Case Study: Commercial Rooftop Unit Replacement in West Hartford
This case study documents a 2024 commercial rooftop HVAC replacement for a 4,200 square foot retail/professional building in West Hartford's Park Road commercial corridor. The original 1997 rooftop unit reached end-of-life; replacement coordinated with tenant operations to minimize business disruption while meeting current commercial efficiency standards. The project demonstrates commercial HVAC project management distinct from residential service patterns.
Customer Situation
The building owner manages a small mixed-use property with 3 commercial tenants (insurance agency, accounting firm, and specialty retail store) under separate leases:
- Existing equipment: 1997 Carrier 48TJ012 packaged rooftop unit (10-ton nominal cooling, gas heating); 27 years old; operating but with substantial efficiency degradation and increasing repair frequency.
- Service history: Annual maintenance via previous contractor; 2023 service identified failing economizer damper, deteriorating heat exchanger sections, R-22 refrigerant at low pressure indicating leakage.
- Tenant impact considerations: Insurance and accounting tenants require business-hours operation; retail tenant has more flexible Tuesday-Sunday operations with Monday closure providing scheduling opportunity.
- Operating cost: Building owner reported 2023 cooling-season electrical cost of $4,800; estimated 30-40% above what modern equivalent equipment would consume.
- Tenant air quality concerns: Tenants reported uneven temperature distribution, occasional odors, dust issues; suggested system reaching service limits.
Diagnostic Visit and Recommendation
May 2024 commercial diagnostic visit assessed equipment and identified replacement requirements:
- Equipment condition: 1997 packaged unit at 27 years; well past commercial HVAC typical service life (15-20 years); heat exchanger inspection showed visible crack development requiring shutdown; refrigerant pressures indicated 40-60% capacity loss vs. original specifications.
- Sizing analysis: Manual N commercial load calculation showed actual building cooling load 75,000 BTU/hr (6.25 tons); original 10-ton unit oversized by 60%; oversizing contributing to short-cycling, dehumidification problems, and inefficient operation.
- Refrigerant transition: R-22 refrigerant phase-out completed January 2020; service for existing R-22 equipment increasingly expensive and parts limited; replacement equipment uses R-454B (new commercial refrigerant standard).
- Building structural assessment: Existing rooftop curb and structural support adequate for replacement equipment; no roof modifications required.
- Electrical service: Existing 480V 3-phase service adequate for replacement equipment; disconnect and wiring sized appropriately.
- Ductwork: Existing roof-to-zone ductwork assessed; some sections required cleaning and sealing; insulation generally adequate.
Solution Scope and Equipment Selection
Equipment Selected
- Carrier 48HC-D08-A-90-A 7.5-ton high-efficiency packaged rooftop unit: 90,000 BTU/hr cooling capacity (7.5-ton), 175,000 BTU/hr gas heating; 14.0 SEER2 / 11.5 EER / 80% AFUE; integrated economizer with outdoor air sensor and indoor air quality controls. Selected for: capacity right-sized to actual load (75,000 BTU/hr need + reasonable margin), high efficiency for commercial, Carrier brand with established service support, R-454B refrigerant.
- Integrated economizer: Outdoor air damper modulating between minimum ventilation and 100% outdoor air based on temperature and enthalpy conditions; provides free cooling when outdoor conditions favorable; required by Connecticut commercial code for new installations.
- Demand control ventilation: CO2 sensor integration adjusting outdoor air based on actual occupancy; reduces ventilation during unoccupied periods saving substantial energy.
- Programmable commercial thermostat: Carrier ComfortLink i thermostat; supports tenant zoning; integrated with building management capability; remote monitoring access for building owner.
- Building automation integration: System communicates with building automation platform; provides remote diagnostics; alerts for fault conditions; performance monitoring.
- Connectivity: Cellular communication module for remote access; eliminates dependence on building Wi-Fi for monitoring.
Installation Process
Project completed July 2024 over 2 working days (single weekend) to minimize tenant disruption:
Saturday (Day 1) — Removal and Setup
- Crane mobilization at 7:00 AM; coordinated with West Hartford traffic and parking; crane positioning in parking lot adjacent to building.
- Old equipment removal: roof access via crane; refrigerant recovery per EPA Section 608 requirements; electrical disconnection; unit lifted off curb.
- Curb assessment: existing roof curb inspected; gasket replacement and curb seal preparation for new equipment.
- New equipment placement: replacement unit lifted onto curb; sealed with weatherproof curb gasket; electrical connections per current Connecticut code.
- Refrigerant lineset connections; system pressure testing; initial commissioning preparation.
Sunday (Day 2) — Commissioning and Testing
- System fill and pressure verification.
- Commissioning per ASHRAE Standard 90.1 commercial requirements: airflow verification at all supply diffusers; static pressure measurement; refrigerant superheat and subcool verification; combustion analysis for gas heating; economizer operation verification across outdoor temperature ranges.
