Aerotech Fans
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Technical answers to common questions about air handling units.
A Fan Coil Unit (FCU) uses a 2-way or 3-way modulating PICV (Pressure Independent Control Valve) to strictly regulate the flow of chilled water through the coil based on real-time thermostat demands. This precise throttling prevents overcooling and maintains strict sensible heat ratios in the occupied zone.
In a draw-through AHU, the fan is located downstream of the cooling coil, placing the coil under negative pressure (requiring a deep P-trap for condensate drainage). In a blow-through AHU, the fan is upstream, pushing air through the coil under positive pressure, which improves air distribution but adds motor heat to the conditioned air.
While an enthalpy wheel recovers general moisture for comfort cooling, an active desiccant dehumidification wheel utilizes a highly reactive silica gel matrix and a heated regeneration sector to aggressively strip moisture from the air, achieving the ultra-low dew points required for lithium-ion battery or pharmaceutical manufacturing.
Industrial Air Handling Units are typically engineered for a chilled water Delta-T (temperature differential) of 10°F to 12°F (e.g., entering at 44°F and leaving at 54°F). Maintaining this exact Delta-T ensures the coil effectively strips latent heat (humidity) without causing the central chiller plant to operate inefficiently (Low Delta-T syndrome).
A Barometric Relief Damper is a gravity-operated pressure valve used in tightly sealed buildings. When the HVAC system brings in high volumes of fresh outside air, internal pressure rises. The barometric damper automatically swings open to relieve this excess static pressure, preventing doors from becoming stuck.
ASHRAE Standard 62.1 dictates the absolute minimum ventilation rates for acceptable indoor air quality. Engineers must size the Fresh Air Unit (FAU) by calculating the combined CFM required per person (occupancy load) and per square foot (building area load) to ensure sufficient CO2 dilution without over-ventilating and wasting energy.
Unlike an enthalpy wheel which requires adjacent ductwork, a run-around coil system uses a pumped glycol loop to transfer heat between two physically separated coils—one in the exhaust duct and one in the fresh air intake. It provides sensible heat recovery with zero risk of cross-contamination.
The Sensible Heat Ratio (SHR) is the proportion of sensible cooling (lowering temperature) to total cooling (sensible plus latent/moisture removal). In a data center, the SHR is nearly 1.0 because there is no moisture load. In a crowded theater or humid factory, the SHR drops to 0.6, requiring the AHU coil to run much colder to condense the heavy humidity.
Electronically Commutated (EC) motors have integrated microprocessors that continuously output rich telemetry via Modbus. The BMS can actively monitor real-time RPM, precise power consumption (Watts), internal stator temperature, and fault codes, enabling a fully digitized, smart-building HVAC architecture.
Yes, modern AHUs integrated with IoT differential pressure transmitters continuously track the pressure drop across the HEPA filter bank. The BMS applies predictive algorithms to the pressure curve, generating an alert precisely when the filter is approaching its terminal resistance, avoiding premature replacement costs.
In sub-zero climates, drawing 100% outside air can instantly freeze and burst hydronic cooling coils. FAUs require a pre-heat coil (electric or hot water) installed upstream, or the chilled water system must be dosed with a precise concentration of Propylene Glycol to lower the fluid's freezing point.
Opposed Blade Dampers (OBD) feature adjacent blades that rotate in opposite directions. Unlike parallel blade dampers which throw air to one side of the duct, OBDs maintain a straight, laminar airflow profile even when partially closed, making them mandatory for precise volumetric balancing in AHUs.
