Hi, I have a Promax Combi HE Plus boiler. I have never had one of these before therefore I don't know whether to have the hot water ON constantly or turn it OFF and put it back ON again whenever I need it. PLEAASE HELP!

Turn it on, and leave it alone. You shouldn't have to mess with it unless there is a problem.

http://www.boilersprices.co.uk/potterton-boilers-prices/promax-combi-he-plus-a/

What does the owners manual recommend?

Your hot water system should be pressured up at all times. Good luck, Tom