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Posted by Heatpro on October 30, 2005 at 20:06:38:
In Reply to: Re: DHW coil to direct fired water heater? posted by John Lotz on October 30, 2005 at 09:34:48:
The idea of the owner that installed the propane water heater was probably to shut the boiler down in the summer to save money on fuel. But, as it does not, unless propane is less expensive than oil, he was mistaken. A tankless coil boiler is useful if the heat loss of the house is large enough to need an input of at least 150,000 btuh. It is not that keeping the boiler hot all year for hot water is any more fuel expensive than a water heater that stays hot all year.
A house built after 1992 would be about 5000 square feet to use that much heat. If it is now in a 1600 square feet home that needs that much heat because it is uninsulated, that also makes no sense to stay there with the recent increase of fuel costs. The sensible thing to do would be to insulate the house to modern standards to use a smaller input boiler to turn off in the summer and use the propane heater, as the cost of propane is about the cost of electric in most areas and water heating is the lesser load.