Calculate supply-side sensible heat-recovery effectiveness from three dry-bulb temperatures.
Why it matters: Temperature effectiveness is a direct field screen of a heat-recovery device.
ΣCALCULATE · VERIFY · INTERPRET
Calculated result
Engineering evaluation
Physically consistent effectiveness
Supply-side sensible effectiveness (ε)60 %
Signed entering-stream temperature potential (ΔTmax)
50 °F
Outdoor entering temperature (To)
20 °F
Exhaust entering temperature (Te)
70 °F
Engineering interpretation
The entered temperatures indicate 60% supply-side sensible effectiveness.
Important limitations
Flow imbalance, leakage, purge, frost control, fan heat, casing heat transfer, bypass, and latent transfer require separate review.
Engineering knowledge center
Understand the calculation—not just the answer
2026-08-07 · Free Library
Governing relationships
ΔTmax = Te−To
ε = (Ts−To)/ΔTmax×100
physical range 0%≤ε≤100%
Current substitution
ε = (50−20)/(70−20)×100 = 60%.
Calculation sequence
Step-by-step method
Confirm all temperatures are measured at the heat-recovery device boundaries.
Calculate the signed entering-stream temperature potential for heating or cooling mode.
Divide the supply-stream temperature change by that potential and check the physical 0–100 percent range.
Equation legend
Inputs and calculated quantities
To
Outdoor-air entering temperature — °F or °C
Te
Exhaust-air entering temperature — °F or °C
Ts
Supply-air leaving temperature — °F or °C
ε
Supply-side sensible effectiveness — %
ΔTmax
Signed entering-stream temperature potential — °F
To
Outdoor entering temperature — °F
Te
Exhaust entering temperature — °F
Applications
How this calculation is used
Building design
Relate scheduled leaving-air temperature to ideal sensible recovery.
Construction
Check sensor locations and flow arrangement.
Commissioning
Calculate sensible temperature effectiveness at a documented operating condition.
Quality controls
Assumptions and limitations
Assumptions
Entered values represent one stable operating condition and use consistent measurement boundaries.
Fluid and air properties are representative of the evaluated condition.
Limitations
This is a preliminary evaluation and field-verification tool, not a final sizing or code-compliance determination.
Manufacturer data, adopted codes, project criteria, and professional engineering review remain controlling.
Field use
Verification procedure
Confirm measurement boundaries, operating mode, and instrument calibration.
Stabilize the system and record simultaneous readings.
Compare the calculation with project requirements and manufacturer data before disposition.
Common engineering mistakes
Mixing values from different operating conditions.
Using nominal rather than measured flow, temperature, power, or fluid properties.
Technical basis
References and source standards
ASHRAE Handbook—FundamentalsPsychrometrics, heat transfer, load relationships, and HVAC calculation context; verify the licensed current edition during professional review.
These engineering tools are provided for educational, preliminary evaluation, field verification, and commissioning support. Results depend on the accuracy of user-entered information and the assumptions stated for each calculation. Every colored status and comparison is a screening indicator only; project criteria, contract requirements, applicable codes, manufacturer instructions, measurement uncertainty, and authorized engineering judgment govern. The tools do not replace project-specific engineering analysis or the judgment of a licensed professional engineer.
