My newly installed ductless split AC, IT WORKS

[DrivingMissLazy]

Jerry, congratulations for your thinking "out-side-the-box".

Your drawing shows what I would have in the past called an autotransformer. One winding with three taps on it. The general purpose to step 120 volts up to 240 volts.

But you talk about an isolation transformer which I would in the past have expected three 120 volt windings (six leads). One input winding on one side of the laminations, and two output windings (or vice-versa) on the other side of the laminations. The purpose to not only step up the voltage from 120 volts to 240 volts, but also to provide complete electrical isolation between the primary and secondary windings. These devices are generally much heavier, larger and more expensive than an auto transformer.

I still do not really understand how you connected it but again I would like to congratulate you on what I consider a brilliant solution to a vexing problem.
Richard 

Here's a try at a picture.

         out
  !---- <240>-----!
  !                      !
  !                      !
  !WWWW!WWWW!  the transformer
  !          !
  !          !
  H<120> N
       in

Regards
Jerry 4107 1120

[Jerry Liebler]

Richard,
     I'll try to clear up what I said.  I started out with what was designed as an isolation transformer that had 2ea. 120 volt primaries and 1ea. 120 volt secondary.  It's intended purpose was to isolate either a 240 volt (primaries in series) or 120 volt (primaries in parallel) source from a 120 volt load.  I then connected the primaries in parallel and connected the secondary in series with the primaries.  The center tap of the now 240 volt single tapped winding is connected to the neutral, the other end of what was intended to be the primary is connected to the 120 volt source's hot side which is also one end of the load connection.  The remaining end of what was the secondary is now the other  side of the 240 volt load.  The advantage of the auto- transformer connection is it effectively doubles the current capacity of the transformer.  Isolation wouldn't be desirable anyway as we really want each leg of the 240volt output to be 120 volts to neutral for safety.  I wanted to make the transformer's capacity significantly more than the rated compressor current to assure that the voltage wouldn't drop too much during the startup surges.  The toroidal transformers have shorter windings than more conventional transformers so they have less winding resistance for similar ratings, this also reduces the voltage drop during the startup overload.
I'm sure glad it works, my wife would really be p--d if I'd wasted the money I gambled to try it.
Regards
Jerry 4107 1120

[DrivingMissLazy]

Thanks Jerry, Now I understand. I think it was really a great idea. I was aware that  an autotransformer connection had a higher rating when connected, but in 50 years I never saw or heard of anybody doing it like that. Making an auto transformer from an isolation transformer. You are a genius.
Richard

[kyle4501]

I'm sure glad it works, my wife would really be p--d if I'd wasted the money I gambled to try it.
Regards
Jerry 4107 1120

Jerry, it looks like you gambled on a sure thing 

We talked about this in Timmonsville, & you lost me when it came to the transformer. But I just knew you had it figured out right. Way to go! You are one handy guy to have around! Thanks for taking the time to share & explain!

Happy bussin! 
kyle4501

[Chaz]

I concur with all the guys above - Way to go!!!!!!!!!!!!!!!!!! You are the man!!!
It's a true gift to have you aboard and for you to share your talents and knowledge. I can't wait to meet you and see your bus in Cincy in a couple weeks.
  As with some of the other guys, I am all but totally lost on how you did what you did and what you did to make it work. But if/when I get to the point of changing AC's, I'll follow in your footsteps. I'm sure a visual in Cincy will help me a great deal.
  Thanx again for all you've done for me,
    Chaz