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By it's very nature a steam heating plant cannot transfer heat to the media as efficiently, part of the boiler is dry.
Three-pass steamers, like the Burnham MegaSteam and its cousin, the Crown Freeport II, have all their heat-transfer surface below the water line. That's why they're as efficient as they are.
Why is the output of an identical input boiler less when steam than hot water?
Because the pick-up factor used to establish the Net rating is higher for steam than hot-water. These are arbitrary factors that have been used for generations.
It's also because pin type steam boilers are a cheap compromise to make a HW boiler also do steam.
It's not a properly engineered "steam boiler" like a 3 pass.
From what I understand NG and LP as products are not very standardized, perhaps even the quality could be questioned.
The gases themselves have no effect on copper, BUT additives for leak detection do as they tend to have sulfur, there was a statement that read -- G2414.5.2 specifies that Copper and brass tubing shall not be used if the gas contains more than an average of 0.3 grains of hydrogen sulfide per 100 standard cubic feet of gas.
Trouble is, how do you know that it's more or less? I also read that different parts of the country have different gas products just like gasoline and diesel and some are worse than others.
air fuel ratio question.
On my oil heater adjusting the air band and shutter I see the flame getting larger and larger as i decrease the air. Set to the smallest air intake the flame is the largest. I never see smoke.
I did a complete tune up last season and noticed this condition, then and again this season.