A/c transformer mod

[Blaine Thorpe]

Can I assume that this is what everyone had before the modification?

[SKYCHENEY]

That's it. See you have power coming from your panel breakers to the transformer. Then it outputs on the H side. This has to be reversed so that the input comes in on the H side and it outputs on the X side. That way you can either tie H3 and H4 together or by switching, you can tie H2 and H5 together. This effectively changes the length of the winding on that side of the transformer and thus changes the voltage.

When you open up the transformer, pull the wires off of the one terminal strip on one side and move them to the other side and vice versa. Then wire up the switch so that you tie one of the two combinations above or the other. Use a meter to test your switch so you know where to hook those leads to get those combinations.

Switch position one: H3 and H4 are combined but H2 and H5 are not.
Switch position two: H2 and H5 are combined but H3 and H4 are not.

If you add the switch without swapping the wires on the input and output of the transformer, your switch will lower the voltage instead of boosting it. Don't ask me how I know this.

Edit: You will also see wires coming from a lightning arrestor in there. Swap those over to the other side when you move the rest of the wires. And one more thing: IF you have the 120v input wires in addition to the 240v wires, it gets more complicated. I'm saying that some of these also had the capability to input from a 50a 120v cord and produce 240v with the transformer. If yours has that, it will have more wires.