01
Define the operating question
Examples include whether an outdoor-air fraction is plausible, whether a cooling section removes moisture, or whether reheat changes temperature without adding water. State the question, operating mode and expected boundary before taking readings.
A psychrometric result can reveal inconsistency but cannot by itself assign cause. Damper position, airflow, fan state, valve command and time belong in the same record.
02
Collect synchronized, representative observations
Measure outdoor, return, mixed and supply dry bulb plus RH or dew point with traceable instruments. Use one station pressure for a connected air handler unless a pressure-changing boundary is explicitly modeled. Allow sensors to stabilize and avoid radiant or stratified locations.
Label measured inputs separately from calculated wet bulb, humidity ratio and enthalpy. Include uncertainty and calibration status so apparent small differences are not over-interpreted.
03
Calculate the moisture and energy story
Compare humidity ratio first: a cooling section that removes condensate should leave a lower W; reheat should leave W essentially unchanged. Compare enthalpy second and use dry-air mass flow for rates. At 101.325 kPa, 32 °C/55% outdoor air is 16.493 g/kg and 74.423 kJ/kg, while 24 °C/50% return is 9.300 g/kg and 47.819 kJ/kg.
A 13 °C/90% supply state is 8.387 g/kg and 34.258 kJ/kg. That supports an air-cooling and moisture-removal interpretation, subject to airflow and uncertainty.
04
Test mixing rather than averaging
Predict mixed air from dry-air mass and energy balances, then compare it with the measured mixed sensor. A disagreement may reflect outdoor fraction, leakage, heat gain, poor mixing, time offset or sensor bias.
Do not average RH or dry bulb alone. If volume flows are used, correct each stream to dry-air mass flow with the appropriate state density.
05
Close the record and know the limit
Retain inputs, pressure, units, calculated states, device conditions and exports. Mark conclusions as observed, calculated or inferred. Repeat a suspect result after stabilization before escalating.
This workflow does not certify ventilation compliance, coil capacity, indoor-air quality or control safety. Next action: enter the four readings in the airside comparison sequence, then test the mixing balance.