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- 13 Dec 2007
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If the installer has used the Vaillant filling loop, then there are two valves for the water to get past, but not impossible I guess... Failing to fill a vaillant combi correctly can result in a damaged primary HE. There is an overheat switch to protect this but it can activate too late. There is a code to signal this that cannot be removed from the boilers memory... Danger Mouse is the guy who knows these boilers well.... What has happened to him?