Installed May 29 and 30, 2025 · Keller, TX 76248
The homeowner's story. The homeowner had two older systems in the attic, and the 2-ton system was down. The homeowner chose Carrier Infinity for better temperature and humidity control and wanted to start with the 2-ton system because it needed no duct changes. The 5-ton system needed more supply and return airflow, so the job also included duct additions on that side.
Short answer. We replaced two older systems, one of them down, in this Keller home with a 5-ton and a 2-ton Carrier Infinity system, each with a variable speed air conditioner and a two-stage gas furnace. The certified heat load calculation results showed 80,667 BTU/h of total cooling load for the 3,383 sq ft house (73,819 sensible and 6,848 latent). The report caps the sizing figure at a 0.85 sensible heat ratio, which gives 86,846 BTU/h, or 7.24 tons (86,846 divided by 12,000), and 2,895 CFM. Glass is the largest cooling item, 30,295 BTU/h or 37.6%, and the home has almost no shade. We also added two 9 inch supplies and a 12 inch return on the 5-ton side to increase airflow, protect the system and support humidity control by maintaining adequate airflow.
Key facts
In plain words. Two older systems, one of them down, were replaced with a 5-ton and a 2-ton Carrier Infinity system, each with its own furnace, coil and control. The table gives the numbers that decided the job and the result: a $32,069.44 install finished in two days that passed the city inspection.
| Item | Details |
|---|---|
| Location | Keller, TX 76248 (Dallas-Fort Worth area) |
| Home | 3,383 sq ft, built in 2008, 12 ft ceilings (the load report uses an 11 ft average), 6 residents, almost no shade, standard insulation (R-11 walls, R-5 floor, R-22 ceiling), two systems with furnaces and coils in the attic |
| Old systems | Two older systems, one of them down, the 2-ton system. Carrier 58STA110 and 58STA045 gas furnaces made October 2008, with Trane R-410A coils made 10/2014 and 5/2015. The old outdoor unit tags were faded and unreadable |
| Heat load result | Whole house, 3,383 sq ft (the certified heat load calculation results): cooling 80,667 BTU/h (73,819 sensible, 6,848 latent, calculated SHR 0.92). At the report's 0.85 SHR cap: 86,846 BTU/h, 7.24 tons, 2,895 CFM. Heating 45,103 BTU/h, 586 CFM |
| Why 5 tons and 2 tons | The two systems were chosen from the equipment available. The 5-ton is the largest size Carrier makes in the Infinity line, so the downstairs system could not be upsized. The upstairs zone served by the 2-ton is only 895 sq ft, and a 3-ton Infinity there would have been oversized. The best option with the available equipment was a 5-ton downstairs and a 2-ton upstairs. We want to be straightforward about the numbers. The two AHRI ratings at 95°F add up to 80,200 BTU/h (56,000 plus 24,200), which sits right at the calculated cooling load of 80,667 BTU/h, and the load was calculated at a 105°F outdoor design, not 95°F. We do not claim the equipment exceeds the load at 105°F. The homeowner asked for the heat load to be run at a 105°F outdoor design temperature because their old systems could not keep up during the hottest part of summer, so this is a deliberately conservative design, stricter than a typical design day. We then selected the exact matched systems and verified their published performance data. |
| New systems | Two Carrier Infinity systems, each with a variable speed 26VNA1 air conditioner (R-454B), a CVAMA cased coil, a two-stage 58TN0B gas furnace, an Infinity System Control and an RGF LED REME HALO: a 5-ton (26VNA160W003) and a 2-ton (26VNA124W003) |
| Ductwork | Two new 9 inch supplies and one new 12 inch return added on the 5-ton side, and manual plenum dampers on the 2-ton side |
| Airflow in Comfort mode | Both systems were set to Comfort mode, which delivers 1,750 CFM on the 5-ton system and 700 CFM on the 2-ton system. Duct capacity from the chart values below: 5-ton supply 1,950 CFM and return 2,155 CFM with the new ducts, 2-ton supply 830 CFM and return 860 CFM |
| AHRI ratings | 5-ton: AHRI 215701358, 26VNA160W*030* + CVAMA6021XMA*+UI + 58TN*B110C21**20, 56,000 BTU/h, 19 SEER2, 10.5 EER2. 2-ton: AHRI 215690168, 26VNA124W*030* + CVAMA2517XMA*+UI + 58TN*B070C14**12, 24,200 BTU/h at 95°F, 18.5 SEER2, 11.5 EER2 |
| Static pressure after install | 0.49 in. W.C. on the 5-ton system and 0.57 in. W.C. on the 2-ton system, both within the 0.3 to 0.8 in. W.C. range Carrier technical support and training recommends for the Infinity airflow test |
| Permit and inspection | City of Keller final mechanical inspection passed June 6, 2025 |
| Installed price | $32,069.44 after two $1,700 Carrier Cool Cash rebates and a $655 discount. See the Cost section. |
| Install time | Two days, May 29 and 30, 2025. Installed by Angel Garcia, Francisco Jimenez and Masiullah Amani |
The problem: two older systems, one of them down
In plain words. The home had two older systems, and one of them, the 2-ton, was down. Both furnaces were made in October 2008, and the coils were from 2014 and 2015. The house has a lot of glass with almost no shade, so we recommended replacing both systems with Carrier Infinity systems for better temperature and humidity control. The result is two matched, variable speed systems.
