Craig Woods System Replacement: 1956 Ranch Matched-System with Zoning

Case study summary: 1956 mid-century ranch home in Kirkwood’s Craig Woods neighborhood; complete matched-system replacement of 2003-vintage AC and 1998-vintage furnace with new Carrier Performance Series 3-ton variable-capacity AC paired with 100,000 BTU 96% AFUE modulating furnace and 2-zone retrofit addition addressing chronic upstairs-downstairs temperature variation; total project cost $17,600; completed in 2 days during March 2026. Outcome: 28% reduction in annual heating gas consumption; resolution of long-standing zone comfort complaints; customer satisfaction high with system performance and zoning flexibility.

The Home

• Built: 1956
• Style: Mid-century ranch
• Location: Craig Woods neighborhood, Kirkwood, MO 63122
• Size: 1,840 sf main level plus 1,400 sf finished basement (3,240 sf total conditioned)
• Construction: Brick veneer over wood frame; original drywall throughout (no plaster); aluminum-frame windows replaced with vinyl windows in 2015; original hardwood floors
• Existing heating: Bryant Plus 90 (80,000 BTU/hr 90% AFUE single-stage forced-air gas furnace from 1998, 28 years old at time of replacement)
• Existing cooling: Carrier Comfort Series 2.5-ton AC from 2003 (23 years old, R-22 refrigerant)
• Ductwork: Original 1956 galvanized steel rectangular ductwork in basement; serviceable condition with some joint leakage; serves entire home through floor and ceiling registers
• Existing thermostat: single thermostat in main floor hallway controlling both upper level and basement

The Situation

Customer contacted us in February 2026 with two issues: AC was past end of service life and would need replacement before summer 2026, and chronic complaint about basement being substantially colder than upstairs in winter (often 8-10°F cooler) and basement being more humid than upstairs in summer. Diagnostic assessment:

• AC equipment status: 23 years old, well past typical 15-20 year service life; R-22 refrigerant phased down with limited supply and high cost for any refrigerant work; single capacitor failure earlier in 2025 was repaired but signaled approaching end of life
• Furnace equipment status: 28 years old, past typical 18-25 year service life; recent hot surface igniter replacement (2024) and inducer motor replacement (2023) indicated component-by-component end-of-life pattern
• Comfort complaints root cause: single-thermostat system with basement and main floor sharing distribution but having very different loads (basement gains heat from upstairs but receives less direct heating supply; basement loses humidity to upstairs but receives less direct cooling supply)
• Ductwork condition: serviceable with joint leakage; supply registers in basement adequate for direct-supply but distribution didn’t match load requirements

Replacement recommendation: matched-system replacement plus 2-zone retrofit addressing the comfort complaints. Customer priorities: resolve the upstairs-downstairs temperature variation that had been ongoing concern since they purchased home in 2018; modernize equipment to current efficiency standards; maintain reasonable budget while addressing the issues.

The Equipment Selection

Carrier Performance Series 3-Ton Variable-Capacity AC (Selected)

• SEER2: 17.0
• Capacity: 3 tons (36,000 BTU/hr); upgrade from previous 2.5 tons based on Manual J load calculation showing 35,800 BTU/hr design cooling load when basement is included as conditioned space (previous system was sized for main-floor-only load)
• Refrigerant: R-454B per January 2025 AIM Act phase-down
• Technology: Two-stage scroll compressor providing variable-capacity operation between 70% and 100% of rated capacity
• Warranty: 10-year parts, 10-year unit replacement
• Why selected: Carrier Performance Series provides variable-capacity benefits at mid-tier pricing (vs. Carrier Infinity premium tier); two-stage operation provides longer cycles improving distribution to basement; mid-tier equipment matches customer’s expressed budget priorities

Carrier Performance 96 Modulating Furnace (Selected)

• AFUE: 96%
• Capacity: 100,000 BTU/hr input (upgrade from previous 80,000 BTU based on Manual J calculation showing 86,400 BTU/hr design heating load with basement included)
• Technology: Modulating gas valve with variable-speed ECM blower; 40-100% modulation range
• Warranty: 10-year parts, 20-year heat exchanger
• Why selected: Matched-system equipment with the AC; modulating operation provides long-cycle heating distribution beneficial for basement zone

EWC Ultra-Zone 2-Zone Retrofit

• Configuration: 2 zones with upper level (1,840 sf) as Zone 1 and basement (1,400 sf) as Zone 2
• Dampers: 2 motorized dampers added to existing supply trunks at basement ceiling level
• Thermostats: 2 wireless smart thermostats (Honeywell T10 Pro) – one in main floor hallway, one in basement family room
• Zone control panel: EWC Ultra-Zone UZC-2 controller in basement mechanical room

