RSES Journal Winter 2025, RETA-RSES

THE FIRST SIGN OF AN UNDER

top equipment like AHUs. Extreme temperatures can interfere with mechanical components, causing dampers, coils or condensate drains to freeze. Cold air and accumulated ice or snow can disrupt airflow. The first sign of an underperforming AHU is often noted by building occupants who may report temperature swings, reduced airflow or a “stuffy” feeling within the building. If neglected, these condi tions can lead to unhealthy IAQ levels, which can decrease productivity and increase the spread of illness-causing airborne viruses and bacteria. As performance slippage progresses, operators may notice longer HVAC system run times, higher motor amper age, frequent cycling and a decreased ability to meet design setpoints. Exces sive fan noise, increased vibration, signs of water and building automa tion system (BAS) alarms may also follow. As these issues escalate, they often manifest in the form of increased energy consumption and rising operat ing costs. In fact, the Department of Energy estimates that organizations can save as much as 20% in operational expenditures by following a preventa tive HVAC maintenance schedule. 1 Winter Maintenance Best Practices Referring to the original equipment manu facturers’ (OEM) installation, operation and maintenance literature and recom mended schedule is a critical first step before beginning service. Additionally, ASHRAE Standard 180 for Inspection and Maintenance of Commer cial Building HVAC Systems provides an excellent baseline of best practices. ASHRAE Standard 62.1 is also a valuable resource for AHU operations as it outlines "Ventilation for Acceptable Indoor Air Quality". If service is related to a system issue, running recent performance and fault reports from the BAS can help identify trending issues and prioritize work based on concerns. As technicians develop their AHU winter maintenance protocols, the follow ing key steps can also be helpful:

5. UV Lights and Humidification— Replace UV bulbs following the manufacturer’s recommended replacement schedule, then test safety switches and controls. Ensure the humidification distribution is clean and undamaged, then test the safety and operation of the steam supply system. 6. Controls and Sensors— Check cali bration of temperature and humid ity sensors, exercise dampers and actuators, validate safeties and review setpoint schedules. 7. Airflow and Performance Verifica tion— Measure static pressures, airflow and supply/return tempera ture differentials and compare the outcomes to design and baseline readings. 8. Final Startup and Documentation— Confirm BAS communication, store trending data, complete main tenance log and provide recom mended next-step items. Safety During AHU Service Safety and preparation are the highest priority for any maintenance practice. When accessing rooftop equipment during winter conditions, first confirm the area is free of weather-related hazards such as ice or snow accumulation. Most Occupational Health and Safety Admin istration (OSHA) standards require fall protection for sites that are at least six feet above ground level. Requirements may vary depending on the location of equipment, so it is important to evaluate the build ing’s safety systems, including guardrails, and plan accordingly. Additionally, some equipment and maintenance materials may require rigging to be arranged. Performing proper lock-out/tag-out (LOTO) procedures is a critical step that must be taken before beginning service. During this process, technicians should ensure control power, fans, heaters and variable frequency drives (VFDs) are de-energized and cannot be turned on during service. Insulated tools should be used during LOTO or when equipment cannot be de-energized. Personal protec

1. Inspection and Verification— Visually inspect the condition of the equip ment’s exterior, access panels, elec trical panels, control panels, hoods, roof and door seals. Verify motor and alignment, vibration baseline and belt condition. 2. Air Filtration and Coils— Replace or clean filters, coils, energy and heat wheels, heat exchangers and other heating elements. 3. Drains and Freeze Protection— Clear or freeze-stat on coils and clean pans. Validate freeze protection concentration in the water system. 4. Fans, Motors, Drives— Lubricate bearings per OEM specifications, measure motor currents, check belt tensions and confirm VFD param eters or soft-start settings. PERFORMING AHU IS OFTEN NOTED BY BUILDING OCCUPANTS WHO MAY REPORT TEMPERATURE SWINGS. REDUCED AIRFLOW OR A 'STUFFY' FEELING WITHIN THE BUILDING. condensate drains, check traps, and verify the operation of the heat trace

WINTER 2025 RSES Journal 11

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