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Adjustable fan speed in this furnace? Old GPM 150

CBRob
CBRob Member Posts: 214
Doing some basic troubleshooting on a home here in the mountains.
I think the ducting it's probably a little mis sized..
They have a couple of bedrooms that are far away from the furnace that are fed with just one 6-inch duck.
Tinkering around with closing off some of the duct to the hot rooms, to see if we can get more heat to the cold rooms.
Is there any way to tell if this is an adjustable fan speed on this furnace? And if it is up to its maximum speed?
They've had out the local furnace guys before, but nothing seems to have improved and that was years ago.

Comments

  • STEVEusaPA
    STEVEusaPA Member Posts: 5,176
    Increasing your fan speed and closing off ducts won't help your situation, but it will make it worse.
    You need proper sized supply and equally important, return ducts.
    You can really only change fan speeds by confirming static pressure (TESP).
    Look at the wiring diagram and the motor to see how many speeds you have and which one is being utilized.
    steve
  • CBRob
    CBRob Member Posts: 214
    > @STEVEusaPA said:
    > Increasing your fan speed and closing off ducts won't help your situation, but it will make it worse.
    > You need proper sized supply and equally important, return ducts.
    > You can really only change fan speeds by confirming static pressure (TESP).
    > Look at the wiring diagram and the motor to see how many speeds you have and which one is being utilized.

    I think Im going to look for a good furnace guy. Unfortunately, all of the ducting is behind drywall.. no attic or crawl space.

    I was hoping I'd find something simple to adjust.. it's over my head.
    I'll let you know how goes when I get with a good HVAC guy.

    Thanks
  • mikeg2015
    mikeg2015 Member Posts: 1,183
    A smaller furnace will result in more even heating. Unless the house is 3000 square feet, you don’t need 112k output.

    I’m 4 speed motor High speed is normally black, med hi blue, med lo yellow and low red. White is neutral. On 3 speed black is still high.

    Upgrading to a properly sized 96% furnace with X13 ECM high effeciency blower would be a good move. Those can compensate better for poor ductwork layouts.
    CBRob
  • CBRob
    CBRob Member Posts: 214
    The house is 2500 SF and 9500 ft elevation.
    We don't see many forced air systems around here. Guys that specialize in furnace installs are a little hard to find.
    I
  • DZoro
    DZoro Member Posts: 1,048
    Sounds like the ductwork is your culprit. That furnace has a 5 ton drive. Pretty much as large a blower that your going to get. Is there A/C on it? You can pull the blower and confirm the blades are clean, H/E and A-coil are all clean.
    Poor duct system is tough to overcome, really need it to be correct, may have a slight improvement with a fully variable drive motor. But I wouldn't hold my breath.
    D
  • CBRob
    CBRob Member Posts: 214
    > @DZoro said:
    > Sounds like the ductwork is your culprit. That furnace has a 5 ton drive. Pretty much as large a blower that your going to get. Is there A/C on it? You can pull the blower and confirm the blades are clean, H/E and A-coil are all clean.
    > Poor duct system is tough to overcome, really need it to be correct, may have a slight improvement with a fully variable drive motor. But I wouldn't hold my breath.
    >
    I think you're right. I think it is a problem with the duct work. Sounds like the system never worked right to begin with.
    There is one thermostat for the whole house on the middle floor, and the middle floor gets way more heat than the other floors. So the middle floor of this three-story house hit 65° and the bedrooms are still cold.
    I'm half tempted too run some conduit around the side of the house and put in some 220 baseboards, for the two cold bedrooms.
  • DZoro
    DZoro Member Posts: 1,048
    I assume that you already tried shutting down the supply vents on the middle floor?
    You're probably on the right track unfortunately, would be helpful to go with wireless thermostat in the troubled area? Just a thought.
    D
  • CBRob
    CBRob Member Posts: 214
    > @DZoro said:
    > I assume that you already tried shutting down the supply vents on the middle floor?
    > You're probably on the right track unfortunately, would be helpful to go with wireless thermostat in the troubled area? Just a thought.
    > D

    Yep I closed off all the vents in the house except for the two cold bedrooms, they still don't get very much flow.
    I'm guessing it's a 6-in duct going through the floor joist Bay, hidden by drywall.
    I just hate to start tearing out drywall and not find anything to fix.

    But then again it's the heat for the house. A million dollar house. A few thousand bucks and drywall repair it's probably money well spent.
    I'll have to talk to the owners, maybe dig deeper into this next time they're away from their second home for a while.
  • DZoro
    DZoro Member Posts: 1,048
    Do they need their air ducts cleaned??? Or hire a duct cleaner with a camera to go through the entire duct system to get a good idea of sizes and duct arrangements throughout.
    D
    CBRob