The homeowner had two older systems in the attic, and the 2-ton system was down. What we found at the survey on May 15, 2025:
- Aging equipment. The two Carrier gas furnaces, a 58STA110 (110,000 BTU/h input) and a 58STA045 (44,000 BTU/h input), were made in October 2008. The coils are Trane R-410A models made 10/2014 (4TXCC060BC3HCBA, 5 tons) and 5/2015 (4TXCB036BC3HCBA, 3 tons). The 3-ton coil was paired with the 2-ton condenser. The data tags had faded off both outdoor units and couldn't be read, so the tech got the size of both units from their compressor data tags. The old outdoor unit data tags were unreadable and not photographed, so the old condensers' model and efficiency are not stated here.
- A large glass load with almost no shade. Glass is 37.6% of the cooling load, with 245 sq ft facing east and 172 sq ft facing west. Rooms facing the sun can run warmer in the afternoon than the rest of the house, and the load report's contractor alert suggests a variable comfort system and room or zone controls for that.
- Humidity. The certified heat load report shows 24 grains of moisture difference, and infiltration alone adds 5,648 BTU/h of latent load. Better humidity control was one of the homeowner's reasons for choosing Infinity.
What the homeowner wanted, and the result
In plain words. The homeowner wanted two new systems with better temperature and humidity control and chose Carrier Infinity for that, starting with the 2-ton system. We replaced both systems, added the airflow the 5-ton system needed, and the homeowner's review is a 5-star one. The table shows each request, what we did and how it turned out, in the homeowner's own words where the review covers it.
| What the homeowner wanted | What we did | Result |
|---|---|---|
| Better temperature and humidity control, so Carrier Infinity | Installed a variable speed Carrier Infinity air conditioner, a two-stage variable speed furnace and an Infinity System Control on each system | The homeowner's review: "I could not be more please with the quality and professionalism in the work." |
| Start with the 2-ton system, since it needed no duct changes | Installed both systems over two days, May 29 and 30, 2025, with the 2-ton system as the homeowner's starting point | The homeowner's review: "The installation led by Angel and his crew went quickly and flawlessly, with minimal disruption and tidy work habits." |
| Duct changes to match the airflow the 5-ton system needs | Added two 9 inch supplies and one 12 inch return on the 5-ton side, and manual plenum dampers on the 2-ton side | The homeowner's review: "The suggested duct modifications aligned with a recommendation ( not revealed) made five years during routine maintenance (different vendor)." |
| Air purifiers on both systems | Installed an RGF LED REME HALO with a 4" Honeywell Filter Base with MERV 11 filter on each system | The homeowner's review mentions both "REME-LED Air purifiers". |
| A price that matched the quote | Built four estimate options (Performance and Infinity) and installed the Infinity 5-ton and 2-ton option | The homeowner's review: "It was perfectly aligned aligned with their web site pricing information; no surprises." |
How the size was chosen
In plain words. The old systems were two older units, one of them down, and we did not size the new ones by copying them. The certified heat load calculation results are for the whole 3,383 sq ft house as one block load: 80,667 BTU/h total, 73,819 sensible, which the report caps at a 0.85 sensible heat ratio for an 86,846 BTU/h, 7.24 ton sizing figure and 2,895 CFM. We selected a matched 5-ton and 2-ton Carrier Infinity pair because the 5-ton is the largest Infinity size Carrier makes and a 3-ton on the 895 sq ft upstairs zone would have been oversized. The two AHRI ratings at 95°F add up to 80,200 BTU/h, right at the calculated load, and the homeowner asked for a conservative 105°F design. We checked the published data of both systems. The outcome is two variable speed systems that can run well below full output on mild days.
