On 6 Feb 2004 12:05:03 -0800, (benwoodward.com) wrote:
You have a house.
You have no 220v outlets easily accessible.
Yes you do.
Even if you don't.
Thank heavens for oscilloscopes.
All the 120v breakers on the left side of you breaker box are 180
degrees(or Pi radians for the less mathematically inclined) out of
phase with all the 120v breakers on the right side.

Usually not. Most residential breaker boxes have the legs alternating
in the same row. That allows you to replace two adjacent single 120
volt breakers with a single ganged 240 volt breaker. If there are any
240 volt breakers in your panel, this is the way it is made. You *can*
find breakers on opposite legs in opposite sides of this sort of panel,
but you have a 50-50 chance of being wrong.

(In a bolted breaker panel, all bets are off. It could be arranged
any sort of way, and you can't know unless you open it up and
trace it out.)

In very rare cases, the box may only be supplied with one hot and
a neutral. In that case, you don't have access to 240. This will
usually be true only of a subpanel, not the service entrance panel.
The utilities do not like to unbalance their neutrals this way, so
this sort of panel as an entrance panel is most likely to be found
in a barn, pump house, or other outbuilding where the owner only
ran a pair of separate overhead wires to it to supply 120 volt power
for lights or utility outlets. Normally, this sort of panel will only have
a single row of breakers, but not always. You have to open it up
and look to make sure what you have.

Find a room or outlet where the lights go out when you flip off a left
side breaker and plug a 25 ft grounded extension cord into it.
Find a room where the lights go out when you flip off a right side
breaker and plug a 25 foot grounded extension cord into it.
Get a voltmeter and measure hot(little slot) to hot and you will get
240v.

As noted above, maybe. Note too that the overhead lights in a
room are usually wired to a different breaker than the outlets in
that room. That's so you won't be fumbling around in the dark
when you plug in something which blows a breaker. So the lights
going out doesn't necessarily mean you've found the right breaker.

Totally usable up to the value of the smaller of the two breakers.

Including all the *other* loads on the circuit. A 120 volt breaker
usually feeds more than one outlet. Unless you're sure all the
other loads on the two 120 volt circuits are disconnected, you
won't have the full rated value of the breaker available (typically
only 15 amps if you do).

If you have a resistive neutral on either circuit (fairly likely in older
wiring), other equipment on the combined circuit can see more than
120 volts (neutral imbalance). This can damage 120 volt equipment
in the house. It *can* also cause a fire.

You can wire nut a third cord with a 240v receptacle into the first
two hot to hot and you will have a female 240v outlet wherever you may
go, provided there are two rooms, one on each 120v side of the breaker
box, within 50ft of each other.

Note that this sort of "suicide cord" wiring is dangerous. Since you'll be
feeding the equipment from two different breakers, tripping one breaker
will *not* make the equipment cold. That's why 240 volt breakers are
ganged, so both have to trip at the same time.

I discovered this accidentally with my oscope a month ago.
So I say screw the dynasty, get the HTP invertig 200.
I'd rather spend 5 extra minutes hunting for an outlet and triple my
welding capability versus trying to get 120v to act like anything more
than a wonderful tool for hampster experiments at NIMH.

I'd rather spend the time once to install a proper 240 breaker and
circuit. Then I wouldn't have to worry about it again. Adding a 240
volt circuit to an existing panel is usually possible, and is much safer
than what you are proposing.

Gary