I'm in a rented property with a Viessmann Vitodens 200 boiler which I think was installed in 2005 - it's driving me mad (and the landlord too!). As far as I can make out this is supposed to be a great bit of kit but it seems to have unsolvable faults. I moved here in June, there were problems getting the boiler signed off then for the lease as it kept cutting out with an 'F5' error. I believe it was cleaned up internally and then seemed to function OK throughout the rest of the summer until, maybe October, the F5 errors returned - I think this is related to a flap valve inside getting stuck shut, the air pressure switch was replaced and it worked OK for about a week and the started cutting out again. About this time it started intermittantly emitting a high pitched screech, which to me sounds like a very loud old fashioned TV test card, bit like a 1KHz tone, if that makes sense. This noise is so loud it's waking up the neighbours. The landlord's heating guy has looked at it, he and seems mystified (don't think he's a Viessmann expert), he's spoken to Viessmann technical who seem difficault to get hold of and vauge about what the issue might be - they suggested replacing a doughnut shaped component made of some sort of heat resistant material that fits around the burner, the existing one was coming apart which I don't think is supposed to happen. This made precisely no difference, the latest from Viessmann is that there are some modified parts for the flue which may cure it. Condensation from the flue has been mentioned as possibly being responisible for the F5 errors too. Are any Viessmann gurus reading? The landlord is now talking of ripping it out - I want to give it a second chance as they're supposed to be top quality german engineering aren't they???