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BTU/hr → Tons
Tons = BTU/hr ÷ 12,000
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Tons → BTU/hr
BTU/hr = Tons × 12,000
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BTU/hr ↔ kW
kW = BTU/hr ÷ 3,412 | BTU/hr = kW × 3,412
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Coil Face Area
Face Area (ft²) = (Fin Height × Fin Length) ÷ 144
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Face Velocity
FPM = CFM ÷ Face Area (ft²) | Keep below 550 FPM on wet coils
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Sensible Capacity
Sensible BTU/hr = 1.08 × CFM × (Entering DB − Leaving DB)
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Latent Capacity
Latent BTU/hr = 0.68 × CFM × Grains H&sub2;O removed per lb.
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Sensible Heat Ratio (SHR)
SHR = Sensible ÷ Total | 0–1; closer to 1 = drier air
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Water Coil Capacity
BTU/hr = 500 × GPM × ΔT | Pure water; adjust multiplier for glycol
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Required GPM from Capacity & ΔT
GPM = BTU/hr ÷ (500 × ΔT)
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Steam Condensate Rate
Lbs condensate/hr = Coil Capacity (BTU/hr) ÷ Latent Heat of Steam
0 psig=970 | 5 psig=960 | 15 psig=945 | 30 psig=929 | 50 psig=915 | 100 psig=895 BTU/lb
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Approximate freeze points for ethylene and propylene glycol. Verify with manufacturer data.
| Concentration | Ethylene Glycol | Propylene Glycol |
|---|---|---|
| 10% | 26°F (-3°C) | 27°F (-3°C) |
| 20% | 18°F (-8°C) | 19°F (-7°C) |
| 30% | 6°F (-14°C) | 9°F (-13°C) |
| 40% | -12°F (-24°C) | -7°F (-22°C) |
| 50% | -34°F (-37°C) | -28°F (-33°C) |
| 60% | -55°F (-48°C) | -55°F (-48°C) |