Chiller Capacity Calculator

Chiller Capacity Calculator – HVAC Sizing & Cost Guide

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Chiller Capacity Calculator – All Presets, SI/IP, Cost & Report
HVAC Sizing Guide

Chiller Capacity Calculator — What It Is, How It Works, and How to Use It (with a Full Worked Example)

This interactive calculator sizes central chillers from first principles. It turns your room-by-room loads, ventilation targets, and design allowances into a clean recommendation: peak kW/TR, chilled-water flow, chiller count & size (with N or N+1), plus a quick cost & energy snapshot. SI/Imperial toggles, sector presets, and standards hints are built in.

1) What this calculator does

  • Segments your building (zones like open office, conference, server, OR/ICU, kitchen, cleanroom, etc.).
  • Applies sensible/latent densities (W/m²) or your direct overrides (kW/TR).
  • Calculates ventilation load from ACH × volume and a user-set enthalpy delta.
  • Rolls in diversity, piping gain, and safety to get a robust peak kW/TR.
  • Derives CHW flow from ΔT; recommends chiller count & size (N or N+1).
  • Estimates budget cost (equipment → installed → with markup) and annual energy.
  • Outputs a clean HTML report with KPIs, tables, and change log (print-ready).
Good to know: Presets for Education, Healthcare, Hospitality, Retail, Data Centers, Cleanrooms, Transport, Museums, and Cold Rooms auto-seed realistic W/m² and ACH guidance that you can fine-tune.

2) How the math works (short version)

  1. Segment loads Sensible: Qs,i = Ai × qs / 1000 kW; Latent: Ql,i = Ai × ql / 1000 kW. (Or enter overrides in kW/TR.)
  2. Ventilation (optional ACH) Qvent,i ≈ ρ × (A × H) × ACH / 3600 × Δh kW, with ρ≈1.2 kg/m³ and Δh (kJ/kg) set by you.
  3. Allowances Qbase = Σ(Qs+Ql) + Qvent + Qproc Q′ = Qbase × fdiversity → piping gain → safety → Qpeak.
  4. CHW flow SI: L/s = Q(kW) / (4.186 × ΔT[K]) ; IP: gpm = 24 × (TR) / ΔT[°F].
  5. Chillers Choose N or N+1. If N+1: (n−1) × size ≥ TRpeak.
  6. Energy & cost kWin = TR × (kW/ton) × loadFactor → annual kWh → tariff; Cost = installed TR × unit rate × install factor × (1+markup).
Full methodology, symbols & unit math

Same detailed methodology used inside the calculator’s “Methodology” panel. Standards notes are shown inline as “Values derived from <Standard> (user must verify).”

3) How to use the calculator

Select a standard & region. Pick ASHRAE/ISHRAE/CIBSE/AHRI profile and India/US/UK for currency & seed unit rates.
Set strategy. Choose climate zone, operating schedule, ΔT (6/8/10 K), and chiller core (scroll/screw/centrifugal/mag-bearing).
Load your segments. Use a preset (e.g., “Education → Classroom”) or click “Add Empty Segment.” Enter area, W/m², overrides, height, and ACH (if you want ACH-based ventilation).
Ventilation basis. “ACH-based” sums each segment’s ACH load; “Manual” uses a single global kW.
Allowances. Adjust diversity, piping gain and safety to your practice.
Selection & costing. Choose N or N+1, optional preferred TR size, and refine unit rate / install factor / markup / kW/ton / hours / load factor / tariff.
Calculate & report. Hit Calculate to see KPIs, table, and chart. Use Generate Report for a print-ready HTML report.

Related tools: You might also like Cooling Load Calculator, Duct Sizing Calculator, Pipe Design Calculator, and Psychrometrics – Moist Air Guide.

4) Worked example — Office floor (full calculation)

Target: Size central chiller plant for an office floor with open office, conference suite, and a small server room. Use SI for the math; show key IP equivalents.

Inputs & assumptions

  • Segments (height H = 3.2 m, Δh = 12 kJ/kg, ACH-based ventilation):
SegmentArea (m²)Sensible (W/m²)Latent (W/m²)Overrides (kW)ACH
Open Office6007015—2
Conference Suite20010025—4
Server Room50——Sensible = 30, Latent = 06
  • Allowances: Diversity 0.90; Piping gain 3%; Safety 10%.
  • CHW: 7 → 15 °C (ΔT = 8 K).
  • Selection: N+1 redundancy.
  • Costing (India): Water-cooled unit rate ₹20,000/TR; install factor 1.5; markup 10%.
  • Energy: kW/ton = 0.70; hours/year = 3,000; avg load factor = 0.55; tariff ₹9/kWh.

