Combo boiler and water heater
Thank you for your advice and opinions. Here is some further information on my existing system. Oil furnace is 98,000 BTU for main house and oil boiler is 105,000 BTU for back room with 56 feet of baseboard and hot water coil for domestic hot water (no longer used). I calculated my design heat load using wintertime oil fill up history and came up with 48,000 using the 1.4 ASHRAE factor (59,000 using 1.7 factor). I am attaching the proposed heating equipment specs for the Buderus gas boiler, 22″ square water-to-air heat exchanger and a future 55 gallon indirect water heater (which says a 140,000 BTU boiler is required). My present 40 gallon gas fired hwh loses hot water on a 3rd consecutive shower. My gut feeling says to use the mid-sized boiler (87,000 BTU output) but I want to make sure I get enough heat transfer across the exchanger since my ductwork is not tight (I lose about 30 degrees from the furnace to the farthest bedroom). I tend to be very conservative and would want to stick with a conventional boiler unless you feel this new system will be very inefficient and/or problematic. Thanks again.I live on Long Island,NY and have a 1600 sf house built in 1950. It currently has an oil furnace for heating the main house and an oil boiler for heating a large back room addition. I have a separate 3 year old 40 gallon gas hwh. Both heating systems are due for a replacement. I am thinking of replacing them with a gas boiler that would have 3 zones…one for the hw baseboards in the back room, one for a water to air heat exchanger with blower unit, and one for a future 50 gallon indirect hot water tank. I would like a more efficient 85% traditional boiler, not a condensing boiler due to simpler and less costly maintenance. I have received estimates from a few contractors who are recommending a 130-140,000 btu/hr unit. This seems to be oversized, perhaps due to my future desire of the indirect hwh. How should the boiler be sized? Does this combined system seem reasonable for my situation?
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