Not sure if this is the correct forum, typed in HRV and go no results from any of the sections. I have a Venmar Constructo 1.5 HRV that has a main core in the center and two smaller filters on each side of the unit. The manual talks about cleaning the filters a couple of times each year. Does the "core" need to be removed and cleaned or just the 2 smaller ones on each end? Thanks for any info. See link for exact unit I have.