EdT

Been round the premises & all inlet valves are open. So that's not it!

Opened up, removed the large Recuperator & all dry inside. Pretty clean too.

Is that in the connection/pipe coming from the underside?

We've got a HRV2 Q Plus (Titon). Works ok, but the unit is on the wall just behind me and it's NOISY! Filters are all new. When I take the front lid off with it running, it's dead quiet, so assume it's fighting with air flow. Which means I reckon there's a blockage. Any tips on how to detect where, and how to sort?