22 minute read
Heat pumps
The government wants to speed up the transition to a low-carbon economy. With heat pumps considered key to decarbonising the domestic heating, Registered Gas Engineer examines the challenges that the industry now faces.
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The government has set out new plans to cut the country’s carbon emissions by 78 per cent by 2035. This would take the UK more than threequarters of the way to becoming net-zero by 2050. More details on how it says these targets can be achieved are yet to be announced, but the coming Heating and Buildings Strategy is expected to set out immediate actions to reduce emissions from buildings, including deploying energy efficient measures and transitioning to low-carbon heating.
To achieve these targets, the way we heat our homes will have to change. Instead of relying on gas boilers, the government wants our housing stock to rely on renewable heating systems. Heat pumps are considered a key ingredient in this low-carbon strategy, and the government’s Ten Point Plan for a Green Industrial Revolution outlined goals for 600,000 heat pump installations a year by 2028.
What is a heat pump?
Although heat pumps use a small amount of electricity for power, they are considered low-carbon, renewable energy systems because, for every kW of electricity they consume, they can generate anything between 3kW and 5kW of heat energy for output, depending on the system and building in which they are installed. There are three main types of heat pumps: • Air source heat pumps • Ground source heat pumps • Water source heat pumps.
Air source systems are the most common type being fitted in the UK. Cheaper to install than ground source, and not restricted to being near water, they are easier to install in new-build properties, as well as in the millions of existing homes that will need to be converted to use low-carbon heating systems.
Retrofitting heat pumps
The UK has an incredibly diverse housing stock, and heat pumps can’t be fitted in every property. Before deciding whether it is suitable, other aspects of the building fabric must be considered.
Andy Hooper, managing director of Unitherm UK, says: “A heat pump is significantly more efficient when operating on lower temperatures, and if the property is poorly insulated or being asked to supply water at a high
temperature, a heat pump is unlikely to be the best option.
“But if the property is well insulated with cavity wall insulation, loft insulation and double glazing, then discussions should continue [into the] siting of the heat pump, replacement of the hot water cylinder, and possibly changing the size of the radiators.”
Heating engineers should always carry out a full heat-loss calculation to assess whether the property is suitable, and what heat pump type should be specified.
Anna Wakefield, head of marketing at Grant UK, says: “A complete heat-loss calculation will account for the room sizes, insulation levels, [and] the height of the rooms. The calculation brings together the amount of space that needs heating, along with the building’s materials and their capability to reduce heat loss. “Suitable heat emitters should be fitted throughout the house,
having been sized specifically for the lower flow temperature of the heat pump system. To effectively transfer the heat from a lowtemperature heating system into the occupied living spaces within the home, heat emitters with larger surface areas such as underfloor heating tend to be the best partners.
“There is no reason, however, why radiators cannot be used with a heat pump. While the mean water temperature (MWT) in the radiators will be lower than with a gas or oil boiler system, the heating needs of each room can be met if radiators are sized using the lower Delta T (ΔT) that will exist between the radiator MWT and the design room temperature.”
Renovation needed
Heat pumps are easier to install in modern properties with lower heat losses than in older homes that have higher heat losses. Here, homeowners may need to commit to more extensive renovation work, such as insulation, double glazing and new heat emitters, to make the building suitable for a lowtemperature system.
Max Halliwell is communications manager at Mitsubishi Electric, and vice-chair of the Heat Pump Association (HPA). He says hybrid systems can offer a solution for these older properties. He says: “It’s a myth that heat pumps can’t heat every building. We believe 70-80 per cent of homes could take a heat pump, though they might need some upgrades. But when you’re dealing with the hardest-to-treat homes, such as those with stone walls, the question becomes ‘do we install a hybrid system that includes a heat pump’?
Number of heat pump installations required to reach the government’s target
“Those homes are likely to have a period over the winter where the heat pump would find it hard to provide enough heat, but at some point the heat pump becomes viable for the rest of the year. Fitting a hybrid heat pump system would still allow you to cut down on your fossil fuel use. I’m a big fan of hybrid systems as a stepping stone for the move to low carbon, much as hybrid cars have been.”
