Worcester oil boiler - Heatslave 20/25?

You go and find the manual. Then you read it.

It took me about 60 seconds using Google. I suspect you may have a paper copy somewhere.

I found this:

https://www.worcester-bosch.co.uk/support/document/download/8716104440

Check page 3

And the user manual:

https://www.worcester-bosch.co.uk/support/document/download/release/8716101859/12822

Mentions reset several times.

XXX
February 2016