Knowledge Hub


Air Source Heat Pumps

What is a heat pump?

A heat pump uses the principles of thermodynamics to absorb energy from the surrounding environment and converts it into usable energy which can provide heating for our homes.

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How do air source heat pumps work?

There are two types of air source heat pump – ‘air to air’ and ‘air to water’. The Grant Aerona³ uses an air to water system which utilises heat energy captured from the air in ‘wet’ heating system radiators or underfloor heating.

The process uses the same vapour/compression cycle that extracts heat in a domestic fridge. A refrigerant with a low boiling point is exposed to external air temperatures in an evaporator. The liquid boils off to a gas and absorbs the latent heat energy of the air. This gas is then compressed increasing the heat content in the refrigerant, before passing through a heat exchanger where it condenses back to a liquid state while transferring the heat to the water of the heating system. The liquid refrigerant is then re-circulated through the evaporator and the cycle is repeated.

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Is an air source heat pump good for the environment?

Yes, the heat source used by Grant Aerona³ heat pumps is entirely renewable which helps reduce the amount of harmful greenhouse gases being released into the atmosphere and, in so doing, lowers the carbon footprint of the household.

What space do I require for an air source heat pump?

An air source heat pump needs to be located outside in the open air and sufficient space must be allowed around the unit (1000mm from front and sides, 300mm from back) so air can flow freely into it. The unit also needs to be installed on a flat trowelled finished concrete base 150mm thick and this base should extend at least 100mm beyond the unit on three sides. Full details are given in the Installation and Servicing instructions supplied with any Grant Aerona³ air source heat pump.

Where should I site an air source heat pump?

The north face of a building will usually have colder ambient air than any other side so, to ensure maximum efficiency from a Grant Aerona³ heat pump, position the unit on a warmer side, preferably south facing. All heat pumps make a noise so take opening windows and doors into account when considering the final position.

What is R32 refrigerant and what is the benefit?

Grant’s latest generation of air source heat pumps uses R32 refrigerant which has a GWP which is considerably lower than other typical heat pump refrigerants such as R410. In addition to having a lower GWP figure of 675, R32 is a single-component refrigerant which means it has no temperature glide. Refrigerant blends that have two or more components exhibit temperature glide but as R32 only has one molecule in its formation, its saturated liquid and vapor temperatures are the same. By removing the risk for the refrigerant to suffer from glide, the system can recharge and recycle with greater ease, making it more efficient.

Do I need planning permission for a heat pump?
All Aerona³ heat pumps are less than 0.6m³ in volume and fall within permitted development for the unit. That is one less thing to consider when working to meet the permitted development requirements, however do keep in mind that there are other requirements to meet which are site specific e.g. where the units will be located, how many there are and the status of the building/land concerned (listed building, etc.). You should always check with your Local Authority Planning Department prior to any work commencing.
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Why is it important to size a heat pump correctly?

Air source heat pumps must be correctly sized to ensure that it can provide the required amount of heat output at the design conditions – typically when the outside temperature is at -3°C. To do this an installer must first accurately determine the heat loss from the property and then, using this information, correctly select the required size of heat pump based on the design outside air temperature. Grant UK can assist with sizing the heat pump model and the heat loss of your building.

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How do air source heat pumps operate in very cold weather conditions?

During winter months when it is particularly cold, condensation can form and freeze on the finned evaporator coil of the unit. It is a normal occurrence and the heat pump is designed to cope with this. The control system will detect when the coil has iced up and will automatically enter a ‘defrost’ cycle. During this short ‘defrost’ period the fan will stop and the heat pump will cease supplying heat to the heating system in order to melt the ice. On completion the fan and heat pump will automatically restart and resume supplying heat to the heating system. This will not adversely affect the building temperature.

Is an air source heat pump noisy?

Heat pumps use either one or two fans to draw air through the unit to extract the heat energy. These fans will produce a moderate sound level that might be perceived by some as a nuisance, either by the occupants of the building with the heat pump system, or the neighbours. In particular this may be a greater problem at night when background noise is much lower. Careful choice of the heat pump location can help to minimise or eliminate the potential nuisance, e.g. not too close to bedroom windows (particularly with a bungalow) or too close to a neighbour’s boundary or property. Two of our latest models, the Aerona³ R32 13kW and 17kW heat pumps have achieved the Quiet Mark, an accolade which recognises some of the quietest, high performing products in the market.

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Will my electricity bills increase with a heat pump?

Your household electricity consumption will increase using an air source heat pump. However there will usually be no gas or oil bill to pay to heat the house, unless a bivalent heating system is chosen (combining the heat pump with a gas or oil-fired boiler as a backup heat source). You should therefore consider the overall cost of heating, i.e. the increased electricity cost compared with the saving in oil or gas bills.

Should I change my electricity tariff when I install a heat pump?

Where electricity is the only energy source used, a change to the electricity tariff might be possible enabling the heat pump to run more economically. It is always worth enquiring with your energy provider, as depending upon your electricity demand, they may have a plan that is more suitable e.g. Economy 10.

