Knocking sound in oil boiler
Whenever the heat is on, there's an intermittent dull knock.
It started a couple of weeks ago. This week we called the oil company to arrange a service call, and the noise stopped, so we told them not to come. Of course it started up again that night!
Searching on the web, I found a sound file that pretty much duplicates the noise, except for the pitch. The (British) site calls it a "knocking, kettling noise" and says it is due to lime and sledge deposits. They sell products to remove the deposits.
I am reassured that it does not sound like the "pipes being hit with a hammer" sound that is dangerous. The sound is not as loud as the ordinary noise of the boiler, which is awful; sitting in our living room you might think you are in a rocket ship that's about to take off. That's how it always is.
The temperature of the boiler is where it should be, and we are of course keeping an eye on it.
If we need a new boiler, we'd been thinking it might be better to switch to a gas system, perhaps with a tankless hot water heater. In fact, the last guy who cleaned the burner advised us to switch to gas! But after reading on this forum, I realize we'd probably spend more in new gas piping, venting, etc., than we are likely to recover. (We have gas now, but only for cooking.) I also learned that a summer-winter hookup that uses the oil boiler to heat hot water is not necessarily a bad thing. Almost every contractor who ever worked in the house said we should get a water heater instead.
Here's the big problem: I have very little confidence in the people who come here to work on this stuff. Too many mistakes have been made. That applies to the plumbing companies and to the heating people. Who should I call for the correct diagnosis?