Gas useage report on new boiler

tim smith

Changed out old cast iron National boiler w/ Economit F400 burner in >5000 ft 5 unit apt bldg, pre 30s bldg. In Mid september installed new Triangle prestige 175. Got gas bill for full month of october, Gas therm useage down 27% over last year and avg temp was down from 55 degrees for last year to 52 this year. I would estimate then the overall savings was appx 33% over prior year vs old boiler. Just fyi, any further input as to savings calcs. Tim

Dave_4

Don't make the same mistake...

I did.

I incorrectly extrapolated annual savings with real fall savings in the 25% range, only to find the coldest weather reduced fuel savings significantly less than fall. ~5% was the winter savings but 5% of $1,000 a month in winter usage as compared to 25% when the fuel bills were only $300 skews the data significantly!

Moral of the story?

Do not assume fall savings will be annual savings. Annual data is reliable - especially given degree day apple to apple comparison/tweaking. True fuel savings are annual percentages, not seasonal.

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tim smith

fall vs annual

Ken, I understand this, as we get colder savings will dwindle on this system. Although here in Seattle are loads are very moderate and I estimated this system will run condensing temps appx 95% of the time as old cast iron emmitters are well oversized and envelope has been updated some over the years.