Are Grant air source heat pumps MCS approved?

Yes, all models within the Grant Aerona³ range are MCS approved.

Are Grant heat pumps Keymark approved?

All of the Grant Aerona³ R32 air source heat pumps have been approved by CEN KEYMARK, an independent European certification mark for all heat pumps, combination heat pumps and hot water heaters.

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Are Grant air source heat pumps eligible for the Boiler Upgrade Scheme?

Yes, Grant's Aerona³ air source heat pumps will be eligible for the Boiler Upgrade Scheme grants provided the installation fulfils the eligibility criteria.

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What type of heating system controls are used with Grant heat pumps?

Normal domestic heating controls, such as a 2-channel programmer, room thermostat and cylinder thermostat are suitable for use with Grant air source heat pumps.

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How often should a Grant heat pump be serviced?

Grant heat pumps should be serviced annually. Failure to do so will invalidate the product guarantee.

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Do air source heat pumps work with normal radiators?

Yes, air source heat pumps can be installed with radiators but the radiators must be correctly sized for the lower water flow temperature. It is important that the system is designed correctly and you can speak to your installer or a member of our Design Team to discuss this further. 

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Can a heat pump be connected to an existing hot water cylinder?

When installing an air source heat pump, a hot water cylinder that is compatible with heat pumps must be selected and, more often than not, an existing cylinder will not be suitable.

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What are the advantages and disadvantages of a heat pump?

It is important that consumers understand that an air source heat pump system differs to a traditional central heating system, such as a gas or oil boiler. They use electricity to power them, they are a low temperature heating system and the system design is different to that of a traditional heating system.

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How does the defrost cycle work on Grant Aerona³ heat pumps?

Grant air source heat pumps feature an in-built 'Defrost' function which automatically operates to assist the heat pump when external temperatures drop below 0˚C. In brief, the defrost cycle reverses the heat pump's operation to direct hot refrigerant vapour back into the ice covered evaporator causing any ice to melt.

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What is the difference between a Monovalent system and a Bivalent system?

In brief, a Monovalent system is when a heat pump covers the whole heating load whereas a Bivalent system is when a heat pump is combined with another heat source.


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Will I save money switching from my current boiler to a heat pump?

It is possible to save money on all fuel types by either improving a home's thermal insulation, reducing the room temperature, shopping around for a better energy deal or upgrading to a more energy efficient heating system.

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Do I have to pay VAT when installing an air source heat pump?

Between 1st April 2022 through to 31st March 2027, the rate of VAT on the installation of certain energy saving materials, such as a heat pump, is 0%. If you have a heat pump installed at your home during this period and you live in Great Britain, you should not have to pay VAT.

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Underfloor Heating

Can only new builds have underfloor heating?

Underfloor heating is not restricted to new build properties, it can be also be installed as a retrofit project into many older properties.

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Can underfloor heating only be used on ground floors?

No. UFH can be installed both upstairs and downstairs in a property. Please read more about underfloor heating specifications here.

How long does installation of an underfloor heating system take?

Grant's underfloor heating systems include, Uflex and Uflex MINI. With a drying time of thirty days, the Uflex underfloor system is best suited to the new build and renovation market, this is so the underfloor system can be fitted as part of the floor construction process. Uflex MINI, however, has a drying time of 3 days. It is suitable for both new builds, as well as retrofits and renovations, when an underfloor heating system is to be fitted in a property with a floor construction already in place. At just 15mm in height, this underfloor system can be installed incredibly quickly and with minimal disruption to a property’s existing floor and door arrangements.

Can underfloor heating be added to my existing heating system?

Underfloor heating is suitable for gas, oil, and LPG boilers as well as heat pumps and biomass boilers. For more information, speak to our Renewables Team.

Do I need to dig up the floors for underfloor heating?

No. The Uflex MINI system is specifically designed to suit retrofits and renovations, when an underfloor heating system is to be fitted in a property with a floor construction already in place. At just 15mm in height, this underfloor system can be installed with minimal disruption to existing floor and door arrangements.

Does underfloor heating work the same way as a radiator?

Radiators use air circulation to emit heat into a room whereas underfloor heating warms a room when the hot air rises from the floor. Radiators do therefore work differently compared to an underfloor heating system. 

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Which type of underfloor heating is best for my flooring?

Not all types of floor finishes are compatible with underfloor heating systems so it is important to research suitable floor coverings which will allow the heat from the underfloor heating system to be transferred into a room.

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Is underfloor heating cheaper to run than traditional heat emitters?

Yes, data suggests that underfloor heating can be 25% cheaper to run than radiators when used in conjunction with a condensing boiler and up to 40% cheaper to run when used with a heat pump (EuRay 2005.)

What is zone control?
A zone is an area or a room that is controlled independently via a room thermostat. A house could be split into two zones for example upstairs and downstairs or each room could be classed as a separate zone. Zone control gives you greater control over your heating and ensures each area is at optimum temperature.
What is overboarding and do I need it for underfloor heating?

