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How to size radiator vents?

JeffrsJeffrs Posts: 31Member
Can someone please help me figure out how to calculate EDR for my radiators and what size vent for the EDR of each. Or could you point me to a source where I can find out how to do it and the chart for vent size per measurement. I've been reading "The lost art of steam heating", I'm not done with it yet but I haven't seen the chart in it yet or calculations.

Also, a side question. How much makeup water is too much water? When I moved in I had to fix leaks with half of my radiator supply valves and unions. The auto water feed digital display reads 442. Sounds like a lot of water.

Thank you all for the help


  • RodRod Posts: 2,067
    edited January 2013
    Radiator Venting

    Hi- I would suggest you get Gerry Gill's Venting book available as a down load in the Shop section of this website

    Earlier this evening in another post I attached a form to help you calculate radiator EDR Look for an attachment that's titled: "Boiler Sizing Chart"

    - Rod
  • Hap_HazzardHap_Hazzard Posts: 1,349Member
    Radiator Venting

    The vent size really has nothing to do with the radiator's EDR. It's related to the volume of air in the radiator and its supply piping from the main, and this assumes the mains are adequately vented. The objective is to fill every radiator with steam simultaneously.

    442 does sound like a lot of water. How long did it take to reach that reading, and is it still increasing? If you think you've fixed the leaks, record the count and the date on the card so you can make sure it's fixed. Normally a water feeder should never activate. It's not intended to maintain the water level. That's your job.
    1983(?) Peerless G-561-W-S
    3" drop header, CG400-1090, VXT-24
  • ChrisJChrisJ Posts: 9,877Member


    I believe the amount of air a radiator has in it is directly related to its EDR.  I have also learned that including the amount of air in the runouts which you mentioned is also very important as it bit me in the butt on several radiators.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • RodRod Posts: 2,067
    EDR to Air Volume

    Hap- I understand what you're saying. It's just that you need the EDR to use the conversion table on page 14 in the Gill- Pajek Venting Book.

    - Rod
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