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Posted by rep on February 18, 2006 at 14:45:08:
In Reply to: Re: Boiler Over Firing? posted by HeatPro on February 18, 2006 at 10:37:41:
: Too many unknowns to give a specific answer as to the effect upon efficiency. Overfiring can increase efficiency or lower it - that is related to the boiler design.
: You would want to know why the boiler is overfiring by taking readings before adjustment. What readings would you suggest? Is it overfiring due to the gas pressure being too high, or is it overfiring because of incorrect orifice - or both? You would also want to know why someone allowed it to be overfired - it is not a factory recommendation. Probably no factory recommendations available, service tech for previous owner had cutout set at 6 psi, with inoperable main and some radiator vents.
: Starting with timing readings would help to guess what would happen later. As piping and pickup allowance for the piping and radiation mass is in the mix, along with venting timing, it is not a simple linear change. As you are heating 125,000 btuh of pickup and radiation with 210,000 output (almost double) I question the need for 60% piping and pickup allowance in the original design. Original pickup and radiation was for coal fired boiler, this or previous boiler. Radiation is current configuration, which is different from original. However, the reason for overfiring might have to be to satisfy that particular need. . Evidence of current burner replaced one previous, maybe tech deliberately or randomly selected high firing rate.
: Also, there are two answers in the one question. As the steam will turn to steam at say 213F, no heating will happen til then. When the steam starts flowing, it will heat the pipe and radiation until satisfaction. If the steam pressure is limited, the steam radiation heating timing will be the same whether inputting with 150,000 or 210,000 btuh (as long as the steam is flowing to keep the pressure over zero throughout.) The usual change in timing is in the running of the boiler burners only. This is not the same question as whether the radiation heating timing will change.
If this is indeed so grossly overfired isn’t a large portion of the heat simply flying past the heating surfaces up the flue?
Gas pressure regulator is currently set 10 turns in which appears be 5.83” wc (see attached). Could I change this to the 6 turns recommended for 3.5” wc without effecting the combustion gas levels dangerously?
If not, could I replace the orifice with one yielding 25% less input and see if it still heats the building satisfactorily? The burner appears to be a Norge Heat by Borge Warner, any idea where I might find a replacement?
Thanks