I wish I could tell everyone with an oil, or gas?, furnace, but this
is a start.
It seems that the current furnace BTU rating method has changed from
earlier method, the one used when my furnace was new, 31 years
Maybe that accounts for many of the people who have
installed the wrong size furnace in their house.
They don't actually *rate*
mine as 85,000, but the brochure and the
owner's manual refer to Model 58V and specifically 58HV085.
The 4th character V was based on the physical arrangement and could
be V, E, H, L or C, for highboy, lowboy, horizontal, upflow, and
The 5th to 7th characters, 085, 100, 125 are the bonnet capacity,
the output K-BTUs. For the horizontal model, this was true for
these numbers and also for 150, 200, 250, and 335. The
number-suffix of the model and the output are always the same.
So that's why I say my furnace was rated on its output. Is that
Someone here pointed out that if it says 85,000 BTU, that refers to
the amount of fuel used, the heat input of the furnace.
And that if the furnace is 90% or 80% efficient, the output is only 90
or 80% of the input.
Since I have now an 85,000 BTU furnace and it's definitely sufficient,
and since the blueprints themselves say 85,000 on them, I was looking
for an 85,000 btu furnace, but since now that woould be the input, I'd
end up with one that was too small. Alas and alack, that would be
Now I'm ignorant, and maybe stupid, and not in the business, but I'll
bet even some young pros could make the same mistake. "You have
150,000 now, we'll put in the same thing."
Later another installer says that there should have been a load
calculation, because that is his first step, and the homeowner thinks
that's the core of the problem, but I wonder how many were first
befuddled by this change in rating method.
When did the current method begin?
BTW, I'm glad I learned all this before I saw this ad on ebay today:
"This is a used Thermopride upflow 85,000 BTU oil fired furnace. It
was installed in November of 2009 and used only four months. The
house was 75% heated with a wood burning stove and the furnace was
only on during sleeping hours. This unit is excellent condition. We
changed over to gas. The return is on the bottom of the unit and as
was told that it also can be from the side. The dimensions 24x33x56,
model # oh5-85. Webside for the unit is www.thermopride.com. "
The requested starting bid is $500. The furnace is shiny clean
inside. picture 1:
It's in driving distance for me, but it's too small for me, but there
are occasionally others with such good stories. Do you believe their