The certified heat load calculation results are for the whole house as one block load, in report 2146594, run by Timothy Carpenter. The certified heat load calculation results are from May 15, 2025, the same day as the site survey. The inputs were 3,383 sq ft, 6 residents, an 11 ft average ceiling, R-11 walls, an R-5 floor and an R-22 ceiling, glass at U 0.5 and SHGC 0.85, 105°F outdoor and 69°F indoor summer design, 45°F outdoor and 72°F indoor winter design, a 74°F summer wet bulb, 24 grains of moisture difference, 0.6 air changes per hour of cooling infiltration and 0.8 for heating, 15% duct gain and 10% duct loss.
| Cooling load item | BTU/h | Share |
|---|---|---|
| Glass | 30,295 | 37.6% |
| Sensible infiltration | 13,705 | 17% |
| Duct gain | 9,872 | 12.2% |
| Ceiling | 9,379 | 11.6% |
| Wall | 6,788 | 8.4% |
| Latent infiltration | 5,648 | 7% |
| Internal | 2,400 | 3% |
| Sensible people | 1,380 | 1.7% |
| Latent people | 1,200 | 1.5% |
| Total | 80,667 | 73,819 sensible, 6,848 latent |
| Heating load item | BTU/h | Share |
|---|---|---|
| Infiltration | 13,705 | 30.4% |
| Floor | 11,507 | 25.5% |
| Glass | 6,548 | 14.5% |
| Wall | 5,091 | 11.3% |
| Ceiling | 4,151 | 9.2% |
| Duct loss | 4,100 | 9.1% |
| Total | 45,103 | 586 CFM required heating airflow |
The calculated sensible heat ratio is 0.92. The report caps the sizing figure at a 0.85 SHR, which gives 86,846 BTU/h (73,819 divided by 0.85), or 7.24 tons (86,846 divided by 12,000), with 2,895 CFM of required cooling airflow. The report's contractor alert says that if the hourly glass load exceeds the average glass load, especially in mid to late afternoon, areas of the home may become uncomfortable, and suggests a variable comfort system (staged or modulating cooling and heating, and variable airflow) and room or zone temperature controls.
Why two systems. The two systems were chosen from the equipment available. The 5-ton is the largest size Carrier makes in the Infinity line, so the downstairs system could not be upsized. The upstairs zone served by the 2-ton is only 895 sq ft, and a 3-ton Infinity there would have been oversized. The best option with the available equipment was a 5-ton downstairs and a 2-ton upstairs. We want to be straightforward about the numbers. The two AHRI ratings at 95°F add up to 80,200 BTU/h (56,000 plus 24,200), which sits right at the calculated cooling load of 80,667 BTU/h, and the load was calculated at a 105°F outdoor design, not 95°F. We do not claim the equipment exceeds the load at 105°F. The homeowner asked for the heat load to be run at a 105°F outdoor design temperature because their old systems could not keep up during the hottest part of summer, so this is a deliberately conservative design, stricter than a typical design day. We then selected the exact matched systems and verified their published performance data. Each 26VNA1 compressor has a capacity range of 25 to 100% (Carrier 26VNA1 product data), so on mild days each system runs well below full output.
Ductwork: more airflow on the 5-ton side
In plain words. The home had two older systems, one of them down, and the existing ducts on the 5-ton side were short of what a 5-ton system needs. Our supply airflow takeoff found the existing supply ducts good for only about 3.75 tons, and our return takeoff found the existing return ducts good for about 4.18 tons. We added two 9 inch supplies and one 12 inch return to increase airflow, protect the system and support humidity control by maintaining adequate airflow. The added return increases available return-air capacity and helps the system maintain the airflow required for Comfort Mode operation. The 2-ton side needed no duct additions and got manual plenum dampers. The tables below break out every duct.
