Stupid HO, trying to learn something. But I promise I'm not going to do the work myself!
My new dual fuel system is going in tomorrow (AS Heritage 16 HP / 80% VS furnace). I have lots of questions about the way ESP, the VS blower, a furnace filter, CFM and watts used work together.
1)In looking at the product data for the furnace, I see that the installer can choose 3 different settings (Low, medium, High) for airflow settings for 1st and 2nd stage for heat and separate settings for cooling. What drives that choice? Is it the system ESP or the temp. rise or something else?
2) If I don't mess with the registers or vents, in theory the ESP of my system will always be the same, but as my filter gets dirtier, the ESP will rise, but the VS motor will compensate for the higher ESP. The motor will work harder to maintain the CFM that was set my installer. In doing so, the motor uses more watts just to maintain the same CFM as when the filter was new/clean. Do I understand that correctly?
3) Since it appears that the VS motor uses the least amount of Watts with a lower ESP, should you not design the system with a 0.1 ESP or try to modify as system to get to the lowest ESP? Can you lower the ESP on an existing system by adding more returns? What is even more baffling to me is that the Watts used is not always linear. Some settings use less power at .9 than at .7 ESP with the same airflow setting. How can that be? Maybe I need to post the chart.
Thanks for putting up with me!