Overboarding involves the fitting of an overlay or base layer in between the screed and the floor finish. Some types of underfloor systems, such as electric UFH, require a form of overboarding to be fitted as standard. However, Grant’s Uflex underfloor system does not need overboarding which allows installers to lay the final floor covering directly on top of the dry screed.

What is an underfloor heating manifold?

The manifold is the system hub for the underfloor. The pipes are connected to it at the installation stage and it then controls the distribution of the water from the heating system's source (boiler/heat pump) throughout the underfloor system. It is at the manifold that the control of the flow to each individual zone or room is achieved.

Where should a manifold for underfloor heating be situated?

The manifold should be located in a central point where the pipework is most evenly distributed.

It's recommended I keep my underfloor system running constantly, why is this?

Grant's underfloor heating systems operate at their most efficient when they are not frequently switched off and on. The floor screed takes time to heat up, but once up to temperature it only requires a small amount of heat to maintain this condition. Switching the system off and on, results in the floor losing temperature, requiring more heat input to reach temperature again.

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Can I fit underfloor heating under a kitchen unit?
Yes, providing there are no fixings that may damage the pipe, we advise to lay the underfloor across the total floor area as the future layout could be different. We do not recommend the underfloor to be fitted below sanitary items as these are often fixed to the floor and could damage the pipes.
What are setback controls?
Operating the system with a 'setback' control, maintains the floor at a minimum temperature at all times and avoids the wasteful use of energy to continually reheat the floor from cold.

Hybrid Heating

What is a Grant VortexAir Hybrid?
It is a combination of a high efficiency condensing blue flame oil boiler and an air source heat pump, interconnected using a control system, such that they operate together as a single unit.
How does a hybrid system work?

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.

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What is the benefit of using a hybrid?
A hybrid unit enables the optimum use of both an inverter driven air source heat pump and a blue flame condensing oil boiler, throughout the year, as the ambient air temperature (and consequently the heat demand of the building) changes, thus providing the most efficient use of both the renewable and non-renewable energy sources.
What is the benefit of using a hybrid over using a heat pump only?

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.

How is the Grant VortexAir Hybrid connected to the heating system?
The boiler is always fitted first and the heating system in the building is connected directly to it, whether or not it is located outside next to the heat pump or indoors. The heat pump is then installed and also connected directly to the boiler.
Where should the Grant VortexAir Hybrid be located?

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.

With a hybrid system, do both the oil boiler and heat pump parts have to be installed at the same time?

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.

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What are the benefits of the blue flame burner technology used in the Grant VortexAir Hybrid?
The boiler used in the Grant VortexAir Hybrid is the latest in a family of high efficiency condensing oil boilers. Whilst maintaining the current high level of efficiency, the use of blue flame technology reduces emissions. In particular, the NOx level in the flue gases, such that the boilers will meet new emissions limits to be introduced in September 2018.
Does the blue flame oil burner have any special servicing requirements?

No. The blue flame burner and boiler is serviced in exactly the same way as any other boiler from the award winning Grant high efficiency Vortex condensing range. The boiler is accessed via a removable door on the right hand end of the casing and most of the electrical servicing can be easily done from the front of the appliance.

What type of flue system is used for the oil boiler part of the Grant VortexAir Hybrid?
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.
What type of oil is used for the boiler of the Grant VortexAir Hybrid?
As with Grant Vortex boilers, the VortexAir Hybrid is only suitable for use with standard kerosene (Class C2 to BS2869). Gas oil (Class D to BS2869) must not be used with the hybrid boiler.
Does the VortexAir hybrid come fitted with a heat meter?

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.

Who can install the Grant VortexAir Hybrid?

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. If an RHI payment is required, the installer will have to be MCS accredited for the installation of air source heat pumps.

Is Planning Permission required for a Grant VortexAir Hybrid?

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.

What would the cost benefits be of installing a Grant VortexAir Hybrid?

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.

Solar Thermal Systems

What is the difference between solar thermal and Solar PV?

A Solar PV system uses panels (usually called ‘modules’) that generate electricity in the presence of sunlight. The amount of electricity produced depends on the intensity of the sunlight. Solar thermal, on the other hand, uses sunlight to heat a fluid. In the case of Grant solar collectors, it heats a glycol/water solution within the collector. This heated fluid is then circulated from the collector to a cylinder where the heat is transferred to produce hot water.

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Who can install Grant Solar Thermal?
The installation of the Grant Solar Thermal system must be carried out by a competent trained person in accordance with the relevant requirements for health and safety, local building regulations, building standards in Scotland and regulations and bylaws of the local water company.
Is planning permission required for solar thermal panels?

In most instances, the installation of a solar thermal system does not require planning permission. 

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Will the solar panels still work on a cloudy day?

Many people believe that solar collectors only work in the summer, however this type of free energy is available throughout the year. From May to September, solar thermal could produce 100% of the energy required for heating your domestic water. Grant collectors operate not just with direct sunlight, but also diffused sunlight, so they even work on cloudy days.

Does it matter what direction the solar thermal collectors are facing?