Our supply airflow takeoff found the existing 5-ton supply good for about 3.75 tons, and our return takeoff found the existing return good for about 4.18 tons. It is factory recommended to have an adequate amount of supply air per system tonnage, so we recommended adding two 9 inch supply ducts and one 12 inch return duct to make the airflow adequate for a 5-ton system. We added them, billed as three new duct runs. Reasons:
- Increase airflow. More supply and return area for the 5-ton system.
- Protect the system. A 5-ton variable speed system with too little duct area works against its own airflow.
- Support humidity control. The added return increases available return-air capacity and helps the system maintain the airflow required for Comfort Mode operation.
On the 2-ton side the homeowner noted there were no duct modifications to make, and the estimate adds manual plenum dampers. The parts order for the job lists two 9 inch collars, a 12 inch collar, register boxes and return grilles, which match the two supplies and one return.
Every duct, with its airflow
In plain words. The 5-ton system had seven existing supply ducts and four existing return ducts, and the 2-ton system had four supplies and two returns. At 400 CFM per ton, our takeoff gave the existing 5-ton supply about 3.75 tons and its return about 4.18 tons, short of a 5-ton system. The two new 9 inch supplies and the new 12 inch return raise those to about 4.87 and 5.38 tons. The 2-ton side came to about 2.07 tons of supply and 2.15 tons of return and needed no additions.
Each duct's airflow is the design airflow for its round size from the NCI field duct sizing chart (flexible duct): 5 inch 50 CFM, 6 inch 75, 7 inch 110, 8 inch 160, 9 inch 225, 12 inch 480, 14 inch 700 and 16 inch 1,000. These are chart values, not measured airflow. Tons are CFM divided by 400, rounded down to two decimals.
| 5-ton system, supplies and returns | |||
|---|---|---|---|
| Duct | Size | CFM | Status |
| Supply 1 | 12 inch | 480 | Existing |
| Supply 2 | 9 inch | 225 | Existing |
| Supply 3 | 9 inch | 225 | Existing |
| Supply 4 | 9 inch | 225 | Existing |
| Supply 5 | 8 inch | 160 | Existing |
| Supply 6 | 7 inch | 110 | Existing |
| Supply 7 | 6 inch | 75 | Existing |
| Existing supply total | 1,500 | 3.75 tons | |
| Supply 8 | 9 inch | 225 | NEW |
| Supply 9 | 9 inch | 225 | NEW |
| New supply total | 1,950 | 4.87 tons | |
| Return 1 | 16 inch | 1,000 | Existing |
| Return 2 | 9 inch | 225 | Existing |
| Return 3 | 9 inch | 225 | Existing |
| Return 4 | 9 inch | 225 | Existing |
| Existing return total | 1,675 | 4.18 tons | |
| Return 5 | 12 inch | 480 | NEW |
| New return total | 2,155 | 5.38 tons | |
| 2-ton system, supplies and returns | |||
|---|---|---|---|
| Duct | Size | CFM | Status |
| Supply 1 | 12 inch | 480 | Existing |
| Supply 2 | 9 inch | 225 | Existing |
| Supply 3 | 6 inch | 75 | Existing |
| Supply 4 | 5 inch | 50 | Existing |
| Existing supply total | 830 | 2.07 tons | |
| Return 1 | 14 inch | 700 | Existing |
| Return 2 | 8 inch | 160 | Existing |
| Existing return total | 860 | 2.15 tons | |
Comfort mode airflow
In plain words. Both Carrier Infinity systems were set to Comfort mode, which delivers 1,750 CFM on the 5-ton system and 700 CFM on the 2-ton system. The duct totals in the tables above show the ducts can carry those airflows.
Comfort mode on the 5-ton system delivers 1,750 CFM. With the two new 9 inch supplies the 5-ton supply ducts add up to 1,950 CFM, and with the new 12 inch return the return ducts add up to 2,155 CFM, so both sides have more capacity than 1,750 CFM. The existing 5-ton ducts alone came to 1,500 CFM of supply and 1,675 CFM of return, below 1,750 CFM, and the new ducts bring both above it. Comfort mode on the 2-ton system delivers 700 CFM. The 2-ton supply ducts add up to 830 CFM and the return ducts to 860 CFM, which is also more than 700 CFM, and that side needed no additions. The duct figures are chart values, as explained above.
