How to Upgrade Existing Systems with Ground Source Heat Pumps for Better Efficiency

Most engineers who’ve spent time in plant rooms know the feeling: an old boiler rattling away, valves whistling, and gas bills creeping up every winter. Across the UK, thousands of these systems are still running in commercial and multi-residential properties. The good news is they can often be upgraded rather than torn out.

By integrating a Ground Source Heat Pump (GSHP) into an existing network, it’s possible to keep the bones of a good system, the pipework, the radiators, the controls, and lift its performance dramatically. For anyone managing Commercial Plumbing Systems, it’s a practical route to better efficiency without a complete rebuild.

Why Upgrade Instead of Replacing Everything?

A total system replacement is disruptive, expensive, and rarely necessary. Much of what’s already in place can stay if it’s structurally sound. The goal is to replace the old heat source with a GSHP that uses renewable heat from the ground and pair it with modern components that help it run efficiently.

The payoff isn’t small. Engineers who’ve done this kind of retrofit report:

• Energy bills are dropping by 30–50%.
  
  
  
• More stable internal temperatures.
  
  
  
• Significantly quieter operation.
  
  
  
• Lower carbon emissions are often halved immediately.
  
  
  

For older properties, there’s another advantage: no need for flues, combustion air, or external plant noise. Once commissioned, a GSHP becomes one of the quietest, cleanest systems you can install.

First Steps: Assessing the System You Already Have

Before any design work begins, take a hard look at the existing Commercial Plumbing System. Its condition tells you how much can be reused and what needs replacement.

Practical checks include:

• Inspecting the pipework for corrosion or dead legs.
  
  
  
• Testing flow rates on each circuit.
  
  
  
• Reviewing the emitter types, underfloor loops or large radiators are ideal for lower water temperatures.
  
  
  
• Verifying expansion space and current pressure maintenance methods.
  
  
  

On many retrofits, the existing network is sound, but the supporting equipment isn’t. Circulators running flat-out, old pressurisation kits that’ve seen better days, these are the bits worth upgrading. Components like pressurisation units from Mikrofill or expansion vessels from Reflex give a modern GSHP the stable base it needs.

The Engineering Mindset for Better Efficiency

A GSHP isn’t just a fancy heat source. It’s a precision machine that depends on balance, right flow, right pressure, and the right ground connection. Achieving better efficiency is about joining all those dots.

Seasoned engineers usually focus on:

• Ground loop design: The loop area must match the site’s heat load. Overshoot, and you waste drilling cost; undersize, and you’ll lose efficiency.
  
  
  
• Pump selection: Choose adaptive-speed pumps from Wilo or Grundfos to maintain flow without overworking.
  
  
  
• Pressure control: Reliable expansion vessels keep water volumes stable through temperature swings.
  
  
  
• Flow balancing: A few extra minutes with a manometer now saves years of uneven heating complaints later.
  
  
  

Get those basics right, and the rest tends to follow.

A Real Example: Office Retrofit in Leeds

A facilities manager in Leeds faced the usual situation: three oversized boilers, rising gas bills, and complaints from staff about cold spots. Instead of ripping everything out, they commissioned an upgrade using a 70 kW GSHP system tied into the existing Commercial Plumbing System.

Here’s how it played out:

• Engineers pressure-tested and flushed the old circuits.
  
  
  
• Installed boreholes in the car park to feed a closed-loop GSHP.
  
  
  
• Swapped constant-speed circulators for variable-speed Grundfos units.
  
  
  
• Added a 200-litre buffer tank and new control sensors.
  
  
  

Once commissioned, the system achieved a 45% energy reduction in its first full heating season. The most telling comment came from the maintenance team: “It’s so quiet, you forget it’s even running.”

Adapting the Old System to Modern Flow Temperatures

Legacy boiler systems often ran at 80°C flow, 60°C return. A GSHP prefers 45°C or lower. That change can make some engineers nervous, but in practice, it’s manageable.