For installations in the UK, solar thermal collectors will perform best when facing due south at an angle of between 30 - 45°. However, collectors facing south west or south east will perform almost as well. Failing that a collectors facing due west will perform better than those facing due east. North facing solar thermal collectors are not usually used.

Can solar thermal collectors be mounted on any type of roof?
Grant solar thermal collectors can be fitted on many different types of roof, both flat and pitched. Collectors can be mounted either just above the roof covering or set into the roof, as required.
Do solar thermal systems require a lot of maintenance?

No. Grant Solar Thermal systems require only basic maintenance in order to ensure that they continue to give trouble free operation.

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Can solar thermal be used to heat my house?

Whilst solar thermal can be used to contribute to the heating of a house using a thermal store, it is more usually used to heat your domestic hot water cylinder and provide hot water to your taps. 

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Can a solar thermal system be used with my existing hot water cylinder?

A Grant solar thermal system requires a cylinder with a solar coil. In many cases this will be a ‘twin coil’ cylinder with both a boiler coil and a solar coil. This may well mean that your existing hot water cylinder will have to be replaced by a suitably sized twin coil cylinder to maximise the performance of your solar thermal system.

Can solar thermal be used to heat a swimming pool?
Yes. Solar Thermal collectors can be used to provide heat for a swimming pool.
Could the collectors of a Grant Solar Thermal system freeze up in cold weather?
No. The solar fluid used in a Grant solar thermal system is a 40% propylene glycol solution. This provides frost protection for the collectors and external pipework down to -25°C.
Do I have to pay VAT when installing solar thermal?

Between 1st April 2022 through to 31st March 2027, the rate of VAT on the installation of certain energy saving materials, such as a solar thermal system, is 0%. If you have a solar thermal system installed at your home during this period and you live in Great Britain, you should not have to pay VAT.

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Oil Boilers

What is a condensing oil boiler and why is it more efficient?

A condensing boiler has second (condensing) heat exchanger where the flue gases are cooled to below their dew point by the water returning from the heating system. This has the effect of condensing the water vapour present in the flue gases, and liberating the heat energy that would otherwise be lost to outside through the flue system.

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Are Grant boilers biofuel compatible?

All Grant Vortex floor standing oil boilers are biofuel compatible (depending on type of biofuel and % blend, for example: HVO or FAME). Biofuels are a renewable energy source, created from organic matter or waste. It will likely play an important role in reducing carbon dioxide emissions in the future. As biofuels emit less carbon dioxide than conventional fuels they can be blended with existing fuels, or used as 100% sustainable fuels, as an effective way of lowering carbon emissions.

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What is NOx?
NOx or Nitrogen Oxides are gases that form when fuel is burned at high temperatures. Emissions of this gas are bad for the ozone layer so the Energy Related Products (ErP) Directive have implemented lower targets, for oil-fired boilers, the NOx emissions target will be a maximum of 120mg/kWh
What is the difference between seasonal efficiency and combustion efficiency?
Seasonal Efficiency is the average annual efficiency achieved in typical domestic situations, and is confirmed by independent testing bodies. These figures are verified on A simplified explanation of Seasonal Efficiency is that this is the average efficiency of the boiler over a year, taking into account climate, housing conditions, occupancy patterns, and controls. Combustion Efficiency is defined as the amount of heat released during combustion over the heating value of the fuel burned. This is usually shown as the net efficiency on a digital flue gas analyser, and may be higher or lower than the Seasonal Efficiency, depending on the time of year and the heat load.
What is the difference between a Vortex and VortexBlue boiler?
Grant Vortex boilers use a burner which produces a yellow flame. The VortexBlue boiler uses a newer blue flame burner that is designed to re-circulate the combustion gases. Within the blue flame burner’s specially designed change to the combustion head, the combustion gases are mixed with atomised droplets of fuel and fresh air drawn in through the burner. This produces a clean blue flame (hence the technology’s name) with those important low NOx emissions.
What is the difference between a Vortex Pro and Vortex Eco boiler?

The award winning Vortex boiler was launched in 2002. In the subsequent years that followed there was a customer demand for a competitively priced ‘A’ rated boiler, so the R&D Team at Grant devised the Eco range to meet this growing demand. The Vortex Pro has a larger heat exchanger area and more case insulation which gives it a slightly higher efficiency than the equivalent Eco model.

What is an energy efficient boiler?

An energy efficient boiler is an appliance which operates as effectively as possible by reducing the amount of energy lost through insulation and out the exhaust. 

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Which boiler is best for my home?

Choosing the best boiler for your home is important so that it meets all of your requirements. Whether you need an internal or external boiler, one for your utility room or garage, your installer will help you find the best boiler type for your property and with sixty-three models available, a Grant boiler should meet your requirements.

