Rooftop Unit (RTU) Service in Kirkwood and West St. Louis County
Rooftop package units dominate commercial HVAC in Kirkwood and surrounding areas for one reason: they consolidate heating, cooling, ventilation, and filtration into a single cabinet that sits on the roof rather than occupying interior mechanical space. For a restaurant on Kirkwood Road, an office along Argonne, or a retail storefront in Crestwood Plaza, the rooftop location keeps interior floor space available for revenue-producing activity, simplifies service access (no walking through customer-facing or operations spaces with tools), and consolidates the entire HVAC system to one location for unified service. The tradeoff: rooftop equipment is exposed to weather (wind-borne debris, ice damming, heat exposure, UV degradation), requires fall-protection-equipped technicians for service, and needs crane coordination for replacement. This page documents the RTU service categories we operate, the major manufacturers we work on, and the specifics of rooftop service logistics.
RTU Configurations
Gas/Electric (Gas Heat + Electric Cool)
The most common commercial RTU configuration. Gas-fired heating section with single-stage or two-stage burner and standard electric AC cooling. Capacity range typically 3–25 tons. Best application: commercial spaces with reliable natural gas service where heating-season operation runs frequently enough to favor gas economics over electric heat.
Heat Pump (Electric Heat + Cool)
Reversing-valve heat pump providing both heating and cooling from electric refrigerant cycle. Auxiliary electric backup heat (electric resistance strips) for design-condition supplemental heating. Best application: all-electric buildings, spaces without natural gas service, and customers pursuing electrification or sustainability certifications. Cold-climate commercial heat pumps from Carrier, Trane, Lennox, and others provide AHRI-rated capacity at 5°F outdoor conditions.
Electric/Electric (Electric Heat + Cool)
Electric resistance heating (no heat pump operation) combined with electric AC. Highest operating cost in heating mode but simplest equipment configuration. Best application: spaces with limited heating-season operation, mild-climate light commercial, or specific spaces where gas service or heat pump operation isn’t practical.
Dual-Fuel (Heat Pump + Gas Backup)
Heat pump primary heating with gas furnace backup for design-condition supplemental heat. Combines the operating cost benefits of heat pump heating at moderate outdoor temperatures with gas reliability at the coldest conditions. More complex configuration; less common in light commercial than residential.
Manufacturer Lineup and Distribution
Carrier WeatherMaker 48HC and 48LC
The market-leading light commercial RTU platform. 3–25 ton capacity range with single-stage, two-stage, and variable-speed compressor options. Distribution through Carrier Enterprise (regional distributor) with strong parts inventory and rapid delivery. AHRI-listed system matching across coil and condenser options. Best for customers wanting Carrier ecosystem support and Infinity-compatible communicating thermostats.
Trane Voyager and Precedent
Trane’s light commercial RTU offerings. Voyager covers 3–25 ton; Precedent covers 3–12.5 ton with value-tier positioning. Distribution through Trane’s regional commercial distribution with strong technician support and parts availability. ComfortLink II communicating thermostat compatibility.
Lennox Energence and LGH/LCH Series
Lennox premium light commercial platform. Energence covers 3–12.5 ton; LGH (gas/electric) and LCH (electric/electric) extend the range to 25 tons. Distribution through Lennox commercial distribution with strong premium feature support. iComfort communicating thermostat compatibility.
York Predator and Sunline
York (part of Johnson Controls) light commercial offerings. Predator covers 3–12.5 ton; Sunline 2000 extends to 25 tons. Strong value positioning with comparable specifications to Carrier and Trane at modestly lower equipment cost.
Goodman CPC/CPG and Daikin DCG/DCC
Goodman (Daikin family) light commercial platform. CPC (electric/electric) and CPG (gas/electric) in 3–12.5 ton range. Daikin DCG/DCC are the parent-brand equivalents with extended Daikin warranty. Value-tier positioning for budget-conscious commercial customers.
Rheem RKKL and Ruud UKKL
Rheem and Ruud (same parent company) light commercial platforms in 3–12.5 ton range. Mid-tier positioning with good warranty terms and reliable parts availability.
Common RTU Service Scenarios
Routine Maintenance (Covered Under Commercial Maintenance)
Quarterly or bi-annual maintenance covering refrigerant verification, coil cleaning, electrical inspection, combustion analysis (gas-fired equipment), economizer service, blower service, and filter replacement.
Compressor Failure
The most expensive RTU failure. Symptoms: outdoor unit silent or making compressor lockout sounds, indoor blower runs but no cooling, electrical lockout codes on equipment with diagnostics. Compressor replacement scope on RTUs:
- Refrigerant recovery with EPA-certified equipment
- Electrical disconnection per three-phase wiring
- Compressor removal and replacement with AHRI-matched specifications
- Oil compatibility verification (mineral oil for R-22 era equipment, POE for R-410A and R-454B)
- Filter-dryer replacement (standard with any compressor change)
- Suction line accumulator inspection or replacement
- Leak testing under nitrogen pressure
- Evacuation to manufacturer-specified vacuum level
- Recharge per nameplate specifications
- Startup verification and performance testing
Compressor replacement typical cost: $2,400–$4,800 (3–7.5 ton) or $3,800–$7,800 (10–25 ton).
Refrigerant Leaks
RTU refrigerant leaks occur at multiple potential points: brazed joints (typically at manufacturer assembly points or field-modification points), schrader valves, line set connections where flexible lines connect to fixed copper, coil tube-to-fin contact points (formicary corrosion in coastal environments, less common in Kirkwood), and compressor connections. Leak detection scope and EPA Section 608 compliance covered on the light commercial HVAC repair page.
Heat Exchanger Failures
Gas/electric RTUs have heat exchangers similar to residential furnaces but at higher BTU input capacities. Failure modes include cracks (visible via Hawkeye inspection borescope), perforation from rust-out, condensate damage on poorly-vented equipment, and impingement damage where flame patterns have damaged metal over time. Heat exchanger replacement is sometimes economical on relatively new RTUs (under 10 years); on older RTUs, full RTU replacement is frequently better economics.
Economizer Failures
Specific to commercial; residential rarely has economizers. Failed economizers (linkage problems, actuator failures, sensor problems, mechanical binding) reduce cooling efficiency by missing free-cooling opportunities and can cause IAQ issues. Service covered on commercial maintenance scope.
Electrical and Control Failures
Contactors, capacitors, control boards, fan motors, blower motors, and similar electrical components fail in patterns similar to residential equipment but at larger sizes and three-phase electrical configurations. Service trucks carry common commercial parts (contactors, capacitors, control board sub-components, ignition components) for same-visit repair when feasible.
