location you want to test. You then have to skin a test point on the K&T conductors and use whatever tester (wiggy, digital, etc).

I did not say it was easy or quick; but it works. If I had to do it today, I'd pull out the non-contact, I have an Ideal, Gardner Bender & a TIF. Any of those are available thru WWGrainger, most electrical supply houses and the big boxes. Look in Tools for Electricians in the right hand border ads right here also, you may find one.

what HotOne said

with one aside...

i have an office cha cha K&T meter, (one of these)>>>>


around here that #12 might need to be run closer to the nuke plant....


~S~

A reminder of days gone by!!! LOL; LMAO

Back in the olden days we used neon testers. They could give you some bad indications but I am not sure a ticker is really any more reliable. I still would not stake my life on either of them. They are just indicators, not testers (to steal the language of U/L)

Greg:
Are you talking about the neon 'tube' with two leads? If so, how did you do that?

You never saw the neon tester pen? They typically have a small screwdriver on one end and a pocket clip. The clip is the "ground" and you are the ground electrode system, capacitively coupled to the earth. There is a megohm resistor there so you won't see circuit current. If you touch the screwdriver to a hot lead, the neon lights. Sometimes you just have to be close to the hot lead. They may not light 100% of the time, particularly if you are very well isolated from ground, like up in an attic on dry truss chords but they usually work OK.

I will root around and see if I can come up with one.

Non contact volt testers can give neutrals a hot indication where part of a circuit is chopped out and the return is through a load as a result of a bad assumption. When it comes to K&T I treat all the wires as hot until I am the one that cut it and I am not perfect so be careful the neutrals can be very dangerous too.

very true Mike

etta> some folks use this sort of 'twin lead' uhmmm indicatorfor K&T>



but what they do (you fellas are probably gonna spank me for this one) is hold one lead to a wire, while holding the other

the light glows, but just dim

~S~

I have held 1 end and touched the other to a live wire. Kind of a bad child of the swipe your finger over the bare end to see if it is live.
I can tell you a neon tester is no match for a High voltage transformer. Not even at the end of a wooden broom handle, wearing leather gloves with insulated boots on an aluminum ladder and only 1 end of the neon touching the live terminal, the other lead from the neon was in the air.
BTW it was a transformer for an electrostatic Air cleaner that did not seem to make the dust go snap. It made me go snap. I learned a few lessons about trouble shooting and high voltage that day. Fortuneately I survived to apply the lessons I learned.

~s~:
That looks like what I thought Greg was talking about, but a more 'modern' version. The guards and the long probes look like a modern touch.

This is a neon pen tester.

Greg:
I must say I do not remember ever seeing/using one of them.

in Europe (Continental) you can buy those in every supermarket and DIYers believe them to be actual accurate meters.

They are probably more reliable at 220v.

Although I never used them, I know what Ther are. Does that make me old?

Why they teach you not to put screwdrivers into receptacles, they make s gizmo like that. Go figure!

I've seen some of those screwdrives labeled 120/230V so they seem to be at least designed to work in the US too. They aren't known to be very reliable here though. I've never had a false negative, but apparently they're quite common. False positives most definitely are (dead conductors showing as hot).

So that is what that is. My Father-in-law had one and when he died none of his family knew what t was for. Hmm, I guess that I am just a know nothing engineer after all.

John,

I have seen them and Guys I know used them. Does that me old too!

I have tried a non-contact voltage tester... they often light for the neutral and maybe a sneeze...I don't like them.

They light when you rub one on your shirt.

evad73:

Keep in mind that there can be return current flowing in the neutral!

PAteen:
Static electricity??

What about static on the line? Wouldn't that set it off?

PAteen:
One of our deep theory members can get into 'static' issues, perhaps Greg or Scott.

Important for all to keep in mind that these devices are indicators of possible live conductors, and NOT a true tester that anyone should 100% 'trust'. Remember Trumpy's cardinal rule....verify, test, verify!

I doubt you can get static electricity in a conductor. What you see there using a high impedance meter is the antenna effect. I doubt that will be enough to light a neon but it may trick a solid state ticker.

For your amusement:

High impedance meters/ digital auto-ranging meters us solid state chips to dope out the values.

In particular they us RC circuits: Resistance + Capacitance. The resistance is considered the known as is the capacitance. An extremely high frequency switching circuit clocks/times the circuit.

