Hydronic Pump Selector

How it works

Use the tool in this order:

• Project — site, client, references, and engineer context. None of these affect the calculation; they label it.
• Sizing — flow, head, NPSH, motor, and pump family.
• Report — engineering report preview with print stylesheet.
• Pro — saved projects & revision history, clean issuable records, and the procurement & commissioning deliverables.

Inputs you'll need

• Flow rate directly, OR cooling/heating load with ρ, Cp, ΔT — the tool derives Q via Q = Load / (ρ · Cp · ΔT).
• Pipe size (DN, schedule) and equivalent length for friction.
• Static head (elevation difference) and component pressure drops (chiller, coil, control valve, balancing).
• Fluid: chilled water, heating water, or glycol mix.
• For Operation: duty profile (constant / variable / office), tariff, hours/year.

Output classes

Each value in the Calculation Summary has an implicit status (see Status column convention in the report when enabled, or per-row colour cues):

• Input You entered this value directly.
• Preliminary Direct physics-based calculation (e.g. Q/A, Q·ρ·g·H).
• Estimate Assumption-heavy derivation (motor efficiency, run hours, tariff) — verify before final design.

Use a sample scenario

The Sizing tab includes 8 pre-loaded scenarios (small chilled-water primary, high-rise pressurised, condenser-water 30% glycol, etc.). Use them to learn the inputs or as starting points for similar projects.

Tips for engineers

• Substitute manufacturer pump curves, NPSHr, and motor efficiency when you select a candidate pump. The generic curves shown are family-typical, not model-specific.
• If your system uses 2-way control valves → specify VSD. At 80% flow the affinity-law power is (0.8)³ = 51%. Cube-law savings assume a friction-dominated system; where static head is significant the realised saving is lower and a minimum VSD speed applies.
• NPSH margin ≥ 0.5 m is the screening benchmark the tool uses. Application-specific margin per ANSI/HI 9.6.1:2024 governs final acceptance and varies by pump type and service.
• Glycol raises viscosity sharply — especially propylene glycol and at low temperature. The tool applies simplified glycol corrections to viscosity, density, and specific heat; for mixes above ~30%, enter verified fluid properties (manufacturer or ASHRAE Handbook–Fundamentals Ch. 31 data) and obtain de-rated pump curves rather than relying on the water defaults.

What this tool is not

• Not a certified compliance check against NCC, AS/NZS, ASHRAE 90.1, CIBSE, or any other code.
• Not a substitute for engineer review. Mark a calculation as reviewed only after independent verification.
• Not for construction documents without independent review by a qualified mechanical engineer.

Product

Hydronic Pump Selector Lite v2.7.1 — BETA. An engineering calculator for hydronic pump selection. Lite gives you the full sizing engine, the Operation tab (pump arrangements, VSD, life-cycle cost, sensitivity), NPSH and friction analysis, and a watermarked report preview. Pro adds project Save/Open, clean issuable records, and the procurement & commissioning deliverable family (ISO 9906-aligned spec, RFQ, BOM) that follows the project from design to record.

This is the Lite edition: in-browser hydronic pump selection with the full calculation engine and printable report. Project Save/Open and the procurement & commissioning deliverables suite are Pro features. All calculations and reports are engineering-grade but remain advisory — final verification rests with the responsible engineer.

Standards Basis

Built on recognised methods: the Darcy–Weisbach head-loss equation with Colebrook–White friction factors (Swamee–Jain initial estimate), the Kell (1975) water-density correlation, pump affinity laws, and the Antoine vapour-pressure relation with the ISO 2533 standard atmosphere for NPSH — with IEC 60072 motor frames and ASME B36.10M / Schedule 40 pipe data, informed by ASHRAE Handbook–Fundamentals (Ch. 22, Ch. 31) and CIBSE Guide C. Built-in pipe, fitting equivalent-length, and motor reference data are provided as guidance drawn from these published standards (the property of their respective publishers); the calculation itself uses the values you enter. As with any professional engineering tool, the output is an engineering estimate rather than a compliance certification — verify fluid properties, fitting allowances, and assumptions against the current standard and project requirements before use.

Methodology

Reference-informed. The tool combines public-domain engineering equations (Darcy–Weisbach with Colebrook–White iteration, affinity laws, Antoine vapour-pressure, ISA atmospheric model) with standard pipe and motor frame data. It does not reproduce copyrighted text, figures, proprietary tables, or licensed datasets from cited standards. No compliance, certification, or endorsement by ASHRAE, the Hydraulic Institute, ISO, IEC, or any manufacturer is claimed.

