Test button not working on 4pole RCD

[Cassien_2009]

If the test button resistor is across L3 and N on a 4pole RCD and you are using the RCD for single phase, why doesn't the test button function if you link all the line poles out on the live side of the RCD? but it works when you just connect to L3 and N.

 

[Rob.]

Draw it out. It'll become clear