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Posted by HeatPro on February 18, 2006 at 10:37:41:
In Reply to: Boiler Over Firing? posted by rep on February 18, 2006 at 00:01:47:
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. 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.
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. However, the reason for overfiring might have to be to satisfy that particular need.
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.
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