boiler insulation

[Yorkie]

An excellent post Mark - there's nothing I'd quarrel with there. I tried not to over-complicate my earlier post, and said for example that combi boiler systems don't store water in a cylinder, unlike open vent systems which have a cold feed tank and cylinder. That isn't the whole story - large systems can and do have a hot water cylinder if desired, but not a conventional open vent one. My son's house in Putney has a large combi boiler and a cylinder about 5Ft tall and 2 ft diam, which is a swelf contained fully insulated jobbie.

As to British Gas, I spent my 40 yr career with them, joining as an apprentice in 1954, progressing through sales and service management, a spell in training service engineers on central heating fault dignosis, then in the labs during the natural gas conversion phase desigining burner kits for obsolete appliances which BG would otherise have had to replace at their cost, then I became service manager at Grimsby, Mansfield and Sheffield, before moving to Hull as General Mananger for North Humberside, where I sank gently to earth in a 'golden parachute' in 1994!

Much has happened since, and time has passed me by, so I can't claim to be up to speed on technical developements. However, on the question of an 'Annual Service ontract' from my experience, any unnnecesary dismantling of boilers for a 'service' to try to demonstate value for money to customers risks making the boilers less reliable. The mere act of distrubing thermocouples, burners, removing the cover of the boiler rirks introducing faults. The cal back rate after an annual 'service' hoverved between 10% - 15% mostly within 24 hours. Open flued boilers did need regulary serving especially where there are pets or when irnoning of clothes takes place in the same room as a boiler (kitchen etc) as the venturi of the burner will draw lint into the burner and cause it to 'lint up'. This elongates the flame, causes incomplete combustion, flame impingement on the heat exchanger, causing 'sooting up' and risks carbon monoxide being generated. There are fewer and fewer open flued boilers, so over time, that problem disaappears.

The benefit of such contracts is the annual breakdown cover, but there's so much small print and exclusions, that personally, I think it's best to stand the risk, and call out a GasSafe installer as needed.

Room sealed boilers rarely need to be dismantled, and a combustion check on the flue gases will reveal if the boier is working at peak efficeincy or needs adjustment. Over the 20 years we had our balanced flue boiler (which I've just remembered was an Ideal Standard - not a Glow Worm!) it never needed touching, but I did however have to replace the pump three times.

As to 'power flushing'' - a nice little earner!

It's true that if a system is drained down, or householders are in the habit of removing and refittng radiators to decorate, and in neither instance flussh th syste ad put inhibitor in whenthey fill up, sludge (corrosion of pressed steel radiators etc) can arise, and itslso true that whn a boiler is changed, it's a requirement to power-flush the system. But other than that, it's a needless expense. Any outfit that wants to charge £700 for it should be laughed off the face of the planet.

BG training was, and I guess still is, second to none, and if their servie engineers din't pass the City and Guilds intermediate a Final exams, they didn't qualify. I don't want to bite the hand the firm that pays my pension, but personaly, if I needed any installtion orservice work done, I'd use a GasSafe (Corgi as was) instller who is Ex BG. Such installers live and work in the neighbourhood, their kids go to school with the kids of their customers, they often operate from home with low overheads, will be trained in diagnostics by the companies whose boilers thay install Vaillant, Worcester Bosch, Baxi etc), and they have a personal reputation to protect. Generally, they'll do go job at a fair price.