Friday and Saturday I had a Carrier Performace 80 two stage furnace (Not the DC varible speed one) installed by a local reputable dealer. I also installed a Honeywell 8320 Vision Pro (multi-stage capable) thermostat.
The new furnace started up friday night when it got cold enough in the house. It started on high stage and later seemed to go to low flame when it got within 2 degrees of it's set point. (I was watching it like a proud pappa!) The problem is the blower speed is suppose to drop as well but doesn't appear to be. I had told the installers this on their return to finish up on Saturday and they said they had to set a "dip" switch on the furnace to allow a two stage thermostat control which they then did. Still on Saturday night I still only notice one blower speed. Are Med-low and low not too much different on these furnaces that I wouldn't notice much?
Just incase you're wondering, I set (programed) the thermostat for option "9" two stage heat, 1 stage cool in the advanced setup so the thermostat should be ok.
The reason I ask is the furnace blower motor is factory set for "high" during A/C, Med-Low for High heat and low speed for low heat/low gas flame.
Call the installing company and express your concerns. Have them go over the sequence of operation with you and demonstrate it.
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Low & medium low can be barely noticable. You'll more likely notice cooler air coming out than less air.
as the other have said, with a 5 speed motor you will hardly notice a difference between 2 close speeds
If you are really concerned call the tech back and get them to check it. It is easy enough to check which leg is getting power in which stage. If you are running medium low and low then you may not notice much difference coming out of the registers. With variable speed I am sure you would notice the difference in speeds.
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You're right... perhaps there is a small difference, one that I can't notice. There is a difference in the way the furnace "fires". Low and high gas burning is quite noticable in sound and by the inducer motor speed.