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high water pressure after bleeding boiler

Familar knocking and tinkling occurring in my 1st and 2nd floor baseboards so went to purge the air yesterday. It was not a cold day here yesterday so I shutdown the system for a few hours before purging. Saw a ton of air come out from my 2nd floor zone and went thru about 15 gallons of water, the 1st floor had very little air (the tinkler). When purging I was throttling the auto fill to try and maintain water level but I did notice the water pressure dropped down to about 5. When complete, I manually opened the auto fill valve until cold pressure got to about 13 and then I heard the auto fill kick in and it seemed to stop around 15. When I turned the heat back on I noticed water pressure creeping up to 20, and then 25, and then 30, at which time I shut off the system worried that I was close to the relief valve spewing water. After a while, I took some water out of the bottom spigot of the boiler,,,probably a few gallons to get the hot pressure back to 15. After an over-night, its sitting hot at around 22. My settings are 180high and 140low. The expansion tank sounds hollow to tap and underneath the see-thru bubble is clear. This is a 30+ year old NY Boiler system, located in my basement (zone 1), with baseboard in 1st floor (zone 2) and 2nd floor (zone 3) with a pretty good run of piping to get to all those zones. Not shown in pic but each zone has a bypass valve. About 10 years ago, the 2nd floor added two more rooms and the piping there was extended about another 30' with no changes to the boiler system. A few years ago, I had a freeze event at the farthest run, so presumably there was a an air-block, and the pipe at that turn leaked. There are no air vents on any of the baseboards but its what I'm looking to get installed. But my question is, do I need to do anything else to deal with this borderline high water pressure?

Comments

  • RhinebeckDude
    RhinebeckDude Member Posts: 8

    Thinking that the auto-fill valve was defective, after removing water from the system, I did turn off the water in-flow so that no new water was being added to the system.

  • hot_rod
    hot_rod Member Posts: 23,508
    edited December 18

    22 psi is fine if that is at shutoff temperature. You could cold fill to 12 psi instead of 15 and pressure would be lower, also

    You might replace the brass air vent on top of the purger, they can stick close


    assuming your gauge is accurate?

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • kaffi
    kaffi Member Posts: 1

    would the boiler still get that hot if the fill valve was adding too much new water? Mine only ever gets as hot at 140f

  • SuperTech
    SuperTech Member Posts: 2,458

    @RhinebeckDude if you are located in Rhinebeck in Dutchess county I could assist you in person. I would check the pressure reducing fill valve and expansion tank and automatic air vents and make sure the entire system is operating safely reliably and as efficiently as possible.

  • RhinebeckDude
    RhinebeckDude Member Posts: 8

    When I was filling the system after the purge I was only paying attn to the water pressure so the temp may have been lagging a bit more,,,I actually didn't think I could overfill the system with water and create more pressure, but I wasn't accounting for heat expansion of the water. But again, if the pipe isn't full then space is filled with air,,,which presumably leads to air knocks in the pipe…?

  • HVACNUT
    HVACNUT Member Posts: 6,374

    How old is the feeder? It's a good B&G brass, so it's a good PRV. But even good ones get hung up. We used to rebuild them. No more. It might be time for water parts across the board if they're old. PRV, relief valve, air eliminators, extrol. You shouldn't have to purge every year. You shouldn't have to purge ever unless it's work related.

    delcrossv
  • BDR529
    BDR529 Member Posts: 314

    Extrol 30. guilty till proven innocent.

    jesmed1
  • jesmed1
    jesmed1 Member Posts: 762

    I just bought @RayWohlfarth 's very informative book "Lessons Learned Troubleshooting Hydronic Heat." He says in it that bladder tanks typically lose 1 psi/yr (pg 16).

    If the tank hasn't had air added in a long time, it's probably lost a lot of air, which the makeup water has displaced.

    RhinebeckDudeSuperTech