As a landlord I had a plumber who unfortunately installed 5 or 6 of these units. In the main they have proved very unreliable. In my experience it was common for major parts such as fans and circuit boards to stop working after two years and sometimes before. The circuit boards in particular are very expensive to replace. The only saving grace in the uk is that that they will come out and fix any problem for '220 including circuit boards which cost around '180. My advice is to avoid at all costs. If you have one that is say 4 years old and it starts to go wrong, cut your losses and install a Vaillant.