RTU Replacement Project Scope
Full RTU replacement involves coordination scope that residential equipment replacement doesn’t require:
Pre-Replacement Planning
- Roof curb assessment: existing roof curb dimensions, condition, weatherproofing
- New equipment selection: matched to existing footprint where possible to minimize curb modifications; sized per Manual J for any capacity changes
- Curb adapter requirements: when new equipment footprint differs from existing, custom curb adapters may be needed
- Electrical service verification: three-phase service capacity confirmation; new equipment electrical specifications
- Gas service verification: gas line capacity for new equipment input rate
- Refrigerant compatibility: R-454B equipment installed since January 2025 requires compatible refrigerant lines and accessories
Crane Coordination
- Crane selection: appropriate crane size for equipment weight (3-ton RTU typically 800–1,200 lb; 25-ton RTU 4,800–7,200 lb) and rooftop reach distance
- Traffic control: street closure or lane restriction permits where crane setup requires public right-of-way
- Building access: parking lot or driveway access for crane positioning
- Rigging: appropriate rigging for safe lift and positioning
- Coordination with municipal authority: some Kirkwood-area jurisdictions require crane operations to be coordinated with traffic and public works departments
Replacement Day Sequence
- Site setup: crane positioning, fall protection setup, work area protection
- Equipment shutdown and disconnection: electrical disconnect, gas line shutoff, refrigerant recovery, condensate disconnection
- Old equipment removal: lift off roof curb, position on ground for disposal
- Curb preparation: cleaning, weatherproofing verification, curb adapter installation if needed
- New equipment positioning: lift onto curb, secure with appropriate fasteners
- Connection sequence: gas line, electrical service, refrigerant lines (if new lines required), condensate, control wiring
- Startup and verification: refrigerant charge, combustion analysis (gas equipment), electrical verification, control verification, thermostat communication
- Crane release: equipment removed from site after final positioning verified
Post-Installation
- Municipal inspection: commercial mechanical permit inspection
- Warranty registration: manufacturer warranty activation with installation date documentation
- Customer walk-through: equipment operation, thermostat programming, maintenance schedule recommendation
- Old equipment disposal: per municipal solid waste requirements; refrigerant retained for proper disposal under EPA Section 608
Pricing
RTU Service Pricing
- RTU diagnostic visit: $189–$280 (business hours), $240–$380 (after-hours). Applied as credit toward same-visit repair if authorized.
- Common component replacement: capacitor $189–$340, contactor $240–$380, hot surface igniter $280–$540, flame sensor $189–$240, pressure switch $240–$420, gas valve $480–$980, blower motor $780–$1,940
- Compressor replacement (3–7.5 ton): $2,400–$4,800
- Compressor replacement (10–25 ton): $3,800–$7,800
- Heat exchanger replacement (3–7.5 ton): $2,200–$4,200 (frequently uneconomic on equipment over 10 years; full replacement often better)
- Coil replacement (evaporator or condenser): $1,800–$3,800 depending on capacity
- Control board replacement: $540–$1,480 depending on equipment
RTU Replacement Pricing
- 3–5 ton RTU replacement: $9,800–$15,800 installed including crane, curb adapter if needed, electrical connection, gas connection, refrigerant lines, startup, permit pull, and post-installation inspection
- 7.5–10 ton RTU replacement: $14,800–$22,000 installed
- 12.5–15 ton RTU replacement: $19,500–$28,500 installed
- 20–25 ton RTU replacement: $26,000–$36,000 installed
- Curb adapter (custom fabrication): $1,400–$3,800 depending on dimensional changes
- Electrical service upgrade (if needed): $1,400–$4,800 depending on scope
- Crane service (line item if separately quoted): $2,400–$4,800 depending on equipment weight and reach
All pricing includes Manual J/S/D analysis where applicable, equipment, installation labor, refrigerant recovery and recharge, post-installation verification, permit pull, manufacturer warranty registration, and Purisync 2-year labor warranty.
Frequently Asked Questions
- How much does RTU replacement cost in Kirkwood?
- 3-5 ton RTU replacement runs $9,800-$15,800 installed including crane, curb adapter if needed, electrical and gas connections, refrigerant lines, startup, permit pull, and post-installation inspection. 7.5-10 ton runs $14,800-$22,000. 12.5-15 ton runs $19,500-$28,500. 20-25 ton runs $26,000-$36,000. Additional scope: curb adapter custom fabrication $1,400-$3,800 when new equipment footprint differs from existing; electrical service upgrade $1,400-$4,800 if needed; crane service $2,400-$4,800 if separately line-itemed. All pricing includes Manual J/S/D analysis, equipment, installation labor, refrigerant recovery and recharge, post-installation verification, permit pull, manufacturer warranty registration, and Purisync 2-year labor warranty. Pricing varies based on specific brand selection (Carrier, Trane, Lennox, York, Goodman, Rheem), efficiency tier within brand, and configuration (gas/electric, heat pump, electric/electric, dual-fuel).
