Page 1 of 2 12 LastLast
Results 1 to 13 of 25
  1. #1
    Join Date
    Jun 2004
    Posts
    69

    Reducing Fan Speed

    Have propane furnace and would like to reduce the fan speed. The lowest speed is 1300 cfms. The total ceiling registers are ~900cfm. Due to HIGH propane costs the furnace burner count was reduced from 3 to 2 burners and a few rooms are not to be heated any longer. Realizing that it is hard on the blower motor to restrict air flow I am hoping for a way to reduce blower speed to better match furnace output.

    Thanks!

  2. #2
    Join Date
    Jun 2006
    Location
    Richmond, VA
    Posts
    2,696
    How did you remove a burner???? How did you change inducer speed?
    It's not the Brand with the fewest repairs-It's all in the install!!! Attention to detail and using the best materials!

  3. #3
    Join Date
    Jun 2004
    Posts
    69
    Soldered in burner hole and moved sensors.

  4. #4
    Join Date
    Jun 2006
    Location
    Richmond, VA
    Posts
    2,696
    I would have never done that because nobody knows or has tested those affects on that furnace......

    Since ya went that far......just remove some blades on the blower wheel
    It's not the Brand with the fewest repairs-It's all in the install!!! Attention to detail and using the best materials!

  5. #5
    Join Date
    Jun 2004
    Posts
    69
    Quote Originally Posted by beshvac View Post
    I would have never done that because nobody knows or has tested those affects on that furnace......

    Since ya went that far......just remove some blades on the blower wheel
    Never asked what you would have done.

    Never mentioned furnace model either.


    At least your graphics have some level of intelligence.

  6. #6
    Join Date
    Jun 2006
    Location
    Richmond, VA
    Posts
    2,696
    Actually, I read some of your other posts, that furnace does not appear to be that old.....how did the mods affect flue size? How did the mods affect potential for flue gas condensation? that furnace is now outside manufacturers spec-who did these mods?
    It's not the Brand with the fewest repairs-It's all in the install!!! Attention to detail and using the best materials!

  7. #7
    Join Date
    Dec 2010
    Location
    La Honda, CA
    Posts
    83
    On some furnaces the only difference between a model that moves 1300 cfm and a model that moves 1000 cfm is the size of the blower wheel...

    I've seen some furnaces with a rheostat installed on the blower motor wiring to control blower speed...

    Check with the manufacturer to find out what safe and proper options are available to you.

    The real solution to your problem is of course to install properly sized equipment and not to "hot rod" the wrong equipment.

    Any modifications to the factory design of your furnace are potentially unsafe and may void any and all manufacturers warranties.

  8. #8
    Join Date
    Jun 2004
    Posts
    69
    Quote Originally Posted by beshvac View Post
    Actually, I read some of your other posts, that furnace does not appear to be that old.....how did the mods affect flue size? How did the mods affect potential for flue gas condensation? that furnace is now outside manufacturers spec-who did these mods?
    It must be very difficult impressing only yourself. And if you want some one to answer your questions, start your own thread.


    Quote Originally Posted by heatsolutions View Post
    On some furnaces the only difference between a model that moves 1300 cfm and a model that moves 1000 cfm is the size of the blower wheel...

    I've seen some furnaces with a rheostat installed on the blower motor wiring to control blower speed...

    Check with the manufacturer to find out what safe and proper options are available to you.

    The real solution to your problem is of course to install properly sized equipment and not to "hot rod" the wrong equipment.

    Any modifications to the factory design of your furnace are potentially unsafe and may void any and all manufacturers warranties.
    Yes, rheostat was something that came to mind.

    Yes, the system is not sized right for heating only a portion of the house. Seven years ago when it was installed propane was not $2.70 a gal and economic times were much better.

    The furnace did have cutouts for different sensor locations. And the documentation leads me to believe that it has several btu options for the same cabinet. Certainly no guarantee and your points are valid and appreciated.

