A Taylorsville customer in a 1998-built two-story home contacted us about replacing their aging AC. The existing 15-year-old AC was past typical service life and showing capacity decline, and the customer experienced the classic two-story comfort imbalance — upstairs uncomfortably warm during summer despite the AC running constantly. They had previously been told by other contractors that this was “normal” for two-story homes and there was nothing to be done besides oversizing the AC.
This case study documents an AC installation paired with two-zone system integration that addressed both equipment replacement and comfort imbalance simultaneously.
Customer Situation
- Home: 1998-built Taylorsville two-story, approximately 2,400 sq ft (1,300 sq ft main level, 1,100 sq ft upper bedroom level)
- Existing equipment: 15-year-old Goodman R-410A AC, 3.5 ton; 96% AFUE furnace from 2018 (not being replaced)
- Symptom: AC running constantly during summer with upstairs 6–8°F warmer than thermostat (located on main level)
- Customer priorities: Address comfort imbalance, reasonable cost, avoid oversized equipment
Manual J Load Calculation
On-site Manual J with per-zone analysis:
- Total cooling load: 32,000 BTU/h (2.67 tons)
- Main level zone: 17,000 BTU/h
- Upper level zone: 15,000 BTU/h
Note: existing 3.5 ton AC was 31% oversized for actual load — common scenario producing short-cycling and poor dehumidification.
Equipment and Project Selection
Recommended approach: Two-stage 16 SEER2 AC paired with two-zone system
- Trane XR16 2.5 ton two-stage AC (right-sized vs. oversized 3.5 ton existing)
- Honeywell HZ322 two-zone control panel
- Zone dampers in supply trunk
- Bypass damper for excess airflow management
- Two Ecobee Smart thermostats
Project cost: $12,400
The existing 2018 furnace has variable-speed ECM blower which integrates properly with two-stage AC and zoning — no furnace modifications needed.
Installation
Duration: 1.5 days
Day 1: AC equipment installation
– R-410A recovery from old equipment per EPA
– Old condenser and evaporator coil removal
– New evaporator coil installation in furnace plenum
– New outdoor condenser placement on existing pad
– Refrigerant line work with nitrogen purge during brazing
– System evacuation to 425 microns
– R-410A charge by weight
Day 2 (half day): Zoning installation and commissioning
– Zone damper installation in supply trunk
– Bypass damper installation
– Zone control panel installation
– Thermostat installations (main level and upper level)
– Low-voltage wiring
– Complete commissioning
Commissioning Measurements
AC operation:
– Outdoor temperature: 87°F
– Suction pressure: 134 psi ✓
– Discharge pressure: 348 psi ✓
– Subcool: 10°F ✓
– Temperature differential: 19°F ✓
– Compressor amp draw stage 2: 10.8 amps ✓
Zoning verification:
– Main only call: zone 1 open, zone 2 closed, bypass partially open
– Upper only call: zone 2 open, zone 1 closed, bypass partially open
– Both zones: dampers open, bypass closed
– AC stage 1 operates during single-zone calls
– AC stage 2 engages during both-zone high-demand periods
Final Cost and Rebate Filing
Customer’s project cost: $12,400
Rebates filed:
– Federal 25C tax credit: $600
– Rocky Mountain Power Wattsmart AC rebate: $150
Effective net cost after incentives: $11,650
Customer Outcome
Summer performance comparison:
| Metric | Old AC | New AC + Zoning |
|---|---|---|
| Main level temperature | 74°F | 74°F |
| Upper level temperature | 80°F | 74°F |
| Indoor humidity | 58% | 48% |
| Average daily run time | 14 hours | 9 hours |
| Average summer electric bill | $245/mo | $185/mo |
Customer assessment: Comfort imbalance eliminated. Significant energy savings ($60/month average summer). Two-stage equipment quieter than old single-stage.
What This Case Study Demonstrates
- Two-story comfort imbalance solved by zoning, not equipment oversizing
- Right-sized 2.5 ton AC outperforms oversized 3.5 ton equipment
- Two-stage AC + zoning integration delivers efficiency AND comfort
- Existing variable-speed furnace compatible with zoning installation
- Significant energy savings ($60/month) plus comfort improvement
Considering Similar Project?
If you have two-story comfort imbalance in your Taylorsville home, call (385) 250-0687.
- Phone: (385) 250-0687
- Address: 4454 Manhattan Ct, West Valley City, UT 84120