Winterization and Cleaning of Coils in Commercial HVAC Systems
- Corey Mullikin
- 5 days ago
- 11 min read
Comprehensive Guide to Winterization and Coil Cleaning in Commercial HVAC Systems
Introduction
The efficiency, longevity, and safe operation of commercial HVAC systems during winter months rely heavily on well-executed winterization and regular coil cleaning. Inadequate preparation results in costly emergency repairs, lost operational continuity, and compromised occupant comfort. The following report delivers a detailed, actionable examination of technical processes and best practices for winterizing commercial HVAC systems and cleaning evaporator and condenser coils.
It addresses practical checklists, safety protocols, and provides an extensive review of OEM-represented manufacturers by Thermal Equipment Sales, Bluegrass Hydronics & Pump, Technical Products Service & Sales, and Thermal Air Quality. Supported by recent technical articles, professional industry guidance, and best-in-class checklists, this resource is designed as a reference for HVAC professionals preparing facilities for the challenges of winter operation.
Technical Overview: Winterization of Commercial HVAC Systems
Winterization is the process of preparing HVAC and associated hydronic systems for sustained cold weather. The purpose is multifaceted:
Freeze Protection: Insulating and protecting all heat transfer surfaces and water-bearing components.
Energy Optimization: Ensuring minimized energy expenditure while maintaining comfort.
Operational Continuity: Preventing breakdowns through preventive maintenance.
Asset Longevity: Minimizing corrosion, freeze damage, and operational stress.
Within a commercial facility—especially in regions with variable winter conditions—winterization should be approached as a systematic project, beginning in late summer and extending through the start of cold weather. Below is a timeline and its corresponding focus:
These actions ensure each subsystem in the HVAC infrastructure is properly addressed before the onset of freezing temperatures.
Air Handling Units (AHUs) and Coils
AHUs mix, filter, and move air throughout the building. Their coils—commonly hot water, steam, or chilled water—are susceptible to freezing. The critical steps for winterization include:
Coil Cleaning and Inspection: Use non-acidic, hydrophilic or foaming coil cleaners to remove contaminants from both sides of the coil.
Physical Inspection: Look for bent, dirty, or corroded fins, leaks, and deterioration that may impair heat transfer. Even minor pinholes in coils can result in catastrophic ruptures if freezing occurs.
Freeze Protection Controls: Regularly test low-temperature cutouts and freeze stats by simulating drops in coil temperature. These controls should trigger fan shutdown and damper closure.
Damper Sealing: Check for improper sealing that allows cold air infiltration, adjust or replace worn seals as needed.
Filter Management: Install clean, appropriately rated filters (possibly with elevated MERV if IAQ is prioritized) while monitoring impacts on static pressure.
Fan and Motor Maintenance: Inspect belts for tension and wear, lubricate bearings, and monitor amperage draw for signs of mechanical issues.
Documentation: Record findings and maintenance actions during each inspection round.
Boilers and Hydronic Systems
Boilers are at the heart of many commercial hydronic (water-distribution) heating systems. Winterization here is critical:
Combustion Analysis: Use calibrated tools to adjust O₂, CO₂, CO, and flue gas temperatures for optimal burner efficiency and safety compliance.
Safety Device Testing: Manually test low-water cutoffs, pressure reliefs, and flame safeguards to ensure timely and reliable operation.
Water Chemistry: Test pH (optimal for steel: 8.5–10), glycol concentration, and corrosion inhibitor levels; flush sediment to prevent scaling.
Glycol Systems: Validate freeze point via refractometer, top up as necessary, and confirm manufacturer-approval for employed glycol blends.
Exposed Components: Insulate all valves, flanges, and components in unconditioned spaces with properly rated insulation to minimize heat loss and freeze risk.
Chiller Winterization
Despite being largely idle in winter, chillers’ water-filled components are vulnerable to freeze rupture:
Draining: Drain both condenser and evaporator water circuits, blow residual water from piping using compressed air.
Glycol Charging: If not fully drained, charge the system with glycol to maintain a safe freeze margin, following manufacturer concentration guidelines.
Electrical Lockout: Power down and lock out chillers; for systems operating year-round, verify crankcase heaters and ancillary freeze protections.
Cooling Towers
Cooling towers and associated pumps accumulate mineral and biological buildup, and are at extreme risk of freeze damage:
Drain and Clean: Remove all water from basins, sumps, and lines; clean fill media of scale and biological growth.
Winter Operation: For operational towers, employ basin heaters, ensure minimum flow rates, and use wind screens to minimize icing.
Legionella Control: Complete chemical disinfection before shutdown; maintain lay-up protection.
Ductwork, Insulation, and Building Envelope
Heat loss in poorly sealed or insulated ductwork and building perimeters directly translates to operational waste:
Leak Detection: Use smoke pencils or infrared thermography for envelope and ductwork leak identification.
Insulation Repair: Replace damaged or wet insulation, and improve R-values as necessary to meet ASHRAE 90.1 or local standards.
