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Steam Rad Problem

Background: House built in 1925.  Steam 2-pipe system.  Originally Coal fired, converted to Natural Gas burner head.  In 1995 old boiler replaced with new Bryant boiler.  It appears that there are no visible traps on the return side of the free-standing rads.

Changes:  About 10 years ago I replaced a free-standing rad on the first floor with a Burnham recessed rad.  It works great.  Then I completely gutted my master bath on the second floor and replaced the free-standing rad with another Burnham recessed rad.  This one is giving me problems.

When I turn on my heating system for the first time after the Summer, the bathroom rad heats up entirely.  However, after that when the boiler recycles during the day/evening, I get some "banging", the feed pipe is hot and only the first section of the rad heats up.  Apparently, there is water blocking the steam from rising which is why there is "banging". 

The rad is pitched very slightly ( .2 degrees) to the return side.  Is this the problem?

What is the minimum pitch needed?


  • Jamie Hall
    Jamie Hall Member Posts: 23,655
    Certainly sounds

    as though something is trapping water somewhere, but it isn't likely to be the radiator itself -- although a little more pitch to the return probably wouldn't hurt.  Is there a horizontal bit somewhere in the return line which might have gotten pitched backwards?

    This sounds like one of the systems for which the steam into the radiator was controlled by an orifice or other restriction on the inlet or outlet.  Did that get changed?  Or?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Woolman
    Woolman Member Posts: 5
    Steam Rad Problem

    The original rad was free standing an had the feed coming in the top and the return at the bottom.  The original inlet valve was a MODULATING VALVE.  The new recessed rad had both the feed and return coming in the botom.  Currently, I set up this rad with NO inlet control valve.  The return line doesn't have any backwards pitch.

    I suspect that condensate is staying in the rad and keeping the steam from heating the entire rad which is also causing the banging. 

    I will probably try to disconnect the rad and verify whether is has water in it or not.  If there is water in it, I'll have to find the cause of the blockage.  I plan on increasing the pitch a few degrees.
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