Frequently asked questions


If a household has to self-isolate during the coronavirus outbreak and is therefore unable to have their Grant product serviced, will the product's warranty be affected?

Grant UK fully understand that some customers may have to self-isolate for a considerable period of time and as such, will not be able to have their Grant product serviced. We are therefore issuing the following guidance.

While it remains important for all appliances, cylinders, stores, tanks, fuel lines and ancillary components to be serviced annually, Grant UK will continue to honour all warranties (on both Standard and Extended) beyond the normal service date up to the 31st July 2020 whether the appliance is serviced or not. This extension relates to Grant oil boilers, Grant Biomass boilers, Grant Aerona Heat Pumps and Grant Cylinders/Thermal stores.

This date may change in line with the recommendations of the UK Government and current information can be found on our website here.

It is imperative that the appliance and connected components are serviced as quickly as possible after this date to ensure trouble free operation.

What is the G1 Scheme and how do I sign up?

G1 is Grant UK's Installer Scheme. Heating engineers can become a G1 accredited installer in one or more of Grant’s product ranges, but each requires a specific set of requirements to be met before being accredited in that technology. For further information, please visit the G1 Scheme pages on our website or contact the G1 Team by emailing:

What is G-CERT and how do I join?

G-CERT is a scheme from Grant UK through which Grant can certify renewable installations for MCS accreditation on behalf of the installer. Under the G-CERT Scheme, engineers who meet the scheme’s criteria can install RHI eligible systems without needing to be MCS accredited. Click here for further information or alternatively, please contact your Area Sales Manager to register your interest in the Scheme and discuss benefits, requirements and eligibility.

I am a G1 Installer, why am I not listed on the 'Find an Engineer' search?
Due to data protection regulations, we are unable to share an installer's details without their written consent. If you wish your details to be visible, please contact
Where can I get brochures and manuals from?

Our brochures and manuals are available to download as PDFs on our website (click here). If you require hard copies, please email Also available for mobiles and tablets is the Grant TechBox app, where all of Grant's current and historic product manuals are freely accessible. This app works in both online and offline mode (for times when there is no internet signal), so you’re never without the information you need.

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:

How can I access extended guarantees on the Grant products that I install?
Installers who join Grant UK’s G1 Scheme can activate extended guarantees on the Grant products that they install. For example, G1 Installers who purchase, install and register a Vortex oil boiler can register the appliance with a five year guarantee (subject to Terms and Conditions), compared to the standard two year guarantee when installed by a non-G1 installer.
Is the G1 Scheme just for oil boiler installers?
No, the G1 Scheme is open to installers of all of Grant’s products. The Scheme encompasses oil boilers, all of Grant’s renewable technologies and their heat emitter range as well.
What is the G1 Portal?

The G1 Portal ( is an online platform which is exclusively accessible to G1 Scheme members. Via the Portal, G1 Installers can register their installations, access useful downloads and order marketing materials and branded items via the G1 Shop.

What is G1 Click?

G1 Click is a product registration app exclusively accessible to G1 Scheme members. This app syncs with the Portal so that G1 installers can be sure that both platforms have their latest account information. Compatible with iOS and Android devices, G1 Click is a handy tool for Scheme members to have on their phones.

Click here for download options.

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:
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:

Oil Boilers

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, the design 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 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.
Can condensing boilers be used on gas oil?
No, condensing oil boilers can only run on kerosene.
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.
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).
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 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.
Does the Vortex Pro and Vortex Eco have the same stainless heat exchanger and turbulator baffle system?
On both the Pro and Eco range the secondary heat exchangers are made of stainless steel and the turbulators are made of 1.5mm aluminium however depending on the output and model of the boiler, the amount and the length of turbulators differ. For further information, please refer to the manual or contact technical directly on 01380 736920

