What Is an RTU HVAC System? Everything You Need to Know About Rooftop Units

Rooftop units have become integral to how facility managers approach climate control, offering advantages that go far beyond their placement. Understanding RTUs is key to making smart decisions about system upgrades, energy savings, and ongoing building performance.

This guide covers:

• RTU HVAC system definition and core applications

• Key components and how rooftop units function

• RTU benefits, drawbacks, and system comparisons

• Sizing, installation, maintenance, and cost essentials

P.S. At HVAC Store, we deliver a wide collection of RTU systems from leading brands like Daikin, Goodman, and Amana. Our platform features over 500 SKUs, technical phone support from licensed HVAC technicians, and a comprehensive library of spec sheets for confident decision-making. We offer same-day quote turnaround on multi-ton commercial units and a price match guarantee!

RTU HVAC Systems at a Glance

What Is an RTU HVAC System?

Rooftop units (RTUs) are a cornerstone of commercial HVAC design, especially for large retail, office, and industrial buildings. These self-contained systems are installed on the roof, combining heating, cooling, and air distribution in a single package. 

RTUs differ from split systems by housing all major components, including compressor, coils, blower, and controls, within one weatherproof cabinet. This design simplifies maintenance and replacement, as technicians can service the entire system from the rooftop without disrupting building operations. 

Key Components and How RTUs Work

Understanding the internal workings of an RTU is essential for both selection and ongoing maintenance. Each component plays a specific role in delivering conditioned air efficiently and reliably, and knowing these details helps ensure optimal performance and longevity.

• Compressor: The heart of the RTU, responsible for circulating refrigerant and enabling heat exchange. Modern RTUs like the Daikin 6 Ton model use a two-stage scroll compressor for quiet, efficient operation and improved part-load performance.

• Coils: Both condenser and evaporator coils are constructed with copper tubes and aluminum fins for high heat transfer efficiency. Large face area coils and draw-through configurations enhance dehumidification and air quality.

• Blower/Fan: Direct-drive, factory-balanced supply fans with aluminum blades ensure quiet, efficient airflow across a range of static pressures. Multi-speed ECM motors reduce maintenance and energy costs.

• Controls & Economizer: Advanced control panels, often with weatherproof internal boxes, manage system operation, safety, and diagnostics. Economizers allow for free cooling using outside air when conditions permit, boosting efficiency.

• Cabinet Construction: High-quality galvanized steel with powder-paint finish resists corrosion, while fully insulated cabinets prevent energy loss and sweating. Tool-less filter access and raised flanged edges simplify maintenance and duct connections.

Looking for a higher-capacity RTU with advanced features? The Daikin 7.5 Ton R32 Packaged Heat Pump 16 IEER Light Commercial RTU delivers 90,000 Btu/H, microchannel heat exchanger technology, and a wide range of electric heat options. Its weatherproof control box, single-point power entry, and tool-less filter access make it a top choice for demanding commercial environments.

RTU vs. Other Commercial HVAC Systems

Selecting the right HVAC system for a commercial building involves weighing the pros and cons of RTUs against alternatives like split systems, packaged units, and variable refrigerant flow (VRF) systems. Each option has unique strengths and limitations, and the best fit depends on building size, layout, and operational needs.

• RTUs: Offer all-in-one heating and cooling, easy rooftop access, and minimal indoor space requirements. Ideal for buildings with flat roofs and limited mechanical room space.

• Split Systems: Separate indoor and outdoor components, providing flexibility for multi-zone applications but requiring more complex installation and maintenance.

• Packaged Units: Similar to RTUs but can be installed at ground level. Suitable for buildings without roof access or where rooftop weight is a concern.

• VRF/VRV Systems: Deliver precise, zoned comfort and high efficiency, but come with higher upfront costs and more complex controls.

When comparing RTUs to these alternatives, consider factors like installation speed, maintenance access, energy efficiency, and scalability. RTUs excel in projects where rapid deployment, ease of service, and cost control are top priorities.

