1. Welcome to Hvacproforums, an interactive community exclusively for HVAC professionals. The collective years of HVAC experience and the knowledge our forum members share make this an invaluable resource for those in the HVAC industry. We have a lot of fun, but make no mistake, we are pros. Hvacproforums is self supporting ...there are NO advertisers here. Do-it-yourselfers and Homeowners are encouraged to seek information elsewhere. Those involved in the HVAC industry are urged to register. its 100% free and easy, Once registered you will have access to the technical forums, Be sure to click over to the new members forum and introduce yourself after registering!

Dumb question

Discussion in 'Residential' started by coldsnap, Jan 4, 2018.

  1. coldsnap

    coldsnap -20 on the money

    Messages:
    4,501
    Location:
    Wisconsin
    What effects would too much airflow have on a gas furnace or rtu?
     
  2. Joeysmith

    Joeysmith New Member

    Messages:
    272
    Poor heat transfer.
     
    SmallChange, Zman and jpb2 like this.
  3. jays 65

    jays 65 New Member

    Messages:
    358
    too much airflows like too much money a car too fast no such thing lol
     
  4. pecmsg

    pecmsg Junior my ASS

    Messages:
    21,714
    Location:
    Eastern LI
    For combustion or over the heat exchanger?
     
  5. Catpower

    Catpower The Crowd Pleaser

    Messages:
    22,461
    Location:
    in the Cabana
    If it is an old one with a bi-metal fan switch the fan will cycle more:D

    But they would need a new one anyway
     
  6. coldsnap

    coldsnap -20 on the money

    Messages:
    4,501
    Location:
    Wisconsin
    Over the hx
     
  7. pecmsg

    pecmsg Junior my ASS

    Messages:
    21,714
    Location:
    Eastern LI
    Lower Delta T
     
    jpb2 likes this.
  8. mike1020

    mike1020 entitled millennial

    Messages:
    18,541
    Location:
    on the roof of target
    Some new equipment, especially RTU’s will come with labels attached saying not to use the unit as a construction heater or in buildings below 55 degrees because there will be excessive condensation and there will also be incomplete combustion.

    I don’t know if the latter is true or not.
     
  9. pecmsg

    pecmsg Junior my ASS

    Messages:
    21,714
    Location:
    Eastern LI
    If they can find a way to void the Warranty
     
  10. flange

    flange Act like you care and do SOMETHING!!

    Messages:
    12,967
    Location:
    IMT--in my truck
    btu=1.08 x cfm x delta t

    example of more air

    1080=1.08 x 1000 x 1

    1080=1.08 x 2000 x .5
     
    Joeysmith likes this.
  11. tuna

    tuna New Member

    Messages:
    2,930
    Condensation in the heat exchanger.
     
    jpb2 likes this.
  12. Zman

    Zman Hanging by a Thread

    Messages:
    1,231
    Location:
    The "I know a Guy" State
    Higher stack temps. More $$$ up the sky!
     
  13. Zman

    Zman Hanging by a Thread

    Messages:
    1,231
    Location:
    The "I know a Guy" State
    Noisey!
     
  14. Zman

    Zman Hanging by a Thread

    Messages:
    1,231
    Location:
    The "I know a Guy" State
    A lean,mean burning machine.
     
  15. Chuck

    Chuck SSP

    Messages:
    8,027
    Location:
    LAX
    That's debatable. I've heard the arguments for it, but never observed it. Definitely not a given, not saying it's impossible in some scenarios but not guaranteed.

    If you look at fluid flow vs heat transfer, the higher the flow the higher the heat transfer gets.
     
  16. Joeysmith

    Joeysmith New Member

    Messages:
    272
    the higher the flow the higher the heat transfer gets.

    That's not always true in my experience. I have seen trucks overheat because someone removed the thermostat.
     
  17. Ballvalve79

    Ballvalve79 It's only fire what could go wrong

    Messages:
    273
    Location:
    Northwest PA
    I have had it happen.

    There is I such a thing called contact factor. It basically is if the air or fluid is moving too fast there isn't time for the heat exchange to happen, pretty simple if you think about it. This applies to dx coils, hot water, steam to water bundles, and anything that heat or cools with a pump or fan
     
  18. Chuck

    Chuck SSP

    Messages:
    8,027
    Location:
    LAX
    I would like to see some documentation.

    All I've ever found regarding this says that the higher the fluid flow the better the heat transfer.
    That's an often repeated myth that if true would break the laws of physics. I did auto repair for 6 years and believed it too until I dove into it a bit. A lot of dirt track race car drivers will remove the thermostats and their engines run cooler not hotter.

    The myth began with old cars that lost coolant through the radiator cap due to too much pressure from the pump when the t-stat was removed.
     
    Jay 41 likes this.
  19. Joeysmith

    Joeysmith New Member

    Messages:
    272
    If you take turbulence out of the equation that's probably true but if you try to shove more flow through it than its designed for then you run into problems.
     
  20. Chuck

    Chuck SSP

    Messages:
    8,027
    Location:
    LAX
    Turbulent flow has better heat transfer than laminar flow. Look up “Reynolds Number”
     
    jpb2 likes this.