Upon test lead contact, current fills up an entire array of femto-capacitors. Then using the wizardry of digital logic resistance or voltage is back calculated in the blink of an eye.

Because the chip's capacitors are s-o-o-o tiny even the tiniest amount of current can fill them up. This is where false positives come from -- especially from either static electricity or by induction or capacitive effects.

In comparison, a Simpson analog meter is driven by a sequence of entirely separate 'ranged' circuits selected by dialing a stepping switch/knob. Thus it can't be 'autoranging.'

However, in an analog meter the current or voltage is shunted through resistors, coils and whatnot so as to provide a nearly linear response to the current or voltage which can then be read out on a swinging beam across a field of values. Such 'analog circuits' can't be faked out because they are driven by the laws of electricity -- directly. ( No brain assumptions )

-----

It is highly desirable to have both types + an influence / non-contact tester if you want to make rapid steady progress at all times.

For super speed, the voltage-tick/ non-contact tester can work wonders, especially on circuits you, yourself installed.

When facing the unknown -- face it -- you just can't trust anything. This is especially true with Churches and any 'owner-installed' projects. With them wire color means nothing. Black could be on any phase and at any voltage and even be neutral or ground. As time goes by you'll be astounded as to how crazy some buildings are wired. That's why:

Always start with voltage-tick,

Then DDM, with auto ranging,

If you're suspicious of false positives fall back to an analog meter.

Analog meters out of China go for a whopping $13 at Harbor Freight. That makes them cheaper than a voltage tick! ( And just about the same weight.)

For DMM I prefer Fluke or Greenlee. If they ever go dead check both batteries AND fuses -- inside.

------

Slightly off topic: DeWalt battery chargers have a hard-wired fuse in them. The VAST bulk of dead chargers have simply blown this fuse! Open yours up, you can't miss it. It's easy to test for 'open.'

Whatch out for 3ways with those non contact testers as well. They light up like there is power on everything sometimes. lol

Ob

PS
I have most of the above mentioned technics. Mostly the Noncontact thing in my ideal tester/wiggy.

I suppose it should be mentioned that K&T has attracted the wrath of big insurance in recent times

at least here in K&T central, New England

I've been lucky to gain a lotta biz from it all, yet i do get asked the Q "Why is it so bad"? from a few sorts keen to what they feel is Big Insurance simply on another one of their infamous jihads


To be truthful, and only due to K&T being original, no other wiring method has lastest 80-90 years.

If (and it's a slim if) it's left alone, unaltered, in a consistent enviroment, consideration to it's legality (sans life saftey issues) by right of grandfathering every other method's install could be granted

One such situation arose for me in town, an entire 2nd floor of a local inn , all K&T, had been handed a cancelation by their insurance co.

I argued that, if they had no $$$ to insulate, they certainly had no $$$ to buy an electrician, so if all the life safety issues (smokes, gfi's) had been met, what was the problem?

I ended up asking them to ask their insurance co about installing an afci on the circuit in question, they were turned down by the original co, but the next one bit

So i simply replaced the type S fuse with an afci in a two ciruit can. The state inspector went along with it all too, although he (and truthfully i as well) considered it buying time, the burden of the devices efficacy being thrown in the lap of big insurance (as it should be)


and so the old new england electrical ambiance was maintained for posterity , the turnkey switching, the single bulb pendants, for tourism's sake via the mighty afci, faster than a speeding arc, more pwerful than a local ahj, able to leap tall shorts in a single click

~S~


~S~

The non-contact indicator is perfect for identifying the hot on K&T provided that there's no load on the circuit in question. That way the neutral won't be energized, and won't show as "hot".
One has to unplug everything from the circuit in question,and the lights need to be turned off. The only possible load that I can see coming back on the neutral in that case would be a transformer such as the doorbell or a smoke detector.

If you know the non-contact's limitations, it can be an invaluable tool. It only indicate the presence of voltage (try one beneath overhead HV lines sometime).
It's not the only tester that you need to carry on your truck, but it does have its uses.

I carry about 10 testers (DVM,analog meters,solenoid type testers,etc.), use them all, depending on the circumstances at the time, and never, never put my trust in any one of them alone to verify the absence of voltage.

