I need a new FHA furnace, many qns (Am. Std?) - Page 2
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  1. #14
    Join Date
    Jul 2000
    Location
    Louisiana , USA
    Posts
    3,280
    [QUOTE]Originally posted by jeffw_00
    [B]I think the heat-exchanger on my 45 yr old Forced Hot Air furnace is beginning to go - we've had two CO alarms in the last month. I live in New England and am going to replace it.

    SNIPPED a MISTAKE

    6) By the way - my old system was a coleman "high-velocity' system with 4" ducts. I assume if i get an oversized (or A/C-sized) fan I should be ok. (I have a separate A/C system in the attic)

    This is Turtle.

    Answer to # 6 is a major Mess up in the making. The only way around the cure for this is to replace duct system or add on more duct to get you cfm to equal the tonage of the furnace heat and cooling. OR get the Manual D run and get ductwork to match it. You will never get a new residentiual furnace to put out the cfm need to supply the house with air through the 4" ducts.

    TURTLE

  2. #15
    Join Date
    Nov 2004
    Posts
    2,927
    cant argue with turtle...because he is TURTLE !


    I think getting the speed up and trying to relieve some pressure is the way to go. Maybe heat the basement... and maybe remove some supply registers if they are whistling.

    And what about return duct size,ect...

    What did the blower wheel on the old Coleman look like?

  3. #16
    Join Date
    Jun 2005
    Location
    New England
    Posts
    905
    old blower was a belt-driven squirrel cage

    Funny that Turtle made the same mistake everyone else (including everyone who quoted the system did), because of the
    design of the old duct system the assumption was that it would be hard to get -enough- cfm for the system, and now (see my more recent posts) I'm unhappy because a same-output-BTU replacement is giving me way too MUCH cfm. (Furnace needs to run only occasional short cycles to maintain temp, but it's noiser, and humidifier never really gets to run).

    I don't feel so stupid now 8-}
    /j

  4. #17
    Join Date
    Nov 2004
    Posts
    2,927
    well the thermostat with "cycles per hour" should help give longer run times

    I cant imagine the new blower giving more CFM's...but we will take your word for it.

  5. #18
    Join Date
    Jun 2005
    Location
    New England
    Posts
    905
    Hi Jacob - the -first- thing I noticed when they turned on the new furnace was how much noisier it was. My guess is that it's working properly, whereas there was excessive heat rise over my old furnace.

    I think everyone looks at the small vents and thinks - oh, you need a LOT of air to get heat out to the end of the ducts, and with a lower temp rise at the furnace. that may be true. I have a plan for the weekend (scroll down on the link below) and we shall see....

    http://www.hvac-talk.com/vbb/showthr...3&pagenumber=5

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