Wiring an Isolation Transformer

120V in 120V out will not yield all that much isolation. Better to wire the xfrm 240V in, single ended 120V out.

Series the primary windings, parallel the secondary windings.
One paralleled leg of the secondary must be connected to earth ground making the new derived ac power system a grounded ac power system.... it's a safety thing. The earth ground used must connect to the main grounding system of the main electrical service.

For this you would need to hire an electrician.....

Please explain

120V in 120V out will not yield all that much isolation. Better to wire the xfrm 240V in, single ended 120V out.

If the purpose of the exercise is to have a balanced secondary then he has no choice but to wire it as stated above. You can't have a 240 primary and balanced 120 secondary. Granted, you can argue that balanced might provide no benefit, but he won't know until he tries it.

Wiring it 240-120 means he will need to run a 240 line to it. I didn't gather from his initial post he was wanting to hire an electrician to run new lines.

And why does 120-120 not "yield all that much isolation"?

I didn't know there were varying degrees. I thought it was either isolated or it was not. How can it be less isolated as 120-120?

.

I have one dedicated 20A line run to my audio system. My plan was just to run digital components (Apple TV, DIP, Pre/DAC, Video Switcher maybe a Tivo) off it. Run the power amp and tv straight to the wall. 220 is not an option right now. Any ideas about what gauge of wire I should use for the jumper cables and in/out cables. Also, is there a definitive asnwer out there about balanced halfing the VA rating? Also, would I use bare wire, or should I solder/crimp spages on the wires?

Also, is there a definitive asnwer out there about balanced halfing the VA rating?

Let me take a stab at it again....
First a power transformer is designed to operate at its rated nominal voltage and frequency. The size of wire used is directly proportional to the power the xfrmr is capable of delivering.

The xfrmr you are looking to buy has dual primary windings and dual secondary windings.

For the rated output voltage/power of the xfmr the primary can be wired for 120V in (paralleled) or 240V in (series)
The FLA (full load amps) rating for the primary would be 15 amps @ 120V (1800Va / 120V = 15 amps) or 7.5 amps @ 240V (1800Va / 240V = 7.5 amps). Output of xfmr fully loaded...

For the rated output FLA of the secondary of the xfmr the xfrm can be wired for 120/240V out (series the two windings, midpoint becomes the neutral) or straight single ended 120V out (parallel the two secondary windings)

The 120/240V configuration is capable of delivering 7.5 amps @ 240V. (1800Va / 240V = 7.5amps)

From each hot lead, leg, to the midpoint neutral of each winding is capable of delivering 7.5 amps @ 120V. (120V x 7.5 amps = 900Va. 900Va x 2 windings = 1800Va)
L1 to neut 7.5 amps @ 120V.... L2 to neut 7.5 amps @ 120V.

For your balanced 60/120V (60V 0 60V) wiring configuration you must use the above 240V calculation.

The most FLA the xfrm will be safely capable of delivering will be 7.5 amps. 7.5amps x 120V = 900Va
>>>>>>>>>>>>>>>

So if each secondary winding is capable of safely delivering 7.5 amps @ 120V (as designed by the manufacture/size of wire used for the winding) then it stands to reason if both windings are connected in parallel (single ended) The xfmr would be capable of delivering 15 amps. 15 amps x 120V = 1800Va.
Jim