As I talked about my basement system in my last thread, we decided to wait on doing anything to it for a few more years. A Contractor came yesterday to quote us on a new furnace for our first floor to replace our current Lennox G40. He did a manual j which turned up to 3.62. This means that the current heat pump (3.5 ton Trane XR15) is sized properly. This contractor is from the same company who installed our upstairs Lennox sl280v and they are a Premier Lennox Dealer. They are one of the top rated companies in my area with five-star reviews. Here's the estimate:
Install Lennox SL280UH090V48B 90,000 BTU 2-stage variable speed gas furnace.
Reconnect/reinstall flue pipe.
New drain pan with float switch.
Sealing of all ductwork
He inspected ALL of the ductwork and surprisingly said that the ductwork is all fine. It just needs some major stretching out. He also said system is short on return air, but unfortunately, another return can't be added, unless it was put in the basement. Is variable speed a wrong choice when there's not enough return air?
I'm also wondering if the cfm for when the heat pump is in heat mode is the same for the gas heat on first stage. After looking at the manual online, The default heating speed is 1035 on low fire and 1135 on high fire. It can be adjusted to a higher speed or lower speed. The heat pump needs 1400 cfm since its a 3.5 ton. Does the cfm for the heat pump in heat mode the same as the furnace in heat mode? The outdoor temp lock out is set at 40*F, just an FYI. Thanks in advance.