3 position switches, how do they work?

[somawheels]

I have a 3 Way AC rotary switch - and dont really know how it works.

I need to wire a 3 position AC 240v switch, which will swap between 2 separate power sources, and an off position (generator, Inverter, off). The power sources must both lead to the same consumer unit/load.

The problem: The 2 power supplies must lead to the same appliance/load, while never both supplying simultaneusly.

All diagrams show the same position switch.

power sources are separate at the "AC IN" side of the switch

I want them combined together at the "AC OUT" side of the switch, so the appliance/load stays the same while the power source can be changed using the switch. The problem: when I combine/connect the terminals at the "AC out" side of the switch, the switch no longer works! current is able to flow in and out of the switch through ALL 4 terminals/poles rather than just 2.

This happens in both my "on" positions, while the "off" position is unafected and works as it should.


If i do not combine the "AC out" terminals, the switch works as it should; only the appopriate 2 poles/terminals allow current through (the first diagram).

This 3rd diagram shows how i expected the switch to work

[Mike90250]

You need "Break Before Make" contacts in the switch. Best to purchase a UL certified Transfer Switch and not homebrew one

[somawheels]

That doesn't answer my question, but on that note:
There is an off position in between the 2 on positions, does this make it safe enough?

[somawheels]

I think i solved my problem. I made a mistake. I just found out my input and output need to be swapped! I put the input at the even numberd side (2, 4, 6, 8) while they should be at the odd numberd side (1, 3, 5, 7). This way it works as iexpected it to when the outputs is linked into one output.