Probably a lot of dust!  But that's normal, and an annual cleaning takes care of that.  But what if there are technical issues  with the system since you last used the heating function?  And last winter was an especially cold one pushing these unique combination heating & cooling systems to their upper limits.

So it just makes sense to be prepared for the inevitable winter that is coming by getting an annual cleaning and check up as a preventative measure.

My family has been using the services of Furnace Factory Direct (613-829-8186) for our personal properties as well as our investment properties.  They are honest, pleasant to deal with and reliable. They have a number of clients in the Towers.