- Demand control ventilation calibration: CO2 sensor verification; ventilation minimum and maximum settings configured per tenant occupancy patterns.
- Building automation integration: connectivity verification; alert configuration; remote monitoring access provisioning for building owner.
- Tenant walkthrough Sunday afternoon: tenants notified of completion; thermostat operation explanation; comfort verification during initial Monday morning startup.
Monday Morning Verification
- Building startup before tenant arrival (6:00 AM); system verified operating across all zones.
- Tenant verification: insurance and accounting tenants confirmed comfort during 9:00 AM startup; retail tenant verified during 10:00 AM opening.
- 30-day comfort guarantee: any issues during first 30 days addressed under installation warranty.
Results
System operating since July 2024. Documented results:
- Cooling season 2024 electrical cost: $3,180 (vs. $4,800 in 2023) — 34% reduction; partially attributable to weather differences but primarily equipment efficiency improvement.
- Tenant comfort: No complaints since installation; tenants report substantial improvement vs. previous equipment's inconsistent operation.
- Heating performance: First winter (2024-2025) gas heating operated reliably; no comfort issues; gas consumption reduced approximately 15% vs. previous winter (right-sized equipment plus improved efficiency).
- Demand control ventilation impact: Tracking data shows ventilation reduced during low-occupancy periods (early morning, late evening, weekend retail off-hours); estimated $800-$1,200 annual savings from DCV alone.
- Remote monitoring value: Building owner receives equipment alerts via app; two minor service items identified proactively during first year (filter replacement timing, condensate drain inspection) before tenant complaints.
- R-454B refrigerant: No refrigerant losses; system charge stable.
Investment Summary
- Carrier 48HC-D08-A-90-A 7.5-ton high-efficiency packaged RTU: $15,400
- Integrated economizer, DCV, and controls package: $2,800
- Curb gasket, sealing materials, structural verification: $640
- Crane mobilization and roof access: $2,400
- Refrigerant recovery, line modifications, materials: $1,640
- Electrical work (disconnect, connections, code updates): $1,840
- Installation labor (2 days, 3 technicians plus crane operator): $5,800
- Commissioning per ASHRAE 90.1: $840
- Building automation integration and remote monitoring: $1,240
- Permit, inspection, EPA Section 608 documentation: $480
- Total project cost: $33,080
- Eversource commercial rebate (high-efficiency packaged RTU): −$2,400
- Federal IRA 179D commercial energy efficiency deduction: Applied to building owner's tax return; varies by tenant lease structure.
- Net customer investment: $30,680 (pre-tax-deduction)
Long-Term Economics
- Annual energy savings: Approximately $2,400 ($1,620 cooling + estimated $480 heating + $300 DCV-specific) based on first-year data.
- Reduced maintenance costs: New equipment under warranty; substantially less repair activity vs. aging 1997 equipment.
- Simple payback period: Approximately 12-13 years on capital investment; faster when reduced repair frequency factored in.
- Tenant satisfaction value: Reduced tenant turnover risk; comfort complaints eliminated; lease retention value substantial for small commercial property owner.
- Equipment lifespan: Typical 15-20 years for properly maintained commercial RTUs; 8-10 years of operational savings beyond payback period.
Lessons Applicable to Other Commercial Properties
- Right-sizing matters for commercial: Original 1997 unit was 60% oversized; right-sized replacement provides better comfort, dehumidification, and efficiency.
- R-22 phase-out drives replacement timing: Equipment using R-22 refrigerant increasingly expensive to service; planned replacement timing produces better outcomes than emergency replacement.
- Economizer mandatory for commercial: Connecticut commercial code requires economizers on new installations; provides substantial cooling energy savings during shoulder seasons.
- DCV provides ongoing operational savings: Demand control ventilation reduces unnecessary ventilation during low-occupancy periods; substantial impact on small commercial.
- Weekend installation minimizes tenant disruption: Friday-Saturday or Saturday-Sunday installation typical; restores operations by Monday morning; coordination with tenants essential.
- Building automation integration valuable: Remote monitoring enables proactive maintenance and prevents tenant comfort complaints; building owner sees value beyond equipment alone.
- Commercial rebates available: Eversource commercial programs provide substantial rebates for high-efficiency equipment; combined with federal IRA 179D deduction, effective cost reduced significantly.
Frequently Asked Questions
- How does commercial HVAC service differ from residential?
- Several substantial differences. (1) Equipment scale: commercial RTUs typically 5-25+ ton capacity vs. residential 2-5 ton; different lift equipment and crane requirements. (2) Code requirements: commercial code requires economizers, demand control ventilation, ASHRAE 90.1 efficiency standards; residential code less stringent. (3) Refrigerant: commercial transitioning from R-410A to R-454B; large refrigerant charges; specialized service capabilities. (4) Building automation integration: commercial increasingly integrates with building management systems; residential typically standalone equipment. (5) Tenant coordination: lease structures, tenant comfort expectations, and business operations affect service scheduling. (6) Project management: commercial projects often coordinate with property managers, building owners, and multiple stakeholders; residential typically single homeowner. (7) After-hours service: commercial often requires evening, weekend, or holiday work to minimize business disruption.