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Can condensing boilers be used on gas oil?
No, condensing oil boilers can only run on kerosene.
I have been told that condensing boilers plume. What does this mean?
As flue gas temperatures are very low on condensing boilers, a plume of water vapour can often be seen at the terminal (similar to your breath on a cold day). This is the boilers normal operating mode, but if this is likely to cause a nuisance to yourself or a neighbour’s property, we recommend you install a high level, vertical or a plume
What is condensate and is it dangerous?
Condensate occurs when the flue gas temperature of an appliance drops to below the ‘dew point’ and the steam present in the flue gases condenses and becomes a liquid. This liquid is slightly acidic but no more so than tomato juice and can be run directly into the household waste system.
Should we have a frost stat fitted to our boiler?
We recommend that external boilers have a frost stat fitted.  Grant outdoor modules come with a factory fitted frost stat set at 5ºC plus or minus 1ºC.  A permanent live is required with a frost stat. For added frost protection, you should fit a pipe thermostat on a return pipe, set at 30ºC and wired to number 5 & 6 on the control panel.  This will prevent the boiler heating the house unnecessarily.  A bypass must also be fitted when wired as above.
What is a combi boiler?

A combi is a combination boiler that produces both heating and hot water from one compact appliance.

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Are combi boilers energy efficient?

Combi boilers which incorporate the latest burner and heat exchanger technology will be highly efficient. When comparing combi boiler efficiency, there will be two ratings – one for the space heating efficiency and one for the hot water efficiency.

Is an outdoor boiler just as efficient as one installed inside?
Yes. The boilers are exactly the same as those fitted indoors, but are fitted inside a highly insulated weatherproof casing instead.
What size of boiler do I need?

The size of oil boiler that you will need will be determined by the heat loss of your property, the size of your home and your requirements for heating and hot water demand.

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I recently ran out of oil, will this cause an issue to the system?
When your oil level falls below a certain level in your tank, there is a risk of air and contaminants that are in the bottom of the tank getting into your oil line which will affect the operation of your oil boiler. We always recommend that there is adequate filtration on your oil line and that your oil tank is kept topped up with fuel. If you have run out of oil, you must contact a competent oil heating engineer to bleed the system.
Can I connect underfloor heating directly to a Grant Vortex Condensing boiler?
Yes, although we recommend the return temperature remains above 40°C. However, it is more usual to connect underfloor heating via a system of mixing valves or even a separate calorifier so that radiators which are normally heated to a higher temperature can be served as well. In order for the boiler to remain under guarantee, we stipulate it must be serviced every twelve months. Any work undertaken must be carried out by a competent service engineer.
Can I connect a Grant Vortex boiler to an older heating system?
Yes, providing the system is cleansed thoroughly and updated to fully pumped operation (not gravity hot water).
Is there anything I can do to help prevent my condensate trap from freezing on my boiler?

It is advisable to let your condensate run into a soil stack or the larger the diameter of pipe the better as this will help to prevent freezing water.  If your condensate trap is not run off into a soil stack pipe and its running into a smaller waste pipe then remove the bung on the condensate trap.

Can I have a new boiler installed that is connected to my existing oil tank?
It is possible, but your installed should carry out a risk assessment on your oil tank to ensure that it complies with current Fire Protection and Environmental regulations.
Does an oil boiler need to be installed and commissioned by a qualified person?
To meet Building Regulations an oil boiler should be installed and commissioned by a Registered oil technician (e.g. OFTEC) or be installed by a competent person under a Building Control Notice
Where can I find the serial number of my Grant Vortex boiler?

The serial number is a 15 digit long number sequence, located on a data plate on the inside panel of your boiler (Example 205122367811171).

I heard that you should oversize your radiators and run a condensing boiler at a lower temperature, is this correct?
Condensing boilers work at their most efficient when they condense, and this requires the return water temperature to the boiler to be around 50°C or less. However, we do not recommend changing radiators for larger versions to achieve this as it is uneconomical, and for most of the year the radiators will be oversized anyway. The Grant Vortex will operate efficiently on any system and even when not condensing, the larger heat exchange area will mean you will still be saving money against a standard boiler.
How energy efficient is my boiler?

You can see how energy efficient a boiler is by reviewing the technical data provided by manufacturers. For Grant boilers, you can find the boiler efficiency rating of individual models via our website – please read more about oil-fired boilers here.

Can a new boiler be connected to the conventional flue that my current boiler uses?
No. Your existing flue system should be replaced when a new boiler is fitted.
What is a flue system?

Grant oil condensing boilers need to be connected to a flue to remove the combustion gasses. Even if you are replacing your Grant boiler with a new version, you will require a new flue system too. It is not possible to connect to the old existing flue or liner, due to build-up of debris, which could fall back into your new boiler and affect its performance. Grant has a range of unique EZ-Fit Flues which are available as low level, high level or vertical kits, for internal and external applications, and even as unique flexi liner packs, designed to enable condensing boilers to utilise an existing chimney. It is also possible to convert existing low-level flues to high level after installation. Apart from the benefits of so many options the Grant EZ-Fit flue systems ensure ‘pluming’ is kept well out of the way of any windows, air vent or doors and out of sight. The flue terminal (end part of flue situated externally) should be positioned so as to avoid combustion gasses accumulating in stagnant pockets around, or entering inside the property. Care should also be taken that the plume from a condensing flue does not cause a nuisance. Please talk to your installing engineer for more information about the Grant EZ-Fit Flue systems.

