A West Valley City customer building a new single-family home in a newer south-side subdivision engaged us for the heating system installation as the home approached completion. Unlike retrofit installations where existing equipment and ductwork constrain decisions, new-build installations let us design the complete heating system from scratch — proper Manual J load calculation drives equipment sizing, ductwork is fabricated to match the equipment and home layout, venting is routed for proper operation rather than working around existing chimneys, and commissioning happens before drywall closes everything in.
This case study documents the new-construction furnace installation process from initial design through final commissioning on a typical new-build West Valley City home.
Customer Situation
- Home: New construction, single-story home, approximately 2,200 sq ft, south-side West Valley City subdivision
- Construction stage: Framing complete, plumbing and electrical rough-in done, HVAC rough-in ready to begin
- Customer priorities: High-efficiency equipment, smart thermostat integration, AC capability (separate AC installation following furnace), proper sizing rather than oversizing
- Builder coordination: Required coordination with builder for venting penetrations, electrical connections, and inspection scheduling
Manual J Load Calculation
On-site load calculation performed during framing inspection:
- Conditioned area: 2,200 sq ft single-story
- Insulation: R-21 walls, R-49 attic (new construction code minimum, verified during walkthrough)
- Windows: Vinyl double-pane low-E, 285 sq ft total glazing
- Air sealing: Estimated 2.5 ACH50 based on construction observation (verified later by blower door test)
- Orientation: Long axis north-south, primary glazing east and south
- Salt Lake design conditions: 14°F outdoor / 70°F indoor heating; 96°F outdoor / 75°F indoor cooling
Manual J results:
– Heating load: 38,500 BTU/h
– Cooling load: 27,200 BTU/h (2.3 tons)
For comparison: many contractors would size a 2,200 sq ft home at 75,000–80,000 BTU/h furnace using rule-of-thumb sizing. Proper Manual J for this well-insulated new construction calls for 40,000 BTU/h — nearly half the rule-of-thumb size. Oversized furnaces short-cycle, distribute heat unevenly, and produce comfort complaints in new construction where actual loads are much smaller than older homes.
Equipment Selection
Discussion with customer covered three tiers:
Option 1: 96% AFUE single-stage (Goodman GMVC960403BN, 40,000 BTU input) — $5,800 installed
Option 2: 96% AFUE two-stage (Trane S9X2, 40,000 BTU input) — $7,500 installed
Option 3: 97% AFUE modulating (Trane S9V2-VS, 40,000 BTU input) — $9,800 installed
The customer selected Option 2 (Trane S9X2 two-stage). Justified by:
– Better comfort than single-stage through extended low-fire operation
– Federal 25C tax credit ($600)
– Dominion Energy Therm-Wise rebate eligibility (~$150)
– Pairs well with later two-stage AC for matched-system operation
– Modulating tier (Option 3) didn’t justify the premium for this customer’s situation
Ductwork Design and Installation
New construction allows proper ductwork design rather than working around existing constraints:
- Manual D duct calculations performed to match Manual J load and equipment specifications
- Supply trunk: 16×8 main supply, reducing to 14×8 then 12×8 as it serves bedrooms
- Return air: 20×14 return at central hallway with filter rack
- Branch ducts: Sized per Manual D for proper airflow to each register
- Register placement: Coordinated with builder for proper floor placement away from exterior walls
- Insulation: R-8 duct wrap on all supply and return ducts in unconditioned spaces (attic)
- Sealing: Mastic sealing on all joints (no duct tape on permanent installations)
Ductwork installation completed before insulation phase, allowing inspection access.
