Results 1 to 9 of 9
  1. #1
    Join Date
    Mar 2019
    Posts
    7
    Post Likes

    Need to replace blower motor on old 1980s furnace - upgrade motor?

    hey there,

    i'm running a 1980 era furnace (Lennox G8D2-55-2) and the blower just died. It looks like an original GE P-8-9662 motor. 5" diameter 1050RPM 3 speed, 1/5HP, frame 42

    I was thinking that since i'm going to have it open, might as well upgrade to a better motor (higher HP, more efficient) if possible. Is this a good idea or should i just stick with a like-for-like replacement?

    I looked at a few retailers and couldn't really find any that had frame 42 5" motors.

    Do they make adapters to switch the frame to a more standard frame 48? or would i have to replace the entire blower assembly?

    thanks in advance for any advice

  2. #2
    Join Date
    Jan 2012
    Location
    Broomall, PA
    Posts
    2,702
    Post Likes
    Supply house has that motor. I wouldn’t 'upgrade' on a 40 year old furnace.
    If I do a job in 30 minutes it's because I spent 30 years learning how to do that in 30 minutes. You owe me for the years, not the minutes.

  3. #3
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    40,280
    Post Likes
    Yea, that isn't an 80s furnace!!!! Time to put it out to pasture.

  4. #4
    Join Date
    Apr 2003
    Location
    Maple Grove, MN
    Posts
    3,141
    Post Likes
    Quote Originally Posted by Sabad66 View Post
    hey there,

    i'm running a 1980 era furnace (Lennox G8D2-55-2) and the blower just died. It looks like an original GE P-8-9662 motor. 5" diameter 1050RPM 3 speed, 1/5HP, frame 42

    I was thinking that since i'm going to have it open, might as well upgrade to a better motor (higher HP, more efficient) if possible. Is this a good idea or should i just stick with a like-for-like replacement?

    I looked at a few retailers and couldn't really find any that had frame 42 5" motors.

    Do they make adapters to switch the frame to a more standard frame 48? or would i have to replace the entire blower assembly?

    thanks in advance for any advice
    Why would you think higher HP would be better? I think it would be worse.

    Motors like to do work. They are happiest when they are running close to FLA. If a motor is oversized then the amp draw would run lower than designed, which is actually LESS efficient. When a motor runs less efficiently it means that the ratio of work that it's doing vs. heat that it's creating starts to go in the wrong direction. In some cases a motor can overheat and trip it's overload because of this.

    Besides that, why do you want to keep this old dinosaur going? On a good day that furnace is probably running around 70% efficient. That means a lot of natural gas that's heating up your neighborhood instead of the inside of your house.
    If at First You Don't Succeed, Skydiving Is Not for You.

  5. #5
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    24,323
    Post Likes
    Quote Originally Posted by Sabad66 View Post
    hey there,

    i'm running a 1980 era furnace (Lennox G8D2-55-2) and the blower just died. It looks like an original GE P-8-9662 motor. 5" diameter 1050RPM 3 speed, 1/5HP, frame 42

    I was thinking that since i'm going to have it open, might as well upgrade to a better motor (higher HP, more efficient) if possible. Is this a good idea or should i just stick with a like-for-like replacement?

    I looked at a few retailers and couldn't really find any that had frame 42 5" motors.

    Do they make adapters to switch the frame to a more standard frame 48? or would i have to replace the entire blower assembly?

    thanks in advance for any advice
    Get a contractor in to check the heat exchanger first!

    If that passes THEN let them change the motor!
    Last edited by pecmsg; 10-11-2019 at 07:55 AM.

  6. #6
    Join Date
    Mar 2019
    Posts
    7
    Post Likes
    Thread Starter
    Quote Originally Posted by ammoniadog View Post
    Why would you think higher HP would be better? I think it would be worse.

    Motors like to do work. They are happiest when they are running close to FLA. If a motor is oversized then the amp draw would run lower than designed, which is actually LESS efficient. When a motor runs less efficiently it means that the ratio of work that it's doing vs. heat that it's creating starts to go in the wrong direction. In some cases a motor can overheat and trip it's overload because of this.

    Besides that, why do you want to keep this old dinosaur going? On a good day that furnace is probably running around 70% efficient. That means a lot of natural gas that's heating up your neighborhood instead of the inside of your house.
    Well I added an a/c in the spring so I figured the extra resistance of the coil along with running the fan 24/7 is what did the motor in, so my thinking is that a more powerful motor would last longer
    Quote Originally Posted by pecmsg View Post
    Get a contractor in to check the heat exchanger first!

    If that passes THEN let them change the motor!
    I had it inspected when we first moved into the house last December 2018. I will book another inspection soon (I do it yearly)



    All that said, I would love to change the furnace but we have a second baby coming any time now and I just don’t have a spare $xxxxkicking around for a new one. A xxxx motor on the other hand is something I can handle including installing it myself.

    Anyways thanks for the advice given so far. Will not bother trying to upgrade it and will just use a like for like replacement with the same specs. Hopefully it will last a few more years until I am in a better position to replace the furnace
    Last edited by Dad; 10-11-2019 at 10:05 AM.

  7. #7
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    24,323
    Post Likes
    Quote Originally Posted by Sabad66 View Post
    Well I added an a/c in the spring so I figured the extra resistance of the coil along with running the fan 24/7 is what did the motor in, so my thinking is that a more powerful motor would last longer


    I had it inspected when we first moved into the house last December 2018. I will book another inspection soon (I do it yearly)



    All that said, I would love to changing e the furnace but we have a second baby coming any time now and I just don’t have a spare $******CAD kicking around for a new one. A $*****motor on the other hand is something I can handle including installing it myself.

    Anyways thanks for the advice given so far. Will not bother trying to upgrade it and will just use a like for like replacement with the same specs. Hopefully it will last a few more years until I am in a better position to replace the furnace
    Then invest additional moneys into low Level CO DETECTORS.

    On that yearly maintenance was the heat exchanger inspected? I’ll bet not.

  8. #8
    Join Date
    Apr 2003
    Location
    Maple Grove, MN
    Posts
    3,141
    Post Likes
    Quote Originally Posted by Sabad66 View Post
    Well I added an a/c in the spring so I figured the extra resistance of the coil along with running the fan 24/7 is what did the motor in, so my thinking is that a more powerful motor would last longer
    Your thinking is a little backwords on this too. It kind of goes against conventional thinking, but "restrictions" in a squirrel cage fan system actually cause a motor to work less hard.

    The air is what places the load on the motor. Less air being moved = less amp draw.

    If you tried 2 different motors of the same rpm in a system with restricted airflow, the larger one will not move any more air. The only thing that would happen is the bigger one would create more heat.

    Propeller fans do work like you were thinking. If you were to put a piece of plywood over your condenser fan, then the motor works harder and amps go up. A larger hp motor could help in that situation.

    Squirrel cages are the opposite.

  9. #9
    Join Date
    Mar 2018
    Location
    Chico, Ca #StateofJefferson
    Posts
    1,333
    Post Likes
    It's not an "upgrade" but finding a 1/4 hp motor would work fine and be easier to locate.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •