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Old 07-19-2010, 04:58 PM   #1
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2 stage AC

Could someone please walk me thru how two stage ac with variable speed air handler is to work. What condition(s) exactly makes unit change from single to second stage and what make handler fan speed increase??? Have american standard allegiance 16 two stage with variable speed handler and american standard ACONT800 thermostat ( no outside temp. sensor). Have used two seasons and I have never noticed any difference at outside unit when running. Equipment is 18 months old. THANKS


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Old 07-19-2010, 07:19 PM   #2
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The thermostat will kick in the second stage when (roughly) the room temp rises more than 1 deg above the cut in point. ie: set at 70/ cuts in 1st stage at 71 /2nd stage at 72. The higher speed of the airhandler is in sync with the Y2 second stage terminal on the circuit board. May only speed the fan up 10-15% which is not that noticeable. Some outdoor units don't vary the condensor fan speed for 2 stage units (Lennox doesn't) so you won't notice a change in sound either.


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Old 07-20-2010, 07:44 AM   #3
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Some people don't read the install instructions. So your unit may be wired wrong.
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