It's generally OK to have a setback of a few degrees. I would start with 1C setback and monitor for a bit. Depending on the impact on energy and comfort, you could increase to 2C.

I'm surprised to hear you need heating in Algarve. Are we talking the same Algarve in Portugal?

Yes it is the Algarve Portugal and temperatures are currently around 11C min at night and 20-22C max in day but with humidity rising (75-85% generally) . The heating season will probably start in December and so my question was raised in preparation for that.

To explain:

I am fully converted to weather compensation and my Tado's will stay at 2-3C above chosen daytime temperature's.

However, we do not need or want the same temperature overnight in our main, downstairs bedroom and I can use the Tado's to adjust that. Comfort is my consideration here.

Also, we have 3 unoccupied bedrooms upstairs and I struggle to accept that it makes good economical sense to keep these at the daytime temperatures overnight, and again, I can use the Tado's to set back to a level which will not significantly affect the whole house heating/ weather compensation. Economics is my consideration here, but avoidance of mould in cold corners will be a factor.

Hope that explains.

@davidalgarve I would probably turn down the heat pump slightly overnight then instead of your Tado's. Your Tado's don't talk to your heat pump so even if you turn them down, your heat pump will continue to work at the same flow temperatures as before.

If you're too warm in your bedroom, you can balance that radiator down.

Posted by: @hcas

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I would probably turn down the heat pump slightly overnight

Thanks for your comment HCas. Is possible to do this on the FTC5, whilst operating on weather compensation? i.e. have one weather compensation for day and another for night?

If you use auto adapt and the Melcloud scheduling you can vary the target temperature across any period. I use it to set back for around 6 hours overnight but vary the target temperature according to the season. So, slightly less severe set back in the depths of winter to ensure a prompt recovery in the morning. I find that Auto Adapt handles the weather comp better than fat fingered fiddling around constantly. 

Thanks for your comment, Abernyte.

Am I correct in assuming that you have a PAR-WT 50 Wireless Controller strategically placed giving the room temperature?

I have no room temperature device and I cannot find out where MelCloud is getting it's "Room Temperature" from and it only occasionally gives the same figure as Th1 which is supposed to be room temperature! Nothing is plugged into CN20 which is supposed to be the input for Room Temperature

Consequently the MelCloud reading means nothing and the "Set Temperature" slide control does nothing

Yes, you need the PAR-WT50 controller which speaks to the FTC5 via the PAR-WT51 receiver which is wire connected to the FTC5. You need both for this to work properly.