I'm replacing a light fixture with a ceiling fan/light. The wires are knob and tube, no ground, and no box.

1) Is a metal box or plastic box more appropriate?

2) I need to pigtail new wire inside the box, as the old knob and tube is not 6" in the box.

So, how do I tell which wire is hot when I don't have a grounded box to test against with my circuit tester?

A neighbor lent me a TONER which can trace cable and test polarity (but looks like that part is for DC) - not clear if this can help me.

You ned a special box attached to a joist for a fan. Some can span between joists and expand as your twist them. Are nboth wires the same color? How to Install a Ceiling Fan | Step-by-Step | Cooling | This Old House - Introduction

It is very hard to tell which wire is the hot wire in a knob and tube job. If you have an ohm meter and a long enough wire you can attach the wire to one of the wires and have the other end in at the fuse box (I say fuse box because that in what we used back then) or what ever kind of panel you have. Now is where you use the ohm meter. With the power off touch your long wire to the ground wire. This should tell you which is which.

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Originally Posted by ballengerb1

You ned a special box attached to a joist for a fan. Some can span between joists and expand as your twist them. Are nboth wires the same color? How to Install a Ceiling Fan | Step-by-Step | Cooling | This Old House - Introduction

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Both wires are, indeed, the same color.

For test purposes only run a insulated wire to the nearest plumbing pipe, touch it to the tester and then test the two wires, test only, do not keep that wire on the plumbing.

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Originally Posted by ballengerb1

For test purposes only run a insulated wire to the nearest plumbing pipe, touch it to the tester and then test the two wires, test only, do not keep that wire on the plumbing.

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Okay, I'm showing my lack of confidence here, assuming I've only got me working on this - how do I keep the insulated wire on the pipe - is electrical tape okay? Can I tape the tester to the other end of the wire as well so I have a free hand?

Also, in poking around to find the nearest copper plumbing pipe - which happens to be in the basement, I noticed some cracks in more knob and tube wiring attached to the joists. Now that I've seen it, it will keep me up at night. Should I be wrapping these cracks somehow?

I'd be calling a licensed electrician and get some sleep. Wrapping the stripped end of the wire around a pipe several times and you will have a good enough connection for a test.

Tk will shoot me for this, but with ceiling fans, it really doesn't matter which wire is hot. Most fans switch the hot but some switch the neutral, so it can end up as the same thing.

Metal boxes always, and a rated fan box/brace.

A Tic Tracer or other non contact tester will make short work of this, about $10.
Never switch a Neutral, you can switch WITH hot.
A Toner can work, you would remove power from the circuit, place a tone on the hot, and see what the inductive amp shows to be live, remove loads if you can to keep the signal off the neutral, giving false readings.

This is so simple to test, using a neon tester, as shown in picture.

I hold one probe in hand and touch the other probe to one of the wires.

The neon lamp will glow a bit once you have the live wire.

This is an old electrician's trick, works fine, no one ever got hurt doing it.

I have done this many times, and it did not affect me any,and it did not affect me any,and it did not affect me any,and it did not affect me any,and it did not affect me any,.

This method ONLY works with the neon tester I show.


CFR, while hot and neutral may not matter with a fan motor, if the fan has a light kit, now it matters greatly, as the shell of the lamp holder (socket) must be neutral. So be careful with that advice.

Honest I won't shoot you, but come here and hold these wires for me.

Hey TK, If you turn the Volume way up at the very end of the Album "Dark side of the Moon", You will hear an English sounding Gentleman say, " Their is no Dark side of the moon really, as a matter of fact its all Dark".
Ever hear it?

I was wondering who would recognize the avatar.

Since I only listen to PF with volume up high:

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Originally Posted by Stratmando

Hey TK, If you turn the Volume way up at the very end of the Album "Dark side of the Moon", You will hear an English sounding Gentleman say, " Their is no Dark side of the moon really, as a matter of fact its all Dark".
Ever hear it?

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I sure did.

Pink Floyd freak here.

Have you heard the latest album put out by David Gilmore Live at Gdansk?

Awesome version of Comfortably Numb. 6 piece band including Dave and Rick Wright, Perry on Sax when necessary, and It is on You tube, if you so desire. The entire set is awesome.