Hi, I am in a process of figuring out a replacement HVAC system for the existing dual fuel HVAC system which is almost 20 years old now. Here is the system and house info Existing System: - Rheem 10 Seer Heat pump - Rheem single stage 100K BTU gas furnace - Vision AIQ thermostat - Aprialair pass-through humidifier, controlled by HW IAQ Home: - Located in Atlanta, GA - 2000 sq ft Ranch house on the slab with Cathedral ceiling - Open floor plan Kitchen, living room, dining room and foyer - 3 registers and three returns - Master bedroom with vaulted ceiling - 2 registers and one return ( return is sized to account master bathroom and toilet) - Master bathroom and separate toilet - each one has a register - Two small bedrooms, second bathroom one register for each and no individual return ( a large return in the hallway for them) - Most of the windows are dual pane energy efficient windows with argon gas except 6 of them are still dual pane aluminum frame windows - Insulation at the attic should be close to R19 We have been heavily using the heat pump throughout the heating season that is set to cut over gas furnace when the outside temperature is below 30 degrees F. The system is still operating fine but due to the age I'd like to get it replaced before it quits working.
The duct work is the flex ducts and installed in unconditioned attic. From previous experience we know that the duct work is not in the greatest shape and needs some work. Actually registers and returns are undersized compared to output of the heat pump. We have one missing register in the living room and as well as missing one or two returns. The equipment was installed in the attic and at the far left side of the house therefore a large supply and return trunks runs from furnace to across other end of the house. I guess it is 30 ft or so long. Return trunk has many sharp turns and supply trunk has a split at the middle without a joint transition. Supply plenum is fiber glass box and the distribution box at the other end of the supply trunk is another fiber glass distribution box that distributes the air six ways. I know it sounds horrible so that the comfort level is not that good. We have hot/cold spots because of to that but overall level comfort we have had wasn't very bad so I am in a process of calling in reputable HVAC contractors to get their suggestions about proper size of a new system and required modifications/changes on the duct work I have gotten quotes from Trane, Carrier/Bryant and Rheem dealers. I thought it is not worth to spend time and effort to get quotes from a Nordyn brand or Goodman/Amana. Based on experience we had at house in several years, I assumed the existing 3.5 tons heat pump should have provided much better performance and comfort with the correct duct work. And I think the 100K BTU gas furnace is too big for the house. As far as technical specs that I have been thinking are - Heat pump with 15-16 SEER and 8.5 or better efficiency - Demand defrost - I hate the timed defrost which what my current unit has - Gas Furnace - two stage, 80% efficiency with variable speed blower - a good quality air cleaner
Based on above here is my short listed options and I am looking at the HVAC experts of the forum in order to avoid overlooking some important points. Trane Dealer #1: - XR17 2 stage heat pump - 4TWR7048 - Coil - 4TXCC049BC3HCB - 2 Stage 80% w/ Variable speed Furnace - TUD2C080A9V4 - Flush and reuse existing line set - Reuse the flue line - Reuse existing HW VP IAQ - New supply and return plenum, manual dampers at the supply plenum - Add two new returns - one for each guest bedroom - Add one new register to the living room - Replace the junction box with manifold with dampers. Supply trunk will be replaced with a larger flex duct due to the additional register - Sealing duct joints and registers - Doesn't want to reinstall the existing AprilAir humidifier unless I am insist because of it is in unconditioned attic Trane Dealer #2: - XR17 2 stage heat pump - 4TWR7048A1 - Coil - 4TXCD063BC3 - 2 Stage 80% w/ Variable speed Furnace - TUD2C080A9V4 - new line set and new flue line - Reuse existing HW VP IAQ - New supply and return plenum, manual dampers at the supply plenum - Instead of too many direct output from the supply plenum, will use WYE splits in order to reduce from 7 direct output to 4 - Add one new 8" return to the kitchen area - high side at the wall - Add one new register to the living room - Replace the junction box with metal pipe and WYE splits - Sealing duct joints and registers - Suggest replacing the register vents with correct type and adjustable register vents for the open floor area. Existing register vents distributes the air three way - Doesn't want to reinstall the existing AprilAir humidifier unless I am insist because of it is in unconditioned attic Bryant Dealer: - Evolution 2 Stage Heat pump - 286BNA048 - Coil - CAP4817A - 2 Stage 80% w/ Variable speed Furnace - 315AAV04890 - Flush and reuse existing line set - Reuse the flue line - New Evolution Controls - New supply and return plenum, manual dampers at the supply plenum - Add two new returns - one for each guest bedroom - Enlarge the return trunk line that goes other side of the house - Add one new register to the living room - Replace the junction box. Instead use a larger supply trunk split WYE and use reducer to reduce the supply trunk at each split in order to maintain velocity - Sealing duct joints and registers - Suggest replacing the register vents with correct type and adjustable register vents for the open floor area. Existing register vents distributes the air three way - Doesn't want to reinstall the existing AprilAir humidifier instead suggest Honeywell steam humidifier - Recommends Bryant air purifier for better air quality as well as removing cooking odor - Also mentioned that he can get higher efficiency with a larger coil and/or furnace but the suggested system would provide a better comfort - This is the only contractor who did the load calculation. Based on that the required load is 44K BTU or 3.7 tons system based on the condition of my house. I was told that a 3 tons system would be enough if the insulation at the attic got improved to R30 or R38. He did the design calculation based on standard design temperature cooling 75/105(indoor/outdoor), heating 70/27degrees. By the way we keep our thermostat 73 degree for heating and 80 degree for cooling I got a few quotes from other contractors but these three I liked the most. Sorry for the very long post but I'd like to hear your comments, suggestions or objections.