The noise emitted by the external heat pump unit is another key consideration to check before installation. Under permitted development, an air source heat pump can be fitted without planning permission so long as the noise limit does not exceed 42dB at 1 metre from the window of any neighbouring residential property.
Many consumers may agree with the environmental benefits of choosing a renewable heating system, but the upfront costs of installing a heat pump are still far higher than the cost of a gas boiler. Caspar Speakman, LG heating sales manager, Southern, says the focus should be on telling consumers about the longer-term cost advantages, rather than focusing on the upfront costs.
He says: “It’s about selling the heat pump concept on the cost of ownership over 15-20 years and highlighting the energy
savings and lower [heating] bills. It needs to begin with new-build, so people begin to expect heat pump technology in their new home and then move into replacement systems.
“As with condensing boilers, there will have to be legislation that says from ‘x’ date you cannot install boilers – in the end that’s the only way to get everyone to comply with the move to renewable heating. The government has already said that, from 2025, all new-build properties have to have renewable heating and hot water systems. They will have to extend this for existing properties as soon as possible after that date.”
Are the targets realistic?
The government’s target of 600,000 heat pump installations a year by 2028 is ambitious, especially considering that just 36,000 heat pumps were fitted in 2020, according to the HPA. In our 2021 reader survey, just 22 per cent of gas engineers said they already work with renewable technologies in some capacity.
HPA modelling believes this uplift is possible, predicting that 714,000 installations could be reached in 2028.
Max says: “It will require three things working together: manufacturers gearing up, consumer confidence, and enough engineers. We need a government campaign to put heat pump technology in the public eye and normalise it, like they have done in northern Europe. The Heat Pump Association is working on an accredited heat pump course to give engineers a base of knowledge and qualifications, so they can then go to a manufacturer to learn more. It’s all about getting the right number of engineers, and we need market demand to encourage that.”
There is already funding available to help homeowners invest in heat pump technology, and to create market demand, adds Max. “The Renewable Heat Incentive (RHI) is ticking along
Peter Thom: ‘The problem with the Green Deal and the Green Homes Grant scheme is the red tape and bureaucracy’
A gas engineer’s view
Gas engineer Peter Thom is managing director of Green Heat, and has been working to make properties more energy efficient for more than 30 years.
He says: “There isn’t a silver bullet. I think we’ll see a mix of hydrogen, heat pumps, and lots of other things that probably haven’t been invented yet.
“I think heat pumps are a great technology. They have their place and I’m sure we’ll all be fitting a lot in future, but they need to be in a framework that the industry can work with. Those of us who got involved in the Green Deal regret it, and now there’s another plethora of engineers who got involved in the Green Homes Grant scheme. The problem is the red tape and bureaucracy.
“Let the engineers come up with a solution. History shows they will find a way, and the politicians need to let the engineers in the industry get on with it. But the government doesn’t trust the engineers, and the engineers now aren’t going to trust any scheme they come up with in the future. I don’t know how they’re going to repair that because whatever scheme the government come up with will now just be deemed as too bureaucratic unless they work with us and use what we’ve got, and perhaps make what we’ve got a bit better.
“Get people to work to an industry standard and qualification, and then let the industry police it. The government just doesn’t understand how the industry works. They can say we’ve got to change, and we probably do have to a bit, but not on the scale they’re talking about, and not in the time they’re talking about.
“The problem is, if you impose too much red tape on a heating engineer they’ll go and fit bathrooms or kitchens or windows. As long as they’re paying their bills, they’ll do whatever they need to do. That’s just common sense, and I think the civil servants forget sometimes that these are real people.”
Can heat pumps alone solve the low-carbon
conundrum? continued
nicely. Although the uptake wasn’t as big as the government wanted to see, it’s still a generous incentive. And the latest consultation suggests that, instead of the RHI’s quarterly payment over seven years, the Clean Heat Grant [which replaces the RHI next March] will offer a £4,000 upfront payment for an air source heat pump, and £6,000 upfront for ground source. So there is a three-year timeline of funding available, and I don’t think the government will stop at that.”