Alternative Equipment Considered

• Carrier Infinity 26 (premium variable-capacity): Excellent equipment but premium pricing exceeded customer budget by $4,000-$5,000
• Trane XR16 (single-stage): Lower cost than Performance Series but single-stage operation doesn’t provide distribution benefits for basement
• Goodman GSX16 (single-stage budget equipment): Budget option; selected against based on customer preference for higher-tier brand and longer warranty
• Heat pump alternatives (Carrier 25VNA, Trane XV20i): Considered but customer preferred natural gas heating for cost familiarity and existing comfort expectations

The Project Scope

Pre-Installation

• Kirkwood Public Works permit: Pulled within 4 business days of quote acceptance
• Equipment ordering: 9 business days for Carrier Performance Series equipment and EWC zoning components
• Installation scheduling: March 2026 in pre-cooling-season scheduling window with mild weather allowing flexible timing

Installation Day 1 (March 16, 2026)

• Existing equipment isolation and shutdown
• Refrigerant recovery from existing R-22 system (EPA Section 608 compliant recovery to certified recovery cylinders for proper disposal)
• Outdoor unit removal and pad preparation
• Indoor air handler and furnace removal
• Existing ductwork condition assessment: confirmed serviceable condition with some sealing improvements appropriate during installation
• Ductwork sealing scope: existing supply trunks sealed at joints with mastic; estimated 12-18% leakage reduction
• New outdoor unit placement: Carrier Performance Series condenser on existing concrete pad (verified adequate for new equipment weight)
• New indoor coil installation in furnace plenum
• Refrigerant line set: existing line set retained (verified adequate condition and sizing for new equipment); flushed and dried before connection
• Furnace placement and connection: gas line, electrical, PVC venting through basement wall to side-yard termination (replacing previous metal venting)
• Condensate management: condensate routed to existing basement floor drain (no condensate pump needed)
• End of Day 1: equipment installed but not commissioned, zoning system not yet installed

Installation Day 2 (March 17, 2026)

• 2-zone retrofit installation: motorized dampers installed on supply trunks at basement ceiling level
• Zone control panel installation in basement mechanical room
• Smart thermostat installation: Honeywell T10 Pro in main floor hallway (replacing existing thermostat at same location) and Honeywell T10 Pro in basement family room (new location requiring low-voltage wire pull)
• Refrigerant system commissioning: nitrogen pressure test, vacuum pull to 500 microns or below, refrigerant charge per equipment specifications, subcooling and superheat verification
• Furnace commissioning: combustion analysis with Bacharach Fyrite Insight Plus (CO 18 ppm air-free, well under 100 ppm safety threshold; CO2 8.8%; O2 6.5%), modulating gas valve calibration verified across 40-100% capacity range
• Zone configuration: damper operation verified, thermostat-equipment communication verified, zone scheduling configured per customer preferences (basement zone allowed to drift slightly cooler in heating mode, slightly warmer in cooling mode reducing energy usage when basement unoccupied)
• System performance verification: heating mode operation with both zones at setpoint verified; cooling mode operation deferred to summer (system commissioned but cooling mode performance verification scheduled for first cooling-season service visit)
• Customer walk-through: explained operation, smart thermostat configuration, zone scheduling, maintenance schedule, warranty registration
• Final cleanup and customer sign-off

Inspection (March 20, 2026)

• Kirkwood Public Works inspector visit 3 business days after installation
• Combustion analysis verified to inspector with Bacharach printout
• Installation passed inspection without modifications

The Pricing

• Carrier Performance Series 3-ton AC condenser and coil: $4,400 equipment cost
• Carrier Performance 96 100,000 BTU modulating furnace: $3,400 equipment cost
• EWC Ultra-Zone 2-zone retrofit (dampers, panel, wiring): $1,400 equipment
• 2x Honeywell T10 Pro smart thermostats: $480
• Installation labor (2 days, 2 technicians): $4,200
• Ductwork sealing scope: $580
• PVC venting replacement: $340
• Refrigerant work (R-22 recovery, R-454B charge): $480
• Permit fee through Kirkwood Public Works: $180
• Old equipment removal and disposal: $260
• Bacharach combustion analysis and commissioning: $240
• Low-voltage wiring for basement thermostat: $180
• Miscellaneous fittings, hardware, and consumables: $280
• Concrete pad assessment and minor leveling: $80
• Total project cost: $17,600

This pricing fell within our standard range for similar mid-century home matched-system replacements with zoning addition ($14,000–$20,000 for 3-ton + 100,000 BTU mid-tier equipment with 2-zone retrofit).

