Connecting 4-wire supply to 3-wire outlet for bathroom fan timer switch
I believe you are in the UK?  Every country has different standards... so not sure how to address your issue.  I went to the site you provided and found their instructions rather lacking... (https://www.venmar.ca/DATA/DOCUMENT/243_5_en~v~installation-manual.pdf) It almost appears that the motor/unit gets the power.  THEN, a &quot;type 22/4&quot; wire (per the installation instructions) goes from the motor to the &quot;push button&quot; controller.  Those strange codes of &quot;OL', 'OC' and 'I&quot; are on terminals in both the motor unit and the controller switch, and all you need to do (if I am correct) is make sure that you connect the OL from the motor to the OL of the switch, and the OC of the motor to the OC of the switch, etc.