My 19 year old gas furnace is scheduled to be replaced next Tuesday with
a newer, 96% efficiency gas furnace. Was I pursuing noble goals with a
more efficient device? No, just trying to avoid death. :-)
It appears that the old furnace has small cracks in the heat exchanger
and is releasing small amounts of CO into the house. Not enough to set
off the CO detectors yet (only 3ppm measured next to the heat exchanger)
but worrying for the future nonetheless.
This is a known problem with this Lennox Pulse model furnace. The Pulse
designation comes from its operation as a continuous series of tiny
explosions (sort of like a ram jet). The vibrations may eventually
induce cracks in the heat exchanger and they finally have. Fortunately,
there's another year left on the 20 year warranty. Unfortunately, there
are no replacement heat exchangers. So I'm getting an $1,100 rebate
from Lennox on the cost of a new furnace. Even so it's still $3,300 of
unexpected expense. :-(
Chuck Norcutt
On 12/6/2012 7:14 PM, Rob Harrison wrote:
> We are just now in the midst of an energy retrofit for our house that
> includes replacing the 1973 gas conversion burner on the original 1950
> boiler (50% efficient) and 1994 electric hot water tank with a new (95%
> efficient) condensing boiler and indirect-fired hot water tank, as well as
> air sealing and adding R-60 insulation to the attic, and new Energy-Star
> refrigerators for us and our mother-in-law apartment. Through a local
> program, Community Power Works, we were able to get a low-interest loan to
> do the work. The loan is repaid on our City Light electric bill. The
> savings we'll get will easily pay for the loan now, and we will be better
> off as energy rates increase over the life of the loan. If we sell the
> house, the loan can stay with the house. This gets around the whole "simple
> payback" issue.
>
> In my practice ground-source heat pumps rarely have made sense. Air-source
> heat pumps are so much better (higher COPs) and less expensive these days.
>
> Rob in Seattle
>
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