I added riser vents and noticed something interesting

jhewings

I have a 1-pipe system with about 920 sqft of radiation (not sure about the EDR of a ceiling mounted radiator). The building is 3 stories. I decided to vent the 4 risers with Gorton "D"s. I did this after hearing a lot of whistling of air through the radiator vents on the 3rd floor. I am hearing much less whistling now. The thing I find interesting is that within a few seconds of the Tstat ending the call for heat, one of the riser vents begins loud whistling which lasts for maybe 10 seconds. I held a match to the vent and air is going in. I suppose a vacuum is being created in the system and the air is rushing in?

jhewings

There are 2 mains each with 2 Gorton #2s

nicholas bonham-carter

Whistling radiator vents usually points to under capacity of the main vents.—NBC

jhewings

I calculated the volume of the mains. 1.43 cuft and 1.75 cuft. I thought they were close enough in size to vent them equally. They each have 2 Gorton #2. The riser vents seem to be helping with the whistling.

ethicalpaul

At the end of a call for heat, all the steam currently in the system will condense at basically the same time and will cause a reduction in pressure (vacuum) in the system that is relieved through one or more vents, as you are seeing.

It's typical that one vent cuts loose first and relieves most of the pressure imbalance. That vent will make some noise. Hopefully it's a main vent, or at least a vent not in your bedroom.

ChrisJ

If my system runs for a long time, I'll often have the long whistle as the system sucks air in.
But it doesn't seem to happen as much with Gorton vents as it did with Hoffman.