Calculator Inputs
Use the 3-column calculator layout on large screens, 2-column on smaller screens, and 1-column on mobile.
Example Data Table
The table below shows sample scenarios to help users understand how inputs affect required steam rate and approximate boiler horsepower.
| Scenario | Basis | Design Load | Pressure | Condensate Return | Efficiency | Estimated Steam | Estimated Output | Approx. BHP |
|---|---|---|---|---|---|---|---|---|
| Office retrofit | Heat load | 1,200,000 BTU/h | 10 psig | 80% | 82% | 1,631 lb/h | 1,688,623 BTU/h | 50.4 |
| Hospital wing | Heat load | 2,500,000 BTU/h | 15 psig | 75% | 84% | 3,699 lb/h | 3,843,840 BTU/h | 114.8 |
| Process laundry | Steam demand | 1,800 lb/h | 30 psig | 85% | 85% | 2,313 lb/h | 2,350,479 BTU/h | 70.2 |
Formula Used
Feedwater Temperature = (Condensate Return % × Condensate Temperature) + (Makeup Water % × Makeup Water Temperature)
Sensible Heat ≈ Cp of Water × (Saturation Temperature − Feedwater Temperature)
Enthalpy Rise ≈ Sensible Heat + Latent Heat of Vaporization
Useful Steam = Adjusted Useful Heat Load ÷ Enthalpy Rise
Adjusted Useful Heat Load = Design Heat Load × Distribution Loss Factor × Pickup Factor × Safety Factor
Generated Steam = Useful Steam × (1 + Blowdown Percentage)
Boiler Output = Generated Steam × Enthalpy Rise
Boiler Input = Boiler Output ÷ Efficiency
Boiler Horsepower = Boiler Output ÷ 33,475
How to Use This Calculator
- Select imperial or metric units.
- Choose whether you want to size by heat load or direct steam demand.
- Enter steam pressure, condensate return rate, return temperature, and makeup water temperature.
- Add distribution loss, pickup factor, blowdown allowance, boiler efficiency, and safety margin.
- Enter expected operating hours per day and days per year for annual energy estimates.
- Click Calculate Boiler Size to view results above the form.
- Review generated steam, output, input, annual energy, and approximate boiler horsepower.
- Download the result summary as CSV or PDF if you want to share or archive it.
Frequently Asked Questions
1) What does this calculator estimate?
It estimates generated steam rate, boiler output, fuel input, annual energy use, and approximate boiler horsepower. It is intended for early sizing and comparison, not final stamped design.
2) Why is condensate return included?
Returning hot condensate reduces how much sensible heat the boiler must add. Higher return percentages usually lower fuel demand and improve overall steam system efficiency.
3) Why does pickup factor matter?
Pickup factor covers startup conditions, piping warmup, and practical system allowances. It helps prevent undersizing when the connected system needs extra steam during ramp-up periods.
4) What is blowdown allowance?
Blowdown removes dissolved solids from the boiler. Because some water and heat are intentionally discharged, the boiler must generate slightly more steam than the useful building demand.
5) Should I size from heat load or steam demand?
Use heat load when you know the building or process duty in BTU/h or kW. Use direct steam demand when your equipment schedule already lists required steam flow.
6) Is boiler output the same as fuel input?
No. Boiler output is the useful thermal energy delivered to produce steam. Fuel input is higher because combustion and transfer losses reduce the portion converted into useful steam energy.
7) Can I use this for modular boiler plants?
Yes. Enter a preferred module size in boiler horsepower. The calculator will estimate how many modules are needed to meet the rounded design boiler requirement.
8) Is this enough for final equipment selection?
No. Final selection should still check steam quality, turndown, emissions, controls, altitude, redundancy, code requirements, manufacturer data, and detailed operating profiles.
Important Sizing Notes
This page uses a practical sizing model based on pressure-dependent saturated steam properties and mixed feedwater temperature. It is best for preliminary planning, budgeting, and comparing alternatives during construction and retrofit studies.