Installed June 6, 2026 · Helotes, TX 78023
Short answer. We replaced only the upstairs system in this two system home in the Fossil Springs neighborhood of Helotes: a mismatched 4-ton condenser on a reused 3.5-ton coil at 0.8 in. w.c. static, and the house felt humid. Our variable-speed calculation for its 1,781 sq ft zone called for 2.71 tons, so we installed a 3-ton Daikin FIT upstairs unit; static dropped to 0.51 in. w.c.
Key facts
| Item | Details |
|---|---|
| Location | Helotes, TX 78023 |
| Systems | Two systems on separate ductwork. This job replaced the upstairs system only. |
| Home | 2,881 sq ft. The upstairs system's zone is 1,781 sq ft: the upstairs (1,381 sq ft) plus the first-floor primary bedroom (400 sq ft). Furnace and coil in the attic |
| Old system | Trane XR13 4-ton AC (made 2011), Trane XR80 80,000 BTU gas furnace (2011), reused 3.5-ton coil (2001). Still running |
| Total static pressure | 0.8 in. w.c. before; 0.51 in. w.c. after the install |
| Heat load result | Zone served by the Daikin FIT upstairs unit, 1,781 sq ft (certified heat load calculation): cooling 31,975 BTU/h (29,243 sensible, 2,731 latent). Variable-speed calculation at 0.9 SHR: 2.71 tons, 1,083 CFM. Single-stage calculation at 0.75 SHR: 3.25 tons, 1,300 CFM. Heating 15,908 BTU/h |
| New system | 3-ton Daikin FIT upstairs unit, variable-speed AC (R-32), Daikin DR80TC 80% AFUE gas furnace, Daikin cased coil, Daikin ONE touch thermostat |
| Rated efficiency | 16.6 SEER2, 9 EER2, 33,600 BTU/h (AHRI 215488551); furnace 80% AFUE |
| Installed price | $11,960.72, no financing; a $300 Daikin incentive covered 3 years of free Annual Performance Agreement visits |
| Install time | One day, June 6, 2026, installed by Israel and Delwis |
The problem: a humid house and a mismatched system
This is a two system home, and this job replaced only the upstairs system. The homeowner wanted better humidity control because the house felt humid. The upstairs system was still running, but it was not a matched system:
- Mismatched parts. In 2011 a prior contractor replaced the condenser and furnace but reused the indoor coil from 2001. That left a 4-ton condenser, an 80,000 BTU furnace and a 3.5-ton coil.
- High static pressure. The old system measured 0.80 in. w.c. total external static pressure. Along with the mismatched equipment and single-stage operation, this was one of several conditions we believed could be contributing to poor humidity control.
- Ducts sized for less than 4 tons. The existing supply and return ducts move about 1,300 to 1,340 CFM, which fits a 3-ton system, not 4 tons.
- A warmer primary bedroom. The primary bedroom ran warmer.
What the homeowner wanted, and the result
| What the homeowner wanted | What we did | Result |
|---|---|---|
| Better humidity control in a house that felt humid | Replaced the mismatched system with a matched 3-ton Daikin FIT upstairs unit, a variable-speed system | The homeowner tells us the new system helped solve the humidity problem |
| A Daikin FIT upstairs unit | Installed the Daikin FIT upstairs unit with a matching Daikin furnace, coil and thermostat | Installed in one day |
| A system that fits the existing ducts | Sized the upstairs system at 3 tons | Total static pressure dropped from 0.8 to 0.51 in. w.c., so no ductwork had to be added or modified |
| Fix the warmer primary bedroom | With static good and no ductwork needed, the homeowner chose to see whether the variable-speed system alone would even out the room | The homeowner tells us the primary bedroom is fixed after a few weeks on the variable-speed system |
Why longer run times even out rooms. A variable-speed system runs longer cycles at lower speed instead of short bursts at full capacity. Air keeps moving through every run for more of the hour, which helps even out hot and cold spots.
How the size was chosen
The home has two systems on separate ductwork, so we calculated the upstairs system's zone as its own block load with a certified heat load calculation (U 0.30 windows, 101°F outdoor and 72°F indoor summer design, on a slab). Window shading was entered as 40% in the certified heat load calculation, estimated from aerial and street level imagery showing mature trees on the south and west sides. The upstairs system serves the upstairs (1,381 sq ft) plus the first-floor primary bedroom (400 sq ft) through its ductwork, 1,781 sq ft in all. That zone's cooling load is 31,975 BTU/h (29,243 sensible, 2,731 latent, a calculated SHR of 0.91). The variable-speed calculation, at a 0.9 sensible heat ratio for variable-speed equipment, calls for 2.71 tons and 1,083 CFM of airflow. The single-stage calculation, at 0.75 SHR, calls for 3.25 tons and 1,300 CFM. The heating load is 15,908 BTU/h.
