My approach on HVAC equipment has been to specify simplicity and quality when possible. My house and all my rentals have 65% effecient or so furnaces. The very efficient running is of course nice, but one service call can eat up four or five years of fuel savings. That said I have not bought any for probably at least 10 years as all mine are still going strong. Everything has conventional metal chimneys.

I have replaced the blower in my furnace at the house and the outside unit at my carriage house.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.