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What is the correct firing rate for boiler?

Our facility has a Smith Model 19 Series 6 boiler with a Carlin 201 burner. The system heats roughly 1100 EDR. Forever, the burner has had a 1.75 GPH Nozzle. But I am not a believer in "that's the way it's always been".

How does one determine the correct nozzle size. The Smith specs say the boiler capacity is 2308 square feet, so the boiler is obviously over sized. The water capacity is 56 gallons. The burner capacity is 6.5 GPH.

So how do you determine the correct burn rate? Is it based on the time it takes to go from a warm boiler to getting steam to the end of the main? The time it takes to heat all the radiators fully? A guess?

I welcome everyone's insight on this. My home boiler (little WM SGO-4 has a 1.1GPH nozzle, so this all makes me wonder.

Steve from Newton, MA


  • Steamhead
    Steamhead Member Posts: 14,457
    edited October 2009
    What pressure

    is that 1.75 running at? Its rating is based on 100 PSI, but at 200 it would fire 2.5 GPH and at 300 it would fire 3 GPH.
    All Steamed Up, Inc.
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • Steve Garson_2
    Steve Garson_2 Member Posts: 638
    Nozzle pressure

    That's a good question. I haven't a clue. But now I can see how perhaps it is the correct nozzle.
    Steve from Newton, MA
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