The home also has a single-stage downstairs unit on its own ductwork. It was installed by another company about a year ago, and the homeowner chose to leave it as is, so it was outside this job. An oversized single-stage system can run shorter cooling cycles and remove less moisture, so the downstairs system may still influence whole-house humidity.
Why 3 tons and not 4. The old condenser on this ductwork was 4 tons. The variable-speed calculation calls for 2.71 tons and 1,083 CFM. The AHRI rated full load airflow of the new system is 1,260 CFM, and the existing ducts move about 1,300 to 1,340 CFM, so they have room for the system's full airflow. A 3-ton variable-speed system fits the load and the existing ductwork. The AHRI rating of 33,600 BTU/h is measured at standard test conditions. The 2.71-ton figure is a sizing calculation for variable speed equipment at a 0.9 sensible heat ratio, and 3 tons is the closest nominal size. A variable speed system adjusts its output to the load instead of cycling on and off at a fixed capacity.
Supply and return airflow
The supply is a large ductboard trunk that tees off the supply plenum and runs about 15 feet in each direction. With large ductboard it is hard to predict static pressure from a calculated duct takeoff. Our supply airflow takeoff shows each of the two 14x8 trunks carries about 670 CFM, about 1,340 CFM total.
| Supply trunk | Count | CFM |
|---|---|---|
| 14x8 ductboard | 2 | 670 each |
| Total | about 1,340 CFM |
Our return takeoff shows a 16 inch return at about 1,000 CFM and a 10 inch return at about 300 CFM, about 1,300 CFM total.
| Return size | CFM per return | Count |
|---|---|---|
| 16 inch | 1,000 | 1 |
| 10 inch | 300 | 1 |
| Total | about 1,300 CFM |
Supply and return are balanced, and both fit a 3-ton system. After the install, total static pressure measured 0.51 in. w.c., down from 0.8 in. w.c. on the old system. It came down because we went with a smaller 3-ton unit matched to the existing ducts, and since static was good, no ductwork had to be added or modified.
What was installed
| Part | Old | New |
|---|---|---|
| Outdoor unit | Trane XR13 4TTR3048D1000AA, 4 tons, R-410A, made May 2011 | Daikin FIT DC6VSS3610, 3 tons, variable speed inverter, R-32 |
| Indoor coil | American Standard/Trane TXH041A4HPA2, 3.5 tons, made August 2001 | Daikin CHPEA3626C3 cased coil, 3 tons, factory EEV, R-32 |
| Furnace | Trane XR80 TUD1C080A9601AA, 80,000 BTU, 80% AFUE, 2011 | Daikin DR80TC0805CN, 80,000 BTU input, 80% AFUE, two stage, variable speed blower |
| Thermostat | Nest | Daikin ONE touch DTST-TOU-A |
The matched system is listed under AHRI 215488551: 16.6 SEER2, 9 EER2 and 33,600 BTU/h of cooling capacity, with a full load cooling airflow of 1,260 CFM. That rated airflow fits the existing ducts, which move about 1,300 to 1,340 CFM.
Daikin describes the FIT as running at slower speeds for longer periods, which pulls more moisture out of the air (Daikin FIT product page). The new furnace is the same 80,000 BTU size and 80% AFUE rating as the old one, so we are not claiming any gas savings.
Estimated cooling savings
The old Trane XR13 4TTR3048 is a 13 SEER unit; the "3" in the model is Trane's family SEER code for 13 (Trane XR13 product data). That is 12.35 SEER2 at RESNET's 0.95 conversion for ducted split systems (RESNET Addendum 71i). The new system is rated 16.6 SEER2 (AHRI 215488551). Helotes is in Bexar County, which the Texas TRM assigns to climate zone 3 (Texas TRM 13.0, Vol. 4, Appendix B), with 2,209 full load cooling hours (Texas TRM 13.0, Vol. 2, Table 29). We used CPS Energy's average residential revenue of 12.50 cents per kWh for its fiscal year ended January 31, 2026 (CPS Energy FY2026 Financial Fact Sheet). The old unit is figured at its actual 4 tons and the new one at 3 tons, so the estimate counts both the higher efficiency and the smaller system.
| System | Tons | SEER2 | kWh/yr |
|---|---|---|---|
| Old Trane XR13 | 4 | 12.35 | 8,586 |
| New Daikin FIT upstairs unit | 3 | 16.6 | 4,791 |
| Estimated savings | 3,795 kWh, about $474 a year |
Math: kWh = tons × 12,000 × cooling hours ÷ (SEER2 × 1,000). Old: 4 × 12,000 × 2,209 ÷ (12.35 × 1,000) = 8,586 kWh. New: 3 × 12,000 × 2,209 ÷ (16.6 × 1,000) = 4,791 kWh. Savings 3,795 kWh × $0.125 = $474. The old and new systems are figured at the same 2,209 cooling hours. These are estimates from rated values, not measured use.
