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Boiler Size Calculator

Boiler gross output with piping and pickup allowance.

Inputs

Inputs and assumptions

Heated floor area.

30 average, 45+ cold climate or drafty.

1.15 radiators, 1.25+ large water volume.

Result

Boiler gross output (BTU/hr)
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Net heat load (BTU/hr)
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What to check

  • Heated area
  • Radiation type and water volume

Related calculators

Rule-of-thumb screening estimate, not an ACCA Manual J calculation. Confirm with a room-by-room Manual J load calculation and installer quotes before buying equipment.

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