replacing conventional boiler and water cylinder with combi boiler

Easy one to answer. First choose a good build quality boiler if your budget will stretch to it, such as Worcester Bosch or Valliant, or a good midrange boiler such as a Idea Logic Plus, saving you around £100 on the previous boilers. All boiler manufacturers state in their M.I that the boiler needs to be installed to a clean heating system, this can be achieved by a simple chemical cleaning agent such as Fernox F3 added to your heating circuit two weeks prior to installation of new boiler, or if you suspect heavy sludge within your system then a power flush is strongly advised. We as installers cannot ignore the manufacturers installation instructions (M.I) and if we do then your warranty may be invalid. After all, you would not fit a new engine to your car and re-use the old oil from your previous engine! Remember the cleaner the heating circuit is, the more efficient the boiler will perform at transferring heat via your radiators. As for your second point, we always add an inhibitor chemical to your heating system on completion such as Fernox F1, not only is it a manufacturers requirement but will help reduce limescale build up and help maintain a clean and efficient heating system.

Best to go with a Baxi Platinum as they are offering 10 years part and labour warranty, plus if you use hj heating to install the boiler, next day callout for ten years as well. Always have a magnaclean fitted on your system £100 in most places, and a decent lime beater e.g. liff on the cold water supply going into the combi