Mine takes about 20-30 mins to warm up to 25C set on controller running on Electric set on 2Kw, with an outside temperature of 10-12C.
I was told by the dealer that if it needs bleeding or topping up other than at an annual service, you have got a leak.
Having said that there are some very good downloadable operating/installation instruction booklets at www.alde.co.uk/alde.php, depending on age of your van.Hope this is helpful.