Weatherstripping and Seals: Replace worn seals at windows, doors, and rooftop penetrations.
Gutter Management: Clear debris to minimize the formation of ice dams that can damage HVAC structure and piping.
Thermostats and Controls
Reliable operation during extreme temperature swings demands:
Calibration: Use a precision thermometer to verify readings, recalibrating or replacing sensors and controllers as needed.
Scheduling: Align programmable thermostats and BAS controls with occupancy and holiday periods.
Freeze Alarms: Test alarm setpoints and notification systems to ensure occupants or staff are alerted if space temperature falls dangerously low.
Hydronic Piping
Frozen pipes can devastate a facility. Winterization involves:
Drain Unused Lines: Use compressed air to remove all residual water, then tag and lock out these circuits.
Heat Tracing: Inspect electric heat trace for continuity and thermostat operation; test regularly.
Expansion Tanks: Compare pre-charge pressures with system specifications; examine for leaking bladders or corrosion.
Pumps and Valves
Flow assurance is essential for both freeze protection and heating capacity:
Seal and Bearing Inspection: Look for leakage and listen for abnormal bearing noise.
Lubrication: Lubricate as per OEM guidelines—avoid over-lubrication to prevent seal deterioration.
Valve Exercise: Fully cycle valves, lubricate stems, and ensure none are stuck or leaking.
Snow and Ice Management
Significant snowfall or ice can impair rooftop access, damage exposed equipment, and block critical airflow:
Snow-Melt Systems: Test electric or hydronic snow-melt panels prior to first snowfall.
Deicing Supplies: Maintain stocks of calcium magnesium acetate or eco-friendly alternatives.
Contractor Coordination: Confirm the operational readiness and response plans of third-party snow removal services.
Cleaning of HVAC Coils: Technical Details and Best Practices
HVAC coil cleaning—encompassing both evaporator and condenser coils—directly impacts performance, energy consumption, and even indoor air quality. Dirty coils impede heat transfer, strain compressors, increase energy bills, and shorten equipment life.
Types of Coils
Evaporator Coils: Located within AHUs or above furnaces, absorb heat from air and often accumulate dust, biological debris, and corrosion.
Condenser Coils: Located in outdoor units, responsible for expelling heat; exposed to outdoor debris, pollen, grass, and weather.
Both require unique approaches and precautions during cleaning.
Inspection and Assessment
The coil cleaning process starts with a comprehensive assessment:
Visual Inspection: Look for obvious dirt, corrosion, algae, or biological growth. Note presence of bent fins, oil spots (signaling refrigerant leaks), or ice buildup.
Performance Testing: Cross-reference air pressure drop across coils with design specs—higher drops generally indicate fouling.
Other Indicators: Diminished airflow, increased energy bills, uneven temperature distribution, or system short-cycling also signal coil fouling.
Coil Cleaning Methods for Commercial HVAC
Special Considerations:
Multi-row Coils: For multi-row condenser coils in large systems, split the coil for access to the interior surfaces. Use temporary supports to avoid coil sagging or refrigerant leaks.
Interior Coils: For coils located deep within AHUs (with high fin density), steam cleaning is an effective, low-mess option, but avoid oversaturating motors or wiring.
Coated Coils: Treat as uncoated—coatings do not reduce fouling risk; follow the same cleaning frequency and procedure to maintain corrosion resistance.
Eco-Friendly Alternatives: Employ enzymatic or steam cleaning as needed, ensuring effectiveness without environmental impacts.
Safety Protocols During Coil Cleaning
Worker safety is paramount due to chemical cleaners and mechanical hazards.
Personal Protective Equipment (PPE): Gloves, N95 or half-mask respirators, face shields, and eye protection.
Ventilation: Ensure sufficient ventilation in mechanical rooms during chemical application.
Chemical Handling: Reference manufacturer MSDS, dilute as instructed (overly strong solutions can corrode coils or cause leaks), and avoid acid-based cleaners unless required by severe fouling and permitted by the coil manufacturer.
Water Recovery: Use containment systems or vacuum extractors on roofs to prevent environmental runoff of chemicals.
Electric Safety: Always fully lock out voltage sources before opening HVAC units.
Common Mistakes and Solutions
Overcleaning: Excessive maintenance can loosen fins or erode surface coatings; adhere to recommended schedules.
Pressure Washer Damage: Use low-pressure water only; high-pressure can flatten fins or split tubes.
Incomplete Rinsing: Residual cleaner can corrode metals or cause coil failures.
Improper Chemical Use: Always select cleaners compatible with aluminum, copper, or coated surfaces.
Ignoring Internal Coils: Spraying only the external surface in multi-row coils will not clean interior rows, leading to hidden inefficiencies.
Cleaning Frequency
Annual: Most commercial evaporator and condenser coils.
Quarterly: Condenser coils in high debris areas, or systems near open cooling towers.
Monthly: Any unit within one mile of saltwater or severe pollution.
