In the end I opted for the *integra* unit from Vent Axia. Basically the
only modestly priced (405 ukp+ VAT) unit that could be fitted
horizontally in the space available.

Lots of hole boring and duct pulling later..... the suction side seems
fine: inlets from two bedrooms, kitchen and bathroom. The bathroom has a
simple humidistat to bring in *boost* speed which I am a bit doubtful
about as humidity levels vary with temperature.

Noise! The return side, so far a single 4" duct feeding a single 4"
outlet in the hall is ***** noisy! How much of this is electrical/fan
blade generated or single duct air flow is difficult to determine. I can
put in a T and halve the flow rate fairly simply or create a padded
discharge box with much bigger outlet vents.

Does anyone have any practical noise reduction suggestions? I suspect
the more expensive DC motors would be electrically quieter but I don't
think they were an option for this model.

More control sophistication would ease the issue. At present a time
clock restricts the trickle use to 6.30am to 10.30pm with boost
triggered by the humidistat. It might be better to arrange a further
limit on boost operation to a timed interval based on bathroom
occupation linked to the light pull switch. Has anyone come across a
suitable timer with a relay output?

regards


--
Tim Lamb