Worth upgrading chimney liner for Burnham ES2 high efficiency (85%) boiler vs. Burnham Series 3 (84%)?
slateandall
| Posted in General Questions on
I am considering installing one of these Burnham boilers (both are 280000 BTU input). The high efficiency boiler is $500 cheaper due to a rebate from NY state.
BUT: the high efficiency boiler is not compatible with my existing chimney, which is masonry, and I would have to upgrade the chimney to some kind of a metal liner.
Is upgrading the liner something I should think about? 3 story house, so the chimney has a long way to go from basement.
Thanks!
oops–I think this belongs in Energy Efficiency and Durability
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Replies
That has to be one HUGE house to need a boiler that big!
Material considerations aside, the flue has to be right sized for the BTU input of the boiler, and almost all masonry chimneys are oversized for a right-sized boiler, ergo properly sized liner is the standard solution. It doesn't much matter if it's an 84% efficiency or 85%, if the masonry liner is oversized the flue velocity will be too low and acidic exhaust will condense, eating way at the mortar from the inside.
It's even worse if the boiler is oversized for the load, which means it operates at such a low duty cycle the masonry liner doesn't stay warm between cycles.
If you have a heating history on the place, run these numbers for sizing the new boiler:
https://www.greenbuildingadvisor.com/article/out-with-the-old-in-with-the-new
Also, the 85% ESC series Burnhams can be side vented with a short section of stainless venting, and can be direct vented with ducted in combustion air, allowing you to seal up that 24/365 parasitic load called a "3 story chimney" driving infiltration year round.
Better yet, with the load numbers in hand it may be cheaper to install a pretty good fire-tube modulating condensing boiler using plastic venting, and probably get even more rebate. An HTP UFT-199W (96% efficiency 190,000 BTU/hr DOE output in condensing mode, 175,000 BTU/hr at non condensing temps) can cost as much as a grand less than a Burnham ES2-7 (85% efficiency 178,000 BTU/hr DOE) or ESC-8 (85%, 180,000 BTU/hr DOE) even before considering the cheaper venting.
But it probably doesn't even need to be that big. Even an uninsulated 3 story 4500' Victorian with storm windows over the single panes on top of a 1500' basement usually comes in well under 150K for a design load even at -5F, which can be verified by the fuel use numbers.
Hi slateandall -
My mason said he would not work on our chimney without including a liner as part of this work. Totally a safety issue.
Then I just found this resource: https://www.csia.org/chimney_liners.html. To describe unlined chimneys as "so unsafe that researchers characterized building a chimney without a liner as "little less than criminal". No equivocation there.
Peter
I'm still curious about the actual boiler sizing issue, which seems ridiculously oversized for most 3 story houses, LUDICROUSLY oversized for an insulated house. I recently consulted on a heating system for a leaky rambling 5000' house, the original being an 18th century structure that had been added onto in the early 1800s then again around 1900 where the heat load prior to insulation and air sealing upgrades came in around 110,000 BTU/hr on a fuel-use basis, with an anticipated design load post-upgrades of about 85,000 BTU/hr @ -5F. They went with a Lochinvar KHN110 (102,000 BTU/hr DOE output) and some radiation upgrades in one of the colder rooms.
If not a fuel-use load calculation, a careful Manual-J using aggressive assumptions (per the manual's instructions) would be the way to determine the boiler sizing. A right sized condensing boiler is almost certainly going to come in substantially cheaper up-front than crazy-oversized cast iron, much cheaper on operating cost too.