Put an AprilAire Model 400 on the furnace last year....Probably the best thing I've done (at least she thinks so...ahahhahaha) ,,,,,....One thing i did do additionally is have someone comeout and clean & sanitize the ductwork. House was built in the late 50's and I doubt the ducts were ever cleaned (you should have seen the nasties that came out of there..YUCK). Sandy(mrs) is very sensetive to dust...so with the addition of the humdifier, the duct work cleaning, and one of the high end 3M furnace filters...she has no issues with the forced hot air now...House is around 1500Sq Ranch and I can easily crank up the RH so theres dew on the windows...So this thing works well..really well
I really can't say enough good things about Aprilaire..awesome unit...
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