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Calcimator

Chiller Sizing Calculator

Size chiller systems based on water flow rate, temperature differential, diversity factor, and efficiency metrics.

Inputs

GPM

Rule of thumb: 2.4 GPM/ton at 10°F ΔT; 3.0 GPM/ton at 8°F ΔT per ASHRAE

°F

Standard CHWR: 54°F (high ΔT systems use 58–60°F for energy savings)

°F

Standard CHWS: 44°F; high-efficiency: 46–48°F; humidity control requires ≤45°F

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Results

Required Cooling Capacity

194.79 tons

≈ 33 elephants

Estimated Chiller Power

155.83 kW

≈ 10 homes' peak draw

Cooling Capacity2,337,500 BTU/hr
Power per Ton0.8 kW/ton
How to Use This Calculator
  1. Enter Chilled Water Flow, Entering Water Temp, and Leaving Water Temp.
  2. Set Diversity Factor and Safety Factor.
  3. Review Required Cooling Capacity (tons) and Estimated Chiller Power (kW).
  4. Use Cooling Capacity (BTU/hr) and Power per Ton (kW/ton) to inform your decision.

How the result changes with Entering Water Temp

Entering Water TempRequired Cooling CapacityEstimated Chiller Power
4638.96 tons31.17 kW
61331.15 tons264.92 kW
79681.77 tons545.42 kW
94973.96 tons779.17 kW

What each input means

Chilled Water Flow
Chilled water flow rate through the evaporator in gallons per minute. ASHRAE 90.1 and AHRI 550/590 govern chiller performance ratings at standard conditions.
Entering Water Temp
Temperature of chilled water returning to the chiller (after absorbing heat). ASHRAE 90.1 standard chilled water design is 44°F supply / 54°F return (10°F ΔT).
Leaving Water Temp
Temperature of chilled water leaving the chiller (supply to building). Standard ASHRAE 90.1 design is 44°F supply; higher supply temps (46–48°F) improve efficiency (COP) but reduce dehumidification.
Diversity Factor
Percentage of total load expected to occur simultaneously. Accounts for partial loading.
Safety Factor
Oversizing factor for future expansion or extreme conditions. 110% = 10% safety margin.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Chilled Water Flow = 500, Entering Water Temp = 54, Leaving Water Temp = 44, Diversity Factor = 85 = 5 input(s) provided
  2. Calculate Required Cooling Capacity
    Required Cooling Capacity
    194.79 = 194.79
  3. Calculate Estimated Chiller Power
    Estimated Chiller Power
    155.83 = 155.83
  4. Calculate Cooling Capacity
    Cooling Capacity
    2337500 = 2337500
  5. Calculate Power per Ton
    Power per Ton
    0.8 = 0.8

Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.

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