For those of you wondering whether or not you should reline your
chimney when installing hi efficiency furnaces. Please read the
instructions for the furnace carefully 3 or 4 times if need be. It
states clearly in 99% of them the need for a corrosion resistant metal
flue liner sized as per ansi z.2331 in national fuel gas code. Their
should be no debate after this easy inquiry, that is if your families
safety is of any concern to you. Listen folks it may not be cheap but
it sure as heck isn't expensive enough to neglect. We are talking
about carbon monoxide in the Flue gases. Other codes like NFPA 211
expound on this too, so do your homework and be safe.
Also, most new HIGH efficentcy furnaces will NOT vent through the chimney,
but through a 2 inch PVC pipe, and will also pull combustion air in through
a 2 inch PVC pipe..
Of course, we no longer install 80% units at all, and replace all units with
90% or better, so none of my customers worry about liners anyway..
Some high efficiency furnaces vent through pvc and therefore don't
require natural draft.
Those that do require natural draft require Flues(chimneys) capable of
eliminating the carbon monoxide from the dwelling. Hence the NFPA
,National fuel gas code and Manufacturers of Gas furnaces state the
necessity of a Flue that is sized correctly and will resist softening
and corrosion due to the nature of the flue gas.
The high efficiency furnaces that mechanically force flue gase through
pvc have a whole set of requirements that also must be followed as per
national fuel gas code, NFPA and manufacturers info.
It is important that they not be confused.
Most residential dwellings in the NE U.S. have heating systems that
require natural draft.
You need only look around in this region to note almost all houses
here have at least one chimney. This is because in colder climates
houses need to be versatile enough to utilize different fuels. Solid
fuels like wood or liquid fuels like oil and gas have appliances that
traditionally rely on natural draft to vent their exhaust and for good
reason. Natural draft has no moving parts and when chimneys are
constructed properly they can last indefinately. Not so with
mechanical draft systems which have a life expectancy that varies but
never exceeds the life of the appliance.
In my house, while I have a high efficiency furnace I also have a gas
hot water heater that exhausts up the chimney. I was told -- and it
makes sense -- that it doesn't get hot enough (like the furnace did)
to properly dry out the chimney when operating. The water that stays
behind can become corrosive to the brick and mortor. Thus the need for
a liner -- which I did have put in. And it wasn't all that expensive
to have done.
On Fri, 15 Aug 2003 22:29:04 -0700, "CBHvac"
Jim is correct in my experience in western New York; my new York (your
brand!) furnace vents outside the basement wall via a PVC pipe, and my
1998 Sears gas water heater continues to vent up the chimney via a
newly installed liner. The liner cost me $350, if I recall correctly,
and it was pretty long, on the order of close to 40 ft.
No, we understood totally about the furnace; our point is that we
still need to vent our water heaters, and we use the existing
configuration (venting through the big old chimneys, which the old
furnaces used to do, but the new 90+% ones do not), but modified
slightly to include a liner to make the space smaller and protect the
So, we needed liners for our chimneys which remain in operation for
the water heaters only; our furnaces vent as you describe, with new
intake/exhaust PVC installations. But let me just reiterate: liners
needed for the 90+% furnaces, no. Liners needed for the water
Also, since this one popped back up, I might add that all the York line over
80% is what we call a condensing furnace..meaning, there is a condensate
drain IN the heat exchanger, and in the vent flue, IF it has any horizontal
travel at all....
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