Andy says: “Engineers need to see a growing and stable market for heat pumps and that, if they invest in the training, tools and time needed to align their business to the heat pump market, they will be rewarded with consistent, profitable work.”
The Green Homes Grant was intended to be the next step towards encouraging homeowners to make energy efficiency improvements, but it was scrapped in March after reaching just 10 per cent of the homes it hoped to improve. The £300 million funding will now be targeted at lower-income households through a local authority programme.
Caspar says: “The Green Homes Grant was a disaster waiting to happen. Sadly, government needs to talk to the industry when devising these schemes to make sure they will work. It has to be simple to administer and apply for, and simple for those carrying out the work to get paid for the work they do. It’s not rocket science.”
Andy adds: “We need to move away from badly administered and complicated government schemes such as this. The introduction of a simple boiler scrappage scheme that rewards consumers who switch to a low-carbon heating system would generate interest from all parties and achieve the market growth.”
The exact route to a fully low-carbon heating industry, and how successful that transition will be, is still unclear. But there will be significant growth in the number of renewable technologies being installed across the UK over the coming years and, whether it’s through government regulation or industry developments, heat pumps are likely to play a large part in the renewable mix. ■
Fitting heat pumps: FAQs
Heat pump technology works in a very different way from boiler-based heating systems, which means they’re not a like-for-like replacement. Vaillant Technologies and Training director Mark Wilkins answers some common questions about air source heat pumps in existing properties.
Is a heat pump sized in the same way as a boiler?
All heating systems follow the same sizing principle. A correct heat-loss calculation should be carried out, whether you’re fitting a new boiler or a heat pump. Heat emitters (radiators) should be sized correctly, flow rates should be calculated, and domestic hot water comfort should be covered, to ensure the new heating system will perform efficiently and provide the optimum heating and comfort required.
The output of the heating system must match closely with the heat loss of the property. An undersized heating system will not heat the building on cold days and an oversized one leads to short-cycling of the boiler or heat pump, which significantly reduces system efficiency.
What information do I need to calculate heat loss?
The formulae used for heat-loss calculations require a number of variables. You need to know the size of the property as well as information such as its location, what it’s made from, and door and window types. In addition to the property’s overall dimensions, you need to know the size of each room to ensure that the radiator and pipework are sized
correctly. The best way to get this information is to carry out a site survey.
Where should the heat pump be sited?
A heat pump needs to be placed outside, and you should consider this when recommending the system. Talk your customer through all available options, as some may prefer a more discreet heat pump placement, farther away from their home.
What about hot water?
If the property currently has a combi boiler for its heating and hot water needs, the customer won’t have a hot water cylinder already. You’ll need to identify a suitable space to fit a hot water cylinder and discuss possible locations with the customer. There are many cylinders available, including slimmer models with smaller footprints, which could be important if space is at a premium.
To minimise transfer heat losses via the pipework, it should be close to the heat pump, and fully insulated. Remember, the cylinder doesn’t have to be in a room; it could go in a garage if space allows.
Is an immersion heater needed?
Because most heat pumps work more efficiently with lower-temperature systems, a back-up heater (direct electric immersion heater) may be required to provide legionella protection. However, Vaillant’s aroTHERM plus heat pump allows a high flow temperature of 75°C for the legionella protection cycle, without the need for a back-up
heater. The hot water storage temperature can then be set in the same way as with a traditional boiler heating system.
Can I use an existing hot water cylinder at the property?
No. A standard boiler cylinder doesn’t have a big enough coil to work with a heat pump.
Can existing pipework and radiators be used?
Lower flow temperatures and lower temperature differentials for heat pump heating systems mean that more water is needed to ensure sufficient heat transfer. You’ll need to calculate the pipework size needed when designing the system to maintain correct flow rates. In addition, pipe runs will depend on where the heat pump and hot water cylinder are to be installed. Heat emitters need to be sized appropriately for the space.
