I've dipped my toe in to the Home Assistant world, currently just polling devices, but I am now keen to move on to some control/automation.

First on the list is being able to control a ventilation fan (on, off and variable speed), which is currently controlled by this switch - http://www.pdlglobal.com/data/product_documents/625F-625FM%20install%20sheet.pdf

I would like to replace the whole switch so that the fan can be controlled via HA or via the switch itself. Also if possible would prefer to still be able to set a variable speed (percentage?) instead of just 3 speeds, which seems common.

I've tried researching this myself but I am not confident that I understand the electrical requirements of the switch in regards to connecting to the fan well enough to take the plunge on my own.

I don't have a Z-Wave hub/stick or such yet, but wouldn't rule out getting one if required, obviously it opens the door for using more Z-Wave/etc devices in the future.

So please, any suggestions would be much appreciated.