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Air in Runtal Rad

kcopp Member Posts: 4,448
Hi All! I just installed a few Runtal rads into a newish system last week.
Wall hung condensing boiler w/ air separator. 1 circ pump to some radiant slab in a garage. 1 circ pump (007e) w 4 zone valves to the panels. all works great. All heat well.
System runs at approx 120F most of the time.
1 Runtal rad that served 2 rads by way of a "manifold" 3/4 x 1/2 x 1/2" tee has air issues. The rad heats but you can still hear a fair amount of air in it.
Its a vertical 20"w x 72"tall version. I have bled it out both ways... with supply open and return closed and vice versa.
If you bleed it out you do get some air. But the issue still persists. between me and the homeowner we have been bleeding for a week.
This last time I added some Adey inhibitor and raised the water pressure to 22psi hoping to drive the air into solution.
Do the vertical rads have more of an issue w/ air?
Any additional thoughts would be apricated. Ty, kevin


  • hot_rod
    hot_rod Member Posts: 22,472
    Does it have a manual bleeder up top? That is where air will collect. There are some auto vents that might fit if you have a port
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • psb75
    psb75 Member Posts: 863
    A LITTLE liquid dish soap in the water is reputed to break up air bubbles. Hotter water and higher pressure can help to "chase bubbles out'. The Runtals have two possible places for air vents at the top. One vent should be sufficient--either auto or manual. A tall rad should be especially good for isolating air bubbles and releasing them. If no success after repeated bleeding...you probably have an influx of air on the system.
  • kcopp
    kcopp Member Posts: 4,448
    Yes they give you a coin vent up top. Its manual.
    I have done the soap trick but am wondering if that would mess w/ the chemistry of the inhibitor. Was hoping the inhibitor alone would do the trick.

  • kcopp
    kcopp Member Posts: 4,448
    Well it would appear that the inhibitor addition and the raised system pressure to 22psi has done the trick.
    Thanks all.