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How do you setup an Adjustable Orifice Radiator?

I’m constantly amazed by Steamhead’s knowledge of these old systems and how he can identify them from some obscure trait in a picture. The latest one he identified is a ARCO Model K (Page 268 in The Lost Art.....) with adjustable orifices. That got me wondering just how does one go about setting up an adjustable orifice valve? Is there a procedure to be followed or do you just randomly try out different settings? What are the indications that you have it adjusted properly?  Do you set it conservatively so there is no chance of steam leaving the radiator or try to get the radiator completely filled  steam?

- Rod


  • crash2009
    crash2009 Member Posts: 1,484

    yea, me too, 3 times in the last couple days.  The hex nut on the Model K, the Trane B-1, and the Dunham Return System. 
  • Steamhead
    Steamhead Member Posts: 16,729
    Thanks, guys

    Most times the orifices are sized to fill the rads to 80-90% full at some pressure, typically 8-12 ounces or so. There are tables you can use to do the initial sizing, and you'd fine-tune them after firing up the boiler and seeing what tweaks you need to make.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
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