On Sun, 8 Feb 2009 19:06:42 -0800 (PST), wrote:

On Feb 8, 6:58*pm, David Nebenzahl wrote:
OK, here's today's electric circuit puzzle:

Client wants a new ceiling fan installed. The old one works, they just
want a different one up there. No problemo, right?

The new fan has a light, just like the old one (actually several hanging
sockets). Unlike the old one, though, the new one has only 3 wires: hots
for the fan and light, and a common neutral. Ugh. Not the way I would
have designed it.

I hook it up, figuring that I can simply use one of the neutrals in the
ceiling box and not the other one. Try it: light doesn't work at all,
while the fan does. That's weird.

So I go up there and measure voltages between wires. Here's what I get
(apologies to those who don't use monospaced fonts):

* * * * *(1) blk * X---- * ----X * blk (2)
* *fan * * * * * * * * * * * * * * * * * * * light
* * * * *(3) wht * X---- * ----X * wht (4)

Measured voltages:

* * * * * *1 * * *2 * * *3 * * *4
* * * -------------------------------
* * *1 * * * * * *90* * 120 * *240
* * * -------------------------------
* * *2 * * 90* * * * * * 0 * * *90
* * * -------------------------------
* * *3 * *120 * * 0 * * * * * *120
* * * -------------------------------
* * *4 * *240 * * 90 * *120
* * * -------------------------------

* The 90 volt readings are from the dimmer switch all the way up.

Hmmm; something ain't right.

I ended up putting the old fan back up, as I couldn't get to any of the
wiring above the ceiling and we decided to leave well enough alone.

I figured out what was wrong after I got back home. It's actually pretty
simple.

For the solution, look hehttp://www.geocities.com/bonezphoto/...redCircuit.gif

--
Personally, I like Vista, but I probably won't use it. I like it
because it generates considerable business for me in consulting and
upgrades. As long as there is hardware and software out there that
doesn't work, I stay in business. Incidentally, my company motto is
"If this stuff worked, you wouldn't need me".

- lifted from sci.electronics.repair

that is crazy to have 240 volts going to one box like that... I would
rewire that circuit at the box so that it is all on one phase
(polarity is actually the correct term) ...

I'm sure the code experts will chime in shortly..

Mark
The drawing doesn't make much sense to me.

The biggest code violation is the dimmer is in the neutral. You can't
switch the neutral.

Also the fan will run all the time.

Also I don't know how you get 90V from black to black. You should get
240V on one and 0V on the other.

He is also marking a hot leg black on one end and white on the other.

It is a puzzle alright. It is not an electrical circuit.