The Outcome

Comfort Resolution

• Upstairs-downstairs temperature variation: Resolved. With separate thermostats for upstairs and basement zones, each level maintains independent setpoint regardless of conditions at other level
• Basement winter comfort: Customer reports basement family room is consistently comfortable at desired 68°F setpoint, where previously it had been 60-62°F when upstairs was 70°F
• Basement summer humidity: Improved substantially with longer AC cycles from two-stage compressor providing better dehumidification
• Zoning flexibility: Customer using basement zone schedule to reduce heating/cooling output when basement unoccupied, reducing energy usage

Energy Performance

• First-winter gas consumption (estimated based on first 2.5 months of data): tracking 28% reduction vs. previous winter
• Annual gas savings projection: approximately $640-$840 reduction in annual heating costs at $1.20/therm
• Simple payback on installation: approximately 8-12 years on energy savings; faster when comfort improvement is valued separately

Customer Feedback

Customer reported high satisfaction with several aspects: the upstairs-downstairs temperature variation that had been ongoing concern for 8 years was fully resolved; system operation is noticeably quieter than previous equipment (two-stage compressor and modulating furnace both run at lower output most of the time); zone control flexibility provides energy savings during typical work-day hours when basement is unoccupied; smart thermostat integration allows remote control and scheduling that previous single thermostat couldn’t provide.

Ongoing Service

Customer enrolled in our maintenance plan covering the new matched system; first cooling-season service visit scheduled for May 2026 including cooling mode performance verification that was deferred from initial installation.

Frequently Asked Questions

Why did you recommend upsizing from 2.5 to 3 tons of AC?

Manual J load calculation showed the home’s design cooling load at 35,800 BTU/hr when the basement is included as conditioned space — between the 2.5-ton (30,000 BTU/hr) and 3-ton (36,000 BTU/hr) standard equipment capacities. The previous 2.5-ton equipment was sized for main-floor-only load calculation (treating basement as unconditioned space), which was a common practice in 2003 when the previous equipment was installed but didn’t reflect the home’s actual usage pattern with finished basement family room being regularly occupied. Sizing implications: undersized AC would have struggled to maintain basement setpoint during peak cooling demand (extended run times approaching 100% duty cycle without reaching setpoint); two-stage compressor operation would have spent most time at 100% capacity (eliminating efficiency benefit of variable-capacity equipment); dehumidification would have remained inadequate during high-humidity conditions. 3-ton sizing provides appropriate margin: equipment can operate at lower stage during typical conditions (more efficient and quieter); reaches setpoint reliably during peak demand without 100% duty cycle; provides better dehumidification through longer cycles at lower capacity. We don’t oversize unnecessarily because oversized AC creates its own problems (short cycling, inadequate dehumidification, reduced equipment life), but Manual J calculation justified the modest capacity increase for this home’s actual usage pattern.

Was the 2-zone retrofit worth $1,880 in additional equipment + labor cost?

For this customer with 8 years of ongoing comfort complaints about the temperature variation, yes — clearly the right addition. Zoning resolved the specific issue that drove the customer’s broader replacement decision (they wouldn’t have done a major system replacement just for efficiency; the comfort problem was the trigger). For customers with similar mid-century homes but without the comfort complaints, zoning addition becomes a judgment call: $1,800-$2,800 added to project cost; benefits include independent setpoint control by area, energy savings from operating only occupied zones, better matching of equipment output to actual load distribution, improved comfort during transitional seasons when different areas of home have different solar gains and occupancy. Zoning isn’t necessary for many homes — single-zone operation with appropriate Manual J sizing and good distribution provides adequate comfort. Zoning becomes valuable when: home has substantially different load characteristics between areas (finished basement, large attic conversion, exposure differences like all-glass sunroom), occupancy patterns differ between areas (basement family room used only evenings vs. main floor used all day), customer is sensitive to comfort variation between areas. For this customer with finished basement family room being regularly used and temperature variation being clear ongoing complaint, the $1,880 zoning premium was clearly worthwhile.

Why R-454B instead of R-410A for the new AC?