Step-by-step math

  1. Segment loads Open Office: Qs = 600×70/1000 = 42.00 kW, Ql = 600×15/1000 = 9.00 kW Conference: Qs = 200×100/1000 = 20.00 kW, Ql = 200×25/1000 = 5.00 kW Server Room (override): Qs = 30.00 kW, Ql = 0.00 kW Totals: Sensible = 92.00 kW; Latent = 14.00 kW; Internal = 106.00 kW.
  2. Ventilation (ACH-based) with ρ=1.2 kg/m³, Δh=12 kJ/kg Volume per segment = A×H. Load ≈ 1.2×Volume×ACH/3600×Δh.
    • Open Office: V=600×3.2=1920 m³ → 1.2×1920×2/3600×12 = 15.36 kW
    • Conference: V=200×3.2=640 m³ → 1.2×640×4/3600×12 = 10.24 kW
    • Server: V=50×3.2=160 m³ → 1.2×160×6/3600×12 = 3.84 kW
    Ventilation total = 29.44 kW
  3. Allowances Qbase = 106.00 + 29.44 = 135.44 kW Diversity: Q′ = 135.44 × 0.90 = 121.896 kW Piping: Q″ = 121.896 × 1.03 = 125.55288 kW Safety: Qpeak = 125.55288 × 1.10 = 138.10817 kW
  4. Convert to TR (1 TR = 3.517 kW): TRpeak = 138.10817 / 3.517 = 39.27 TR
  5. CHW flow SI: L/s = 138.10817 / (4.186 × 8) = 4.124 L/s IP: ΔT=8 K=14.4 °F → gpm = 24×TR/ΔT = 24×39.27/14.4 = 65.45 gpm
  6. Selection (N+1) Choose 3 × 20 TR. Check: (3−1) × 20 = 40 TR ≥ 39.27 TR ✓ Installed nameplate = 60 TR.
  7. Budget cost Equipment = 60 × ₹20,000 = ₹1,200,000 Installed = ×1.5 = ₹1,800,000 With markup (10%) = ₹1,800,000 × 1.10 = ₹1,980,000
  8. Annual energy Input kW at average = TR × kW/ton × loadFactor = 39.27 × 0.70 × 0.55 = 15.12 kW Annual kWh = 15.12 × 3,000 = 45,355 kWh Energy cost (@₹9/kWh) = ₹408,199 / year

Peak Cooling

138.11 kW (39.27 TR)

CHW Flow

4.124 L/s (65.45 gpm)

Recommended Plant

3 × 20 TR (N+1)

Budget Installed

₹1,980,000

Segment breakdown (kW)

Bars show sensible+latent per segment; ventilation shown in the table below.

SegmentArea (m²)Sensible (kW)Latent (kW)Total (kW)ACH Vent (kW)
Open Office600.042.009.0051.0015.36
Conference Suite200.020.005.0025.0010.24
Server Room50.030.000.0030.003.84
Totals92.0014.00106.0029.44

Use in the calculator: Enter the same segments, set ACH-based ventilation, allowances, ΔT=8 K, choose N+1 and India (Water-cooled). Click Calculate → the KPIs will match these numbers. Then Generate Report for a print-ready sheet.

5) Notes, tips & references

  • Validation: Always sanity-check W/m² seeds against your project’s envelope, lighting, equipment and occupancy. Presets are starting points.
  • Ventilation: If your jurisdiction mandates L/s·person or L/s·m² (e.g., ASHRAE 62.1/ISHRAE/CIBSE), convert to ACH or directly compute a ventilation kW and enter it as a manual global value.
  • ΔT strategy: 8–10 K reduces pumping power; validate coil performance and valve authority.
  • N+1 choices: For small TR peaks, 3× modules often land better than 2× big units for serviceability and turn-down.
  • Energy KPI: kW/ton is a planning value; verify AHRI-rated performance and part-load curves before final selections.
Citations (highlighted):
  • AHRI 550/590 performance rating for water-chilling packages.
  • ASHRAE Fundamentals / 90.1, ISHRAE Handbook (India), CIBSE Guide B for typical setpoints and practices.

Values derived from <Standard>, clause ranges vary; users must verify against current editions and local codes.

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