I have an old oil furnace driving a forced air system. Sometimes when the
furnace kicks on it makes a loud thunderous sound that lasts for about a
second. I'm pretty sure it's not the air ducts since this happens before
the blower kicks on. Any ideas what this could be and could it be something
to be concerned about?
Yup...What is happening is your furnace dosen't light right away. You
have to clean the burner igniter. I get the same thing when this happens in
my hobby shop in the back yard.
An oil fired furnace does not have a pilot light like a gas furnace...it
has to relight itself everytime it is about to cycle heat.
What is happening is when the furnace starts it's heat cycle, it
starts injecting Deisel fuel into its burner but in your case it is not
igniting right away so fuel starts to collect...then when it does light it
ignites with a big roar because there is lots of residual fuel that has
started to burn....after the flame catches up...it settles down...usually
after a few seconds... get your furnace cleaned by an oil burner
Worse case escenereo is having the furnace fire up
and not light for about 15 seconds or so and then there will be LOTS of
unburnt fuel in the system...then have it eventually light which will fill
your home with black smoke and deisel fumes and possibly rupture your heat
exchanger... Yes.. this is something to get looked at ASAP
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