It seems that the current furnace BTU rating method has changed from earlier method, the one used when my furnace was new, 31 years ago!!!!!** 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 downflow.
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 fair?
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 bad.
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: http://cgi.ebay.com/ws/eBayISAPI.dll?VISuperSize&item30523771185 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 story?