Andrew Gabriel wrote:
In article .com,
Several people have reported vibrations like you would get from
a 32' organ pipe. I suspect this is either combustion oscillating
back up into the pre-burner area or maybe an undamped feedback
loop in the venturi gas valve. I had this on initial installation
as the preset mixture adjustment was preset incorrectly.

I think its a combination of a very powerful fan and the small diameter
of the air intake. Your analogy of the pipe organ might not be too far
out. The powerful fan is needed to overcome the maximum resistance from
the 50mm system. The 'fix' chokes off the air intake pipe to the fan.

I also used a non-setting sealant on the exhaust spigot gasket.
(Initially I had thought that's where the leak was. However, it
turned out the leak was in the manufacture of the flue spigot.)

They now ship a new and improved spigot which extends a little way
inside the gasket. Presumably to prevent the condensate seeping through
gasket.

The reason I asked about the jointing compound was to see if anyone
else used a non-permanent seal, to aid future maintenance. I've used
LSX which is also smeared on the gasket. Its a pity there isn't a more
robust method of connecting the flue to the unit. IMO this is the weak
link in the chain. A male flue pipe should go into a female port on the
unit, which is how almost all other boilers are designed.

martyn