Questions
I would like to lower the output capacity of my furnace if possible. How can I do this? Is it worth doing, or should I just live with it? Is there an easy way? Some ideas: replace burner nozzles with smaller nozzles, replace burner with smaller burner if this exists, close the left of the four nozzles on the burner and move the flame sensor to the third. Since the burner and heat exchange seem to be designed to work together I assume that adjusting the burner output would screw with the efficiency of the system.
Reasoning
I purchased a house with furnaces that have a higher capacity than necessary for the space they heat. I found this out recently when I closed a small vent to one room that is not used often. Closing this one vent, not fully maybe 75% closed, triggered the high limit switch a few times and eventually the lockout. After opening the vent and resetting the system things have been fine. The cycles are still pretty short, but the high limit has not been triggered again since. The system is a Trane 80k BTU 80% efficient, forced air unit. Blower seems to be set to highest setting for heat rather than a lower setting. The heated space is around 1,100 square feet, upstairs with decent insulation and on the south side of Atlanta GA where it does not get too cold. Square footage is potentially lower due to the system not actually interacting with the hall if doors are closes. Returns and positive vents are all in rooms; hall stays warm from lower system. I did some rough estimation and figure I need somewhere between 30 and 40 thousand BTUs of output and am getting around 64k BTUs.
Saftey
I figure tinkering with the furnace to lower its capacity is not safe and will keep this in the forefront of my mind. No lectures necessary.
Best Answer
Cut the gas back some by slightly closing the gas valve (the one on the pipe, not in the unit), however be prepared to have to reset the furnace occasionally if your local gas pressure drops intermittently. Watch the flames as you do it. Just, "take the edge off".
This will cost you more in electricity, as it'll run longer to come up to temp, but it will bring you a more even comfort level. I'm unsure what effect this will have on the efficiency of the heat exchanger, but at least it will work.
The last place that I lived where I had to do this, I also kept the fan set to
onin the winter. My concern was comfort over efficiency. Note, part of my problem was the T-stat becoming satisfied before it should have, but I think the same solution applies - unless you want to start spending money.A quick hop online* tells me efficiency probably drops like a rock if you do this, but it sure is one way to lower the output of an oversized furnace.