What was installed
In plain words. Both old systems were replaced. In their place went two matched Carrier Infinity systems: a variable speed air conditioner, a cased coil, a two-stage variable speed gas furnace, an Infinity control and an RGF LED REME HALO on each. The furnaces are two-stage 80% AFUE models, and each new system has a documented, tested install. The table links every installed model to Carrier or RGF.
| Part | Old | New, 5-ton system | New, 2-ton system |
|---|---|---|---|
| Outdoor unit | Two older outdoor units (data tags faded and unreadable) | Carrier Infinity 26VNA160W003, variable speed, R-454B (product data) | Carrier Infinity 26VNA124W003, variable speed, R-454B (product data) |
| Indoor coil | Trane 4TXCC060BC3HCBA, 5 tons, made 10/2014, and Trane 4TXCB036BC3HCBA, 3 tons, made 5/2015, both R-410A | Carrier CVAMA6021XMA cased coil with TXV (product data, spec sheet) | Carrier CVAMA2517XMA cased coil with TXV (product data) |
| Furnace | Carrier 58STA110 (110,000 BTU/h input) and 58STA045 (44,000 BTU/h input), made 10/2008 | Carrier Infinity 80 58TN0B110C21--20, two-stage, variable speed, 80% AFUE (product data) | Carrier Infinity 80 58TN0B070C14--12, two-stage, variable speed, 80% AFUE (product data) |
| Control | Nest thermostats | Carrier Infinity System Control SYSTXCCITC01-C on each system (product data) | |
| Air treatment | None listed | RGF LED REME HALO with a 4" Honeywell Filter Base with MERV 11 filter on each system | |
| Ductwork | Existing ductwork | Two new 9 inch supplies and one new 12 inch return | Manual plenum dampers |
| Line set | Existing line set acid-flushed and reconnected, with a new filter drier (from the estimate) | ||
| Surge protection | Not recorded | Surge protectors included at $0.00 on the estimate | |
Carrier lists the 26VNA1 as an Infinity 21 variable speed air conditioner with a 25 to 100% capacity range and sound as low as 55 dBA in low speed (26VNA1 product data). Carrier lists the 58TN0B as a two-stage, 80% AFUE, variable speed furnace with an IdealHumidity system (58TN0B product data), and says the Infinity control and furnace together give control of temperature, humidity and indoor air quality. The matched systems are listed in the AHRI Certification Directory under AHRI 215701358 (5-ton: 26VNA160W*030* + CVAMA6021XMA*+UI + 58TN*B110C21**20, 56,000 BTU/h, 19 SEER2, 10.5 EER2) and AHRI 215690168 (2-ton: 26VNA124W*030* + CVAMA2517XMA*+UI + 58TN*B070C14**12, 24,200 BTU/h at 95°F, 18.5 SEER2, 11.5 EER2).
How the install went
In plain words. Two older systems, one of them down, came out and two matched systems went in over two days, May 29 and 30, 2025. The homeowner asked to start with the 2-ton system, and the 5-ton system went in with its duct additions. Both systems were pressure tested with nitrogen and evacuated, and the city inspection passed on June 6, 2025.
Angel Garcia led the crew, with Francisco Jimenez and Masiullah Amani. The install crew was Carrier Infinity trained. Bryce Duprey did the site survey on May 15, 2025. Atlas AC Repair operates under Texas ACR license TACLB00153401E, held by Timothy Carpenter.
The install took two days, May 29 and 30, 2025. The homeowner asked to start with the 2-ton system, since it needed no duct changes, and the 5-ton system went in with its three new duct runs.
Line set, evacuation and commissioning
In plain words. The existing refrigerant lines were reused after an acid flush, and a new filter drier was added to each system. Each system was pressure tested with nitrogen and evacuated before startup. The table lists what was recorded. The outcome is two systems started on the existing lines.
| Item | Recorded | Source |
|---|---|---|
| Line set | Existing line set acid-flushed and reconnected, new filter drier | Estimate line items |
| Nitrogen pressure test | About 411 to 448 psig on the digital manifold across the photos, one shown below (test pressure, not a running pressure) | Gauge photos |
| Evacuation, 2-ton system | 468 microns, still falling about 20 microns per minute | Micron gauge photo |
| Evacuation, 5-ton system | 246 microns, falling about 9 microns per minute | Micron gauge photo |
| Blower settings, 2-ton furnace | High cooling 875 CFM setting, low cooling 650 CFM setting (Carrier app settings, not measured airflow) | Install photos |
| Blower settings, 5-ton furnace | High cooling 2,100 CFM setting, low cooling 1,400 CFM setting (Carrier app settings, not measured airflow) | Install photos |
| Return filters | 4" Honeywell Filter Base with MERV 11 filter (20x25x4), on each system | Install photos and parts order |
Static pressure after the install
In plain words. The existing ducts on the 5-ton side were short of what a 5-ton system needs, so we added two 9 inch supplies and a 12 inch return there. After the install, total external static pressure was 0.49 in. W.C. on the 5-ton system and 0.57 in. W.C. on the 2-ton system. Carrier technical support and training recommends 0.3 to 0.8 in. W.C. for the Infinity airflow test, so both are within that range.
