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The problem isn't with the blower fan or motor Posted by MI-Roger [Email] (#882) [Profile/Gallery] (more from MI-Roger) on Tue, 3 Jul 2012 04:50:59 In Reply to: OT: HVAC Fan Motor Upgrade, Bruce, Mon, 2 Jul 2012 11:54:02 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The problem is inherent with all homes designed with two story vaulted spaces and using standard residential HVAC systems. You need toi get the hot air out of the elevated spaces to achieve the temperatures levels you desire.
Cold air falls due to gravity which displaces the lighter hot air to higher elevations. With 8 foot ceilings this is not too much of an issue, but with 16 to 20 foot tall vaulted spaces you get a tremendous heat gradient from floor level to ceiling level. this can be great in industrial spaces where only the lowest levels are occupied, but in a home the higher spaces are usually open to the sleeping areas making them intolerable in the summer time.
IIRC the temperature difference in tempered spaces due to vertical heat stratification is 3/4 degree F for each foot of elevation difference. Your thermostat is at the 5 ft level on the first floor, but the temperature difference on the second floor areas overlooking the vaulted spaces conceivably is 6 degrees higher. 74 degrees in the Great Room, but 80 degrees in the second floor hallway overlooking the Great Room.
Two solutions:
1) Install ceiling fans in the vaulted spaces to drive the hot air back down where it can be collected by the return ductwork system and cooled by the AC equipment.
2) Best solution (but more costly and maybe impossible) install return air inlets high on the sidewalls of the vaulted spaces and eliminate the inlets at the 7 to 8 ft level. (I am guessing the HVAC installer treated these spaces as normal 8 foot ceiling rooms rather than as a 16 to 20 ft ceiling space).
Option #2 may require more HP from your blower fan, and in a worst case scenario may even require larger return ductwork since you are adding substantial length of duct to these inlets.
posted by 198.208.25...
_______________________________________ Saabs owned: 2008 9-5 Aero Sedan, sold at 227K miles 2006 9-3SC 2.0T - Wife's daily driver 2000 Viggen Convertible - Sold May, 2022 1964 Quantum IV Formula Car - Retirement project 2000 9-5lpt Sedan, sold at 318K miles
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