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LoadCairn / Cooling load

Data center cooling load calculator.

Explore a transparent first-pass estimate from IT power, lighting, occupants, and your envelope heat-gain estimate. Calculate in your browser, then save valid estimates to a LoadCairn Pro project.

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Inputs

Illustrative example · editable

Starting values: 8 kW IT load, 1,200 W lighting, 6 people, and 5,000 BTU/hr envelope heat gain. These are examples, not building facts or recommended design values.

Use IT equipment input power in the conditioned space.

The estimate treats all entered lighting power as heat in the space.

Each person adds 250 BTU/hr sensible + 200 BTU/hr latent heat.

Enter your own estimate for net heat gain through the building envelope.

Live estimate

Rounded for display; calculations retain full precision.

Total cooling load
39,092BTU/hr
Refrigeration capacity
3.26tons
Thermal cooling load
11.46kW thermal
Chilled water? Chilled water flow (GPM) →
Checking Pro access…Download cooling load reportExport CSV

Estimates for planning only, not a substitute for a licensed engineer’s design or manufacturer data.

Calculation details

Inputs used

IT electrical load
8 kW
Lighting electrical load
1200 W
People
6 people
Envelope heat gain estimate
5000 BTU/hr

Formula and calculation trace

  1. Step 1: Total BTU/hr = (IT kW × 1,000 + lighting W) ÷ 0.2930711
  2. Step 2: + people × 450 + envelope BTU/hr
  3. Step 3: Refrigeration tons = total BTU/hr ÷ 12,000
  4. Step 4: Thermal cooling kW = total BTU/hr × 0.0002930711
  5. Step 5: IT heat = 8 kW x 1,000 / 0.2930711 = 27,297.1303 BTU/hr
  6. Step 6: Lighting heat = 1200 W / 0.2930711 = 4,094.5695 BTU/hr
  7. Step 7: People sensible heat = 6 x 250 = 1,500 BTU/hr
  8. Step 8: People latent heat = 6 x 200 = 1,200 BTU/hr
  9. Step 9: People heat = 1,500 + 1,200 = 2,700 BTU/hr
  10. Step 10: Total = 27,297.1303 + 4,094.5695 + 2,700 + 5000 = 39,091.6998 BTU/hr
  11. Step 11: 39,091.6998 BTU/hr / 12000 = 3.2576 tons
  12. Step 12: 39,091.6998 BTU/hr x 0.0002930711 = 11.4566 kW thermal

Results and conversions

Total cooling load
39,091.7 BTU/hr
Refrigeration capacity
3.26 tons
Thermal cooling load
11.46 kW thermal
IT electrical power as heat
27,297.13 BTU/hr
Lighting power as heat
4,094.57 BTU/hr
People sensible heat gain
1,500 BTU/hr
People latent heat gain
1,200 BTU/hr
People heat gain
2,700 BTU/hr
Envelope estimate
5,000 BTU/hr

Temperature difference and solar gains

The calculator has no indoor/outdoor temperature-difference (ΔT), U-value, or area inputs, so it does not calculate an envelope conduction term such as Q = U × A × ΔT.

Solar gain is not modeled separately. You may include an estimated net solar contribution in the single envelope BTU/hr input; the calculator adds that value once to the total.

Assumptions

  • All IT electrical input power is assumed to become heat in the conditioned space.
  • All entered lighting power is treated as heat released into the conditioned space.
  • Each person contributes an illustrative 250 BTU/hr sensible plus 200 BTU/hr latent (450 BTU/hr total) for moderately active office work at 75°F.
  • Envelope heat gain is the value you supply; it is not estimated from building details.

What this estimate does not model

  • Design weather, solar gain, envelope construction, or thermal storage and time delay.
  • Ventilation, infiltration, airflow, or cooling distribution.
  • Schedules, load diversity, simultaneous peaks, or HVAC fan and system effects.
  • Cooling redundancy or heat rejected outside the room by liquid-cooled equipment.
  • Changes in occupant activity or room conditions that alter people heat gain.

Sources

This arithmetic sum is a first-pass estimate, not a peak design-load calculation, compliant design, or equipment recommendation. For real equipment sizing, use model-specific manufacturer performance data at its stated rating conditions. Estimates for planning only, not a substitute for a licensed engineer’s design or manufacturer data. This report reflects the saved inputs and stated assumptions; verify results against project conditions and model-specific information before making design or purchasing decisions.

Refrigerant room screen

A2L room-safety screening

Small split and in-row cooling units are moving from R-410A to A2L refrigerants such as R-32 and R-454B, which add leak-safety considerations in small rooms like IDF/MDF closets and edge sites. Use this RCL-based planning screen to compare entered charge with room volume; it is a planning estimate only — not a code-compliance determination and not an engineering design.

Room and charge inputs

Browser-local · editable

Enter room area for context, room volume for the calculation, and the equipment charge. The screen converts sq ft and cu ft to SI units before applying RCL.

Required room context; it does not infer a ceiling height.

The volume used by this concentration screen.

Use the charge you intend to screen from equipment or circuit data.

Initial options are limited to source-backed common comparison cases.

Live screening

Results retain full precision; displayed values are rounded for readability.

R-32 · A2L

Within this RCL-based screen

The entered charge does not exceed this RCL comparison. This result is not a statement that the installation is safe or code-compliant.

