Drawing on Navien’s field experience with the PEM750 heat pump and the company’s installer training partnership with Ultimate Renewables, Gareth Prescott, National Trainer at Navien UK, explores five areas every installer should look to master.
The heating industry is undergoing its biggest transformation in decades. With the UK Government targeting 600,000 heat pump installations annually by 2028, and regulatory changes now making them simpler to fit, demand is climbing fast.
According to figures from the Microgeneration Scheme (MCS), in 2024, nearly 60,000 heat pumps were installed across the UK – a figure set to rise steeply each year. For installers, this is both a challenge and a unique opportunity: those who master heat pumps now will place themselves at the front of tomorrow’s heating market.
But success depends on getting every stage right. Heat pumps work to much tighter tolerances than many conventional systems, so any errors in sizing, siting, or commissioning can quickly affect performance and customer satisfaction. Installed correctly, however, they can deliver efficient, low carbon comfort and help installers build long term trust and loyalty.
1. Pre-installation essentials
Preparation is the foundation of a successful install. A full site survey should always be the first step: assessing heat loss, electrical capacity, and insulation levels. A UK Parliament POSTnote report states that “heat pumps are technically suitable for most UK homes if installed appropriately,” but actual suitability depends heavily on insulation quality. Ensuring walls, lofts, and floors are properly upgraded unlocks both efficiency and customer satisfaction.
Correct system sizing is critical. An oversized unit raises upfront costs and wastes energy, while an undersized system leads to frustration and complaints. Accurate heat loss calculations, combined with manufacturer guidance, ensure the PEM750 – or any other model – is correctly specified for the property’s demand.
Don’t overlook compliance. Meeting planning requirements, building regulations, and MCS standards from the outset prevents headaches mid-project. Finally, clear communication builds confidence – explaining that heat pumps deliver steady, lower-temperature heat over longer run times helps set realistic customer expectations and reduces call-backs.
2. Outdoor and indoor unit installation
Positioning matters more with heat pumps than almost any other heating technology. For outdoor units like the PEM750, unrestricted airflow is essential: sufficient clearance on all sides must be maintained to avoid recirculation and performance drops. Because the PEM750 uses R290 (propane) refrigerant, careful siting and ventilation are particularly important to ensure safety and compliance. Condensate discharge from the external unit should also be correctly routed and protected to prevent freezing during winter conditions.
With the one metre boundary rule now scrapped and unit size allowances expanded in 2025’s regulation updates, installers have greater flexibility for siting – but acoustics and neighbour proximity remain key considerations.
Indoors, integration demands precision. Cylinders and pipework should be carefully planned, with insulation on all exposed pipework to reduce heat loss. Spending extra time at this stage ensures smoother operation and long-term reliability.
3. Electrical and control set-up
Electrical connection is one of the most sensitive stages. Units must be wired and earthed in line with IET regulations and manufacturer instructions. Even small errors can lead to nuisance tripping or system faults.
Control set-up deserves equal attention. Sensors should be correctly positioned and calibrated for accurate readings. Programming must be kept simple and intuitive – many customer complaints stem not from the heat pump itself, but from overly complex or unclear controls. Setting straightforward schedules and demonstrating them clearly during handover significantly boosts customer satisfaction.
4. Commissioning and optimisation
Commissioning is where an installer’s professionalism truly shines. This stage verifies that the system operates safely, efficiently, and as designed. For Navien’s PEM750, commissioning includes confirming water flow rates, verifying expansion vessel pressures, and ensuring control settings are correctly configured.
Optimisation at this stage – fine-tuning flow temperatures and balancing heat emitters – secures peak efficiency and comfort. Recording performance data completes the job, providing a valuable reference point for future servicing and customer reassurance.
5. Troubleshooting and customer handover
Even with careful planning, small issues can arise. Common early problems include limited airflow, vibration noise, or wiring faults. A structured approach – checking airflow first, then electrics, then control logic – resolves these quickly and avoids unnecessary call-backs.
The customer handover is equally vital. Demonstrating system operation, controller settings, and basic maintenance gives the homeowner confidence and reduces aftercare issues.
Supplying warranty and servicing documentation not only secures compliance but strengthens your professional reputation. A comprehensive, confident handover is often the difference between a one-off job and repeat business.
Shaping the future
Heat pumps are no longer niche; they are rapidly becoming the backbone of the UK’s low carbon heating future. For installers, this is a pivotal chance to grow both skills and business. Success depends on attention to detail at every stage – surveying, siting, electrical work, commissioning, and handover.
Navien is committed to ensuring installers are supported every step of the way. Through the PEM750 heat pump, hands-on training courses with Ultimate Renewables, and accessible digital resources, Navien is equipping the trade with the expertise to deliver reliable installations, happy customers, and sustainable businesses.
Image: Navien