High-finned coils or those exposed to manufacturing debris may require more rigorous cleaning schedules.
Best Practices and Comprehensive Checklists
Winterization Best Practices
Adopt a timeline for early planning, staged inspections, and final freeze protection before the first freeze.
Assign responsibility: Maintenance tasks should be logged and follow accountability chains.
Use proactive materials management: Stock filters, insulation, glycol, belts, and repair parts before peak demand.
Integrate with Building Automation: Schedule controls and freeze alarms for holidays and off-hours.
Train staff: On test procedures for controls, chemical handling, cleaning methods, and safety.
Comprehensive Winterization Checklist
Review and check off each task prior to the expected first freeze or as per organization policy.
Coil Cleaning Checklist
4. Manufacturer Representation and Equipment Overview
Understanding the major manufacturers supported by leading regional representatives allows facility owners and engineers to align maintenance practices with OEM guidelines and access appropriate spare parts or technical support. Below is a summary of key representatives, their brands, and equipment offerings.
Summary Table: Regional HVAC Manufacturers, Brands, and Equipment Types
Note: Each of these representatives supplies full technical and warranty support in line with the brands they represent, and most stock OEM parts to reduce downtime due to maintenance or repairs.
Practical Field Guidance and Manufacturer-Specific Points
Manufacturer-Supplied Parts: Always use OEM parts from the regional representative listed above to maintain system compatibility, avoid operational problems, and ensure warranty compliance.
Maintenance Documentation: Follow each brand’s official service manual for specific cleaning agents, filter specifications, operating ranges for glycol mixes, and control calibration.
Warranty Adherence: Regularly scheduled and documented preventative maintenance—including coil cleaning—may be required to maintain warranty coverage. Use only recommended cleaners and procedures.
Winterization and Coil Maintenance: Advanced Considerations
Chiller, Boiler, and Cooling Tower Specifics
Chillers: For facilities retaining water in chillers over winter, use manufacturer-approved glycol blends only, test with a refractometer, and check electrical heaters for compressors.
Boiler Freeze Protection: Test low-water cutoff, check pH and inhibitor, review expansion tank precharge, insulate all external components.
Cooling Towers: Comprehensive cleaning and disinfection are mandatory for legionella control; include layup chemicals and submit to regulatory testing where applicable. Consider basin heaters for towers that must operate year-round.
Hydronic and Radiant Heating Systems
Antifreeze Use: Only employ propylene glycol in systems with potential potable cross-connection. Target 20–50% concentration for protection; test pH and inhibitor levels at least annually.
Piping Insulation and Heat Trace: Insulate all hydronic lines in unconditioned spaces; test all electric heat trace and thermostats before the season.
Ductwork, Insulation, and Thermostat Optimization
Duct Sealing: Use mastic or UL-listed tape to address air leaks. Clean before sealing for optimal adhesion; follow up with pressure testing as needed.
Thermostat and Control Calibration: Use a certified thermometer for calibration; manufacturer guidance should be followed for advanced programmable and smart thermostats.
Snow and Ice: Protection of Outdoor Units
Mechanical Protection: Shield outdoor RTUs and condenser units with breathable covers or wind baffles, ensuring snow/ice cannot accumulate on coils or air intakes.
Elevated Platforms: For snow-prone regions, mount units on platforms above the typical snowline.
Routine Clearance: Establish regular removal of snow and ice, paying special attention after storms; never use metal tools that may damage coils.
Operational Cautions: Never run air conditioners or heat pumps with heavy snow or ice accumulation; this can damage fans, coils, and compressors, and may void warranties.
Sustainability, Compliance, and Long-term Efficiency
Sustainable Cleaning: Opt for non-acidic biodegradable cleaners wherever feasible to minimize environmental impact and comply with local regulations on hazardous waste disposal.
Documentation Compliance: Record all cleaning, repairs, chemical additions, and inspections for regulatory and insurance purposes.
Long-term Asset Planning: Document coil, filter, and insulation replacements. Upgrade to materials or designs (e.g., wider fin spacing, protective coatings, Freeze Block™ technology) that facilitate maintenance, especially when ordering custom or replacement coils.
Conclusion
The intersection of thorough winterization and coil maintenance is where facility managers and HVAC technicians can deliver lasting asset durability, safe winter operation, regulatory compliance, and minimized cost of failures. Approached as preventive maintenance—structured by checklists, performed in compliance with OEM and industry best practice, and supported by knowledgeable regional representatives—these tasks transform the winter season from a period of risk to one of opportunity.
In summary, prioritize early planning, follow a rigorous schedule, utilize OEM parts and materials as per manufacturer and regional representative guidance, and ensure all work adheres to modern safety and environmental standards. For the brands represented by Thermal Equipment Sales, Bluegrass Hydronics & Pump, Technical Products Service & Sales, and Thermal Air Quality, alignment with their product-specific guidelines will ensure your commercial HVAC systems are winter-ready, safe, and energy-efficient for years to come.