When working on HVAC systems in commercial spaces like malls, you’re often given:

• ✅ Available chilled water flow rate (GPM)

• ✅ Tapping pipe size (diameter)

But the question is:
“How much HVAC tonnage can we actually use from this available flow?”

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✅ Tonnage Calculation Formula

Use this standard HVAC formula:

Tonnage = (GPM × ΔT × 500) ÷ 12,000

Where:
• GPM = Chilled Water Flow Rate (in gallons per minute)

• ΔT = Temperature difference between chilled water supply and return (°F)

• 500 = Constant (8.33 × 60)

• 12,000 = BTUs/hr per cooling ton

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🧮 Example:

If the mall provides:
• Chilled water flow = 120 GPM
• Chilled water ΔT = 10°F (typical design)

Tonnage = (120 × 10 × 500) ÷ 12,000 = 50 Tons

💡 Final Tip:

Always confirm:

• The actual ΔT used by the central plant (can vary from 8–12°F)

• If the GPM is continuous or peak load-based

• Pressure drop limits of your internal chilled water system

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