On Sun, 25 Jul 2010 06:06:44 +0000 (UTC), Elmo wrote:
I just want advice for the conversion I just did before I plug it all in.

Here's the summary after reading all the posts, especially djb's (Dave
Bot..o perhaps?) posts.

1. The BEST approach is, all agree, to replace the NEMA 10-30R dedicated
dryer receptacle and 30 amp breaker with a NEMA 6-20R and a 20 amp breaker.

2. However, the use of a well-made adapter will be just as safe and
"compliant" to code, for temporary use (e.g., once every few months for a
few minutes).

3. The two 120V hot wires match up one-to-one; what doesn't match (at
first) are the two inconsistencies (a) amperage, and (b) ground/neutral

4. Taking amperage first, the 30 amp circuit is protecting the house
wiring, not the load. The 15 amp load will not cause a safety hazard to the
house wiring. The load has its own overcurrent protection on the motor.

5. Taking the contentious ground/neutral situation next, djb summed it up
best by clarifying the W wire in the grandfathered NEMA 10-30R receptacle
is a ground for the 240 volts of the compressor. So it's a one-to-one match
of the NEMA 6-20P plug ground to the NEMA 10-30R receptacle ground (via the
adapter cord).

6. If we were to plug in a non-existent dryer, then (and only then), would
the NEMA 10-30R receptacle ground wire be also carrying dual duty as the
110 volt neutral (for the dryer 110V circuitry).

In summary, it appears, as long as my adapter is well made (picture of it
below), it's safe (even safer than plugging in a dryer) to plug in the cord
that I made.

A picture of the adapter cord and compressor is he
http://img534.imageshack.us/i/006ary.jpg/
http://img153.imageshack.us/i/005tqn.jpg/
http://img714.imageshack.us/i/004wtt.jpg/
http://img525.imageshack.us/i/003zpn.jpg/
http://img809.imageshack.us/i/007pet.jpg/
http://img828.imageshack.us/i/002nd.jpg/
http://img265.imageshack.us/i/001aaz.jpg/