Would Brad75, B Star and other experts here offer some help please.
Apart from getting the Plumbing inspector to deal with the cowboy who install the system. I am also thinking of re-locating the return air vent from down stairs to the ceiling in the landing area up stairs near the stair well. (See Pics with red circle) Would this works?
The whole return air path has never been properly designed and sealed anyway, there is no ways they can rectify this issue without ripping up all those plaster board along the path, and I don't believe they will.
Also, I suspect my whole family have been breathing in all sort of rubbish that the system is pumping out. My 2 little one have been coughing since we moved in a few weeks ago.
My system: Brivis HX35i heating with 21KW ICE 3 Phase.
Thanks