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Heat pump satisfaction, guaranteed
Heat pumps hold great potential for delivering effective low- carbon heating to homes across the UK, but they don’t always meet the expectations of end users. Griff Thomas, MD for GTEC and Heatly, part of the United Living Group, explores the factors that contribute to underperformance and explains how installers can rectify issues to ensure customer satisfaction
R
eplacing gas central heating with a heat pump system is not rocket science but there is a lot of ‘information’ out there that muddies
the water for installers and end users. Errors with surveying, design or sizing, overselling the benefits of heat pumps or miscommunication between installer and customer can lead to inefficiencies and ongoing problems. By contrast, heat pumps that are designed,
installed and maintained by qualified experts reliably deliver efficient and affordable heating. End user understanding is also critical to overall satisfaction.
Why do heat pumps sometime fall short?
People often wonder why a heat pump does not deliver the manufacturer stated kWh and COP. The answer lies in the parameters under which these values are stated. Typically, manufacturers test heat pumps at A7/W35 conditions—7°C outdoor air temperature and 35°C water flow temperature. Any deviation will affect performance: ¡ Lower outdoor air temperature reduces kW output and COP. ¡ Higher water flow temperature similarly lowers both kW output and COP. This means that during colder winter months, when demand is highest, heat output and efficiency naturally decline. This is normal and not a system failure—but it underscores the importance of careful planning and design.
Get the design right
The key to achieving maximum efficiency lies in correctly sizing every component of the system. It starts with a whole-house heat loss calculation conducted room by room to determine precise heat emitter requirements and heat pump capacity. There are so many variations that small discrepancies at this early stage can result in inefficiencies down the line. Consider investing in digital tools that will improve accuracy while saving time.
Critical design parameters in- clude:
1. Heat emitter sizing - Radiators or underfloor heating (UFH) must be sized for lower flow temperatures to maintain adequate heat output. 2. Flow rates - Calculating the correct flow rate involves balancing the required heat output (kW) with water capacity and temperature differential (∆T). Missteps here, such as oversized circulation pumps or unbalanced systems, lead to inefficiencies. 3. Pipework design - Pipes must be correctly sized to handle the flow rate within permitted velocities (0.5–1.5 m/s) while minimising pressure losses. This requires meticulous planning, accounting for lengths, fittings and the cumulative load on the circuit.
The circuit with the highest resistance—known as the index circuit—determines the system’s total pressure loss. A circulating pump is then selected to handle this flow rate and pressure loss. Any miscalculations, from undersized pipes to poorly balanced emitters, can compromise the system’s performance.
Common installation errors
If all the calculations are correct, the heat pump should be able to deliver anywhere between its minimum output and maximum output at the temperature ranges stated and at the COP stated. So why doesn’t that always happen?
DOMESTIC HEATING
Above: Griff Thomas, MD for GTEC and Heatly
In most cases I see, it’s either one of or multiples of
the above detail that hadn’t been effectively carried out: ¡ Incorrectly sized radiators or UFH systems. ¡ Oversized or undersized heat pumps. ¡ Poorly balanced flow rates or mismatched circulation pumps. ¡ Inadequate controls, such as improper valve settings. With proper design and commissioning, heat pump performance can meet and exceed customer expectations, delivering the intended energy efficiency and comfort. Mistakes are avoidable but can, in most cases, be rectified.
Use digital tools
Digital tools, like Heatly, are revolutionising heat pump installation by providing heating engineers with advanced capabilities to ensure accuracy at every stage of the process. Installers can use software to streamline calculations, enhance specification and simplify complex tasks, saving time and ultimately delivering high quality heat pump systems with fewer operational issues. Management of customer expectations is key to
overall satisfaction. Digital tools, apps and software provide greater insight into the installation process and the system in general, helping end users to understand how everything works and what to expect. Heatly, for example, will enable simulated heat loss projections based on the addition of certain levels of insulation to clearly demonstrate the benefits and cost-savings associated with different energy efficiency measures while helping homeowners to make informed decisions.
Deliver high quality
The heating engineer’s role extends beyond installation to troubleshooting and optimising systems. By addressing the technical details and helping customers to understand their new heating system, you can ensure customers reap the full benefits of their investment—delivering satisfaction and strengthening the reputation of the sector as a whole.
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