HEATING PRESSURISATION • ENGINEERING TOOL

Expansion Vessel Engineering

Domestic and commercial vessel sizing, design pre-charge and commissioning verification with method-specific engineering logic.

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CONTROLLED VERIFICATION — REMEDIATION COMPLETE Primary BS 7074-2 evidence has been integrated into the controlled low- and medium-temperature engine. Independent competent technical sign-off remains the final gate before production-approved status.
EMERY-EV-DOMESTIC-7074-1.2

Domestic / Quick vessel sizing

BS 7074 / GES-style quick sizing is kept separate from commissioning. The sizing pressure Pi is the cold-fill assumption used by this quick calculation; it is not automatically issued as the vessel recharge target.

Pressure guide — badge / target / measured / cold-fill
Keep sizing and commissioning separate. The Domestic sizing pressure Pi is a BS7074/GES-style calculation input. A recharge target is only issued when a separate commissioning basis is explicitly selected. The badge value is record-only; measured pre-charge is the unloaded gas-side reading; actual cold-fill is the water-side pressure after filling.
System-volume estimate: if the actual content is not known, the controlled quick estimate is 12 L/kW. For commercial work, use the component-by-component water-volume builder in the EN 12828 tab instead.

Actual vessel selection check

Enter the nominal capacity of the actual vessel or combined vessels you intend to use. EMERY will check it against the calculated minimum rather than assuming a universal manufacturer stock size.

Minimum calculated nominal vessel capacity
— L
Enter system water volume.
Expansion volume
— L
Sizing pressure Pi
— bar
Final pressure
— bar
Minimum nominal capacity
— L
Show domestic workings
Enter system water volume to calculate.
EMERY-EV-COMMERCIAL-EN12828-1.2

Commercial fixed-vessel system water content

Preferred commercial route in this release. Exact known water content overrides the component sum. Boiler count means hydraulically connected boilers, not merely burners currently firing.

Firing status does not change system water volume. Count boilers that are hydraulically connected to this calculation case.

Pipework sections

Enter actual internal bore and measured length.
Internal Ø (mm)
Length (m)
System water volume used by engine
0.0 L
Pipework: 0.0 L • Connected boiler duty: 195 kW

Commercial EN 12828 design inputs

Water-only controlled release. Automatic expansion data is currently verified only from a 10°C cold reference. Other cold temperatures require a manual verified expansion factor and source.

Pressure separation: p0 (vessel gas pre-charge/minimum operating pressure), initial/cold-fill pressure and final design pressure are separate variables in this commercial engine.

Selected / existing vessel & commissioning

Record the vessel badge separately from the commissioned pressure. The factory/badge pre-charge is informational only and is not automatically used as the design target.

BS EN 12828 minimum nominal vessel capacity
— L
Enter a valid system water volume and design inputs.
Expansion volume Vex
— L
Water reserve Vwr
— L
Design p0
— bar
Final pfin
— bar
Vessel commissioning / recharge
Calculated target p0— bar
Factory / badge— bar
Measured actual— bar
Cold-fill pressure— bar
Safety valve @ vessel level— bar
Complete the design inputs to establish the target pre-charge.
Show EN 12828 engineer calculation
Enter valid inputs to calculate.
EMERY-EV-COMMERCIAL-BS7074-2-2.0

Commercial BS 7074-2 controlled calculation

Primary-evidence implementation of the current BSI code of practice. Low-temperature (≤100°C) and medium-temperature (100–120°C) routes are kept separate. The automatic calculation is controlled for the lowest-point/basement vessel arrangement demonstrated by the standard; unsupported arrangements fail closed.

Optional base working-pressure verification
BS 7074-2 also requires the pressure at the base/component to be checked against its working pressure where applicable. Enter all four values together; this verification does not alter the vessel sizing result.
Controlled boundaries: water only for automatic BS 7074-2 expansion values; glycol remains HOLD. High-level vessel arrangements require a manufacturer-recommended acceptance factor. Multiple boilers that can be isolated and fired require the additional boiler-specific expansion protection described by BS 7074-2.
BS 7074-2 minimum nominal vessel capacity
— L
Enter valid design inputs.
Initial design pressure Pi
— bar
Final design pressure Pf
— bar
Acceptance factor
—
Expansion volume
— L
Anti-flash allowance Pa
— bar
Clause-derived Pmax after vessel selection
— bar
Show BS 7074-2 engineer calculation & evidence trace
Enter valid inputs to calculate.
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Pressurisation-unit engine locked

BS EN 12828 treats pump- and compressor-controlled pressurisation differently from a fixed diaphragm vessel and uses the equipment utilisation efficiency / manufacturer-specific control data. This app will not pass a pressurisation unit through the fixed-vessel formula. Add a manufacturer/model-specific engine only after the required utilisation and pressure-control data are verified.

Source-controlled method status

BS EN 12828:2012+A1:2014 — current BSI water-based heating design standard, used for the commercial fixed-vessel architecture.
BS 7074-1:1989 — current BSI domestic code of practice; domestic quick mode remains method-specific.
BS 7074-2:1989 — current BSI commercial/industrial low- and medium-temperature expansion-vessel code; primary evidence integrated for Sections 2/3, Tables 2/3 and Appendix A.
BS EN 13831:2007 — current, under review, BSI product standard for closed expansion vessels with built-in diaphragm; product/rating evidence is controlled separately from system sizing.
Caleffi heating-vessel technical literature — used for the controlled 10°C water-expansion formula and optional published final-pressure margin.
GES — secondary benchmark only for domestic quick-mode comparison, not the authority for commercial sizing.
BS EN 14336:2025 — current BSI installation/commissioning standard; added to the commissioning source architecture.