  9. #9
    Join Date
    Mar 2007
    Location
    tx
    Posts
    986
    There are a lot of options to equipment that are outside of the "normal" configuration the equipment is shipped in. Just make sure you read that information well on the installation and setup instructions, or check with the manufacturer if you are not 100% sure. In most cases there is a lot more riding on a safe setup than the price of propane or the shape of the economy. But I know you alread understand that for sure. Good luck, let us know how it turns out or what you learn.
    Bad information is worse than no information at all.

    There are three kinds of people in this world. Those who can count and those who can't!

  10. #10
    Join Date
    Jun 2006
    Location
    Richmond, VA
    Posts
    2,696
    Quote Originally Posted by kuma View Post
    It must be very difficult impressing only yourself. And if you want some one to answer your questions, start your own thread.

    .
    Those questions were intended to illustrate you should NEVER modify a fossil fuel burning appliance outside it's design parameters, because nobody knows the exact answers to those questions and you just moved your furnace operation to cause those issues. The design of that furnace, including it's UL listing and standards, are set and it has to operate within safe parameters.

    So anybody reading this thread:

    NEVER modify a furnace in this way. There is no way to get even a combustion analysis on this furnace. The inducer is sized or internally restricted to work with 3 burners-take one off and it puts out the wrong combustion airflow.

    I believe you also have a 5ton ac on that furnace.....how are you planning to reduce its capacity? Don't bother answering.
    It's not the Brand with the fewest repairs-It's all in the install!!! Attention to detail and using the best materials!

  11. #11
    Join Date
    Feb 2011
    Location
    Ontario
    Posts
    73
    Interesting thread...and I sure am glad none of this is DYI.

  12. #12
    Join Date
    Sep 2006
    Location
    Montana
    Posts
    983
    Quote Originally Posted by kuma View Post
    Have propane furnace and would like to reduce the fan speed. The lowest speed is 1300 cfms. The total ceiling registers are ~900cfm. Due to HIGH propane costs the furnace burner count was reduced from 3 to 2 burners and a few rooms are not to be heated any longer. Realizing that it is hard on the blower motor to restrict air flow I am hoping for a way to reduce blower speed to better match furnace output.

    Thanks!
    Quote Originally Posted by kuma View Post
    Soldered in burner hole and moved sensors.
    Right now, the best thing you could do is remove that furnace and install the proper size. By modifying it the way you have, you've changed all the ratings and the UL listing on it. You have NO warranty on the furnace anymore, and if something should happen like your house burns down or someone dies due to improper operation, guess who's responsible? I doubt an insurance company would even honor a claim if your house burned down because you altered the design of the furnace. It's pretty clear by your statements that you have no intelligent knowledge when it comes to HVAC, so bad mouthing a pro in this forum is ill advised, especially by what you're doing. Because you don't like the fact that beshvac is being honest with you, you attack him for his comments. He's telling you that what you did is WRONG, WRONG, WRONG!!! Even the worst hacks in our industry know better than to do what you did. FYI, psc motors really aren't desinged to use a speed controller(rheostat), but who am I kidding, you aren't going to listen anyway. Good luck with you hack job.

  13. #13
    Join Date
    Jun 2004
    Posts
    69
    Quote Originally Posted by beshvac View Post
    ....


    I believe you also have a 5ton ac on that furnace.....how are you planning to reduce its capacity? Don't bother answering.
    AC is fine as it is needed only a few weeks of the year.

    The flue is type B double walled vertical 7 ft run. No bends or slants. Feel free to check the vent tables.


    Quote Originally Posted by big sky hvac View Post
    ....

    so bad mouthing a pro in this forum is ill advised, especially by what you're doing. Because you don't like the fact that beshvac is being honest with you, you attack him for his comments.

    ....
    Please take the time and read the entire thread. Your so called "pro", beshvac, drew first blood with his cute graphic, "remove some blower wheel blades" remark and lost all credibility. If that is your definition of a "pro" and you support that behavior from a "pro" then please do not waste your time with this thread.

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event