- What RTU brands do you work on?
- All major light commercial RTU manufacturers. Carrier WeatherMaker 48HC and 48LC platforms (3-25 ton range with single-stage, two-stage, and variable-speed compressor options). Trane Voyager and Precedent (Voyager 3-25 ton, Precedent 3-12.5 ton value-tier). Lennox Energence and LGH/LCH Series (Energence 3-12.5 ton; LGH/LCH to 25 tons). York Predator and Sunline 2000 (Predator 3-12.5 ton; Sunline to 25 tons). Goodman CPC/CPG and Daikin DCG/DCC equivalents (value-tier 3-12.5 ton). Rheem RKKL and Ruud UKKL (mid-tier 3-12.5 ton). Brand differences are smaller than tier differences within a brand. We provide replacement quote options across multiple brands at each customer’s chosen tier so customers can compare specifications, warranty terms, and pricing. Service capability is similar across brands; replacement parts availability favors Carrier, Trane, and Lennox in our local distribution.
- How long does RTU replacement take?
- Single-RTU replacement (3-25 ton range) typically completes in 1 day for straightforward replacements where the new equipment matches the existing footprint and no curb modifications are needed. Replacements requiring curb adapter fabrication or installation extend to 1.5-2 days. Multi-RTU replacements (typical for larger commercial spaces with 2-4 units) typically run 2-4 days depending on unit count and project complexity. Crane coordination, traffic control if needed, and municipal inspection scheduling are the typical timeline-controlling factors beyond actual installation labor. Equipment delivery typically 3-10 business days from contract signing; for after-hours work scheduling (common for restaurant and retail customers), additional 1-2 weeks of advance scheduling allows coordination with all parties. We provide detailed project schedules during quote development so commercial customers can plan around the installation timeframe.
- Will I lose HVAC service during RTU replacement?
- Yes, during the actual replacement day. Replacement scope includes equipment shutdown (electrical disconnect, gas line shutoff, refrigerant recovery), old equipment removal, new equipment installation, and startup verification — the space being served by that RTU is without HVAC during this period (typically 6-10 hours of the installation day). For restaurants, retail stores, medical practices, and similar businesses where extended HVAC loss affects operations, we schedule replacements on closed days or after hours: Sundays or Mondays for restaurant customers, after-closing for retail, weekends for medical practices, and weekends for office buildings. Spaces with multiple RTUs can sometimes maintain partial service from other units while one is being replaced. Temporary cooling or heating (portable units) is available for replacements during peak season when going without HVAC isn’t acceptable; pricing for portable equipment quoted separately. We discuss scheduling constraints during quote development to minimize business disruption.
- Why do RTU replacements need a crane?
- Equipment weight and rooftop location. Light commercial RTUs weigh 800-1,200 lb (3-ton) up to 4,800-7,200 lb (25-ton) — far beyond manual handling capability. Rooftop location requires lifting the equipment from ground level to roof (typically 12-25 feet vertical) and positioning precisely on the existing roof curb. Crane coordination scope includes: appropriate crane size selection for equipment weight and rooftop reach distance, traffic control or street closure permits where crane setup requires public right-of-way, building access for crane positioning (parking lot, driveway), appropriate rigging for safe lift, and coordination with municipal authority for crane operations in some jurisdictions. Crane service is typically included in replacement quotes as part of project scope; if line-itemed separately, runs $2,400-$4,800 depending on equipment weight and reach. We coordinate crane scheduling as part of project planning so customers don’t deal with crane vendors directly.
Contact Purisync Heating and Air
For RTU service, repair, or replacement quotes, contact our 325 N Kirkwood Road office at (314) 338-5111. Replacement quote consultations include site walk-through with rooftop equipment assessment, Manual J/S/D analysis for capacity verification, equipment options across multiple brands and tiers, crane and project logistics planning, and written project schedule with business-operation accommodation.
- 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
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)