References

Standards and sources the calculations are informed by:

1. ASHRAE Handbook — Fundamentals (2021). Chapter 22 (Pipe Design), Chapter 31 (Physical Properties of Secondary Coolants (Brines)). American Society of Heating, Refrigerating and Air-Conditioning Engineers.
2. CIBSE Guide C (2007). Reference Data — Heat Transfer, Fluid Flow, Reference Data. Chartered Institution of Building Services Engineers, London.
3. Colebrook, C. F. (1939). "Turbulent flow in pipes, with particular reference to the transition region between the smooth and rough pipe laws." Journal of the Institution of Civil Engineers, 11 (4): 133–156.
4. IEC 60072-1:2022. Dimensions and output series for rotating electrical machines — frame numbers 56 to 400 and flange numbers 55 to 1080.
5. ASME B36.10M-2018. Welded and Seamless Wrought Steel Pipe.
6. ISO 2533:1975. Standard atmosphere. Used for altitude pressure correction in NPSH.
7. Antoine, C. (1888). "Tensions des vapeurs; nouvelle relation entre les tensions et les températures." Comptes Rendus, 107: 681–684, 778–780, 836–837. Used for water vapour-pressure correlation in NPSH.

References cited are publications by their respective copyright holders. All trademarks acknowledged.

Recent updates

v2.7.1: Post-audit refinements to the Manufacturer Pump Curve — the operating point now intersects the physical system curve (design safety margin excluded and shown separately as a selection target), with guards against a non-physical curve fit and against extrapolation beyond entered points. Refreshed the closed-loop static-head and glycol advisories to match the v2.7 engine. v2.7: Engineering refinements from the independent methodology audit. Closed-loop static head — for closed CHW/HHW circuits, static elevation now correctly cancels and is excluded from circulating-pump TDH (retained only for open, transfer, and condenser-water systems); this can materially reduce computed head in tall-building closed loops. Added a transitional-flow advisory (Reynolds ≈ 2300–4000) noting that friction loss is approximate in that band. Added an optional closed-loop fill / pressurisation input to the NPSH calculation (default 0 = open/vented, so existing results are unchanged). Glycol properties now distinguish ethylene from propylene glycol — propylene is modelled as less dense and significantly more viscous, correcting friction and power for PG systems. Added an optional Manufacturer Pump Curve panel: enter or paste a few Q–H points from the datasheet and the tool fits the pump curve, intersects it with the live system curve to locate the duty point, and checks it against the minimum continuous stable flow and the preferred / allowable operating regions (MCSF / POR / AOR) per Hydraulic Institute practice.

v2.6.2: Release-readiness review against an independent methodology audit. Repositioned as a preliminary pump sizing / pre-selection tool — final selection must be confirmed against manufacturer pump curves and the project system curve (operating point, NPSHr margin, minimum continuous stable flow, and preferred/allowable operating region). Clarified that static elevation does not belong in closed-loop circulating-pump head; escalated the high-glycol and static-head advisories; labelled the motor 10% margin as a DENOVA screening criterion (not an IEC service-factor requirement); and labelled annual energy as a single design-point screening estimate. Calculations are unchanged.

v2.6.1: Water density now uses the Kell (1975) equation (accurate to ~0.01 kg/m³ across 0–100 °C); this affects elevated-temperature (heating-water) results, while chilled-water results are unchanged. The system schematic was redrawn so each parallel pump is a complete branch (suction isolation valve → pump → non-return valve → discharge isolation valve) on common headers, with in-line series staging. The report identity was aligned to the DENOVA house style: an upright mixed-case tagline, a grey brand band with the wordmark and tagline inline, and a single source driving the print-footer status and the diagonal “NOT FOR CONSTRUCTION” watermark (consistent on screen and in PDF).

v2.6: Pump arrangements — parallel duty plus standby (N+1) and series staging — now flow through the head and power calculation, the KPI tiles, the report, and the live and report pump curves (per-pump and combined).

Disclaimer

DENOVA outputs are reference-informed and based on entered inputs, selected assumptions, and the stated methodology version. Results are provided for preliminary engineering review and are not a substitute for professional judgement, project-specific verification, manufacturer-certified data, or authority approval. This tool provides preliminary pump sizing and pre-selection; final pump selection must be confirmed against manufacturer pump curves and the project system curve — including the operating point, NPSHr margin, minimum continuous stable flow, and preferred/allowable operating region. Electrical sizing is indicative only — final design by a licensed electrical engineer per local code.