- How to Maximise Energy Efficiency with Heat Recovery Systems
Real energy efficiency in a commercial building isn't about one magic box; it's about how the entire system performs. A heat recovery unit is a key player, but just having one installed doesn't guarantee results. The gap between a system that delivers impressive HRV energy savings and one that’s just a costly fan on the roof comes down to three things: design, control, and maintenance.
Maximising heat recovery efficiency is something you have to work at. The job starts long before the unit is ever switched on, with proper sizing and component choice, and it continues for years with smart controls and regular upkeep. Get it right, and you turn wasted heat into lower running costs. Get it wrong, and you've just installed a very expensive ornament.
Understanding What Peak Efficiency Looks Like
Before you can aim for maximum efficiency, you need to know what you're looking for. It’s not just the percentage printed on the side of the heat exchanger. True efficiency is about how little energy the system uses to deliver the fresh, temperate air the building needs. A unit with a 90% efficient core is useless if its fans are running flat-out 24/7, burning electricity because the controls are all wrong.
The car analogy is perfect here. The engine's design is like the heat exchanger's rating, it sets the potential. But your actual miles per gallon depends on how you drive (the controls), if the tyres are inflated correctly (system balancing), and whether you get it serviced (maintenance). Focusing only on the heat exchanger is like buying a hybrid and then driving it everywhere with your foot to the floor.
It Starts with the Design: Sizing and Selection
The biggest killer of heat recovery efficiency is getting the size wrong. A unit that's too big will constantly short-cycle and never run properly. A unit that's too small will be on at full blast all the time, failing to keep up and wasting a huge amount of energy. Getting the heat-loss calculations and ventilation requirements right from the start is absolutely essential.
Component selection is just as vital. Going for standard, fixed-speed pumps and fans to save a few quid upfront is a mistake. High-efficiency, variable-speed commercial circulators are a must. They let the system match its output to what the building actually needs, slowing down when rooms are empty and saving a fortune in the process. Brands like Grundfos have nailed this technology; their smart pumps are the foundation of an efficient system.
The Brains of the Operation: Advanced Control Strategies
A great design with top-tier parts is still just a pile of metal without smart controls to run it. This is where the serious HRV energy savings come from.
Demand-Controlled Ventilation (DCV)
Running a ventilation system at a fixed rate, whether a building is full of people or completely empty, is a massive waste. Demand-Controlled Ventilation uses sensors to see what's happening inside and adjusts accordingly. CO2 sensors are the most common way to do this. As more people enter a room, CO2 levels rise, and the system automatically brings in more fresh air. When the room is empty, it backs off to a minimum level, saving energy on both fans and heating.
Time Schedules and Occupancy Settings
The most basic control is a time clock. The system should be set to match the building's working hours, switching off or to a setback mode in the evenings and on weekends. Tying this into occupancy sensors that detect movement gives you even tighter control, making sure you're not wasting money ventilating empty offices.
An Engineer's Tale: The Overlooked Commissioning
A newly opened regional office was reporting shockingly high energy bills. On paper, the HVAC system was state-of-the-art, complete with a high-spec heat recovery unit. The facilities manager was baffled. During a system audit, the problem became clear: the system had never been properly commissioned.
The variable-speed fans were set to run at a constant 80% capacity, and the CO2 sensors were disabled. The system was treating the building as if it were at full occupancy, 24 hours a day. After a few hours of work, re-enabling the sensors, setting up a proper time schedule, and balancing the airflow to each zone, the system's energy consumption dropped by over 60%. It was a powerful lesson: the most advanced hardware is only as good as its setup and programming. The potential for HRV energy savings was always there; it just needed to be unlocked.
The Importance of a Supporting Cast
A heat recovery unit is only as good as the system around it. Its efficiency is directly affected by the performance of the wider HVAC installation.
System Pressure and Hydronics
In systems that use recovered heat for hot water, stable pressure is vital for good heat transfer. An incorrectly sized or failing expansion vessel will cause pressure swings that hammer the effectiveness of the entire loop. Regular checks on the pre-charge pressure are a basic part of keeping the system efficient.
Building Envelope
Finally, the building itself is a huge factor. Pumping energy into a leaky building is like trying to fill a bucket with a hole in it. Better insulation, sealed drafts, and high-performance windows all reduce the heating and cooling load. This gives the heat recovery system less work to do, allowing it to run far more efficiently.
Sourcing the Right Components for Maximum Efficiency
Building a system for peak heat recovery efficiency means using components that are proven to work. Cheap parts will always compromise the final result. This is where a supplier with real technical knowledge becomes an essential part of the project.
The team at National Pumps and Boilers understands the details of commercial HVAC design. They supply parts from top manufacturers known for efficiency and reliability, like Wilo and Remeha. Working with a supplier who gives expert advice ensures every piece of the system is optimised for performance. If you need guidance on selecting the right components to get the most out of your system, get in touch with their specialists.