How to Select the Right Pressurisation Unit for Your Heating System

Choosing the right pressurisation unit is a critical step in pressurisation unit selection for any pressurised heating system. Get it right, and your system will run efficiently, quietly and reliably; get it wrong, and you risk inefficiency, high energy bills and unexpected breakdowns. In this guide, we’ll walk you through everything you need to consider so you can pick the perfect unit for your commercial heating setup.

Understanding the Role of a Pressurisation Unit

What a Pressurisation Unit Actually Does

In a closed-loop pressurised heating system, water circulates from the boiler to radiators, underfloor loops or heat exchangers, then back to the boiler. Small leaks, bleed-off and thermal expansion can make system pressure fall or rise unexpectedly. A pressurisation unit automatically maintains that pressure within a narrow band, typically around 1.0 bar when cold and 1.5 bar when hot, preventing:

Boiler lock-outs due to low-water cut-off
Airlocks that create cold spots and noise
Over-pressurisation that damages pipes, valves and expansion vessels

By ensuring stable pressure, these units safeguard efficiency, occupant comfort and component lifespan.

Why Pressurisation Unit Selection Matters

In large commercial sites, office blocks, hotels or industrial plants, a mismatched unit can struggle to keep up with demand, cycling on and off too frequently or failing to compensate for rapid temperature swings. Investing time in proper pressurisation unit selection leads to:

Reduced energy consumption by matching pump output to actual system demands
Lower maintenance costs, thanks to fewer component failures
Enhanced system reliability, with fewer unplanned shutdowns
Compliance with standards such as BS EN 12828 and the Pressure Systems Safety Regulations

Explore our range of Pressurisation Units to see how we can help.

Key Factors to Consider When Choosing a Pressurisation Unit

System Size and Water Volume

Large Complexes (multi-storey hotels, campuses): Require high-capacity units, often variable-speed, to handle large water volumes and rapid demand changes.
Smaller Buildings (single-zone offices): A basic fixed-speed unit may suffice, keeping costs down without sacrificing performance.

Type of Heating System

Radiator Systems: Standard pressure ranges apply; most pressurisation units will fit.
Underfloor Heating: Operates at lower pressure and temperature, so ensure the unit’s minimum set-point is appropriate.
Dual-Loop or Hybrid Systems: May benefit from combined pressure and expansion units to simplify design.

For specialised applications, consider accessories like Expansion Vessels and Pump Valves.

Energy Efficiency and Operating Costs

Fixed-Speed Units run at a constant rate, simple and robust, but may waste energy during low-demand periods.
Variable-Speed Units adjust pump speed in real time, delivering only the water volume needed, ideal for fluctuating loads and significant long-term energy savings.

One of our clients, a busy office block, achieved a 25% reduction in pump electricity bills by switching to a variable-speed pressurisation unit paired with a Grundfos Magna3 circulator.

Comparing Pressurisation Unit Types

Fixed-Speed vs Variable-Speed Pressurisation Units

Upfront Cost

Fixed-Speed: Lower
Variable-Speed: Higher

Energy Efficiency

Fixed-Speed: Steady output, but energy is wasted when demand is low
Variable-Speed: Automatically adjusts to demand, offering up to 50 % energy savings

Suitability

Fixed-Speed: Best for small, stable systems with fairly constant demand
Variable-Speed: Ideal for large installations or multi-zone systems with varying demand

Maintenance

Fixed-Speed: Mechanically simpler but undergoes frequent on/off cycling
Variable-Speed: Fewer cycles, which extend pump life and reduce wear

Standard vs Digital Pressurisation Units

Standard Units: Manual or basic electronic controls. Perfect for smaller or less critical systems.
Digital Units: Offer touchscreen interfaces, remote BMS integration, real-time pressure trending and alarm notifications. Indispensable in mission-critical environments like hospitals or data centres.

Brands to consider include Armstrong, EBARA and Wilo.

Combined Pressure & Expansion Units

If your system sees large temperature swings, a combined unit merges pressurisation and thermal expansion functions in one skid. This space-saving solution reduces pipework and simplifies maintenance, especially valuable in plantrooms with limited room.

Vacuum Degasser Pressurisation Units

For systems plagued by airlocks or corrosion, vacuum degasser units remove entrained air, improving hydraulic efficiency and reducing maintenance. Ideal for closed-loop chillers in data centres or sterilisation loops in hospitals.

Additional Considerations for Pressurisation Unit Selection

System Complexity and Controls

Advanced features like leak detection, automatic air venting and remote diagnostics can pay dividends in complex systems. If you have multiple loops, duty/standby pumps or integration with commercial circulators, factor these into your choice.

Maintenance and Spares Availability

Choose units from established manufacturers, Lowara, DAB, NPB, to ensure spare parts and technical support are readily available.

Total Cost of Ownership

While budget constraints are real, remember to calculate lifecycle costs, including energy consumption, routine servicing, emergency call-outs, and component replacements. Often, a higher upfront investment in a variable-speed or digital unit delivers a lower overall cost over 5–10 years.

A Step-by-Step Pressurisation Unit Selection Process

Site Survey
- Assess water volume, elevation changes and loop configuration.
- Identify existing boiler and pump capacities.
Demand Analysis
- Map out peak and off-peak heating loads.
- Determine if multi-zone control or variable flow is required.
Evaluate Unit Types
- Match load profile to pressurisation unit type: fixed-speed, variable-speed, digital, combined or vacuum degasser.
Integration Planning
- Ensure compatibility with BMS, circulators, expansion vessels and safety relief valves.
Cost–Benefit Assessment
- Perform payback analysis, factoring in energy savings, maintenance and downtime risk.
Installation & Commissioning
- Engage certified engineers to install, calibrate pressure set-points and integrate alarms.
Ongoing Support
- Enrol in maintenance contracts, smart monitoring and 24/7 emergency cover via our Contact page.

Why Partner with National Pumps and Boilers?

At National Pumps and Boilers, we’ve perfected pressurisation unit selection for a wide range of commercial clients:

Tailored Solutions for hotels, office blocks, hospitals and industrial sites
Multi-Brand Expertise: From Grundfos and Stuart-Turner to Atag and Flamco
Full-Service Offering: Site surveys, system design, installation, commissioning and maintenance
Smart Monitoring Packages: Real-time dashboards and proactive fault alerts

Whether you need a basic fixed-speed model for a small office or a sophisticated digital, variable-speed pressurisation unit for a multi-zone campus, we’ll help you make the best choice for your pressurised heating system.

Next Steps: Get Your Pressurisation Unit Right First Time

Don’t leave your system to chance with trial-and-error equipment choices. For expert advice on pressurisation unit selection, visit our Homepage or get in touch via our Contact page. Let us guide you to the ideal, energy-efficient solution that will keep your heating system in peak condition for years to come.

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