| System | Total external static pressure | Recommended range for the Infinity airflow test | Result |
|---|---|---|---|
| 5-ton | 0.49 in. W.C. | 0.3 to 0.8 in. W.C. | Within range |
| 2-ton | 0.57 in. W.C. | 0.3 to 0.8 in. W.C. | Within range |
Total external static pressure, in inches of water column (in. W.C.), shows how hard the blower has to push air through the ducts, filter and grilles. The recommended range of 0.3 to 0.8 in. W.C. for the Infinity airflow test is from Carrier technical support and training. Both systems read inside it after the install. The 5-ton reading was taken after the duct changes described above, which added supply and return area to that system. We do not have a reading from before the changes, so we cannot say how much the added ducts changed it.
Permit and inspection
In plain words. The City of Keller final mechanical inspection passed on June 6, 2025. The homeowner's review says the inspector commented on the installation quality.
City of Keller final mechanical inspection: passed June 6, 2025.
Cost
In plain words. The homeowner had two older systems, one of them down, and chose the Infinity 5-ton and 2-ton option from four estimate options. The final installed price was $32,069.44 after two $1,700 Carrier Cool Cash rebates and a $655 discount. The table shows the line items. The review says the price matched the quote with no surprises.
We wrote four options on May 15, 2025: Performance 5-ton and 2-ton ($31,318.66), Performance 5-ton and 3-ton ($33,608.61), Infinity 5-ton and 3-ton ($35,826.10) and Infinity 5-ton and 2-ton ($32,069.44). The homeowner approved the Infinity 5-ton and 2-ton option on May 21, 2025.
| Line item | Amount |
|---|---|
| 5-ton Carrier Infinity gas system | $17,548.58 |
| Carrier Cool Cash rebate, 5-ton | -$1,700.00 |
| LED REME HALO with 4" Honeywell Filter Base with MERV 11 filter, 5-ton system | $1,309.88 |
| Three new duct runs, 5-ton side (3 at $570.00) | $1,710.00 |
| 2-ton Carrier Infinity gas system | $13,996.10 |
| Carrier Cool Cash rebate, 2-ton | -$1,700.00 |
| LED REME HALO with 4" Honeywell Filter Base with MERV 11 filter, 2-ton system | $1,309.88 |
| Plenum manual dampers, 2-ton side | $250.00 |
| Surge protectors | $0.00 |
| $655 discount | -$655.00 |
| Installed price | $32,069.44 |
For typical ranges, see our Carrier Infinity cost guide and HVAC replacement cost guide. This price covers two complete systems, three new duct runs, two air treatment products and the permit. Learn about our HVAC financing options.
Warranty
In plain words. The homeowner had two older systems, one of them down. The new Carrier equipment was registered with Carrier on June 9, 2025, and the estimate lists a 10-year Carrier factory parts warranty and a 2-year Atlas labor warranty. The LED REME HALO units carry their own warranty certificate.
The estimate lists a 10-year Carrier factory warranty on parts, which requires registration, and a 2-year Atlas warranty on labor. Atlas registered the new equipment with Carrier on June 9, 2025. The LED REME HALO units were registered on a warranty certificate showing install on May 29, 2025 and coverage to May 27, 2032.
Service visits after the install
In plain words. The new systems have had three Atlas visits since the install. Maintenance visits were made on December 1, 2025 and June 24, 2026. On June 24 the tech made a charge adjustment on the 2-ton system and replaced a faulty surge protector. On September 8, 2026 the 5-ton system's control showed a high humidity alert after a sudden humidity jump that came after the Carrier thermostat updated to version 2.10. We believe the control's humidity sensor was reading about 10 points high, and a 10% offset brought it into line with a reference hygrometer.
