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1/8in vent in vertical riser

I bought a new house and there are two headers with 2 quick vents where they droo to wet returns and new vents on all radiators. Finally balanced system well.

but there was a hoffman 1a adjustable vent  in a 2in riser that goes through a powder room to heat that room on its way to second floor rads. It had been turned aideways when someone remodeled bathroom and dropped ceiling and painted ten tines, so i cut in half, spun out, scraped to identify and decided I could put a variabalve in it since it seemed to be an adjustable vent.

at the end of heat cycle once in a while it seems to release a lot of pressure, like just spit air pretty loudly. Seems like system should not have that much pressure. 

I am not sure it even should have a vent. 

Comments

  • Jamie HallJamie Hall Member Posts: 13,852
    May not need a vent there -- but if the system is balanced well with it, leave it alone. But at the end of the cycle -- are you quite sure it is releasing air, and not allowing air in? When the boiler stops, the steam in the system collapses very quickly and can create a significant vacuum. If this vent is one of the first to open, it can be quite apparent.
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
    ethicalpaul
  • betweentheframebetweentheframe Member Posts: 110
    Interesting, let me make sure it is coming out. Found one more rad upstairs built into cabinets that needed sloping back, that this riser feeds I am pretty sure. I had to track down the quick vent for second riser in finished basement, open up wall and sure enough find a plug someone put in cause needed to run a water line for a hose bib lol. Reinstalled that although I had to put it at a 40 degree angle because of said copper hose line, which in spring i can reroute. Still getting hammering beginning/mid cycle in my return. Think it needs flushing(mud leg last portion was replaced with copper but about 30 feet of it is old steel and pita to change cause most is behind finished walls! But I can make 1/2 copper and flush the rest. Have a hose drain in mud leg and can run out to dry well in driveway
  • betweentheframebetweentheframe Member Posts: 110
    You were right! It is sucking air! Is there any reason it does that or something I shoukd do to fix? 
  • LardLard Member Posts: 91
    You were right! It is sucking air! Is there any reason it does that or something I shoukd do to fix? 
    I had the same issue with excess vacuum at shutdown. This was in a church and the vents made a “flatulent” sound when pulling air—not desired during a sermon!
    I put vacuum breakers in the basement and tweaked the springs so they are the first thing to pop open and suck air. Problem solved!
  • betweentheframebetweentheframe Member Posts: 110
    These temp change hoffman #4’s are at the ends of my mains, The diagram for their installation shows them differently than they are in this 1929 house. They are each installed where the pipe in this reducing fitting drops into the wet return, the pipe drops about two feet them makes its way to the boiler before dropping into a mud leg with drain.  

    I am attaching the one I found plugged behind drywall in finished basement, I put the old one I had replaced when I bought the house just as a good measure and to see if would lessen water hammer in wet return below, though as water runs I hear rusty crap moving around so I think needs a good flush, I can just hook a hose bib to main vent and open drain and run house out to driveway drywell and flush her out, careful not to use too much pressure to flush stuff into boiler ne I 
  • betweentheframebetweentheframe Member Posts: 110
    Lard said:
    You were right! It is sucking air! Is there any reason it does that or something I shoukd do to fix? 
    I had the same issue with excess vacuum at shutdown. This was in a church and the vents made a “flatulent” sound when pulling air—not desired during a sermon!
    I put vacuum breakers in the basement and tweaked the springs so they are the first thing to pop open and suck air. Problem solved!
    I ended up taking pressuretrol off, pigtail totally clogged, cleaned out, added in a 0-5 psi gauge and sure enough even set to .5 and 1 diff it is not shitting down til 4 psi! So my vaporstat delivers today and I will install that and set and see if the vacuum issue goes away because it only happens after a long run 

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