Chiller Tonnage Calculator – Chiller Sizing & TR Calculation

Chiller Tonnage Calculator – Chiller Sizing & TR Calculation (BTU)

Free chiller tonnage calculator: chiller sizing, TR calculation and BTU/kW cooling load for AHRI-rated chillers. Formula + example. No sign-up.

📐 Standard: ASHRAE / AHRI

✅ Free to use

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Chiller Tonnage Calculator Calculator

Reference: ASHRAE / AHRI

❄️ HVAC

Free chiller tonnage calculator: chiller sizing, TR calculation and BTU/kW cooling load for AHRI-rated chillers. Formula + example. No sign-up.

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ℹ️ About This Calculator

A chiller is the heart of a central HVAC system - it produces chilled water that is distributed to AHUs and fan coil units throughout the building. Selecting the correct chiller tonnage is critical: undersizing means the building cannot be cooled; oversizing means the chiller cycles on and off, reducing efficiency and increasing maintenance costs. 1 TR (ton of refrigeration) = 3.517 kW of cooling.

AHRI Standard 550/590 governs chiller rating conditions. Air-cooled chillers are rated at 35°C ambient; water-cooled at 29°C entering condenser water. IPLV (Integrated Part Load Value) is the weighted average efficiency over a full operating season - more important than full-load efficiency for Indian buildings where the chiller runs at part load for most of the year. BEE (Bureau of Energy Efficiency) star ratings for chillers are based on IPLV.

📐 Chiller Sizing Formula

ASHRAE / AHRI

Cooling Capacity:
  TR = Total Cooling Load (kW) / 3.517
  or
  TR = Total Cooling Load (BTU/hr) / 12,000

Chiller kW Input:
  kW_input = TR × 3.517 / COP
  Typical COP: Air-cooled: 2.8–3.5 | Water-cooled: 4.5–6.5

Chilled Water Flow:
  Q_chw (L/s) = Cooling (kW) / (ρ × Cp × ΔT)
             = kW / (4.187 × 5)    [for 7/12°C CHW system]

Condenser Water Flow (water-cooled):
  Q_cw = (Cooling kW + Compressor kW) / (4.187 × 5)  [for 29/34°C CW]

🧮 Worked Example

An office building has a calculated cooling load of 350 kW. Chiller capacity required: TR = 350 / 3.517 ≈ 99.5 TR - select a 100 TR chiller.

For a water-cooled chiller with COP 5.5: Input power = 100 × 3.517 / 5.5 ≈ 64 kW. Chilled water flow at 7/12°C (ΔT = 5°C): Q_chw = 350 / (4.187 × 5) ≈ 16.7 L/s. Condenser water flow: Q_cw = (350 + 64) / (4.187 × 5.5) ≈ 18 L/s - this sizes the condenser pump and cooling tower selection.

❓ Frequently Asked Questions

How many TR is needed per 1000 sq ft of office space? +

A typical commercial office in India requires 0.8–1.2 TR per 100 m² (0.07–0.11 TR per sq ft). For 1000 sq ft ≈ 93 m²: approximately 0.75–1.1 TR. Actual requirement depends on glass area, orientation, occupancy density, lighting load, and outdoor climate. Always perform a full heat load calculation.

Air-cooled vs water-cooled chiller - which should I choose? +

Water-cooled chillers are 40–50% more energy efficient (COP 4.5–6.5 vs 2.8–3.5) but require a cooling tower, condenser water pumps, and chemical treatment - higher first cost and maintenance. Air-cooled chillers are simpler, cheaper to install, and suitable for rooftop installation but consume more electricity. For systems above 200 TR and where year-round operation is required, water-cooled is usually more economical over the lifecycle.

What is a good COP for a chiller in India? +

BEE minimum standards: Air-cooled chillers: COP ≥ 2.80 (IPLV). Water-cooled centrifugal: COP ≥ 5.0 (IPLV). BEE 5-star rated chillers achieve COP 3.3+ (air-cooled) and 6.0+ (water-cooled). Premium inverter-driven variable speed centrifugal chillers achieve IPLV up to 9.0 - these are the benchmark for green building projects.

What is chiller staging and why does it matter? +

Chiller staging means running multiple smaller chillers in parallel rather than one large chiller. A building with 500 TR total load might use two 250 TR chillers. At 40% load, you run one chiller at 80% - close to its peak efficiency. A single 500 TR chiller at 40% load runs very inefficiently. Staging improves part-load efficiency and provides redundancy. Minimum recommended: two chillers for any system above 100 TR.

How do I convert chiller capacity from BTU to TR to kW? +

1 TR = 12,000 BTU/hr = 3.517 kW. So 100 TR = 1,200,000 BTU/hr = 351.7 kW. To convert kW to TR: divide by 3.517. To convert BTU/hr to TR: divide by 12,000. To convert BTU/hr to kW: multiply by 0.000293.

Chiller Tonnage Calculator – Chiller Sizing & TR Calculation (BTU)

ℹ️ About This Calculator

📐 Chiller Sizing Formula

ASHRAE / AHRI

🧮 Worked Example

❓ Frequently Asked Questions

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