The January 2025 AIM Act phase-down requires new residential AC equipment to use refrigerants with GWP (Global Warming Potential) under 700. R-410A has GWP of 2,088 — well over the limit, so it can no longer be used in new equipment. R-454B has GWP of 466 — well under the limit, so it’s the primary replacement refrigerant for residential equipment. From a homeowner perspective, R-454B works identically to R-410A: same operating pressures, similar cooling performance, similar service procedures, no impact on AC operation or maintenance. From a service contractor perspective, R-454B is slightly different: A2L mildly flammable classification (requires updated installation practices for sparks and ignition sources during refrigerant work, but not a safety issue once installed); POE oil compatibility same as R-410A; long-term cost expected to be lower than R-410A as production scales up. For this customer’s previous R-22 system, the refrigerant transition is essentially complete: R-22 was phased out in 2020, R-410A is being phased down starting 2025, R-454B is the current standard. Existing R-22 systems can continue to be serviced (with limited and expensive refrigerant supply) or replaced (which is what happened here). The refrigerant transition wasn’t a driving factor in this customer’s replacement decision — equipment end-of-life was the driver — but it did affect equipment selection (had to be R-454B compliant equipment) and slightly increased refrigerant work scope ($80-$120 extra vs R-410A installation).

How long does it take to recoup the cost of a 96% AFUE furnace vs lower efficiency?

Depends on specific equipment compared and energy costs. For this customer’s situation: 96% AFUE Carrier Performance modulating furnace ($3,400 equipment) vs hypothetical 80% AFUE alternative ($2,400 equipment, $1,000 less); efficiency difference 16 percentage points; annual gas consumption (estimated 1,200-1,500 therms typical for this home’s heating load); annual gas savings from 96% vs 80% AFUE: approximately $230-$290 per year at $1.20/therm; simple payback on $1,000 efficiency premium: approximately 3.5-4.3 years. For 92% vs 96% AFUE comparison (typical decision in current market since 80% AFUE equipment less common): efficiency difference 4 percentage points; annual savings approximately $60-$75; cost premium $500-$800; simple payback 8-13 years. For modulating vs single-stage 96% AFUE comparison: efficiency similar; benefits of modulating beyond pure efficiency include comfort distribution, quieter operation, and matched-system integration with two-stage AC. For this customer’s actual situation (modulating 96% AFUE selected for matched-system benefit and comfort distribution, not just efficiency), the efficiency payback was a secondary consideration. Customer chose modulating equipment primarily for the long-cycle distribution benefit serving the basement zone with separate thermostat control, with efficiency being additional benefit rather than primary justification. We provide explicit efficiency cost-benefit framing during quote development so customers can make informed decisions weighting their priorities.

What happens to my old R-22 refrigerant during replacement?

Recovered per EPA Section 608 requirements — recovery is a regulatory requirement, not optional, for any HVAC technician working on refrigerant systems. Our certified technicians (James and our service team) hold EPA Section 608 Universal certification (#608U-2014-385721 in James’s case, with each technician holding individual certification) which authorizes recovery, recycling, and disposal of refrigerants. Recovery process: refrigerant is recovered from the existing system into certified DOT-compliant recovery cylinders using EPA-certified recovery equipment; recovery cylinders are sealed, labeled with refrigerant type and date, and returned to refrigerant reclamation facility (in our case, Hudson Technologies in Pearl River NY for R-22 reclamation); reclamation facility processes recovered refrigerant for resale to service contractors needing R-22 for existing equipment service (the supply of R-22 for service work comes entirely from reclamation now that production has ceased); proper handling means R-22 doesn’t enter the atmosphere where it would contribute to ozone layer depletion. This recovery process is included in our installation pricing — the customer doesn’t see a separate line item for “refrigerant recovery” but the $480 refrigerant work line item covers both R-22 recovery and R-454B charge for the new system. Documentation: we provide recovery documentation including recovery cylinder serial number and reclamation facility receipt to customers who want it for environmental records; this isn’t typically requested by residential customers but is sometimes valued for environmentally-conscious customers wanting verification of proper disposal.

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Contact Purisync Heating and Air

For your mid-century home matched-system replacement or zoning retrofit, contact our 325 N Kirkwood Road office at (314) 338-5111. Initial consultation includes Manual J load calculation, ductwork condition assessment, equipment options across multiple manufacturers and efficiency tiers, zoning analysis for homes with comfort distribution issues, and written quote with itemized pricing.

• Emergency Line (24/7): (314) 338-5111
• Address: 325 N Kirkwood Rd #245, Kirkwood, MO 63122
• Email: info@purisyncheatingairconditioning.xyz
• St. Louis County Mechanical Contractor License: #MC-2014-08439-STL
• Kirkwood Business Registration: #BL-2014-1187
• EPA Section 608 Universal: #608U-2014-385721

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