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Pressure upto max nearly im my bolier - Heating & Cooling

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  • keypad4 Dec 19, 2008

    thanks bob , ya sorry its a gas waterboiler combi and its leaking water when i turn on boiler . i changed a tap yesterday and turned off a water valve but opened it up to much when finishing with the new tap .. there seemsto be 3 valves, two have black little thunb levers and the one in the middle looks like a nut that looks like itcould be adjusted .. should i losen or tighten that ?
    thanks for your help mate :)



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You don't say what kind of boiler this is but I'm going to guess that it is a hot water boiler.  If so, you have a combination valve which adjusts the water by pressure and bleeds off excess.  These valves do get corroded and dirty.  Shut down the boiler, shut off the feed water valve.  Replace the valve assembly.  Do not try to adjust these things.  Your new valve should maintain about 15 psi.

Posted on Dec 19, 2008

  • Robert Hirst Dec 22, 2008

    Keypad...thanks for getting back.  There is a valve set which feeds the boiler with water which contains a few parts: a pressure regulator with a screw on the top and a safety unit with a drain tube or fitting at the bottom...sometimes, these units are separated with the safety drain unit set on the boiler.  

    I'm assuming that the leak is coming from the part of the valve set which has a drain line...just a fitting where a pipe is probably screwed in.  This is the overpressure relief.  It is saving your boiler by not allowing excess pressure.  The pressure builds up in the system when the water in it expands as it is heated.  It is not adjustable but it has a lever which you describe on it which will allow you do 'dump' pressure.  

    If you want to adjust the feed valve which has a nut on the top, loosen the nut and then use the lever on the safety to let water out...slowly.  If the boiler is cold, you should allow the reading to go down to about 1/3 of the scale or so say 8-10 pounds...if hot, no more than 2/3 of the scale (that's 15 pounds per square inch...100 KPa).  If the adjustable valve starts bleeding water in, back it off a bit more.  If it is bleeding at 15 or lower, it will need to be replaced.

    Watch the boiler through a cycle...stop by occasionally...and see that the needle is at that 15/100 point and the safety is not bleeding. will likely need to change the valve set out if it is more than about 15-20 years old.  They are not expensive and will be pre-adjusted.  I've tried cleaning them up but found it a giant waste of time.



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