The diagram at left teaches you more than most folks want to know about boiler internals, specifically horizontal three-pass cast iron. There are many clever variations on the theme of torturing hot fumes before releasing them to the chimney and the heavens, and this one has been used for two generations in big commercial boilers powering factories and hospitals. Only lately do we rise above the heavy, hollow cast units many of you still have in the basement.
Don't think me smug, I service boilers performing at 75% efficiency all over the county, and the Biasi in my attic gets around 87%. There's not a huge harvest of energy to be reaped yet from changing boiler designs until we find a way to deal with the acids and sludge condensed in boilers at lower temperatures. In Europe they've refined the sulfur almost entirely out of their fuel, yielding something almost as clear as kerosene. The link is to a British site listing oil boilers boasting 97& efficiency. Shame on us Yanks. I won't delve into the technology of boilers with condensing exhaust, but just imagine something vented through a light metal tube at less than 200 degrees, with sulfuric acid and dissolved ash dripping from a draincock on the flue.
My Biasi is among the high society of boilers,sold in the US, but it hails from Italy. Its nearest competitors are made in Germany, Germany and Italy, respectively. There are American multipass designs being sold, but they lag behind in the critical qualities of low mass, low volume and low stack temperatures. Makes you think, don't it? At app. 2.10 US dollars per gallon on Labor Day weekend, heating oil is as cheap as it's been in years, and we Americans see no reason to respond, apparently to anything but brute market forces. Price, in other words.
The little B4 model weighs in at 300 lb. dry weight. We hauled it up through the scuttle hatch with a light comealong rigged to a single unbraced rafter. Piece of cake. Why am I in such a lather to get it up there? It doesn't require a conventional chimney (my house doesn't have a conventional chimney), and the vent is through a single length of capped stainless steel chimney pipe extending through the roof on the leeward side of the house. It's also within 6 feet of the blower unit that heats my house. The water heated by the boiler travels no distance at all, losing almost no heat to the surrounding air. It sits in a metal pan piped to a nearby sewer vent pipe.
For domestic hot water, imagine a stainless steel block heat exchanger the size of a shoebox hanging off the back of the boiler. When someone hits a switch either in the kitchen or bath, the control starts the boiler water circulating through the exchanger, heating domestic water in one pass hot enough to do dishes, shower or operate the laundry. But you have to hit the switch, otherwise the little Biasi sits there cold. Time to hot water, from a standing start? Three minutes by the stopwatch. I know, America can't wait for its hot water, and can't be bothered to hit a switch. But this is how it goes at my house. You get up to an hour of glorious hot water from a twist of the timer. Otherwise you wash your hands in cool or tepid water warmed a little by its passage through the house pipes.
For domestic hot water, imagine a stainless steel block heat exchanger the size of a shoebox hanging off the back of the boiler. When someone hits a switch either in the kitchen or bath, the control starts the boiler water circulating through the exchanger, heating domestic water in one pass hot enough to do dishes, shower or operate the laundry. But you have to hit the switch, otherwise the little Biasi sits there cold. Time to hot water, from a standing start? Three minutes by the stopwatch. I know, America can't wait for its hot water, and can't be bothered to hit a switch. But this is how it goes at my house. You get up to an hour of glorious hot water from a twist of the timer. Otherwise you wash your hands in cool or tepid water warmed a little by its passage through the house pipes.
Antifreeze protects the boiler, blower coil and heat exchanger from freeze damage, and the attic is insulated against bitter outdoor temperatures. I have to use a little pump, fashioned from an old oil burner, to lift fuel to the attic for the boiler. That adapted unit sits in the basement next to the oil tanks, pushing a dribble of oil up to a heavy steel reservoir which feeds the burner by gravity. My house, insulated through various remodeling projects over thirty years to respectable R values and tightness, will be comfortable this winter without any renewable energy resources other than some carefully planned passive solar (click to see an older post on our sunroom).
Will I put a system like this one in your house? Not until we talk. Talk a lot. Show me your old copies of the Whole Earth Catalog, or the original pulp-format Mother Earth News. Tell me you were at Woodstock, and why I didn't see you there (I missed Woodstock, that's why). Show me your green-friendly stock portfolio, your Energy Star appliances, your first pair of Birkenstocks. And assure me you're willing to wait three minutes for hot water at any tap in the house, think before you hit the switch whether you really want to spend that energy, and let Dirty Phil into your house at least once a year for a boiler cleaning and efficiency check. And then, maybe. How can I be sure you're ready to take this step? Soon I'll be blogging about the solar hot water system that will be incorporated into my attic this fall. Stay tuned.
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