Calculation sequence
Step-by-step method
- Confirm even sampling and valid binary state values.
- Divide ON samples by total valid samples.
- Count OFF-to-ON transitions and divide by represented hours.
CommissioningBeginnerControls
Trend Runtime and Cycling Calculator
Calculate runtime percentage, runtime hours, and starts per hour from evenly sampled trend data.
Why it matters: Runtime and cycling metrics help identify short cycling, unstable control, excessive wear, and operational mismatch.
Calculated result
Engineering evaluation
Runtime percentage (RP)50 %
- Calculated runtime (RH)
- 12 h
- Starts per hour (C)
- 0.5 starts/h
Engineering interpretation
The trend indicates 50% runtime (12 h) and 0.5 starts per hour. Review sampling interval, missing data, command versus proof status, and the entered equipment-specific cycling limit.
Engineering knowledge center
Understand the calculation—not just the answer
Governing relationships
RP = Non/N×100
RH = H(Non/N)
C = Ns/H
within entered cycling criterion when C ≤ L
Current substitution
RP = 720/1440×100 = 50%; RH = 24(720/1440) = 12 h; C = 12/24 = 0.5 starts/h.
Equation legend
Inputs and calculated quantities
- H
- Trend period — h
- Non
- Samples in ON state — samples
- N
- Total samples — samples
- Ns
- Counted starts — starts
- L
- Entered cycling limit — starts/h
- RP
- Runtime percentage — %
- RH
- Calculated runtime — h
- C
- Starts per hour — starts/h
Applications
How this calculation is used
Building design
Define expected runtime and cycling review criteria.
Construction
Evaluate startup and controls-trend behavior.
Commissioning
Reduce binary trend samples and counted starts into repeatable operating metrics.
Quality controls
Assumptions and limitations
Assumptions
- Entered values represent the same stable operating condition.
- Measurements and reference values use consistent units and boundaries.
Limitations
- This is a screening and field-verification tool, not an automatic acceptance decision.
- Project criteria, manufacturer data, governing standards, and measurement uncertainty remain controlling.
Field use
Verification procedure
- Confirm the approved reference values and test boundary.
- Stabilize the system and record calibrated field measurements.
- Review calculation assumptions, uncertainty, and supporting evidence before disposition.
Common engineering mistakes
- Comparing readings taken at different loads, modes, or reference conditions.
- Treating a calculated status as proof of code, contract, or manufacturer compliance.
Technical basis
References and source standards
- ASHRAE Commissioning ResourcesCommissioning-process context for defining test methods, acceptance criteria, evidence, and owner requirements.
- NIST/SEMATECH e-Handbook of Statistical MethodsPublished reference for averages, variability, standard deviation, calibration, and engineering data analysis.
Engineering calculation disclaimer
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.
Read the full use and limitation statement