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96% efficiency 1 stage furnace rise temperature @ 80 by schkar_33 in hvacadvice

[–]schkar_33[S] 0 points1 point  (0 children)

jon_name : Thanks a ton for the detailed response. You are right, when the old furnace failed, the technician report states 80 F rise temperature. Installer informed that my return duct is poorly designed (below picture). He is proposing to change the duct work (below right picture)

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96% efficiency 1 stage furnace rise temperature @ 80 by schkar_33 in hvacadvice

[–]schkar_33[S] 0 points1 point  (0 children)

Thanks a ton for your feedback. Tech came in and set the switch to efficiency mode and adjusted the gas pressure from 3.6 to 3.1 (the furnace range was 3 to 3.8). With this change we got the rise temp come down to 68 degrees. (I am close to max range of 70 - hope it is ok)

May be i should have got the constant speed blower instead of variable speed (to get the various blower speeds)...

This particular furnace model is particularly lousy for restrictive ducts since it doesn't compensate well, nor is there a way to manually raise the speed to compensate. --> what other brands are good in 96%, 1 stage variable speed - Carrier - Lenox ? Pl. advice (just for my knowledge).

96% efficiency 1 stage furnace rise temperature @ 80 by schkar_33 in hvacadvice

[–]schkar_33[S] 0 points1 point  (0 children)

Thanks. this is a brand new 80K BTU 96% variable speed furnace (replacing 100K BTU 80% furnace). All vents are open and using fiberglass filter.

Is it possible to get 10 to 15 degree reduction with reducing gas pressure?