Benefits and Drawbacks of RTUs

RTUs have earned their popularity in commercial HVAC for several compelling reasons, but they also come with specific challenges that must be managed for long-term success. Understanding both sides helps ensure the right fit for your building and operational goals.

Benefits

• Energy Efficiency: Modern RTUs, especially those using R32 refrigerant and multi-speed ECM motors, deliver high SEER ratings and lower operating costs.

• Space Savings: Rooftop installation frees up valuable indoor space for tenants or equipment.

• Simplified Maintenance: All components are accessible from the roof, reducing disruption to building occupants.

• Scalability: Multiple RTUs can be installed to serve different zones or building expansions.

Drawbacks

• Weather Exposure: RTUs must be built to withstand harsh outdoor conditions, requiring robust construction and regular inspections.

• Roof Load: Not all buildings can support the weight of large RTUs, especially older structures.

• Access Challenges: Roof access may be limited or require special safety measures, impacting serviceability.

Looking for a commercial RTU that balances performance and ease of installation? The Daikin 6 Ton R32 Packaged Heat Pump 16.7 SEER2 Light Commercial RTU 208/230V 3-Phase is a standout, offering 68,000 Btu/H cooling capacity, two-stage scroll compressor, and a fully insulated, corrosion-resistant cabinet. This unit is designed for direct replacement of most existing rooftop systems, minimizing downtime and installation costs.

Sizing an RTU: Getting Capacity Right

Proper sizing is the foundation of RTU performance, energy efficiency, and occupant comfort. An undersized unit will struggle to maintain temperature, while an oversized system can short-cycle, leading to humidity issues and higher energy bills. Here’s how to get it right:

• Conduct a Professional Load Calculation: Use Manual N or an equivalent method to assess the building’s heating and cooling loads, factoring in square footage, insulation, occupancy, equipment, and local climate.

• Account for Zoning Needs: For multi-tenant or large open spaces, consider whether multiple smaller RTUs or a single larger unit best matches your operational needs.

• Plan for Future Expansion: If building use may change, select an RTU with some capacity buffer or modular expandability.

• Consult Manufacturer Specs: Always cross-reference your load calculation with the RTU’s published capacity (Btu/H, SEER, EER) to ensure a precise match.

RTU Installation: Best Practices for Success

A well-executed installation is crucial for RTU reliability, efficiency, and warranty compliance. Even the best unit can underperform if installed incorrectly. Here’s what to prioritize:

• Direct Replacement Design: Choose RTUs engineered for direct replacement to avoid costly curb adapters and minimize downtime. Daikin’s packaged units are designed for fast swaps.

• Check Roof Structure: Verify that the roof can support the RTU’s weight, including snow or wind loads, and reinforce as needed.

• Align Ductwork and Electrical: Ensure supply/return ducts and electrical connections match the new unit’s configuration. Raised flanged edges and flexible electrical access simplify this process.

• Seal and Insulate: Properly seal all duct and curb connections to prevent leaks and energy loss. Use high-quality insulation to avoid condensation and thermal bridging.

• Commissioning: Perform a full system startup and commissioning, checking refrigerant charge, airflow, and control settings for optimal operation.

RTU Maintenance: Keeping Your System Running Strong

Routine maintenance is the key to maximizing RTU lifespan, efficiency, and indoor air quality. Neglecting maintenance can lead to breakdowns, higher energy bills, and voided warranties. Here’s how to stay ahead:

• Quarterly Filter Changes: Replace or clean filters every 3 months, or more often in dusty environments. Tool-less filter access on modern RTUs makes this quick and easy.

• Annual Coil Cleaning: Clean condenser and evaporator coils at least once a year to maintain heat transfer efficiency and prevent system strain.

• Compressor and Fan Checks: Inspect and test compressors, fans, and motors for unusual noise, vibration, or wear. Lubricate and balance as needed.

• Control and Safety Inspections: Test all safety switches, control panels, and economizer functions to ensure reliable operation and code compliance.

