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pressure relief keeps blowing off.

matt_59
matt_59 Member Posts: 1
I've been at this game for a lttle while now and for me this issue of the pressure relief blowing is a common problem. It is caused by one of three things. Either bad expansion tank, fast feed/ pressure reducing valve or the relief valve itself. I have changed the expansion tank once, and both the fast feed/ pressure reducing valve and the relief valve twice. When I shut the 1/2" ball valve that supplies water to the system the problem does stop. This would lead me to believe that it is definately the fast feed/ pressure reducing valve. The thing is that I can't believe that I have installed two defective ones. I I really am about to replace all three devices again and hope for the best but there is one thing that I'm wondering about. There is a indirect hot water tank located close to the system and the cold water feed to the boiler is tee'd off of the cold water (domestic) that feeds the indirect tank. Is it possible that the aquastat that regulates the temp. of the domestic hot is allowing the domestic hot temp. to rise hire than it normally did before and therefore creating more expansion than before and this expansion is pushing through the fast feed/ pressure reducing valve. The guage on the boiler reads 35 to 40 lbs. when the p.r. valve blows. It is a regular residential system with 4 zones including the indirect tank using zone valves. Please help.

Thanks Matt

Comments

  • JOHN_103
    JOHN_103 Member Posts: 54


    matt check the coil in the indirect if it is leaking that could overfill your boiler
  • bill_97
    bill_97 Member Posts: 172
    What brand indirect ?

    If it's a tank in tank design like a Phase 3 , this is a symptom of a tank failure . To rule that out you can shut the supply and return valves going to it from the boiler ( if they're installed ) . How long did you shut off the boiler feed valve ? When it's open , how long does it take to increase the pressure to 30 ?

    I doubt it's a defective but new PRV , expansion tank or relief valve . Does the pressure increase as the temperature increases ? What size expansion tank ? Another thing to check is the water pressure . The PRVs we use can only work with 100 psi incoming water . Any higher and it could bypass right through .



  • Weezbo
    Weezbo Member Posts: 6,232
    does your system have a domestic HW recir?

    three tanks water feeds and backflow preventors and relife valves add up to

    a leak.

    over temp.

    wrong piping arrangement to begin with.

    cross contamination thru a heat exchanger....

    wrong system pressurization in conjunction with setting of captive air tank.
  • RELIEF VALVE

    HEY MATT MY NAME IS TODD. THE FRESH WATER FEED FOR THE INDIRECT, IS IT BEFORE THE REDUCING VALVE? IT SHOULD BE.IS THE WATER VOLUME MORE THAN THE EXTROL CAN HANDLE? IVE SEEN #15 EXTROLS THAT ARE JUST TO SMALL FOR YOUR WATER VOLUME. WE RECENTLY HAD A 'SUPER STOR' INDIRECT THAT HAD A HOLE IN THE COIL, ALLOWING DOMETIC PRESSURE IN THE BOILER WATER ATMOSPHERE. IT IS EASY TO CHECK. ISOLATE THE RADIATION, AND IF YOU CAN, ISOLATE THE EXPANSION TANK. SHUT THE FRESH WATER SUPPLY TO THE BOILER AND THE INDIRECT. IT MAY TAKE A FEW MINUTES. TAKE THE FRESH WATER PRESSURE OFF THE INDIRECT. IF THE BOILER PRESSURE DROPS , YOU HAVE A WHOLE IN THE COIL. BY ISOLATING THE EXPANSION TANK,YOU REMOVE THE EXPANSION CAPABILITY, AND YO SEE A PRESSURE DROP MUCH FASTER.WITH COLD START CONTROLS,I'VE SEEN BOILERS COOL IN DOWN TIME. WHEN THIS HAPPENS, THE SYSTEM WILL FEED,AND THEN WHEN REHEATING, WATER VOLUME IS BEYOND EXPANSION TANK CAPACITY. WHEN YOU INSTALL A NEW EXTROL, THE DIRECTIONS TELL YOU TO BRING THE ENTIRE SYSTEM UP TO OPERATING TEMP. THEN REAJUST THE PRESSURE.WITH COLD START, AFTER YOU DO THIS THE SYSTEM COOLS DOWN NO BODY HAS USED ANY HOT WATER, BOILER HASN'T RUN, SYSTEM COOLS DOWN,SYTEM PRESSURE DROPS, REDUCING VALVE FEEDS, SYSTEM WARMS UP, PRESSURE RISES, RELIEF VALVE GOES OFF,THATS JUS WHAT WAS MEANT IN THE DIRECTIONS.
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