- What's the typical commercial RTU replacement timeline?
- Variable based on equipment size, building configuration, and tenant requirements. Common timelines: (1) Same-day swap: small packaged units (5-7 ton) with existing curb match, weekend coordination, minimal tenant impact — possible in 1 day. (2) Weekend project: typical 5-15 ton commercial RTU replacement — Friday-Saturday or Saturday-Sunday installation; this case study's 2-day timeline typical for 7.5-ton equipment. (3) Multi-day project: larger equipment (15-25+ ton), multiple units, structural modifications, code-compliance updates — sometimes 3-7 days. (4) Coordinated project: planned during business hours with tenant coordination — sometimes preferable for tenants with overnight operations or critical day-time business; longer overall timeline but less business disruption. Specific timeline depends on building, equipment, and tenant requirements.
- What does demand control ventilation actually do?
- Demand control ventilation (DCV) adjusts outdoor air ventilation based on actual occupancy. Standard commercial HVAC ventilates at design rate continuously; DCV reduces ventilation when occupancy is low. How it works: (1) CO2 sensor monitors indoor air quality; CO2 rises with occupancy due to human respiration. (2) System minimum ventilation maintained always; additional ventilation triggered only when CO2 exceeds setpoint indicating occupancy. (3) During unoccupied periods (early morning, late evening, weekends for offices, off-hours for retail), ventilation reduces substantially; system uses recirculated air with minimum outdoor air contribution. (4) During high-occupancy periods (lunch hours, meetings, busy retail), ventilation increases to maintain air quality. Energy impact: ventilation requires heating or cooling outdoor air to indoor conditions; reducing unnecessary ventilation saves substantial energy. Typical 15-25% reduction in HVAC energy use during low-occupancy periods. Required by Connecticut commercial code on new installations.
- What are R-22 refrigerant phase-out implications for my commercial HVAC?
- If your commercial equipment uses R-22 refrigerant (manufactured before 2010 typically), several implications. (1) Phase-out completed: U.S. R-22 production and importation ended January 1, 2020; only reclaimed and recycled R-22 available; supply diminishing rapidly. (2) Service cost increase: R-22 refrigerant cost has increased 5-10x since 2015; refrigerant losses for older equipment increasingly expensive. (3) Parts availability: replacement components for R-22 equipment increasingly limited as manufacturers focus on current refrigerant. (4) Service expertise: technicians increasingly trained on R-410A and R-454B; R-22 service expertise declining. (5) Practical timeline: R-22 equipment can be serviced with reclaimed refrigerant but at increasing cost; replacement timing depends on equipment condition, available R-22 supply, and customer budget. We typically recommend replacement consideration during major service events or efficiency upgrades; emergency R-22 service often justifies replacement decision.
- How disruptive is commercial RTU replacement for building tenants?
- Properly planned, minimal disruption. Specific impacts: (1) Crane operations: 1-2 hours of crane work outside building; usually planned for weekend or evening; minimal tenant impact during planned timing. (2) HVAC system off: during equipment swap, HVAC system off for 4-8 hours typical; if scheduled appropriately (weekend, evening), tenants not present. (3) Roof access: technicians on roof during installation; no interior building access required for most work. (4) Indoor work: thermostat replacement, sensor installation, controls integration; brief interior work usually 1-3 hours; can be coordinated with tenant schedules. (5) Air quality: equipment startup includes filter and damper verification; air quality typically returns to normal within first day of operation. (6) Communication: regular tenant communication essential; advance notice of work schedule, completion verification, contact information for any concerns. For this case study, tenants reported minimal disruption with weekend installation timing.
Contact Biozura Heating and Air
For commercial HVAC replacement projects, contact us for consultation. Connecticut DCP Unlimited HVAC License #S1-0414829 covers commercial work. Specialized commercial coordination and after-hours scheduling available.
- Emergency Line (24/7): (860) 955-4428
- Address: 10 N Main St #377, West Hartford, CT 06107
- Email: info@biozuraheatingairconditioning.xyz
- Connecticut DCP Unlimited HVAC License: #S1-0414829
- EPA Section 608 Universal: #608U-2008-381467 (Joshua Scruggs), #608U-2009-512784 (Marcus Petrowski), #608U-2010-447831 (Tomás Reyes)
- Eversource Participating Contractor: #CT-EVS-22-04612
Office Hours
- Emergency Service: 24 hours a day, 7 days a week
- Office Staff: Monday – Saturday, 9:00 AM – 5:00 PM
- Closed: Sundays and State/Federal Holidays (emergency line always active)