:x we have an ideal isar HE35 combi boiler and occasionally there is a extreme vibration when the burner fires, i have visually checked the burner and heat exchanger and all looks OK.
Thew problem happens only occasionally but is very alarming when it does happen, it seems that the boiler is about to explode.
Boilers can make some strange noises sometimes and it can be for a number of reasons. Without actually hearing your boiler's noise, it's difficult to say exactly what it might be, even more so, because it's intermittent.
If you take a look on YouTube, there are a number of videos showing the Isar making noises, maybe you can associate with one of those.
By the way, unless you are gas safe registered and qualified to mess with boilers, you shouldn't be dismantling your boiler to visually inspect the burner. In order to look at the burner, you have disconnected a gas union (connected to the fan) and have then opened the combustion chamber. These actions are illegal and dangerous.
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