- December 1, 2025. Maintenance visit on both systems. The homeowner answered "Great" to how the systems had been treating them.
- June 24, 2026. Maintenance visit. The tech made a charge adjustment on the 2-ton system and replaced a faulty surge protector.
- September 8, 2026. The 5-ton system's control was giving high humidity error codes after a sudden humidity jump that came after the Carrier thermostat updated to version 2.10. The control read 58 to 62% humidity while other monitors in the home read about 45%. The tech set the control's humidity offset to minus 10%. Afterward the control read 51% beside a reference hygrometer reading 50.2%. We believe the control's humidity sensor had been reading high.
What the homeowner said
In plain words. The homeowner wrote a 5-star Google review about three weeks after the install, covering the estimate, the duct changes, the crew, the city inspection and the two systems. The full review is below, word for word.
"I recently had Atlas AC provide and install two Carrier Infinity systems (5T and 2T) with gas furnaces and REME-LED Air purifiers. The work also included modifications to the existing ducting systems. I could not be more please with the quality and professionalism in the work. Starting with Bryce, who came to assess the existing system and provide alternative cost estimates for the Performance and Infinity series. It was perfectly aligned aligned with their web site pricing information; no surprises. The suggested duct modifications aligned with a recommendation ( not revealed) made five years during routine maintenance (different vendor). The installation led by Angel and his crew went quickly and flawlessly, with minimal disruption and tidy work habits. There were no issues found by the city inspector who commented on the "superior" installation quality. The system has been running about three weeks with no issues or call backs. Kudos to Kenneth and his excellent and informative web site. Would recommend that you spend time reviewing the wealth of information provided."
David B, Keller · 5-star Google review, June 21, 2025. Quoted word for word. Written about three weeks after the install; see the service visits above for later visits.
Related pages
- HVAC replacement cost guide
- Carrier Infinity cost guide
- Carrier Infinity guide
- Ductwork replacement cost guide
- Case study: sizing a 2,000 sq ft house with a heat load calculation
- Case study: 4-ton Carrier Infinity replacement in San Antonio
- Indoor air quality
- Carrier HVAC guide
- AC replacement
- Better Air Bundle
- Atlas AC Repair's Arlington office, serving the Dallas-Fort Worth area
- Atlas AC Repair AC installation in Dallas
- Atlas AC Repair AC installation in Fort Worth
- HVAC services from our Arlington office
- AC repair help from our Arlington office
- Heating help from our Arlington office
- All Atlas AC Repair case studies
Common questions
Why were a 5-ton and a 2-ton Carrier Infinity system installed?
The two systems were chosen from the equipment available. The 5-ton is the largest size Carrier makes in the Infinity line, so the downstairs system could not be upsized. The upstairs zone served by the 2-ton is only 895 sq ft, and a 3-ton Infinity there would have been oversized. The best option with the available equipment was a 5-ton downstairs and a 2-ton upstairs. The certified heat load calculation results showed 80,667 BTU/h of total cooling load for this 3,383 sq ft house (73,819 sensible and 6,848 latent). The report caps the sizing figure at a 0.85 sensible heat ratio, which gives 86,846 BTU/h, or 7.24 tons, and 2,895 CFM. We want to be straightforward about the numbers. The two AHRI ratings at 95°F add up to 80,200 BTU/h (56,000 plus 24,200), which sits right at the calculated cooling load of 80,667 BTU/h, and the load was calculated at a 105°F outdoor design, not 95°F. We do not claim the equipment exceeds the load at 105°F. The homeowner asked for the heat load to be run at a 105°F outdoor design temperature because their old systems could not keep up during the hottest part of summer, so this is a deliberately conservative design, stricter than a typical design day. We then selected the exact matched systems and verified their published performance data. The homeowner had two older systems, one of them down, and chose Carrier Infinity for better temperature and humidity control.
What size AC does a 3,400 sq ft home need?
It depends on the house. For this 3,383 sq ft Keller home, the certified heat load calculation results showed 80,667 BTU/h of total cooling load and 45,103 BTU/h of heating load. Glass was the largest cooling item at 30,295 BTU/h, 37.6% of the cooling load. These numbers depend on the glass, shade, insulation and air leakage, so they are not a rule for another home.
Does window glass affect the cooling load?
