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  1. #1
    Join Date
    Dec 2009
    Posts
    5

    Reduce BTU output of natural gas furnace?

    I live in Texas, where the summer A/C load is high and the winter furnace load is not. It seems most furnace manufacturers design for the middle of the country with regards to A/C blower power vs. furnace output. This is the case with my current system and the furnace is 2X what I need. Consequently, it blasts all of the moisture out of the air in the winter. I don't have the money to swap out with a 2-stage unit or add a whole-house humidifier. Is there are relatively inexpensive way to reduce the output of the furnace to reasonable levels for my area? I was thinking of asking an HVAC company to swap out the gas jets in my furnace with smaller ones. Is this recommended or safe?

    Thanks.

  2. #2
    Join Date
    Oct 2003
    Location
    Valdosta Ga
    Posts
    847
    is the unit short cycling ? (on for short periods) would have to check with manufacture for orifice size

  3. #3
    Join Date
    Apr 2009
    Posts
    523
    A service tech can reduce the BTU output of a furnace to a certain extent with just tools. However its only too a certain extent.

    Its dry out this time of year. Humidifiers are a solution to dryness, you might be able to convince yourself its better but in reality you will probably make the humidity issue worse with longer blower cycles....

  4. #4
    Join Date
    Jul 2009
    Location
    Ontario, Canada
    Posts
    913
    Quote Originally Posted by erik337 View Post
    I was thinking of asking an HVAC company to swap out the gas jets in my furnace with smaller ones. Is this recommended or safe?

    Thanks.
    No, your furnace was approved for the application it was intended for. You should not change the orifice unless they were incorrectly installed by the manufacturer. The unit must run according to its rating plate!

  5. #5
    Join Date
    Sep 2002
    Location
    Northeast Ohio
    Posts
    4,842
    Derating is not a good idea. There are other whys to increase interior humidity levels without adding a humidifier although that is the most effective way.
    A good HVAC tech knows how, an educated HVAC tech knows why!

    DEM


  6. #6
    Join Date
    Jul 2005
    Posts
    5,574
    Quote Originally Posted by erik337 View Post
    I live in Texas, where the summer A/C load is high and the winter furnace load is not. It seems most furnace manufacturers design for the middle of the country with regards to A/C blower power vs. furnace output. This is the case with my current system and the furnace is 2X what I need. Consequently, it blasts all of the moisture out of the air in the winter. I don't have the money to swap out with a 2-stage unit or add a whole-house humidifier. Is there are relatively inexpensive way to reduce the output of the furnace to reasonable levels for my area? I was thinking of asking an HVAC company to swap out the gas jets in my furnace with smaller ones. Is this recommended or safe?

    Thanks.
    A smaller furnace won't do a thing to remediate your moisture problems, and derating your existing furnace won't either, not to mention the fact that it would be a reckless thing to do.

    If you can't afford a humidifier, then you'll probably just have to suffer through it, because the other options aren't any less expensive up front, though they would pay for themselves in energy savings over time. Those would be things like sealing the ducts, sealing windows, outlet boxes, doors, etc., providing fresh air directly to the furnace (if it is currently pulling combustion air from the house), things of that nature. The idea is to reduce the air infiltration into the house, because that's what causes the low indoor RH. As the colder outside air enters the house and warms up, the RH drops. Though the air picks up some moisture from the house (toilets, showers, sinks, people, floor cleaning, etc.) it is constantly being displaced by the fresh outdoor air coming in. HTH.

  7. #7
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,174
    Its not the furnace size that is reducing your humidity.Its your homes leakage rate.
    Seal your house, and your humidity will improve.

    Its also possible that your duct work is bringing in fresh due to the return and or supply duct leaking.

    A furnace have the size of your existing one. Would make the air just as dry. And possibly drier. if its caused by a leaking duct system.
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