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Baseboard radiator venting

We have a long (c 8 feet) baseboard radiator, fed via a lengthy feed emerging from near the end of the steam main, that we are having trouble getting adequately heated.  We are pretty sure the problem is inadequate venting.  We recently installed a Maid O Mist "D" size apeture (I think the largest apeture available for these) and, although the season is early, that venting may still be insufficient.  My question is whether you can, and if so whether it makes sense, to tap another vent hole midway through the radiator, in effect two vents on the radiator, one half way and the other at the end.  I would then experiment with the vent size on each to optimize steam fill.  I think I have seen that suggested on old upright radiators and I would think that the same approach could work with baseboard. (Or maybe the same idea, but both vents near the end of the radiator run? - but as to that, as with most baseboards, aesthetics plays a role and in part I thought the 1/2 and 1/2 approach might not look as odd as two vents side by side).  Is the mid way tapping feasible?


  • Unknown
    edited October 2009
    Baseboard Radiator.

    You didn't mention whether this radiator on a one or two pipe steam system?

      You might want to try testing the venting capacity using a ball valve.  This would simulate the maximum venting available from this 1/8 inch vent opening. Remove the vent and attach a 1/8 ball valve to the vent hole. Use some nipples,elbows etc with the ball valve so that any steam is ducted safely away where it can't do damage to yourself or wall etc.  Time how long it takes for steam to reach the vent normally and then time it using the ball valve.  Theoretically an open 1/8 inch pipe is equal to about 4 of Maid of the Mist # Ds. If the open pipe (ball valve setup) shows an improvement then I think I'd try attaching a nipple/tee/elbow (Use brass fittings as they are less likely to corrode) and use two Maid of Mist # Ds and see how that works. I'd be a little worried if you added more that you would might get problems with water hammer.  Possibly you could do what you were suggesting , that is tap another vent hole, but I'd try multiple vents on the vent hole you have now first and see what that does.

    You mentioned that this baseboard radiator is at the end of a steam main. Does this main have adequate venting? . It maybe that you need more venting on the main as your problem maybe that the radiator vent is now venting both the radiator and the main.

    - Rod
  • Amateur
    Amateur Member Posts: 2

    Thanks; very helpful!  I'm going to look into adding extra venting on the main.  (BTW, it is a one pipe system.)
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