What installers need to know about ASHP technology to make sure they get the best out of it

With fossil fuel dependency still firmly engrained in UK culture, heating and plumbing professionals have a tendency to stick with what’s familiar. Robin Adderley – Sales and Marketing Director at Nibe – takes a look at the opportunity air source heat pumps represent for off-grid heating installers.
Costly, outdated and inefficient systems, such as oil and LPG-fuelled boilers, remain widespread in rural, off-mains homes, while other, more cost-effective, energy-efficient renewable solutions are often overlooked. However, for many installers, fitting and maintaining off-grid renewables has become a central part of their day-to-day work – and therefore a significant source of income. For these industry pioneers, success is all about choosing the best system for the job at hand.
Air source heat pumps (ASHPs) are a case in point. Ideal for both new-build and retrofit domestic applications, for the end-user they deliver substantial ongoing savings on running costs, energy consumption and carbon emissions (especially in comparison to other off-grid alternatives). For the installer, they signify a lucrative, largely-untapped career opportunity in a market that is only going one way: up.
In fact, in recognition of the compelling benefits heat pumps offer as a long-term energy solution for homes, the UK Government has set itself the challenge of reaching 6.8 million domestic installs by 2030. So, as the market heats up, what do installers need to know about ASHP technology to make sure they (and their customers) get the best out of it?
How the technology works
An ASHP is a renewable heating technology that operates in a similar way to a fridge, but in reverse. A fan on the front of an outside unit draws air into the internal system. Here it meets an evaporator, which contains a refrigerant that turns into gas when the air hits it (even at subzero temperatures). A compressor then brings the gas up to a high enough temperature to be transferred, via a condenser, to the property’s heating and hot water system.
Suitable applications
As a cleaner, lower-maintenance and more secure alternative to oil and LPG, ASHPs have the capability to fulfil 100% of the space heating and hot water requirement in off-grid properties. They operate at lower flow temperatures than conventional heating systems – which means they are designed to deliver best results in well-insulated homes.
As ASHPs harness renewable energy from the air outside, there is no need to allocate any space for fuel stores (although properties must have room to accommodate the heat pump’s external unit).
The need for qualifications
As the market has expanded, so have the training opportunities for installers. Anyone fitting ASHPs should undergo productspecific training. Installers should be accredited under the Microgeneration Certification Scheme (MCS).
MCS accreditation is essential for installations to qualify for ongoing RHI payments, which is an additional benefit for customers. To help ensure high standards industry-wide, MCS accreditation is also a condition of NIBE’s heat pump warranty.
Ongoing success
Once the ASHP is up and running, it’s vital to remember that the job doesn’t end there. It may sound obvious, but showing the customer how to operate the system correctly – and explaining its maintenance requirements – is the key to long-term success (particularly if they are used to a traditional on/off boiler) and as a result the system itself will function more effectively.
From an ongoing upkeep point of view, the good news is that ASHPs are very low maintenance. Because they use the outside air as an energy source, there is complete security of supply – so end-users don’t need to worry about unpredictable fuel pricing, delivery or storage.
Just like traditional boilers, ASHPs do require annual servicing. Look at this as a health check – using it as an opportunity to spot and address any problems, such as clearing the fan and filters of leaves and other debris. It’s also a chance to talk to the customer about usage and performance, to ensure they continue to get the best results from their system.
Reaping the benefits
Installers who focus purely on conventional off-mains heating solutions could be seriously missing a trick. Those who take the time to get trained up and add ASHP fitting to their skillset are opening up a wealth of new business opportunities for themselves at a time when renewables are gaining increasing recognition in the UK. Not only this, but the potential for ASHPs to deliver the most significant savings is often greatest in off-grid homes – meaning there’s a readymade customer base just waiting to be tapped into.
This checklist provides a guide to the key stages of the design and installation process:
A full heat-loss calculation (carried out room-by-room) will indicate the space heating load of the property. To meet MCS guidelines, installers must use a method that complies with BS EN 12831.
The results of the calculation will determine the required output for the system – including heat emitters and the heat pump itself. ASHPs are available in different outputs to fulfil varying heat demands (for example, NIBE’s market-leading F2040 range includes 8kW, 12kW and 16kW models).
100% sizing ensures the system is set up to fulfil the property’s entire heating power demand, taking into account the external design temperature (which varies according to location). This must be carried out in accordance with MIS 3005 installation standards.
Because ASHPs operate at significantly lower flow temperatures than combustion-based systems, it’s important to specify the right heat emitters. Water-based underfloor heating, for instance, is an ideal match as it runs at similarly low-flow temperatures. If a property has existing radiaators, these may need resizing to make them compatible.
As long as they fulfil the criteria set out in the MCS Planning Standards (MCS020), ASHPs are covered under Permitted Development Rights – so there is no need to seek planning permission before installation. MCS020 outlines correct positioning and noise constraints (including minimum clearances) in full, but over and above this installers should ensure that there is an accessible drain or soakaway nearby for disposal of the condensate from defrost cycles.
For best results and efficiency, it’s worth opting for a complete ASHP package from one manufacturer. This should include a hot water storage cylinder that’s designed to work in partnership with a heat pump, as well as intelligent system controls.
For example, Nibe has developed Uplink, an advanced online control and monitoring system, to provide remote access to the heat pump’s vital stats via a computer, tablet or smartphone. This not only allows installers to monitor all of their ASHP systems from one place and address any issues straight away, but it also gives customers more control over their home heating system.

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