Confused by Selector Switch Contact Blocks

[bolts]

I have managed to get myself completely confused trying to understand selector switches. I'm hoping somebody can shed some light. I'm planning to use the metal Automation Direct switches linked below.

This is what I think selector switches are doing (or at least this brand). If the switch (2 position or 3 position) is turned to the side the contact block(s) is attached too, then that contact block goes from it's 'Normal' state to the opposite (NO -> Closed; NC -> Open). In a 3 position switch the center position activates no contacts, hence they are all in the 'Normal' state (NO or NC). Is that right?

In my circuit, I have simple 2 position maintained selectors for the pumps (e.g. on/off). I'm intending to use the GCX1252-120L switches. So far so good. I need two circuits per switch that toggle between [O-X] and [X-O] to handle the pump and the interlock circuit so only one is ever closed at the same time. If so, I believe I need two of the same (NO or NC) -- or I could stack a NO and a NC on the same side (if physically possible)?

 

[Electro4]

You have it right. The NO/NC refers to the resting state of the contact so a NO will close when activated.

With your 2 position switch both sides will be activated when the switch is thrown. So a NO contact block will close when the switch is thrown no matter which side you put it on or even if you stack it on another contact block (which does also work if you need to).

If you are doing the safe start interlock from theelectricbrewery.com you will need one NO and one NC per pump switch. The NO will go to the pump and you safe start circuit runs though the NC contact blocks.