In short, the site survey needs to assess whether the existing infrastructure is suitable for a new heat pump system, and what renovation is required.
What training do I need?
Currently, in order for property owners to access Renewable Heat Incentive (RHI) funding, installations must be carried out by a MCS (Microgeneration Certification Scheme) certified installer.
To become MCS certified, you will need to: • Undertake formal training to obtain the right qualifications that cover the work you wish to carry out (including Part L, Water
Regulations and a recognised course in heat pump technology), and/or demonstrate experience and competency to your MCS certification body • Have installations that meet
MCS standards • Be a member of the Renewable
Energy Consumer Code (RECC) or the Home Insulation & Energy
Systems Quality Assured
Contractors Scheme (HIES) • Show that you have an effective quality management system in place to prove your commitment to continual improvement.
As part of these requirements, you are expected to have undergone manufacturer-specific training.
While the revenue opportunities offered by lowcarbon solutions are clear, knowing where to start may seem a little daunting. But armed with further training, upskilling and support from manufacturers, diversifying your heating and plumbing business with lowcarbon offerings is within arm’s reach. ■
Take a connected approach to controls
It’s important to remember the role that controls can play in unlocking further savings from heat pumps. Rob Whitney from Resideo looks at the considerations that need to be addressed when it comes to setting up and installing controls correctly, especially where multiple zones are involved.
It is important to remember that heat pumps work in a different way from boilers and this has implications for how the heating controls are set up, especially for more complex installations where the building is separated into multiple zones.
Typically, a gas boiler takes about half an hour to heat a house, so it can run in quick bursts to provide heating for a short time if needed. But because heat pumps work with lower system temperatures, they take a lot longer to warm the property to the desired temperature, especially from cold, so they need a cycle pattern in place to
maintain constant comfort levels. Equally, a certain amount of flow needs to be maintained to the heat pump. If the flow rate drops below a threshold, the heat pump will stop operating regardless of what the controls ask for.
To enable the heat pump to operate in the most energy efficient way, heat has to be provided for sufficiently long periods. The amount of time when heat is not needed also needs to be long enough so that the heat pump does not cycle on and off.
To ensure this can be done simply, the ‘minimum on time’ on the Evohome’s installer settings are adjustable to suit heat pumps and boilers. For the heat pump, for example, this can be set to one cycle per hour, 20 minutes minimum run, and 10 minutes minimum off time, to make sure temperatures can be maintained.
Zoning strategy
A heat pump that switches on and off regularly cannot run efficiently, leaving the billpayer unable to reap the full financial benefits of this technology. This is why, when a property is split into different zones to save energy, the zoning needs to be configured so that the amount of heat called for through the controls stays within the modulation capabilities of the heat pump.
The best way to give householders the flexibility they need without over-zoning is to group rooms or spaces into areas according to common usage patterns. For example, first thing in the morning, the bulk of the house – which tends to be the biggest zone – could call for temperatures to reach 19°C, allowing the heat pump to operate at 70 per cent of its capacity, before the bedrooms also call for heat. Then, the bedrooms return to set-back temperatures as the homeowners start to follow their daily routine.
For instance, the home office could then be warmed up and the main house zone kept warm throughout the day, before all zones are set back to 16°C overnight.
This is where a heating control with smart zoning system comes in handy. Using radiator controllers, it wirelessly measures and controls temperatures in zones individually, without needing to disturb décor during installation.
More flexibility
If the customer needs more flexibility in how the property and useable water are heated with a heat pump, a buffer or volumiser can separate the system into two hydraulic circuits. In the primary circuit, the heat pump heats up the buffer tank, from which the heat emitters on the secondary circuit draw heat when the controls call for it.
Separating the hydraulic circuits in this way means that the property can have up to 12 heating zones, each set to call for different amounts of heat at different times, without making the heat pump switch on and off or reducing its efficiency. ■
Advanced features
As well setting the timings and temperature for heating in different parts of the home, the most advanced thermostat systems can monitor their surroundings and communicate closely with the heat pump. The thermostat can tell the heat pump to adjust its output to deliver the desired temperature at the right time, saving energy in the process.
