Calculate how much money you could get from different pension options - are you likely to be better off with an annuity or income drawdown? Viessmann vitodens -w system a-rated gas boiler. Dann deaktivieren sie adblock für leo oder spenden sie! Here, francis, a gas safe registered boiler engineer, discusses what size combi boiler is right for your home and hot water needs. Call us with confidence! we are fully licensed (lic#cfc) bonded and insured plumbing contractor.