Mine was also wired with an isolating switch in the ceiling, but on hot day like today I just switch it off at the mains distribution board in the garage. As mentioned above, from around 9pm it IS useful to draw down fresh (filtered) cool air from the ceiling, but we just switch it off again in the morning so it doesn’t feel the need to draw down the 40-60C air from the roof.

Unfortunately HRV decided to only allow a 4 hour ‘off’ period when you use the controller, which is why it keeps turning itself on, as it’s ‘job’ is to be a “Positive Pressure System” and force the air inside to be higher pressure to move the (generally higher humidity) house air outside.

On the plus side, this year (the first time I’m intentionally switching it off) is the first time my hay fever has come back, so I might actually try leaving the (very slow) fan bringing warmer air down next year and see if the filtering is what has kept me allergy free for the last two years too!

(Anyone know how often the filter needs changing?)