If I upgrade to a new Grant boiler, will I need to change my flue system?

In almost all applications you will not be able to use the existing flue. With condensing boilers there is a lower flue gas temp which leads to condensation/ moisture in the chimney/flue. The condensing boiler will need a Grant approved flue which is stainless steel and properly sealed at the joints to prevent leakage. All Grant external modules come with a factory fitted flue system.

How often should a Grant oil boiler be serviced?
Grant oil boilers operating on kerosene, the most common heating oil in the UK, should be serviced annually. However, those operating on biofuel should be serviced twice a year.
Why should you regularly service boilers?

A boiler service is recommended to help the appliance operate correctly. Grant recommend that your oil boiler is serviced every twelve months (even when the guarantee has expired) to prolong the lifespan and ensure it is operating safely and efficiently. 

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Can I reduce the carbon emissions from my boiler?

Biofuels, which are a type of renewable energy, produce significantly less carbon dioxide emissions compared to traditional fossil fuels so their use could help reduce the emissions of a biofuel compatible oil boiler. 

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What does an ISO 14001:2015 mean?
ISO 14001:2015 sets out the criteria for an environmental management system and can be certified to. It maps out a framework that a company or organization can follow to set up an effective environmental management system. It can be used by any organization regardless of its activity or sector. Using ISO 14001:2015 can provide assurance to company management and employees as well as external stakeholders that environmental impact is being measured and improved. External audits are completed yearly to ensure the business is maintaining these principles.
What does an ISO 9001:2015 certification mean?
This standard is based on a number of quality management principles including a strong customer focus, the motivation and implication of top management, the process approach and continual improvement. Using ISO 9001:2015 helps ensure that customers get consistent, good quality products and services. External audits are completed yearly to ensure the business is maintaining these principles.
What is Cyber essentials?
In June, Grant UK completed an assessment against the Cyber Essentials Standard which they passed. Having met the requirements of the scheme, Grant UK have been awarded a Certificate of Compliance which acknowledges the strength of the Company’s ICT defence protocols.
I've seen a logo on certain products 'Energy Saving Trust Endorsed product', what does this mean?

The Energy Saving Trust endorsed energy efficient products that met industry agreed standards for energy performance and for over 15 years, all Grant oil boilers were endorsed by the Energy Saving Trust. Please be advised that the Energy Saving Trust's product endorsement scheme closed on 1st March 2022.

What benefit is an 'MCS Approved product' to me?

The Microgeneration Certification Scheme is a government driven scheme to promote renewable technologies. It is an internationally recognised quality assurance scheme which demonstrates the quality and reliability of Approved Products by satisfying rigorous and tested standards. MCS is linked to the Governments’s finance schemes and incentives. If you wish to take advantage of these schemes, an MCS approved product must be used. For further information visit

What is a WRAS Approved product?
Any water fitting, which when installed, will carry or receive water from the public mains water supply in the UK, must comply with the Water Supply (Water Fittings) Regulations or Scottish Byelaws. These require that a water fitting should not cause waste, misuse, undue consumption or contamination of the water supply and must be ‘of an appropriate quality and standard’.

