Not only is total air volume considered, but also the proper velocity, quantity and throw of the conditioned air to each part of the conditioned space, along with the delivered air conditioned and its impact on the surrounding surfaces. Total HVAC performance testing is principally based upon airflow, enthalpy and their accurate measure. Sufficient pressure at the combustion air zone of an appliance.Air returned to the appliance from the conditioned space for conditioning (return air).
Delivered airflow to each space (supply air).Airflow across the heat exchanger or evaporator coil.So what does airflow measurement encompass? Without proper airflow the system and or equipment efficiency and operation are compromised resulting in unsatisfactory equipment operation, customer dissatisfaction and utility waste. Airflow must be correct at the equipment, and then delivery at the registers or terminal outlets must be verified to assure proper capacity, velocity, and throw assuring stratification or noise problems do not exist. An airflow measurement that is not repeatable, accurate, and representative of mass flow will result in calculations of system operation that are not representative of the systems efficiency, capacity or latent sensible split and resulting humidity removal. The trend to improve efficiency by installing 13-seer equipment and higher and high efficiency furnaces is in turn requiring accurate airflow measurement. Measuring airflow accurately can be very difficult. Measuring airflow should be the first step in the commissioning process and the first step when servicing equipment, it is the key component for proper equipment operation. Refrigerant charge cannot be verified until it is correct, an accurate or final combustion analysis cannot be performed, system performance cannot be measured, and really no part of the commissioning process will remain uncompromised or unaffected if airflow is anything but correct. It’s not what we consider when measuring airflow that matters its what we don’t consider that causes problems.Īirflow is the key to proper system performance. In reality they were never really measuring airflow they were simply estimating airflow at best.
For years technicians have been using standard air equations and formulas, making non-corrected airflow measurements, or making no measurement at all, simply leaving the airflow at factory settings or selecting high for cooling and medium or low for heat. When making an airflow measurement, what should it be, and how are you going to measure it? Are you selecting a blower speed from four possible choices, or quantifying equipment or system performance? Measurements made without knowledge of their expected outcome is a valueless proposition.