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savings from low mass conversion
I am wondering what sort of savings are typically seen with a conversion to a low mass boiler.
I have 1200 sq ft ranch in Maine 7500 HDD currently consuming 650 gallons # 2 for heat & hot water.
We use an average of 16 cubic feet of hot water per day.
The Heat loss at -2 design is 40,000 BTU. We have bedrroms and living space zoned off and only heat to 65 in living space from 9:00 A.M. to 6:00 PM with setback to 53 nights.and one bedroom sees 68 days and 65 nights other two bedrooms are 62 degrees nights and 58 days.
Boiler is an old Utica 180,000 BTU boiler from 1967 with a carlin 99 CRD burner on it and a Honeywell AQ 251 series control unit and an indirect 40 gallon heatflow tank.
Looking to replace with a DK2-3 Pensotti this summer.
Any guesses what sort of percentage savings I might see?
At design temps outside we typically boost up the heat in the house as it is not as comfortable at our normal temps when it is zero outside. We typically turn up to around 68 all rooms upstairs. Even there it is not terribly comfortable on a 60HDD day. Floors are too cold and 36 sq ft picture windows units in dining and living room are big sinks.
At design temps outdoors with lower setback at night we are burning about 30 K of total consumption. Combustion test shows furnace to be 80 % efficient. Yes I know combustion test efficiency is not the same as AFUE...
Basement is insulated to R-10 but not heated with a zone. The zone is there but I am too cheap to turn it on.
On a 30-40 HDD day 65 is plenty fine for my tastes...
Boiler is fired with a .85 nozzle More than we need for actual heatloss but needed due to mass of Boiler. 5 Big thick cast iron sections unit is about 4 feet by 3 feet by 2 feet. pin with wet base.
AQ251 purge is active to bring out as much heat as possible after a firing is done. Have indirect tank on a timer too in order to bring that up to temp first thing in morning right before thermostats call for heat to warm the house back up. Mostly empty the tank at night before bed too.
So any SWAG'S a(Scientific Wild Ass GUess)s to what oil savings might be all other aspects staying the same IE temps in house day and night??