Larger radiators, fan coils, or underfloor systems help distribute heat at lower temperatures. For commercial buildings, adding weather compensation controls lets the flow temperature rise only when truly needed. It’s an easy way to maintain comfort while ensuring better efficiency.

Sometimes a plate heat exchanger acts as a divider between the new and old systems. This approach works well when you can’t guarantee water quality or if parts of the old network still use steel pipe.

Electrical and Control Integration

A GSHP needs more electrical finesse than a boiler. Compressors, circulation pumps, and sensors all tie into the controls, so coordination matters. Many modern systems use BMS integration, giving live readouts of flow, pressure, and energy consumption.

Linking variable-speed pumps such as the Wilo Stratos MAXO to the control logic keeps flow perfectly aligned with heat demand. Over time, this constant adjustment saves a surprising amount of electricity.

Avoiding Common Retrofit Mistakes

Even experienced contractors make avoidable missteps on their first GSHP retrofit. The most frequent issues include:

• Poor flushing and water treatment, sludge kills performance fast.
  
  
  
• Undersized buffer tanks are causing compressors to short-cycle.
  
  
  
• Fixed-speed pumps left running at full tilt.
  
  
  
• Glycol mix too weak, leading to freezing risk.
  
  
  

A good rule is to treat commissioning as carefully as design. Once the system’s balanced and logged, it should run for years with minimal adjustment.

Maintenance and Long-Term Reliability

One of the joys of a GSHP upgrade is the simplicity of upkeep. There’s no combustion, no flue gas path, and hardly any moving parts apart from pumps and compressors. Regular checks are still important, especially glycol concentration and pressure stability, but major maintenance is rare.

A small pressurisation unit from National Pumps and Boilers can even automate top-ups, so pressure stays steady without manual intervention. It’s a simple add-on that prevents call-outs later.

How These Upgrades Affect the Environment

Beyond saving money, there’s a clear environmental gain. Every GSHP retrofit reduces on-site emissions, and when powered by renewables, operational carbon nearly disappears.

For businesses and councils under carbon reporting obligations, that matters. It’s an easy win for sustainability goals and ESG statements. In practice, the shift to renewable heat also improves working conditions, no combustion noise, no flue, and cleaner air around the property.

Choosing the Right Equipment for the Job

The heart of every upgrade lies in component choice. Buying cheap inevitably costs more in efficiency loss and callbacks. Engineers trust proven names:

• Pumps: Wilo, Grundfos, or Lowara.
  
  
  
• Pressure maintenance: Mikrofill.
  
  
  
• Expansion control: Flamco or Reflex.
  
  
  

Pairing high-quality auxiliary components with the GSHP ensures not just efficiency but peace of mind.

The Business Case for Upgrading

It’s easy to justify the numbers. Initial investment may be higher than a replacement boiler, but running costs quickly make up the difference. Many facilities see a return on investment within seven to ten years, sooner if gas prices spike.

There’s also less downtime. A well-installed GSHP, supported by efficient commercial circulators and proper controls, can run all year with minimal attention.

For landlords or site operators, that consistency translates directly into lower operational risk.

When to Bring in Expert Help

Even skilled mechanical teams sometimes need a second opinion on sizing or loop design. It’s worth contacting the National Pumps and Boilers technical team early. They can help specify the right circulators, valves, and expansion gear for any retrofit project. Getting that advice upfront avoids costly redesigns later.

Final Thoughts: Upgrading for a Better Future

A GSHP retrofit isn’t just about new technology. It’s about making what you already have work smarter. Done right, it delivers quieter, cleaner, and more economical heating that will serve for decades.

For anyone managing Commercial Plumbing Systems, now’s the time to start planning. Upgrading isn’t just an energy decision; it’s a strategic one that improves comfort, cuts running costs, and supports sustainability goals. With the right design and components, you’ll see better efficiency from day one and fewer maintenance headaches along the way.