We changed from a 'very' low efficiency 1970's furnace to a Trane XV90 93% eff. one about two months ago. Link:
http://www.trane.com/residential/pro...aces/xv90.aspx
In our case it works much faster than before. It's their top end dual burner, constantly variable speed fan model and can really pump out the heat when it needs to. Could be that it's simply relative to our previous one. My only complaint is that it's a little bit louder when running full bore.
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