Furnace and Venting Installation
Installation duration: 2 days (Day 1: ductwork; Day 2: equipment and commissioning)
Crew: Travis Hollings (lead installer), Mike Reyes (technician)
Equipment installed:
- Trane S9X2 furnace, 40,000 BTU input, two-stage, 96% AFUE
- PVC venting (Schedule 40, 2″ diameter) per manufacturer specifications
- Combustion air intake routed to same termination as exhaust (concentric)
- Condensate drainage with neutralizer to existing floor drain
- New 80% AFUE compatible gas line connection
- New 120V electrical from builder-provided dedicated circuit
- Smart thermostat (Ecobee Smart) with proper two-stage configuration
Venting specifics:
- Termination location: Side wall, 24″ above grade, 4 ft minimum from operable windows per code
- Slope: 1/4″ per foot back to furnace for proper condensate drainage
- Joints: Solvent-welded per manufacturer specification, supported every 4 ft
- Penetration: Through 2×6 stud bay, fire-stopping at exterior penetration
Commissioning Measurements
After equipment startup with 15 minutes of operation:
Combustion analysis (altitude-corrected for 4,300 ft elevation):
– CO ppm air-free: 8 ppm ✓ (target <100, ideally <50)
– O2: 7.2% ✓ (target 6–9%)
– Flue gas temperature: 138°F (proper for condensing operation)
– Combustion efficiency: 95.8% ✓
– Draft pressure: -0.04″ wc ✓
Gas pressure (altitude-corrected for natural gas):
– Inlet pressure: 7.2″ wc (target 7″ wc) ✓
– Manifold pressure low-fire: 1.4″ wc (manufacturer specification at altitude) ✓
– Manifold pressure high-fire: 3.5″ wc (manufacturer specification at altitude) ✓
Equipment operation:
– Temperature rise across heat exchanger: 42°F (target 35–65°F) ✓
– Static pressure: 0.38″ wc (within manufacturer 0.5″ wc max) ✓
– Blower amp draw: 5.4 amps (nameplate 7.5 amps) ✓
– Inducer amp draw: 0.9 amps (nameplate 1.2 amps) ✓
– Flame sensor microamps: 7.2 µA ✓ (healthy 4–10 µA)
– HSI resistance: 52 ohms (within 40–80 ohm range) ✓
Safety verification:
– Pressure switch operation: confirmed
– Limit switch operation: confirmed
– Rollout switch operation: confirmed
– Indoor CO measurement: 0 ppm ✓
Two-stage operation confirmed — low fire activates first on thermostat call, high fire engages if low fire can’t satisfy within 20 minutes. Smart thermostat configured for two-stage equipment with proper recovery rate settings.
Inspection
City of West Valley City mechanical inspection passed on first visit. Inspector specifically noted clean PVC venting installation and proper combustion air provisions. Pass certificate filed with builder for certificate of occupancy.
Final Cost and Rebate Filing
Customer’s cost:
– Equipment and installation: $7,500
– New construction ductwork: $4,200
– Total: $11,700
Rebates filed on customer’s behalf:
– Federal 25C tax credit: $600 (customer claims on tax filing)
– Dominion Energy Therm-Wise: $150 (mailed to customer in 4 weeks)
Effective net cost after incentives: $10,950
Customer Outcome
One-year follow-up:
- Heating bills averaged $42/month during winter heating months — significantly lower than customer’s previous rental that was similar size
- Indoor temperature maintained within 1°F of setpoint throughout home
- Two-stage operation produced quiet, comfortable heating
- Smart thermostat reduced unnecessary cycling through learned patterns
- AC installation completed by us 6 months later as separate matched project
Annual maintenance plan enrolled — covers both furnace and AC tune-ups.
What This Case Study Demonstrates
- Manual J sizing for new construction — well-insulated new homes need much smaller heating equipment than rule-of-thumb sizing suggests; oversizing causes problems
- Manual D ductwork design — proper duct sizing matched to equipment and load delivers comfort and efficiency that oversized or improperly designed ducts can’t
- New construction coordination — proper coordination with builder for venting, electrical, and inspection scheduling prevents delays and rework
- Altitude-corrected commissioning — Salt Lake’s 4,300 ft elevation requires specific manifold pressure settings, not nameplate defaults
- Documented commissioning — written measurements provide baseline for future service and warranty documentation
- Rebate filing — $750 in incentives reduced net cost by 6%
Considering a Similar Project?
If you’re building a new home in West Valley City or considering HVAC installation, contact us or call (385) 250-0687. We coordinate with builders, perform proper Manual J and Manual D calculations, install equipment with documented commissioning, and file applicable rebates and tax credits.
- Phone: (385) 250-0687
- Address: 4454 Manhattan Ct, West Valley City, UT 84120