Best time to run dehumidifier?

[StephenStephen]

I need to run a dehumidifier a couple of hours a day for a few weeks.
It's in an unheated sitting room, which has a large south facing single glazed window. The opposite (north facing) wall is showing signs of damp.

I'll likely run a fan heater for a couple of hours 2 till 4am ish.

I'm thinking best to run dehumidifier in the morning, rather than afternoon, but can't work out why I'm thinking that...

Any thoughts?

 

[Burnerman]

I think you'll need to keep it running 24hr Stephen, to get the most out of it.
Unfortunately the average Screwfix type dehumidifier work incredibly well in the summer, but much less so in the winter.
Air exchange and heat is what you need in that room, assuming that the wall and guttering or whatever is in good nick.
John