Field tools & calculators
Pocket calculators for the van and the exam — gas rate, heat loss, drainage fall, ventilation, CO/CO₂ ratio, head & pressure and water heat-up. Each shows the working and the standard it follows.
Gas Rate & Heat Input
Heat input from a timed meter-dial reading.
Open calculatorHead ↔ Pressure
Convert vertical head of water to static pressure.
Open calculatorDrainage Fall & Gradient
Convert a drain run and gradient ratio into fall in millimetres.
Open calculatorGas Pipe Sizing Pre-Check
Load, gas volume and route worksheet before the BS 6891 table lookup.
Open calculatorExpansion Vessel Sizing
Estimate vessel volume from water volume, expansion and pressure range.
Open calculatorHeat Loss & Radiator Size
Estimate room heat loss and the radiator catalogue output to look for.
Open calculatorOpen-Flued Ventilation
Air-vent free area for an open-flued appliance (revision rule).
Open calculatorCO/CO₂ Ratio
Combustion ratio and pass/fail vs the 0.004 limit.
Open calculatorWater Heat-Up Time
Time to heat a volume of water at a given power.
Open calculatorTraining & revision aids — live installations follow the full standard, the manufacturer’s instructions and calibrated instruments.