Why is heating on at night?

Many boiler installations are fitted with a frost-stat - to stop the pipes freezing up even when the timer says the boiler should be off. Often found in an attached garage - nothing to do with the boiler specifically but part of the installation. A trigger point of +4° C is usual.

It may well be that during the day a) you're not there and will not therefore notice - or b) if you are there you will have turned the heating on yourself - or c) the temperature will be greater than the frost-stat threshold.

Good Luck...
January 2016

Is the timer set corectly? Find the manual online, download and check.

For how long does the boiler come on at night? All night? For a minute or two? iIs section 4.23 of the manual (se http://www.vaillant.co.uk/downloads/ecomax-use-installation-and-servicing-manual-261444.pdf) applicable?

XXX
January 2016