How the install went
The crew installed the system in one day on June 6, 2026, from 7:43 AM to 4:49 PM. Installed by Israel and Delwis. The install crew was Daikin factory trained for the FIT. Atlas AC Repair operates under Texas ACR license TACLB00153401E, held by Timothy Carpenter. The system was pressure tested with nitrogen and evacuated to 313 microns before startup. The job passed the city inspection on June 9, 2026.
Cost and maintenance plan
The final installed price was $11,960.72 for the Daikin FIT upstairs unit, furnace, coil and thermostat, paid by card with no financing. A $300 Daikin incentive went toward 3 years of free Annual Performance Agreement maintenance visits for the homeowner. The first visit is scheduled for March 3, 2027.
Warranty
The Daikin registration covers 12 years on parts, 12 years of unit replacement and 20 years on the furnace heat exchanger.
Warranty visit
June 22, 2026. The thermostat showed error alerts. Our tech found a clogged drain tripping the float switch, blew out the drain and flushed it with vinegar and 3 gallons of water, and the system was running properly. It was covered at $0 to the homeowner.
What the homeowner said
"We have two complete HVAC systems. The first was fully replaced by another San Antonio HVAC company, and the experience was disappointing. The installation extended over several days, with different technicians arriving on multiple occasions. It then required more than a year of follow-up visits before the system was finally leak-free and no longer needed frequent refrigerant recharges. When it came time to replace our second 4-ton unit, I discovered several HVAC presentations featuring Kenneth from Atlas Air Conditioning Repair. He demonstrated a high level of expertise and professionalism. After reviewing multiple videos, I was pleased to learn that Atlas services Northwest San Antonio, so I scheduled an inspection and requested a quote. Their pricing was fair and transparent, and they delivered exactly as promised. Special recognition goes to Israel and Delwis, the installation technicians, who were professional, courteous, organized, and efficient. Their technical expertise and attention to detail were evident throughout the installation process. The entire process progressed efficiently from my initial call. There was no sales pressure and no excessive promotion of service plans or warranty packages. I called on May 25, Kenneth inspected the system the following morning to address concerns regarding attic space, and the matter was resolved promptly. Just 11 days later, we had a fully operational, state-of-the-art Daikin Fit 3-ton variable-speed air conditioner and gas furnace system. Atlas Air Conditioning Repair has set a high standard for customer service, professionalism, and operational efficiency in Texas."
John M, Helotes · 5-star Google review, June 6, 2026. Quoted word for word.
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Common questions
Why does my house feel humid even though the AC runs?
In this house the likely cause was a mismatched system and high static pressure. In 2011 a prior contractor replaced the condenser and furnace but reused the 2001 indoor coil, leaving a 4-ton condenser, an 80,000 BTU furnace and a 3.5-ton coil. The old system measured 0.80 in. w.c. total external static pressure. Along with the mismatched equipment and single-stage operation, this was one of several conditions we believed could be contributing to poor humidity control.
What is a mismatched AC system?
It is a system whose outdoor unit, furnace and indoor coil were not sized to work together. Here the condenser was a 4-ton Trane XR13 from 2011, the furnace an 80,000 BTU Trane XR80 from 2011, and the coil a 3.5-ton unit from 2001 that was reused when the other parts were replaced.
Why 3 tons when the whole house is 2,881 sq ft?
The house has two systems, and this job replaced only the upstairs one. The new 3-ton Daikin FIT upstairs unit serves a 1,781 sq ft zone: the upstairs (1,381 sq ft) plus the first-floor primary bedroom (400 sq ft). Our variable-speed calculation for that zone shows 2.71 tons and 1,083 CFM, and the existing ducts move about 1,300 to 1,340 CFM. The rest of the house is on a separate system.
Why replace only the upstairs system?
