Hybrid Heating Systems FAQs

A hybrid heating system combines more than one heat source to fulfil the space heating and hot water requirements for a property. Such hybrids usually bring together a renewable heating product, such as an air source heat pump, with a traditional fossil fuel appliance, such as an oil or gas boiler. Hybrid technologies provide households with a solution to incorporate renewable energy into their central heating system when a heat pump, or other renewable product, is unable to fulfil the entire heating and hot water demand.

The VortexAir Hybrid is a combination of a high efficiency condensing oil boiler and an air source heat pump, interconnected using a control system, such that they operate together as a single unit. It is intended to be installed where a heat pump alone may not be suitable for a particular application.

The Grant EvoLink Hybrid System Hub is a compact wall-mounted unit that allows an Aerona³ air source heat pump to be installed alongside most existing domestic heating systems, such as a gas boiler. The EvoLink allows renewable energy to be incorporated into a heating system while keeping the existing boiler as a supplementary heat source.

Each type of hybrid system works differently depending on its design and configuration. With the Grant VortexAir Hybrid, the control system on the hybrid unit monitors the ambient (outside) air temperature and allows only the heat pump to operate when the air temperature is high enough for it to meet the heat demand of the building on its own. At lower ambient air temperatures the boiler will operate alongside the heat pump, providing a boost to the flow temperature. When the ambient air temperature falls lower still, the boiler is operated at its full output at a higher flow temperature to enable the hybrid unit to meet the higher heating demand of the building.
With the EvoLink Hybrid System Hub, there are two core operating modes – Comfort and Green. With the Comfort mode, the EvoLink will ensure that the desired comfort level is maintained with the boiler being called in when the heat pump is unable to satisfy the space heating or hot water load. With Green mode, the EvoLink will ensure that the heat pump supplies as much of the heat energy to the system as possible and, during instances when the boiler is required to satisfy the space heating or hot water load, the EvoLink will only operate the boiler for as long as necessary and will ensure the heat pump remains operating for as long as possible.

A hybrid unit enables the optimum use of both an inverter driven air source heat pump and a traditional heat source, whether that be a highly efficient condensing oil boiler with the VortexAir or an existing fossil fuel appliance with the EvoLink. Throughout the year, as the ambient air temperature (and consequently the heat demand of the building) changes, a hybrid will provide the most efficient use of both the renewable and non-renewable energy sources. The VortexAir Hybrid and EvoLink Hybrid System Hub allow end-users to benefit from low carbon heating for the majority of the year with the boiler used as a back-up during colder periods.

Heating system radiators in existing properties are usually sized using the higher water flow temperatures produced from a boiler and so, to meet the same heat demand using the lower flow temperatures produced by a heat pump, the radiators would normally need to be increased in size. Using a hybrid unit combines the higher flow temperatures produced by a boiler, with the efficient operation of a heat pump, to meet the buildings heat demand throughout the year.

When the weather is warmer, i.e. in the spring and autumn, the heat pump works independently and the existing radiators can meet the heat demand with the lower flow temperature. This allows the very efficient use of electrical energy to drive the heat pump for large periods of the heating season. When the weather gets colder, the boiler operates to provide the additional energy required negating the need to increase radiator sizes.

The VortexAir is designed to be installed outdoors, i.e. both the boiler and heat pump are located next to each other outside the building. However, it is also possible for the boiler to be installed internally with the heat pump still outside. Full details for both types of installation are given in the installation instructions supplied with the unit.

No. The boiler can be installed and, if necessary, operated as a stand-alone unit for an indefinite period until the heat pump can be installed and connected to it. This is particularly useful when an existing boiler has to be replaced in an emergency due to a breakdown. The installation of the heat pump can follow at a later date when convenient.

The VortexAir Hybrid uses the Grant low level balanced flue system (or Yellow system) irrespective of whether the boiler part is located inside or outside the building. In the case of it being located indoors, the flue system exits at the rear of the unit and passes through the external wall of the building. If the boiler is outside it is fitted through the right hand side of the unit, above the boiler access door. The hybrid unit must be located such that the flue terminal clearance requirements of BS5410-1:2014 are complied with.