Data Protection

What is the GDPR?
The EU General Data Protection Regulation (“GDPR”) comes into force across the European Union on 25th May 2018 and brings with it the most significant changes to data protection law in two decades. Founded on the basis of privacy by design and taking a risk-based approach, the GDPR has been designed to meet the requirements of the digital age. The 21st Century brings with it broader use of technology, new definitions of what constitutes personal data, and a vast increase in cross-border processing. The new Regulation aims to standardise data protection laws and processing across the EU; affording individuals stronger, more consistent rights to access and control their personal information.
How is Grant UK safeguarding my data under the GDPR?
Grant UK is committed to ensuring the security and protection of the personal information that we process, and to provide a compliant and consistent approach to data protection. We have always had a robust and effective data protection program in place which complies with existing law and abides by the data protection principles. However, we recognise the requirement and importance of updating and expanding this program to meet the demands of the GDPR and the UK’s Data Protection Bill. Grant UK is dedicated to safeguarding the personal information under our remit and in developing a data protection regime that is effective, fit for purpose and demonstrates an understanding of, and appreciation for the new Regulation.
What is a Subject Access Request (SAR)?
A Subject Access Request (SAR) is the right of an individual to request any personal data that Grant UK hold on their behalf. This right is a principle of the GDPR, designed to regulate the processing of information from which a natural living person can be identified either from the information itself or when combined with other data. We are committed to upholding the rights of individuals and have dedicated processes in place for providing access to personal information. Where requested, we will provide the following information: - • the purposes of the processing • the categories of personal data concerned • the recipient(s) or categories of recipient(s) to whom the personal data have been or will be disclosed • the envisaged period for which the personal data will be stored (or the criteria used to determine that period) • where the personal data was not collected directly from the individual, any available information as to its source
How can I make a Subject Access Request (SAR)?
A subject access request (SAR) is a request for access to the personal information that the Company holds about you, which we are required to provide under the GDPR (unless an exemption applies). The request doesn't have to specify it's a SAR or refer to the GDPR; it can be a general request for personal information. You can make this request in writing to our registered office address: FAO The Data Protection Manager, (GDPR Governance Group), Grant Engineering (UK) Ltd, Hopton House, Hopton Industrial Estate, Devizes, Wiltshire, SN10 2EU. Or, you can submit your access request electronically by email to Where a request is received by electronic means, we will provide the requested information in a commonly used electronic form (unless otherwise requested by the data subject).
How do Grant UK process a Subject Access Request (SAR)?
Subject Access Requests (SAR) are passed to the Company’s Data Protection Governance Group as soon as received and a record of the request is made. The person in charge (Our Data Protection Manager) will use all reasonable measures to verify the identity of the individual making the access request, especially where the request is made using online services. We will utilise the request information to ensure that we can verify your identity and where we are unable to do so, we may contact you for further information, or ask you to provide evidence of your identity prior to actioning any request. This is to protect your information and rights. If a third party, relative or representative is requesting the information on your behalf, we will verify their authority to act for you and again, may contact you to confirm their identity and gain your authorisation prior to actioning the any request. Information Gathering If you have provided enough information in your SAR to collate the personal information held about you, we will gather all documents relating to you and ensure that the information required is provided in an acceptable format. If we do not have enough information to locate your records, we may contact you for further details. This will be done as soon as possible and within the timeframes set out below. Once we have collated all the personal information held about you, we will send this to you in writing (or in a commonly used electronic form if requested). The information will be in a concise, transparent, intelligible and easily accessible format, using clear and plain language.
Is there a charge for a Subject Access Request (SAR)?
SARs are always completed within 30-days and are provided free of charge. Where the request is made by electronic means, we provide the information in a commonly used electronic format, unless an alternative format is requested. Whilst we provide the information requested without a fee, further copies requested by the individual may incur a charge to cover our administrative costs. The Company always aim to provide the requested information at the earliest convenience, but at a maximum, 30 days from the date the request is received. However, where the retrieval or provision of information is particularly complex or is subject to a valid delay, the period may be extended by two further months. If this is the case, we will write to you within 30 days and keep you informed of the delay and provide the reasons.
What if you hold information about me that isn’t correct?
Under the GDPR, you have the right to request rectification of any inaccurate data held by us. Where we are notified of inaccurate data, and agree that the data is incorrect, we will amend the details immediately as directed by you and make a note on the system (or record) of the change and reason(s). We will rectify any errors within 30-days and inform you in writing of the correction and where applicable, provide the details of any third-party to whom the data has been disclosed. If for any reason, we are unable to act in response to a request for rectification and/or data completion, we will always provide a written explanation to you and inform you of your right to complain to the Supervisory Authority and to seek a judicial remedy. In certain circumstances, you may also have the right to request from the Company, the erasure of personal data or to restrict the processing of personal data where it concerns your personal information; as well as the right to object to such processing.
Where can I find further information on the GDPR?
If you would like further details on the Regulation or are unhappy with the way your data has been handled, please contact the Supervisory Authority - The Information Commissioner’s Office (ICO). They can be contacted at: - Wycliffe House, Water Lane, Wilmslow, Cheshire, SK9 5AF. Telephone: 0303 123 1113 (local) / 01625 545 745 (national). Fax: 01625 524 510. Email: Web:
Where can I find further information about how Grant UK process personal data?
We are dedicated to safeguarding any personal data under our remit and process this information in accordance with our Privacy Policies, see:
How can I make a data protection complaint?
Every individual has the right to lodge a complaint with the supervisory authority - the Information Commissioner’s Office (ICO), where they consider that the processing of personal data relating to them infringes the General Data Protection Regulation (GDPR) or we have breaches data protection law. The ICO with which the complaint has been lodged, is responsible for informing the complainant on the progress and the outcome of the complaint, including the possibility of a judicial remedy where the supervisory authority does not handle a complaint or does not inform the data subject within three months on the progress or outcome of the complaint lodged. The ICO can be contacted at: - Wycliffe House, Water Lane, Wilmslow, Cheshire, SK9 5AF. Telephone: 0303 123 1113 (local) / 01625 545 745 (national). Fax: 01625 524 510. Email: Web:


Where can I buy Grant products?

Grant UK distributes through a network of independent and national plumbing and heating merchants. Please use our Merchant Search tool to locate a distributor near you.

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What does ‘net zero carbon’ mean?

Net zero carbon refers to achieving a balance which ensures that the level of carbon dioxide within the atmosphere is not added to or increased. The Government has set the country a target of achieving net zero greenhouse gas emissions by 2050 which will mean that society, its behaviours and everything it produces, will need to collectively not increase the overall level of emissions, including carbon. Wherever possible, no carbon emissions should be produced but when they are, society needs to counteract these emissions with an environmentally friendly solution to absorb any excess carbon from the atmosphere.

