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My furnace (Bryant 926TA) has to arrays of setup switches.

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I am particularly concerned with SW1-3 (off in my picture) and SW1-4 (on in my picture).

The manual calls SW1-3 Low Heat Rise Adjustment and says Turn ON to increase Low Heat airflow by 18 percent. This compensates for increased return air temperature caused with bypass humidifier.

SW1-4 is named Comfort/Efficiency Adjustment and says Turn ON to decrease low heat airflow by approximately 7 percent and high heat by approximately 10 percent for maximum comfort.

I do indeed have a bypass humidifier, and I have a few rooms that do not seem to have enough airflow to them.

I am considering turning SW1-3 on and SW1-4 off to try to increase airflow throughout the house, rather than installing a few duct fans.

If you have experience with HVAC/furnace installation/etc, are you aware of a reason the installers might have configured the furnace the way they did? Maybe it was just an oversight, but maybe there is a good reason for it that I am not aware of.

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  • I plowed ahead and set SW1-3 to ON. The air flow was barely perceptible in the rooms in question before, and now it is noticeable. That might be enough by itself, will continue monitoring. – negacao Feb 8 at 18:39
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    Use caution if increasing the fan speed, yes this may push more air and when pushing two much it can blow out the trunk lines, push flex off of connectors to the room registers or at the trunk. Some times it’s the lack of air being able to get out of a room that causes the problem. – Ed Beal Feb 8 at 19:45
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    @EdBeal, thank you for the warning. The return air ducts in the rooms in question seem fine, though I have been sealing a bunch of leaks. So far, so good - I was able to turn off all four space heaters. FWIW the increased air flow isn't very noticeable in the rooms where it wasn't an issue previously - only in the problematic rooms. – negacao Feb 9 at 20:16
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    Negacao, that’s awesome you are having such good luck with your changes. You should write up what you did and accept it as an answer, this helps others searching for similar problems to find what worked for you. – Ed Beal Feb 9 at 20:21
  • Thank you, @EdBeal. I'm not quite sure what to post as an answer, because I do not really know the Right Answer - I just tried something figured "what's the worst that could happen?" and it happened to work out for me - but it could easily have gone wrong, and I am still not clear on if the installers did that intentionally. :) – negacao Mar 13 at 21:11

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