Best of both worlds

Hybrid heating systems offer homeowners a viable renewable heating system

Hybrid heating systems offer homeowners a viable renewable heating system to replace their gas boiler and will be eligible for the domestic Renewable Heat Incentive. Nancy Jonsson highlights the benefits offered by this latest approach.
As more UK households look to switch to sustainable heating, opportunities for renewable installers are set to rise, particularly with the impending introduction of the domestic Renewable Heat Incentive (RHI).

Hybrid heating systems offer homeowners a viable renewable heating system

Several renewable systems are eligible under the domestic RHI, but perhaps the most versatile are hybrid systems, which combine familiar technology – a gas boiler – with a more efficient renewable heating solution, such as an air-to-water heat pump. For homeowners looking to replace their gas or LPG boilers, a hybrid system will deliver lower running costs and provide the opportunity to take advantage of RHI payments, with minimal disruption during installation.
The Daikin Altherma hybrid heat pump system combines a gas condensing combi boiler and an air-to-water heat pump, and can be connected directly to existing pipework and radiators. The system operates at water flow temperatures of up to 80°C, eliminating the hassle usually associated with replacing radiators, and is typically suitable for homes with a heat load of 12kW- 20kW – typically 2-3 bedrooms, a bathroom and perhaps even an en-suite.
The Daikin Altherma hybrid system is up to 35% more efficient in heating than the most efficient gas condensing boilers. It has two settings for heating – ecological or economical.
In ecological mode, the user can decide to minimise the ecological impact of their heating system by limiting carbon emission rates.
When using the economical setting, the smart controller automatically monitors the operating conditions, heat pump efficiency and heat load to determine the most economical running mode that achieves the lowest running costs, based on energy prices (electricity and gas).
The Daikin Altherma hybrid heat pump uses a weather compensation curve to determine the required flow temperatures and will automatically switch between four operating modes to achieve the most cost-efficient operation.
At higher outdoor temperatures, when the heat pump has sufficient capacity to cover the heat load and the heat pump is at its highest efficiency, it will work alone. As the outdoor temperature falls and the heat load increases, the first hybrid mode is selected and the boiler is switched on to provide additional capacity to support the heat pump. At this point, the heat pump efficiency means that it’s still cost effective to run.
As the heat load increases yet further, the Daikin Altherma hybrid heat pump’s unique flow control function automatically reduces the flow rate, thereby reducing the return and flow temperature to maintain the heat pump efficiency and cost effectiveness. This delays total dependency on the gas boiler for as long as possible. Finally, on the coldest days, and as the heat pump capacity becomes insufficient and less cost-effective, it switches off and the boiler provides the full heating capacity.
Over an entire year, up to 70% of the energy required for space heating can be provided by the heat pump – either on its own or in combination with the condensing boiler in hybrid mode. In this mode, heating water is pre-heated by the more efficient heat pump, reducing the energy consumed by the boiler.
The unique control logic in the Daikin Altherma hybrid heat pump optimises this combined operation, making it cost-effective – whatever the outdoor temperature. This helps customers to reduce their energy bills and ensures comfort all year round.
The compact indoor unit is designed to fit in the same space as a conventional wall-hung boiler. The heat pump hydrobox is mounted first onto a wall bracket and then the gas boiler is lifted onto the front and fixed to it. All the connections are easily accessible, making the unit quick to commission and simple to maintain.
The 33kW combi boiler provides instantaneous domestic hot water, with flow rates of 13 l/min (dT 35°C). The system is completed with a 5kW or 8kW outdoor unit, which is based on split refrigerant technology and can be sited up to 20m away from the house.
Hybrid heating systems are an excellent way to introduce customers to renewable energy technologies, especially where the system is packaged with a familiar gas combi boiler. For the 21 million homes in the UK that are connected to mains gas, a traditional condensing boiler will only be around 90% efficient for up to a typical operating life of about 15 years. Hybrid systems are, therefore, a much more efficient alternative to gas boiler replacement, providing even greater running cost savings than a new boiler alone.
Daikin UK has launched a comprehensive support package for hybrid installers, with tailored training and specialist advice throughout the design, installation and commissioning process. To install a Daikin Hybrid heat pump system, installers will need to be Gas Safe registered and F-gas qualified. If the householder wants to apply for domestic RHI payments, they will need to choose an installer certified by the Microgeneration Certification Scheme (MCS) and select MCS-accredited products.
Because they run alongside traditional heating, hybrid systems have to be metered to be eligible for domestic RHI payments. Homeowners also have to prove their system is being properly maintained to continue to receive tariff payments, so installers should advise customers to ensure that the system is regularly serviced.
Installers have a crucial role to play in helping homeowners understand the financial and environmental benefits of these innovative systems. For Gas Safe Registered installers who are prepared to invest in MCS, F-Gas and product training, hybrid heat pumps offer a fantastic business opportunity to target a much wider market of households looking to improve their energy efficiency and reduce fuel bills.