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No water visible in sight glass during operation
I have a recently -installed boiler with a curious problem: Within a minute or so of the boiler turning on, whatever water is visible in the sight glass drops an inch or so, pauses at that level for about ten seconds, and then completely disappears from view.
In other words, there is no water visible in the sight glass within a minute or so of the boiler turning on.
This is the case regardless of whether the water level in the chest is at maximum or near cut-off level. In other words, this issue is independent of the actual water level in the boiler.
When the boiler turns off, within a few seconds the water level rapidly climbs back up to where one would expect it to be at the end of a run. From there, all of the remaining inch or two water that one would expect to be up in the radiators is back within 10 minutes, and we are back up to the beginning level in the sight glass.
The boiler heats the house fine and otherwise operates about as one would expect, apart from some minor short-cycling at the end of a run when ambient is below 30F, which may be due to lack of an anticipator setting on the thermostat, or perhaps we need some more venting.
The boiler mfr and installer are both very reputable. I am not going to use their names here.
I have reviewed the near-boiler piping based on my own amateur knowledge, and I have also compared and contrasted it with the mfr's installation specs. I have also reviewed it with another amateur who has over 60 years of experience as a user/operator of household steam heat, and he has also compared to mfr's installation specs. We don't see any obvious problem with the piping.
It seems like there is some kind of funky localized pressure issue inside the boiler that forces all of the water out of the sight glass without causing any other obvious problems.
How serious is this? Will it impact longevity of the boiler?