Hissing when boiler shuts off and issues on 2nd floor

noran01

I have an old peerless steam boiler and this season, so far, there has been an issue with the 2nd floor not getting much heat. I have (2) two main vents in the basement and everything is quiet with one exception; my master bedroom. When it does get steam you hear a small hiss, but when the boiler shuts off (due to downstairs thermostat being satisfied), you hear a loud hiss as if the vent is sucking IN air. I suspect this may be part of my issue with the 2nd floor heating.....any advice on what to check?

nicholas bonham-carter

checklist

check the pressuretrol settings, and verify with an accurate low-pressure gauge.

check the pigtail for blockage which could cause swings in pressure.

check the waterline for unsteadiness, and deris/oil.

check the main vents for blockage, and capacity.--nbc

Big-Al_2

Perhaps Normal

At my house, I put faster vents on the upstairs radiators so they get steam faster.  This may not be your issue, but it helped me.



As far as a vent making a whistling/sucking noise when the boiler shuts down, this is normal.  As the last of the steam condenses, air has to re-enter the system somewhere.  The first vent to open will let in the air, and if you have a radiator vent that never closed in the first place, then that will be the one.  I've found that the cheap Watts style vents are especially noisy under vacuum, and the bullet shaped Hoffman vents are the quietest.  The radiator vent in our main bedroom used to generally be the first to open and made quite a whistle.  It just seemed to open more quickly than the others.  I switched it out to a different room away from where we sleep and life is better.