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What is ErP?
The Energy Related Products (ErP) Directive has been designed to aid the EU in achieving reductions in energy usage: carbon, NOx and SO2 emissions and other environmental issues such as noise and the use of refrigerants in heat pumps. The Directive is also designed to help consumers identify the most energy efficient products on the market with energy efficiency labelling. The ErP details energy efficiency requirements which appliances must meet and preferably exceed. Manufacturers must ensure that their products are prepared for the new legislation changes, incorporating product updates to improve efficiency levels (e.g. fitting high efficiency circulating pumps).
What is the Renewable Heat Incentive (RHI)?

The Renewable Heat Incentive (RHI) was a Government initiative introduced to encourage and reward people for using renewable fuels to heat their properties. The Domestic RHI Scheme closed to new applications in March 2022.

Who is eligible for the Boiler Upgrade Scheme?

The Boiler Upgrade Scheme (BUS) is a new Government funding programme that will open once the Domestic RHI Scheme closes in March 2022. The BUS will be open to eligible applicants in England and Wales who make the swap from a fossil fuel boiler to a low carbon heat pump.

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What is the standard guarantee on your products?

All Grant products have a statutory 12-month guarantee. If the product is registered via our website within 30 days of installation, this is upgraded to a standard warranty: 2 years on oil boilers, air source heat pumps and hybrids, 5 years on solar thermal, 2 years on cylinder components and 25 years on the cylinder body. These warranty periods are subject to Terms and Conditions.

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How do I find out if my boiler has a guarantee?
When a product is registered via our online system, we send an email confirmation with your guarantee paperwork detailing the product registered along with Terms and Conditions. If you have not received anything, please contact our customer services department on 01380 736920.
I have heard I can get a ten year guarantee on my oil boiler, is this correct?
We do offer a ten year guarantee on our VortexBlue range; however, this is subject to certain Terms and Conditions such as the product being installed by a Grant G1 installer and a Grant Mag One filter being fitted to the system. For details on how to find a G1 Installer, please visit our ‘Find an Engineer’ page.
How can I find G1 Installers and/or service engineers in my local area?

Grant UK’s Find an Engineer search facility allows homeowners to find local installers and engineers in their area. Simply click on ‘Find an Engineer’ under the ‘Support’ header and then enter your postcode. The search will then bring up a selection of G1 installers and service engineers based locally to you. You can also filter your search to suit your requirements.

Can G1 Installers offer extended guarantees on Grant’s renewable products as well as oil boilers?

G1 Installers can activate extended guarantees on the Grant products they are accredited to install. This can include Grant’s Aerona³ air source heat pumps and VortexAir Hybrid models. In order to activate the longer guarantee periods, the G1 Installer must install the appliance in full accordance with the installation instructions and then register the product via their online G1 Portal.

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My Grant appliance was installed by a G1 Installer so who should register my product?
If your Grant product was purchased and installed by a G1 Installer, it is your installer’s responsibility to register the appliance via their online G1 Portal. Once they have registered your product, your G1 Installer will receive a copy of the registration paperwork and they can then forward this through to you for your records.
Can I add anything to my heating system to prevent it from freezing?
Yes, there are a number of products which may be used to give frost protection to domestic central heating systems.  For total system protection against freezing particularly during extended periods without electrical power, we recommend the use of a combined heating system antifreeze and corrosion inhibitor used in accordance with the manufacturer’s instructions.
Is Grant UK a member of RECC?

Yes - Grant Engineering (UK) Ltd is a member of RECC (Membership No. 00070263). 

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How can I make a general complaint to Grant UK?

We consider and respond to all complaints and issues, no matter how they are raised or what they refer to. We take every opportunity to resolve complaints at the first point of contact where possible. To make a complaint, please use the contact forms on this site, or alternatively email:

Biomass Boilers

Do Grant UK supply biomass boilers to the UK mainland market?

Grant UK no longer supply new biomass boilers and ancillary products to the mainland UK market (including England, Scotland, Wales, Isle of Man and Channel Islands).

Are Biomass Spares still available from Grant UK?

Grant UK supply the full complement of spares to support Grant biomass installations in the field – please visit for further details.

Is Technical Support available for Grant biomass installations in the field?

Technical support for all Grant biomass installations that are under warranty is available, subject to the Terms and Conditions of the product's guarantee and subject to the product being correctly registered with Grant UK. Please call 01380 736920 to speak to a member of Grant UK’s Technical Team with the biomass boiler’s serial number and installation address details to hand.

Fan Convectors

Do Grant UK supply fan convectors to the UK mainland market?

Grant UK no longer supply the Solo Fan Convector range to the mainland UK market (including England, Scotland, Wales, Isle of Man and Channel Islands).

Is Technical Support available for Grant Solo Fan Convector installations in the field?

Technical support for Grant Solo Fan Convector installations that are under warranty is available, subject to the Terms and Conditions of the product's guarantee and subject to the product being correctly registered with Grant UK. Please call 01380 736920 to speak to a member of Grant UK’s Technical Team with the installation address details to hand.

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