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Steam radiator inlet orifices

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Schvenzlerman
Schvenzlerman Member Posts: 41
in Strictly Steam
Henry Gifford of Gifford Fuel Savings, Inc., New York City, wrote an article in ABMA in 2003 on this topic. It was titled How to Make a Two-Pipe Steam Heating System Really Work. It had a table that showed how large to drill a hole in inlet orifice blanks, for radiator square feet EDR. This table was, however, for 2 psig. I need a table for steam systems operating pressures from 1/2 to 1 psig. Also, if I'm using such pressure and have radiator inlet orifices, can I still configure my boiler for modulating operation; e.g., hi-lo-hi?

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  • Rod
    Rod Posts: 2,067
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    Radiator Orifices

    Hi-  Getting the right orifice size seems to be a matter of trial and error. There was a post a while back that suggested starting out with 1/8 inch orifices and if that isn't enough then just drill the hole out a bit more.

    Theoretically if you can get a certain amount of steam through an orifice at 2 PSI you would need a larger orifice to get the same amount through in the same time frame at 1 PSI.

    Here are a few orifice sizes and their corresponding cross sections.

    Orifice Size           Cross Section

         1/8                        0.01227

         5/32                      0.01917

         3/16                      0.02761

         7/32                      0.03758

          1/4                       0.04908

    For example if you wanted try double the cross section of a 1/8 inch orifice, it would be 0.02454 which would come roughly between 5/32 and 3/16  so you might want to use an 11/64 drill bit.

    Orifice plates are available from Tunstall,  either as blanks or with the orif0ces pre drilled.

    http://www.tunstall-inc.com/tunstall-steam/inlet-orifice/



     I think I'd make a list of the radiators and their individual EDR . After a bit of experimentation you should be able to guess and pretty close to what you need for a certain size radiator based on what you used previously on a similar size radiator.

    As what would work best with the Hi -Lo is also an area that you will probably need to do some experimenting. Please let us know what you find out.

    - Rod
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