No. As not all installations will require a heat meter and electricity meter, the Grant VortexAir Hybrid is supplied without any meters fitted. However, in accordance with MCS metering requirements, the Grant VortexAir Hybrid is supplied ‘meter ready’ to allow both the heat meter and electricity meter to be easily fitted if required. The heat meter and electricity meter are available as accessories from Grant.

Installation of the hybrid unit requires an installer who is both competent in the installation of oil fired boilers (preferably a registered oil installer, e.g. OFTEC registered or similar) and also able to install an air source heat pump. Grant strongly recommends that any installer intending to fit a VortexAir Hybrid should first attend a Grant training course. Find a local hybrid heating installer here.

Usually, compliance with the Town and Country Planning legislation for England, and the MCS Planning Standards, for permitted development means that Planning Permission is not usually required to install a Grant VortexAir Hybrid. However, this should be checked with the Local Authority Planning Department in all cases. It is the responsibility of the householder to undertake this check.

This is a complicated question to answer. Any cost benefit is dependent on a variety of different factors, including the heat demand of the property, the type of heating system currently installed, the pattern of heating usage, the cost of both electricity and heating oil at the time of installation. Consequently, cost benefits will vary from one installation to another.

The EvoLink is designed to be wall-mounted and installed indoors with sufficient access clearances which are outlined in the Installation Manual. The EvoLink has a white case so it is ideally suited for installation in a kitchen or utility room. The EvoLink should not be installed outdoors.

The EvoLink can combine an Aerona³ heat pump with a traditional fossil fuel heating system including oil boilers, gas boilers, LPG boilers and modulating biomass boilers. The Grant Evolink has a maximum output to the system of 32kW and is suitable for use with boilers of up to 36kW output.

Both the VortexAir Hybrid and EvoLink Hybrid System Hub are designed for properties where an air source heat pump alone is unable to fulfil the entire space heating and hot water demand, unless significant changes are made to the property such as energy efficiency improvements or changing the heat emitters.
The VortexAir Hybrid is designed for properties which are currently on kerosene oil and would like to introduce a renewable heat source to their property, or whose existing boiler has broken down and needs replacing – the VortexAir provides a more sustainable replacement solution because the hybrid boiler can be installed straightaway, to restore heating and hot water to the home immediately, and then the heat pump can be fitted at a later date.
Meanwhile, the EvoLink Hybrid System Hub is designed for properties which have a traditional fossil fuel boiler which is operational but the household would like to incorporate a renewable heat pump into their heating system. With the EvoLink, the original boiler can be a back-up supplementary heater which is operated as and when required to support the heat pump in fulfilling the property’s desired temperature requirements.

Yes, both the Aerona³ air source heat pump and the existing boiler are controlled by the EvoLink in response to either space heating or hot water demand from the heating system controls (ie. room thermostats and taps).

Yes, the EvoLink Hybrid System is suitable for installation with combi boilers as well as standard and system boilers.

A hot water cylinder is usually made from stainless steel with insulation surrounding it and an outer casing. Inside the cylinder, there will be one or more coils which transfer the heat generated by the heat source into the water contents of the cylinder. Cylinders are designed to store the hot water which then feeds to the taps in your home. Unless you have a combination boiler, it is likely that you will have a separate cylinder for your domestic hot water. All air source heat pumps, solar thermal systems and hybrid installations require a separate cylinder.

Cylinders typically come in sizes from 150litres up to 300litres. The size of hot water cylinder that you require will depend on the number of occupants in your home and your demand for hot water. For example, a family of four will have a larger hot water demand compared to a single occupancy home because they will use the taps, showers or bath more often. If you are researching a new heating system for your home, please speak to your installer who will be able to advise you about the most suitable size of cylinder you will need.