Hey guys,
Was quoted: Ducane 95G2DF090CV20
Installed: Ameristar A952V060BD3S
Looks like the installed furnace is lower BTU, but that's all I know. If anyone could provide any pricing (retail or wholesale) for either unit it would be muchly appreciated. I don't care that there's a mark-up on the unit, it's normal and expected, but if I paid for a more expensive unit I best be getting what I paid for.
Thanks!
Cory
The up-charge for a ~30KBTU/hr larger burner and slightly higher cfm blower within a model line is typically $200. I'm not sure if the Ducane & Ameristar are similar enough (or possibly the same series under a different brand from the same manufacturer, which is common), but in some ways the contractor may have done you a favor. Even a 60KBTU/hr furnace is ridiculously oversized for a normal sized house at Vancouver's 25F/ -4C
99% outside design temp (maybe not too ridiculous if you moved the house to Whitehorse without upgrading the insulation & windows). A 90K furnace is usually grotesquely oversized for a normal sized house, so oversized that it becomes a comfort problem during colder weather.
A "right sized" furnace would have a max output of about 1.4x the heat loss of the house at the 99% outside design temperature (only 87 hours per year are colder than that, averaged over 25 years) , which is sufficient to cover the load during Polar Vortex disturbance cold snaps, but runs a (1/1.4 =) 71% duty cycle when it's -4C outside, which is FAR more comfortable than the brief hot blast followed by the extended chill & draft typical of >3x+ oversized factors. As temperatures drop below the 99% outside design temp the duty cycle grows, so even when it's -15C outside you're still comfortable.
If you have a heating history on the place you can estimate your actual design heat load (including duct losses, etc) to a reasonable accurate level
factoring fuel use against heating degree-day data, as outlined here. A typical 2500 square foot 2x4 framed house with clear-glass double-pane windows (no low-E) would have heat load somewhere around 20,000 BTU/hr @ -4C if the basement walls are insulated to R10 and the house is reasonably tight, 25-30,000 BTU/hr if the foundation is uninsulated and it leaks air like a tennis racquet.
Assuming a 99% design load of 25K the right-size unit would be a 35-40KBTU-in furnace, and a 60K-in/57K-out unit would be fully 2x oversized- not great, but not miserable either, whereas a 90K-in/85K-out furnace would be >3x oversized, and something you really
don't want in your house. Even at it's lowest speed the
95G2DF090CV20 would be >2x oversized for a 25K load, meaning it's variable speed modulation would be pretty useless.
The minimum speed output of the
A952V060BD3S appears to be ~39K, which may mean it still never needs more than the low firing stage, but the duty cycle would be sorta-reasonable for a 25K load if locked to the lower stage. Another aspect of right-sizing/down sizing is the quieter more comfortable (less wind-chill & whistle at the registers) of a lower cfm blower. With the variable speed units you may be able to keep it from ever running at it's highest cfm (I'm not going to read the manual, but you should), which would be better for comfort overall.