Replace 1960 vintage boiler?

[dstrutto]

I have a burnham holiday boiler no. 8-60 series 2 that recently combustion tested at 80% efficiency. I think the boiler was probably manufactured in 1960 based on the boiler no. It's 172k input and 140k btu output.

All the advice that I see is that if the boiler's over 15-20 years old it should be replaced. Why? If it's 80% efficient and has been reliable for 50 years, why drop $ for something only marginally better? (I'm not interested in ModCon because the extra cost of servicing and shorter lifespan make them uneconomical for my limited needs).

Presumably a new one would be smaller (my heatloss calculation is 90K btu Max) and have sealed combustion, electronic ignition, and perhaps less jacket loss (though hard to tell). Does anyone have any real world experience with the savings expected with a newer smaller boiler?

Right now we're using about 1150 CCF of gas per year or about $2300. I estimate that about 250 CCF of the 1150 are for DHW.

[BaldLoonie]

There's a couple kinds of efficiency. What is measured by that test is combustion efficiency. What is real life is annual efficiency or AFUE. While under perfect conditions that heap may test out at 80%, in actual practice it is probably getting 55-60% in annual efficiency. Like a car and MPG. At 35 steady speed the car may get great mileage but go to stop and go traffic and it drops like a rock. Same with your boiler efficiency.

So there are savings to be had going into a boiler with AFUEs in the 80s. If this is baseboard heat, some of the mod cons don't do a whole lot better trying to provide 180° water. They really do the job on radiant or converted gravity.