Room context
100 sq ft · 800 cu ft
Converted volume
22.6535 m³
RCL used for screen
0.061 kg/m³
Entered charge
3 lb · 1.361 kg
Calculated concentration
0.0601 kg/m³
Maximum screened charge
3.046 lb · 1.382 kg (RCL × room volume)

Assumptions and method

  • Inputs are entered in the initial US-facing units: square feet, cubic feet, and pounds.
  • Room volume is the screening basis; area is retained as room context and does not infer a ceiling height.
  • A2L maximum screened charge is calculated as RCL × room volume in cubic metres.
  • The selected charge represents the refrigerant charge being screened; confirm the actual circuit and equipment data from the manufacturer.

Planning formula: charge kg ÷ room volume m³ gives concentration. For A2L selections, the screen compares it with the selected RCL of 0.061 kg/m³ and calculates the maximum screened charge as RCL × volume.

Limitations

  • This RCL-based planning screen is not a code-compliance determination, not an engineering design, and does not establish that an installation is safe or compliant.
  • Actual requirements depend on the adopted jurisdiction and code, occupancy/use, installation arrangement, equipment listing and manufacturer instructions, refrigerant circuit and charge details, and detection/ventilation design.
  • A result above the screen indicates that leak-mitigation review may be needed; a transfer grille or mechanical fan are examples to review, not automatically required measures.
  • A qualified engineer and the authority having jurisdiction must evaluate the actual installation. This screen does not model all Standard 15 restrictions, leak scenarios, airflow paths, or equipment-specific limits.

Sources

LoadCairn / GuideData center planning

Cooling load, with the method in view.

This guide explains what the LoadCairn cooling-load calculator asks for, how it turns those values into BTU/hr, refrigeration tons, and thermal kW, and where the estimate stops being a design calculation.

Open the cooling-load calculatorCalculator updates

01 / Method

Four inputs. Three visible outputs.

The calculator first converts the electrical inputs into an arithmetic heat-load total, adds people and the envelope estimate, then expresses that total in three planning units.

Formulas used

Total BTU/hr = ((IT kW × 1,000) + lighting W) ÷ 0.2930711 + (people × 450) + envelope BTU/hr

Refrigeration tons = total BTU/hr ÷ 12,000

Thermal cooling kW = total BTU/hr × 0.0002930711

These are unit conversions and an arithmetic sum. They do not add equipment efficiency or fan power. Thermal kW is a cooling-load quantity, not electrical demand.

02 / Inputs

What to enter

Use values for the scenario you are screening. The envelope value is intentionally a planner-supplied estimate; this tool does not infer it from area, construction, or weather data.

IT electrical loadkW
Enter the IT electrical load in kilowatts. The calculator treats this input as heat in the conditioned space.
Lighting electrical loadW
Enter the lighting electrical load in watts. The calculator treats all entered lighting power as heat.
People countwhole number of people
Enter a whole-number count of people in the conditioned space.
Envelope heat-gain estimateBTU/hr
Enter a planner-supplied estimate. The calculator does not derive envelope heat gain from building details.

03 / Boundaries

A first-pass planning estimate.

The result is useful for inspecting the arithmetic behind an early planning scenario. It is not a peak design-load calculation, compliant design, or equipment recommendation.

Assumptions

  • IT electrical input is treated as heat in the conditioned space.
  • Lighting electrical input is treated as heat in the conditioned space.
  • Each person contributes 450 BTU/hr: 250 sensible and 200 latent, under the illustrative moderately active office-work assumption at 75°F.
  • Envelope heat gain is supplied by the user and is not derived from building details.

Not modeled

  • Design weather, solar gain, envelope construction, and thermal storage.
  • Ventilation, infiltration, airflow, and distribution effects.
  • Schedules, diversity, simultaneous peaks, and changing occupant conditions.
  • Fan or other cooling-system effects and equipment redundancy.
  • Liquid-cooled heat rejection that does not become room heat in the same way.

Review project-specific design weather, construction, schedules, airflow, redundancy, heat-rejection paths, and manufacturer data with the responsible engineering team before sizing or selecting equipment.

04 / Next step

Run the worked calculation with your values.

Enter your own inputs, inspect the live outputs, and expand the calculation details in the existing calculator.

Try your own inputs

Questions / Engineering estimates

Cooling load questions

Why does the calculator treat IT electrical power as heat?

The calculator uses the entered IT electrical load as an equivalent heat contribution to the conditioned space for this first-pass arithmetic. It does not model where heat is rejected by liquid cooling or other equipment, so confirm that the chosen boundary represents the load the cooling system must serve.

What does the people assumption include?

The page uses an illustrative 450 BTU/hr per person, split into 250 sensible and 200 latent BTU/hr, for moderately active office work at 75°F. It is a fixed assumption in the calculator, not a measurement of occupants or a substitute for a project-specific people-load basis.

Does the calculator estimate envelope heat gain from the building?

No. Envelope heat gain is an input that the user supplies in BTU/hr. The calculator does not inspect orientation, wall and roof construction, glazing, solar exposure, thermal mass, weather, or schedules to derive it.

How does it convert the total load to refrigeration tons?

It divides the computed BTU/hr total by 12,000 BTU/hr per refrigeration ton. The result expresses the same calculated thermal load in another unit; it is not a selected chiller capacity and does not include redundancy or an added reserve.

Is the displayed thermal kW the same as electrical kW?

No. The displayed thermal kW is a unit conversion of the heat-load total. It is not the electrical demand of the chiller or other cooling equipment, and the calculator does not model cooling-system efficiency or input power.

Can I use this total as the final design cooling capacity?

No. This is a planning estimate from four entered contributions. Weather, ventilation, infiltration, schedules, diversity, equipment losses, controls, heat rejection, and project criteria may affect a complete design. Validate inputs and assumptions with the project team and equipment documentation.

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