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Posted by Heatpro on December 15, 2005 at 13:01:48:
In Reply to: Energy Savings 101- Electric vs. Steam? posted by J. C. on December 15, 2005 at 11:43:40:
Your confusion comes from the various specifications of the boiler.
DOE output is the heat in the steam that comes out of the boiler to the main.
AFUE is an idealized computer program measurement to give an idea of the output at an average temperature near 45F outside so that all heating systems can be compared. It is not a 'real-world' situation of what happens to a boiler in a home; just a standardization to give a comparison with other boilers, not necessarily systems.
IBR rating takes 25% off the DOE output to account for heating up the pipes and the radiation before you get the output at 215F. Some systems with oversized pipes can require as much as 50% extra to get it all heated up. Hot pipes in a basement, making it as warm as rooms upstairs, are a waste when considering zoning or using electric heaters in one room for supplementation. Heating where you are not is a waste of energy. You can't really effectively zone a steam system without large expense. Steam pipes in crawl spaces are even worse, and steam pipes should be insulated well.
If you set the system back to 60f, you'll find that the steam has to heat the radiation up to 215F to put heat into the house, so the house will overshoot for a while until it settles back on each cycle. In that way, there will be some fuel savings; but steam is not able to make fuel reductions as hot water can. The intent of the AFUE test is to give an idea of a system that can change water temperature to average around 45F outside. As steam has to go to maximum temperature and settle back from there, it is not an even comparison; it cetainly can't compare to a warm air furnace that requires almost no heat-up, nor electric.
A problem here is that you are probably in a house smaller than 2000 sq ft, which is effectively heated in a house with full insulation to today's standards with a 50,000 btuh heater. Putting 175,000 btuh into a house to achieve what a new house will do with about 1/4th that is the 'buy the premise - buy the bit' concept. A new house would mean cutting the bill to 1/4 of what you have to pay in fuel every year.
I heat my 1100 sq ft house with 28,000 btuh input and supplement with electric heater(s) in the room I occupy, letting other rooms dip below 65F. This is what you want to achieve; but the steam medium in an uninsulated house has poor expectations in comparison. It would cetainly be a help to others to observe the differences in the bills with your proposed method over a few years to give a comparison.
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