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Big old Crane boiler revisited

I have been taking care of this big old Crane for about three or 4 years now, and every year it has to be cleaned up. It soots up real bad. Like the last post about a big old Crane, I need stop this - it a dirty, lousy job.
It is rated something like 450,000 to 900,000 BTU/Hr and is firing about in the middle of that now. The flames lick the bottom of the heat exchanger and it looks like a crematoria in there. Gas pressure is something 1.5" - 2" w.c. It really roars when you turn it up. Maybe it needs the full 3.5" w.c. manifold gas pressure.
I have them pretty well trained to leave the door open all the time except when having church service. The flue and the connector are clear.
Flames come back out the burner tubes at you when it lights in a couple of the burners, there are ten of them. Anything less than full primary air is worse - just gets yellower and the inner blue cone disappears.
I am thinking the orfices are too big.
If any body answers this post I will explain all my reasoning to want to put new smaller orifices in it


  • Steamhead
    Steamhead Member Posts: 16,942
    Two things:

    1- Pull the burners and clean them. Dust and dirt will restrict the primary air input.

    2- If the gas valve is an instant-opening type, it is possible that switching to a slow-opening one will give smoother starts.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    HVACNUT Member Posts: 5,870
    edited November 2019
    Flames licking the bottom of the HX means way too much over fire draft. Control the draft and the ignition and air adjustment (with a combustion analysis) should be easier. The way it is now is like trying to strike a match in a wind tunnel.

    And doors open unless its prayer time? It needs sufficient combustion air, always, with the doors open or closed. Even when the boiler is idle. No outside air transfer ducts? WWJD?
    EBEBRATT-Ed Member Posts: 15,746
    you can find gas charts for orafices. Find how much your input needs to be, then using the charts and install the correct orafices (depending on boiler rating) and set the gas pressure to 3.5. CClean and check the burners and check with test equipment.

    A gas boiler that makes that much soot is also making C0. Use caution