Wiser UFH - Why can I add 3 controllers but only get 16 zones in total?

Due to the limitation in the number of rooms (16) you can add to the wiser system, it is only possible to create 16 zones in total. 

However, this does not mean that you will lose any underfloor heating actuator or channel control, you will still have access to the full range of 18 channels (6 per control strip) to assign to the rooms on your system.