Lab Freezer Holdover Time Estimator
Critical sample storage depends on accurate holdover estimates. Supply the validated holdover energy from your ultra-low freezer and the measured heat gain during outages to see how many hours you have before temperatures drift beyond alarm limits, even after reserving a safety buffer.
Planning aid only. Validate holdover performance with manufacturer data, on-site testing, and GMP documentation.
Examples
- 9.5 kWh reserve, 450 W heat gain, 15% buffer ⇒ Effective energy available: 8.08 kWh • Heat gain assumed: 450.00 W • Holdover window before alarms: 17.95 hours (1,077.00 minutes / 0.75 days)
- 12.2 kWh reserve, 520 W heat gain, buffer blank ⇒ Effective energy available: 12.20 kWh • Heat gain assumed: 520.00 W • Holdover window before alarms: 23.46 hours (1,407.71 minutes / 0.98 days)
FAQ
Where do I find the holdover energy?
Manufacturers list it in service manuals or thermal mapping reports. If you only have holdover hours at a given heat load, convert to kWh by multiplying watts × hours ÷ 1,000.
Can I model dry ice or liquid CO₂ injection?
Yes. Convert the latent heat provided by the backup system into kWh and add it to the holdover energy before running the calculation.
What if ambient temperatures spike?
Increase the heat gain input to reflect worst-case facility HVAC failures. The runtime will shrink accordingly, letting you plan faster relocation.
Does this replace annual thermal mapping?
No. Use it for planning only and continue to validate holdover with ASHRAE-compliant thermal mapping and data-logger studies.
Additional Information
- Holdover energy should reflect the interval from set point to the highest allowable product temperature (e.g., −80°C to −50°C).
- Heat gain rises if doors open during an outage—include door-open studies or add margin when facilities staff perform emergency access.
- Buffers account for temperature sensor lag and cabinet stratification so alarms trigger before samples breach thresholds.