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07-18-2012, 02:38 PM #1
Evolution Airflow with Single Stage AC
I have an Evolution 3 stage 80K BTU gas furnace with the Evolution Controller. My AC unit is a single stage 2.5ton Bryant unit.
On the Evolution controller under Furnace settings there are some airflow control settings for the Air Conditioning. (EFF=efficiency I presume) EFF325, EFF350, Comfort, Max if I remember right.
I presume Comfort would use a somewhat lower air flow? How to choose the setting to use & why? Pros & Cons of each?
I'm thinking if I choose a setting with too low airflow I could have icing problems?
07-18-2012, 03:44 PM #2
Is the outdoor unit communicating?
Even if no communicating, there are build in limits on the reduced airflow in Comfort based on indoor temperature and indoor humidity to prevent icing. It also looks at ourdoor tmperature as well if it's a communicating unit and will run lower airflows in hot weather since there's less system capacity... at least that's what I've observed with my system. Carrier doesn't publish the finer details of how it determines what airflwo to use. But the manaul does say that below 70F it will not lower the airflows to dehumidify. When not dehumidifying, the system seems to use 325cfm/ton as the typcial CFM setting, but in cooler outdoor conditions when humidity levels are satisfied, I've seen it ramp up to 350CFM/ton. WIth a 2 stage unit, it gets very, very aggressive in 1st stage on reducing airflows.
The other downside of comfort mode is that supply air temps will be very low. IF you have a attic or crawlspace installation or even a basement installation, you may need a higher amount of ductwork insulation to prevent sweating on the outside of the ductwork.
Personally I'd use comfort. Its' one of the primary benefits of the Evolution/Infinity control.
Also if you like to use the continous fan in summer, I'd set the coil drain time to the full 60 minutes to limit how much moisture gets reintroduced into the home when the fan only comes on.
The downside of the other settings is that airflow isn't changed to dehumidify, so you won't get much out of the Evolution controller.