The upstairs system was the one with the problems. It was mismatched, with a 4-ton condenser and an 80,000 BTU furnace on a reused 3.5-ton coil from 2001, total static pressure measured 0.8 in. w.c., and the house felt humid. The home's single-stage downstairs unit is newer, installed by another company about a year ago, and the homeowner chose to leave it as is. An oversized single-stage system can run shorter cooling cycles and remove less moisture, so the downstairs system may still influence whole-house humidity.
How much airflow do the existing ducts carry?
Our supply airflow takeoff shows two 14x8 ductboard trunks at about 670 CFM each, about 1,340 CFM total. Our return takeoff shows a 16 inch return at about 1,000 CFM and a 10 inch return at about 300 CFM, about 1,300 CFM total.
Is ductboard harder to size than other duct?
Yes. With a large ductboard trunk it is hard to predict static pressure from a calculated duct takeoff, so the measured static pressure on the old system mattered when choosing the new size.
Did static pressure improve after the install?
Yes. Total static pressure measured 0.8 in. w.c. on the old system and 0.51 in. w.c. after the install. It came down because the smaller 3-ton system is matched to the existing ducts, and since static was good, no ductwork had to be added or modified.
Can a variable-speed system fix a room that runs warmer?
It did in this house. The primary bedroom ran warmer, and since static was good and no ductwork was needed, the homeowner chose to see whether the variable-speed system alone would fix it. Longer cycles at lower speed help even out hot and cold spots, and a few weeks after the install the homeowner told us the primary bedroom problem was fixed.
Did the new system fix the humidity?
The homeowner tells us the new system helped solve the humidity problem.
Does window glass affect the cooling load?
Yes. The zone the Daikin FIT upstairs unit serves has 129 sq ft of east facing glass and 90 sq ft of west facing glass, and glass makes up 38.3% of that zone's cooling load in the certified heat load calculation.
How efficient is the new system?
The matched Daikin system is rated 16.6 SEER2 and 9 EER2 with 33,600 BTU/h of cooling capacity (AHRI 215488551). The old Trane XR13 was a 13 SEER unit, about 12.35 SEER2.
How much could the new system save on cooling?
We estimate about 3,795 kWh a year, roughly $474, comparing the old 4-ton 12.35 SEER2 unit with the new 3-ton 16.6 SEER2 system over 2,209 cooling hours at 12.5 cents per kWh. This is an estimate from rated values, not measured use.
What size AC does an 1,800 sq ft zone need?
For this 1,781 sq ft upstairs zone in Helotes, our certified heat load calculation block load was 31,975 BTU/h. The variable speed calculation called for 2.71 tons and 1,083 CFM, so we installed a 3-ton Daikin FIT upstairs unit.
How much does a Daikin FIT upstairs unit cost?
This 3-ton Daikin FIT upstairs unit with a Daikin DR80TC gas furnace, cased coil and Daikin ONE touch thermostat cost $11,960.72 installed in Helotes in June 2026.
Will the new furnace save gas?
We are not claiming gas savings. The old Trane furnace and the new Daikin DR80TC are both 80,000 BTU furnaces rated 80% AFUE, so the furnace was a like for like swap.
How much did it cost?
The final installed price was $11,960.72 for the Daikin FIT upstairs unit, gas furnace, coil and thermostat, paid by card with no financing. A $300 Daikin incentive went toward 3 years of free Annual Performance Agreement maintenance visits for the homeowner.
How long did the install take?
One day. The crew worked from 7:43 AM to 4:49 PM on June 6, 2026.
Has there been any problem since the install?
On June 22, 2026 the thermostat showed error alerts. Our tech found a clogged drain tripping the float switch, blew out the drain and flushed it with vinegar and water, and the system was running properly. It was covered at $0 to the homeowner.
Proof and sources
- Atlas certified heat load calculation block load for the upstairs system's zone (variable-speed calculation and single-stage calculation); survey findings and photos; install photos; invoice; Daikin registration; warranty visit record.
- Daikin FIT DC6VS product page; Daikin DC6VS spec sheet; Daikin DR80TC product page; Daikin DR80TC spec sheet; Daikin CHPEA3626C3 data; Daikin ONE touch spec sheet.
- AHRI 215488551, AHRI Directory listing.
- Trane XR13 product data; RESNET Addendum 71i; Texas TRM 13.0 Vol. 2; Texas TRM 13.0 Vol. 4; CPS Energy FY2026 Financial Fact Sheet.
- TDLR license search for TACLB00153401E, the license Atlas AC Repair operates under.
About the author
Kenneth Carpenter is Co-Owner of Atlas AC Repair. He writes the content on this site and created the Atlas AC YouTube channel. More about Kenneth Carpenter