Yes. This house has 245 sq ft of east facing glass, 172 sq ft of west facing glass and 34 sq ft each on the north and south sides, with almost no shade. In the certified heat load calculation results glass is 30,295 BTU/h, 37.6% of the cooling load, the largest single item. The report's contractor alert says areas of a home may become uncomfortable when the hourly glass load exceeds the average, and suggests a variable comfort system and room or zone temperature controls.
Why did the 5-ton system get two new supply ducts and a new return?
The existing ducts on the 5-ton system were short of what a 5-ton system needs. Our supply airflow takeoff found the existing supply on the 5-ton system good for only about 3.75 tons, and our return takeoff found the existing return good for about 4.18 tons, short of what a 5-ton system needs. We added two 9 inch supply ducts and one 12 inch return, which raise the totals to about 4.87 tons of supply and 5.38 tons of return at 400 CFM per ton. The added ducts increase airflow, protect the system and support humidity control by maintaining adequate airflow. The added return increases available return-air capacity and helps the system maintain the airflow required for Comfort Mode operation.
Why Carrier Infinity?
The homeowner chose Carrier Infinity for better temperature and humidity control. Carrier describes the Infinity 80 furnace as a two-stage, variable-speed furnace with an IdealHumidity system, and the 26VNA1 air conditioner has a variable speed compressor with a 25 to 100% capacity range.
What furnaces were installed?
Two Carrier Infinity 80 furnaces: a 58TN0B110C21--20 on the 5-ton system and a 58TN0B070C14--12 on the 2-ton system. Carrier lists the 58TN0B as a two-stage, 80% AFUE, variable speed furnace.
What was the static pressure after the install?
Total external static pressure after the install was 0.49 in. W.C. on the 5-ton system and 0.57 in. W.C. on the 2-ton system. Carrier technical support and training recommends a static pressure range of 0.3 to 0.8 in. W.C. for the Infinity airflow test, and both readings are within that range. The 5-ton reading came after the two new 9 inch supplies and the new 12 inch return were added to increase airflow on that system.
How much did the two-system replacement cost?
$32,069.44 installed in Keller in May 2025, after two Carrier Cool Cash rebates of $1,700 each and a $655 discount. That covered a 5-ton and a 2-ton Carrier Infinity system with gas furnaces, an Infinity control on each, an LED REME HALO with a 4-inch Honeywell Filter Base with MERV 11 filter on each, three new duct runs on the 5-ton system, plenum manual dampers on the 2-ton system and surge protectors.
Did the install pass inspection?
Yes. The City of Keller final mechanical inspection passed on June 6, 2025.
How long did the install take?
Two days, May 29 and 30, 2025. The homeowner asked to start with the 2-ton system. Angel Garcia, Francisco Jimenez and Masiullah Amani installed it.
What indoor air quality equipment was added?
An RGF LED REME HALO with a 4-inch Honeywell Filter Base with MERV 11 filter on each system. The homeowner's review mentions the REME-LED air purifiers.
Has there been any problem since the install?
Yes, a few small items, all handled on service visits. Atlas visited for maintenance on December 1, 2025 and June 24, 2026. On June 24, 2026 the tech made a charge adjustment on the 2-ton system and replaced a faulty surge protector. On September 8, 2026 a tech visited after the 5-ton system's control showed a high humidity alert, with the control reading 58 to 62% while other monitors in the home read about 45%. The sudden humidity jump came after the Carrier thermostat updated to version 2.10. The tech changed the control's humidity offset by 10% and the reading came into line with a reference hygrometer. We believe the control's humidity sensor was reading high. The homeowner's review, written about three weeks after the install, reports no issues or call backs at that time.
Proof and sources
- NCI field duct sizing chart (flexible duct) for the per-duct airflow values; Atlas certified heat load calculation results, block load for the whole house (report 2146594); site survey (May 15, 2025) findings and photos; estimate and invoice; install photos and completion forms; Carrier registration (June 9, 2025); permit and inspection record; maintenance and service visit records.
- Carrier product pages and data: 26VNA1 product page and product data; 58TN0B (Infinity 80) product page and product data; CVAMA coil product page, product data and spec sheet; SYSTXCCITC01-C and control product data; RGF LED REME HALO.
- AHRI Certification Directory listings: AHRI 215701358 and AHRI 215690168.
- TDLR license search for TACLB00153401E, the license Atlas AC Repair operates under.
