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Posted by Ron on December 13, 2005 at 08:46:46:
In Reply to: Do boilers decrease in efficiency over time? posted by Mike on December 12, 2005 at 14:18:43:
Boilers will decrase in efficiency very slightly over time. The decrease comes from dirt build-up and mechanical tolerances changing.
Could you save money in fuel costs by updating? YES! The boiler efficiency will go up some with another cast iron boiler and even more with condensing boilers providing it can modulate and condense. To replace with a properly sized cast iron boiler you should see about a 25 - 40% savings. These numbers are of course estimates, but also an average savings I have seen over the last 15 years when I started doing heat losses. I have an 85 year old home with no sidewall insulation. Eleven years ago I added attic insulation. I now have R30 up there. I did a heat loss and my 2100 sq ft 85 year home heat loss in PA is 60,000. I removed a six year old 120,000 btu boiler and installed a 68,000 btu boiler and indirect and saw a 52% fuel savings. I installed a low water volume steel boiler and indirect water heater. My boiler is operating at 86% combustion efficiency. The boiler which was removed was operating at 82%.
The key to proper sizing is startig off with a heat loss and properly sizing the boiler. The second most important part of fuel savings is proper piping. I was on a job about a year ago where the system piping (primary/secondary) was improperly applied. Repiped properly, used same boiler and fuel bill went down about 30%. The added advantage house was warmer after repiping.