Analog multimeters can still show false positives, but usually in the form of weird ghost voltages because they are Hi-Z meters. They have a high impedance designed to keep influence on the circuit being measured as low as possible. This is great for electronics with low voltages where a current flowing through the meter could cause a significant voltage drop), and to some extent for line voltage too (where a current flowing through the meter from hot to ground could trip a GFI) but on the other hand those meters can show ghost voltages caused by induction or capacitive coupling that would vanish if a current flowed through the Lo-Z meter. Unless I want to know the exact voltage +/- a few volts I have been able to work quite nicely with just a Lo-Z meter with a bunch of neon lamps or LEDs indicating different voltage levels (12, 24, 48, 120, 230, 400V) that allows to switch off the load resistor for Hi-Z measuring.

Yeah, been fooled by the ghost V thing Tex

so basically what can we say?

we don't trust testers

there's a big surprise...

and what do we do as a final test?

touch the wire to ground? backhand it?

i.e.- everything we were taught NOT to do...

~S~

Ranger...

You must be using a really high quality analog meter...

The cheap junk out of China has never shown me a false positive.

But then it's not bench-tech worthy.

I haven't had one personally so far but I read about a few.
At school I mostly used high-quality analog meters in lab setups, for a simple reason: they were more likely to be intact since I was the only one who used them! All other students preferred DMMs and frequently fried them. After much hair-pulling with one setup that gave seriously odd voltage readings I started to suspect faulty meters, switched to the old analog stuff - and never turned back! Those were mostly Goerz (Germany) and Norma (Austria) meters, probably from the late 70s or early 80s. The DMMs weren't cheap either, mostly Fluke but apparently most of them were destroyed at some point, resulting in quite weird readings.

In house wiring I use a simple neon tester (either across L-N with the load resistor on, across L-ground without the load or just on the hot, working capacitive like a neon screwdriver or if I want to check for over/undervoltage a cheap DMM. The single pole neon testers do occasionally give false positives, but thankfully I never had a false negative so far, not even on a wooden ladder wearing shoes with rubber soles.

well i noticed the poco guys using the base Fluke models , they do resistance or voltage on the same setting

less chance of blowin' it up on R with V

~S~

You really can't blow up a digital meter on the volt/ohm ports as long as you are within the top voltage limit.
It is not like an analog meter in that regard.
On the amps ports you can easily blow the fuse or even the meter in extreme cases, if you get volts in there.

That's what the fuse is for

If you put 480 across the amps inputs of a Fluke 8060A the fuse loses the race on who clears the fault.

... or so I hear

not if you wrap the blown fuse in a piece of tin foil from your lunch like my bro did....

~S~

Trying to measure the short-circuit current of a 230V receptacle was the cause for many blown fuses in my old school
For some odd reason, the classrooms were on breakers, but the shops had Diazed fuses. Thanks to penny-pinching, bureaucracy and who-knows-what-else spare fuses were always in short supply. I never encountered "repaired" fuses, but did have some fun with fuses "borrowed" from "less important circuits". We needed more receptacles for our setup (or at least one closer to our work place, there was only one long extension cord) but our lab teacher told us: "Those don't work, never did while I was here!". We pressed the issue though and got a look at the panel... no fuse for the afflicted circuit! Someone had "borrowed" it!

I don't know how the flukes died, but they ended up giving seriously whacky voltage readings. We had one lab setup where we considered the voltages odd, so we swapped the meters (we had used one for amps and one for volts) and got equally weird but completely different readings! When a third DMM didn't improve the situation I grabbed an analog one and we immediately got the result we expected.

I'm not sure if those Flukes were auto-range, if not they might have been damaged by setting the wrong voltage range I guess.

With a lot of use there are many ways for a DMM to go south.

The leads

The lead-sockets

Internal connections -- particularly wire to solder...

And fried chips, displays...

Further, they DO have internal fuses. Corrosive opportunities also exist.

------

Your tale of abused equipment is the primary reason why I started bringing my OWN 'company provided' tools.

Every time Company Tools showed up they were broken. What happens is the troops lie -- constantly -- about their tool experience. So their forman gives them a brand new tool and they promptly ruin it and then hide it from the foreman.

This happened on one of my jobs -- a Greenlee hydraulic punch ruined before a SINGLE Knock Out was performed. It cost the fool his job.

If he'd asked for help I could have solved his mistake in 10 seconds. Instead he tried to dis-assemble the tool while it was stuck in the panel can!