Air Source Heat Pumps (ASHPs) have much in common with boilers, so most installers already have a strong base for adding them to their portfolio. Ian Trott, Head of Training at Baxi, explains where ASHP installations can most often be improved to deliver stronger performance and better customer satisfaction.
For experienced heating engineers, ASHPs should not feel like unfamiliar territory. The core disciplines still apply; accurate heat loss calculations, sound pipework design, suitable emitters, effective controls and a clear handover all remain central to the finished result. Boiler experience gives installers a strong base, particularly when they already understand the relationship between system design, customer comfort and long-term reliability.
The important difference is that ASHPs are less forgiving of assumptions. They operate at lower flow temperatures, depend on steady water movement, and rely on the homeowner understanding the controls. Get those details right and the installation is far more likely to perform as intended; miss them and the customer may notice quickly.
Pipe sizing and emitter selection matter
Heat loss calculations are the foundation of good heating system design, whether that system is connected to a gas boiler or a heat pump. That process is familiar and should give installers confidence, because it is not a new skill so much as a skill being applied with greater precision. The difference comes in how the calculation is used, particularly when selecting emitters and judging whether the existing pipework can support the required flow rates.
ASHPs run at lower flow temperatures than traditional boilers, which means the heat delivered into the property is less intense. To heat the same room to the same level of comfort, the system needs enough surface area to transfer that heat energy effectively. In practice, that may mean upsizing radiators or bringing underfloor heating into the design.
Pipe sizing deserves the same attention. Heat pumps typically need to move water around the system faster than a boiler, so larger pipes are often needed. That affects the installation route, and the way practical obstacles are handled on site. Routing 28mm or 32mm pipe through joists, cupboards and existing services requires planning before the job starts.
This is particularly important on retrofit work. With a boiler replacement, fitting a 30kW unit where a 28kW boiler used to sit is usually manageable, provided the wider design remains suitable. ASHPs are not quite so forgiving. If the existing pipework cannot carry the flow rates required, the system will struggle to deliver the performance the customer expects. Taking time to get this right protects the customer experience and the installer’s margin, because remedial work after the event quickly eats into profit.
Treat ASHPs as a different running strategy
The biggest mindset shift, both for installers and homeowners, is how an ASHP is designed to run. A gas boiler and an ASHP can both provide heating, but they reach that outcome differently. If the system is commissioned or explained as though it behaves like a boiler, the homeowner is likely to use it in the wrong way and then question the performance.
Today’s gas boilers are low content, meaning they hold smaller quantities of water than older models. They heat that water quickly, then transfer high-temperature heat into the property over a relatively short period. ASHPs work in the opposite way. They keep a larger volume of water moving steadily at a lower temperature, running for longer and maintaining comfort through consistency rather than short, high-output cycles.
That is where controls come into their own. Weather compensation is standard for ASHPs, adjusting the flow temperature according to outdoor conditions rather than waiting for the room thermostat alone to call for heat. Installers need a clear picture of how the homeowner will live with the system, because occupancy, comfort levels and room use all inform setup. This can be one of the more rewarding parts of working with heat pumps. The technology responds well to careful design and commissioning, so the choices made before handover have a clear impact on running behaviour and customer confidence. It also rewards installers who take pride in the technical detail; the system is not simply fitted, it is tuned to suit the property and the people living in it.
Make the handover part of the installation
With a new boiler, many homeowners can manage with a brief explanation of the programmer, the thermostat and the pressure gauge. ASHPs need a more considered handover, because the best way to use the system is different from the heating habits many customers have built up over years of living with gas boilers. Assuming they will work it out for themselves is one of the most common ways a technically sound installation ends up generating unnecessary complaints.
Installers benefit from planning the handover as part of the job, not something squeezed in once the tools are packed away. It is good practice to walk the homeowner through how the system works, why it runs for longer periods, and what they should and should not do after the team has left site. Talking through the controls helps them have a clearer idea of what they will see across seasons.
Follow-up contact tends to pay for itself. A quick call or visit a few weeks after commissioning can catch small issues before they become complaints and gives the homeowner a chance to ask questions they did not think of during handover. That second conversation often builds confidence, particularly if the customer has noticed the unit run differently from the boiler it replaced.
This may be one of the biggest differences for installers moving from boiler work into ASHP installations. The handover has not always carried the same weight, but with heat pumps it protects the installation, the customer relationship and the installer’s reputation. A well-informed homeowner is less likely to interfere with settings, less likely to misread normal operation as a fault, and more likely to be satisfied with the finished job.
Customer confidence
ASHP installations are not a leap into the unknown for an experienced heating engineer. The fundamentals of good heating work carry across, but they need to be applied with a sharper focus on planning, sizing, commissioning and handover. Done properly, those details improve day-to-day performance, reduce the risk of avoidable call-backs and help the customer feel confident in the system they have chosen.
For installers and contractors, the opportunity is clear. Heat pumps open up a growing part of the heating market, but success will depend on the quality of the work delivered at property level. The installers who prioritise ASHP system design and customer education, rather than treating the job as a like-for-like swap, will be best placed to build trust and benefit from the market as it develops.
Baxi.co.uk