• Document Everything: Keep detailed records of all maintenance and repairs for warranty and regulatory purposes.

Cost of RTU HVAC Systems: What to Expect

Budgeting for an RTU project involves more than just the sticker price. Understanding the full cost picture helps you plan for both upfront investment and long-term savings.

• Equipment Cost: Light commercial RTUs typically range from $6,000 to $15,000+ depending on tonnage, efficiency, and features. For example, the Daikin 6 Ton R32 Packaged Heat Pump is priced at $6,715, while the 7.5 Ton model is $9,488.

• Installation: Professional installation can add $2,000 to $6,000, depending on roof work, duct modifications, and electrical upgrades.

• Operating Costs: High-efficiency RTUs with advanced controls and R32 refrigerant can reduce annual energy bills by 10–30% compared to older models.

• Maintenance and Repairs: Plan for routine maintenance costs and occasional repairs. Investing in quality units with tool-less access and robust warranties can lower lifetime expenses.

• Financing Options: Many suppliers, including HVAC Store, offer financing through Affirm, allowing you to spread costs over manageable monthly payments.

Troubleshooting and Upgrading RTUs

Even the best RTUs require occasional troubleshooting and, over time, upgrades to maintain peak performance. Knowing the most common issues and available enhancements helps keep your system running efficiently and extends its useful life.

• Common Issues: Watch for airflow restrictions, refrigerant leaks, and control faults. Addressing these early prevents larger failures and costly downtime.

• Diagnostic Steps: Use onboard diagnostics and control panels to identify error codes. Inspect filters, coils, and electrical connections regularly.

• Upgrades: Consider adding advanced economizers, smart controls, or higher-efficiency motors to boost performance and energy savings.

• Replacement Triggers: Upgrade when repair costs exceed 50% of replacement value, or when newer models offer significant efficiency gains.

READ MORE:

• How Rooftop HVAC Units Work
• 5 Most Common Types of HVAC Systems for Commercial Buildings

Next Steps for Confident RTU Selection

Selecting the right RTU HVAC system is a strategic investment in your building’s comfort, efficiency, and long-term value. By understanding the unique advantages of rooftop units, their key components, and the essentials of sizing and maintenance, you can make informed decisions that pay off for years to come.

• Assess your building’s load requirements and roof capacity before choosing an RTU.

• Compare RTUs to split, packaged, and VRF systems to find the best fit for your needs.

• Schedule regular maintenance and leverage expert support for troubleshooting and upgrades.

Facing a complex RTU project or need help navigating product specs and installation options? At HVAC Store, we understand the challenges of commercial HVAC selection and are committed to providing the resources, technical expertise, and product range you need. Our mission is to deliver superior solutions for indoor air quality and comfort, with a focus on innovation, reliability, and customer satisfaction at every step.

FAQs

1. What is an RTU HVAC system?

An RTU (Rooftop Unit) HVAC system is a self-contained heating and cooling solution installed on a building’s roof, combining all major components in one weatherproof cabinet for efficient, centralized climate control.

2. How does an RTU differ from a split system?

RTUs house all components in a single rooftop cabinet, simplifying installation and maintenance, while split systems separate indoor and outdoor units, offering more zoning flexibility but requiring more complex setup.

3. What are the main benefits of using an RTU?

Key benefits include space savings, easy rooftop access for maintenance, energy efficiency, and scalability for large commercial spaces.

4. How do I size an RTU for my building?

Proper sizing requires a detailed load calculation based on building size, occupancy, insulation, and climate. Consult a licensed HVAC professional or use Manual N guidelines for accuracy.

5. What maintenance does an RTU require?

Routine maintenance includes filter changes, coil cleaning, compressor checks, and regular inspections of electrical and safety components to ensure reliable operation and compliance.

6. Where can I buy commercial RTU HVAC systems?

Commercial RTU HVAC systems from brands like Daikin, Goodman, and Amana are available at HVAC Store, which offers technical support, spec sheets, and a price match guarantee for commercial buyers.