The smart weather feature on the Evohome system, for example, follows the set programme on cooler days, but when it warms up outside it will automatically turn off the heating and save energy. It does this by monitoring outside temperature, room temperature and setpoint, and acts when heat demands are very low. It also limits inefficient high return temperatures and runs the heat pump in its most efficient mode.
Conversely, in rooms with poor insulation or large windows, it could feel less comfortable when the outside temperature drops. The Evohome learns the heat loss in each room and will increase the set temperature when it detects a drop outside, and automatically goes back to the normal programme when the outside temperature rises.
As the transition towards a low-carbon future gathers pace, heating engineers can get ahead of the curve now by taking the time to invest in product training that complements heat pump technology. You can find further information and training on the Honeywell Home Evohome smart zoning system at:
www.resideoinstallertoolbox.com
Heat pumps vs H-ready boilers
Heat pumps will play a vital role in decarbonising the nation’s heating. But they may not be the best solution for every home, says Martyn Bridges, director of Technical Communication and Product Management at Worcester Bosch.
There is a debate in national newspapers around future energy requirements, and it crystallises around two options: in the red corner is the heat pump, and in the blue corner is the hydrogen-ready boiler. Is a straight-swap replacement hydrogen-ready boiler the best approach or should we be fitting heat pumps into homes? And what are the costs and training requirements associated with each option?
While firm policy implementation is still on the back burner, probably due to the lifting of Covid restrictions, statements of intent have been issued that outline the government’s plans for heat pumps, hydrogen boilers, and new-build properties with reduced CO2 emissions.
Furthermore, training to upskill heating engineers who have not fitted heat pumps before is due to have launched by the time you read this, which will indicate progress and movement towards the government’s plans for fitting heat pumps across the UK.
Heat pumps
Heat pumps are a mature technology that have been installed in hundreds of thousands, if not millions, of properties in Europe and other parts of the world. In the UK, however, they are still very much a niche option, with installation numbers last year reaching only 30,000.
At present, if you want to buy a heat pump, it will probably be one of the models that are currently on sale in Europe. UK bespoke and built products are unlikely to be made here until there is a bigger market for them.
From a physical perspective, it is more difficult to fit a heat pump into a home that already has a boiler than it is to replace the boiler with a hydrogen-ready equivalent. This is not down to the footprint of the external unit, which generally can be accommodated in most gardens. However, having to find space for the hot water storage cylinder and making modifications to the home’s pipework and radiators is what will generally get people’s hackles up, and understandably so.
While heat pumps are undoubtedly a brilliant technology, well suited to new-build properties, their cost and the disruption means that uptake in existing UK homes will be limited for now.
Hydrogen-ready boilers
Hydrogen-ready boilers are the main alternative to heat pumps and can provide an answer to the question of existing homes. The case for hydrogen is still being proven from a safety and performance perspective but I have every confidence that their use will be accepted, most importantly because of their price and suitability for existing homes.
Several public trials are taking place, increasing in volume, in both unoccupied and soon-to-be occupied properties. Once these trials have concluded successfully, we are likely to see policy changes that require only hydrogen-ready appliances to be placed on to the market, as an alternative to heat pumps.
So far, there have been no further policy updates or statements made by government about heat pump systems in homes, other than into new-build properties.
The government has announced a 75-80 per cent reduction in carbon emissions in new-build properties in 2025 compared with equivalent properties built in 2013. Heat pumps will be the only way to achieve this target in the majority of individual homes because hydrogen will not be available on a mass scale.
Training
As we move toward heat pump installations, the industry has been preparing to upskill heating engineers, many of whom have not yet fitted them.
The training programme will provide guidance on how to size heating systems, pipework and radiators, heat-loss calculations and a range of other skills needed. And appliance manufacturers will introduce heat pump training courses to their own heating engineer customers.
Trials and training are taking place in the coming months but the industry is still awaiting the government’s decision on which technologies will be required to meet the challenge of decarbonisation. ■
Modifying radiators and pipework for heat pumps will cause disruption in homes