Oil Boiler Flues

Can you run a flexi-liner inside an existing flue?
Part J Building Regulations do not have any specific rulings relating to this. Installers should check with their local authority.
Can you have more than one 90° bend on a balanced flue?
We do not supply 90° bends in our flue systems, only in a starter kit. If it is absolutely necessary, then a “long turn” 90° bend may be constructed horizontally i.e. by connecting two 45° bends together.
Can you extend the “White System” Vertical Balanced Flue above the roof and terminate at high level?
It is not possible to extend the “White” Vertical Balanced Flue above the roof as the sections are not weatherproof and are designed purely for internal use.
Can the flex-liner be at an angle into the adaptor?
The flex-liner MUST be fitted vertically into the adaptor. Any deviation from the upright may allow condensate leaks through the liner.
Can you extend the flue on an external boiler?
There are hybrid kits in our flue guide, to allow horizontal or vertical extensions from an external boiler.
Can you run a “White System” vertical balanced flue inside a chimney?
It is not possible to fit a vertical balance flue inside a chimney. The chimney is open to the elements and the “White” system is not weatherproofed.
On the “White System” high level balanced flue, can you run horizontally as well as vertically?
It is possible to run horizontally as well as vertically. The total length must not exceed ten metres.
Can the Plume Diverter be fitted horizontally?
The plume diverter cannot be fitted horizontally. There are extra sections available, which include 45 bends, allowing the diverter to be angled but only at 45°. These bends can be used to install the diverter around soffits etc. The maximum height can be six metres but deduct 0.5 metres for every 45° bend used.
Can you have a 90° bend on a conventional flue?
OFTEC regulations do not allow any 90° bends. The reason is that it will cause restriction in natural draught flues.
Can Grant EZ-Fit flues be top or side exits?
The flues are suitable for rear, side and top exits.

Air Source Heat Pumps

How do air source heat pumps operate in very cold weather conditions?
During winter months when it is particularly cold, condensation any 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.
Are Grant air source heat pumps MCS approved?
Yes, all models within the Grant Aerona range are MCS approved.
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.
Is it possible to use radiators with a heat pump?
Yes, but they must be correctly sized for the lower water flow temperature.
Can a heat pump be connected to an existing hot water cylinder?

The coil of an existing cylinder will almost certainly be too small and this will result in longer cylinder reheat times at the lower water flow temperatures from a heat pump. For best performance a Grant High Performance cylinder should be used. This has a larger coil to reduce reheat times.

What is R32 refridgerant and what is the benefit?
Grant’s latest ASHP uses R32 refrigerant which has a GWP which is considerably lower than other typical heat pump refrigerants such as R410, thus complying with the upcoming legislative targets. 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.
What is Blygold treatment?
Blygold anti-corrosion treatment is designed to preserve the heat pump against the sea air and prevent unnecessary energy consumption or product failure due to corrosion. Grant offer Blygold anti-corrosion treatment for all of their Aerona³ R32 heat pump models to help preserve and maintain heat pumps installed in the vicinity of the sea. For further information, speak to our sales team on 01380 736920


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.
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 parts are located next to each other outside the building. However, it is also possible for the boiler part 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.
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.
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 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.
Are Grant ASHPs eligible for the RHI?
To qualify for an RHI payment, the unit must be MCS approved. The Grant Aerona meets this requirement. Furthermore, the heat pump must be installed by an MCS approved Installer. However, it should be understood that using both an MCS approved product and installer is not a guarantee that the installation will be eligible for an RHI payment.
Does the VortexAir 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. Usually only installations qualifying to receive an RHI payment will require both of these meters to be 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.
Does the Grant VortexAir Hybrid qualify for a Government RHI?
To qualify for an RHI (or Renewable Heat Incentive) payment, the unit must be MCS approved and both of the Grant VortexAir Hybrid models meet this requirement. Furthermore, the unit must be installed by an MCS approved Installer and fitted with both a heat meter and electricity meter in accordance with MCS requirements for the RHI. However, it should be understood that using both an MCS approved product and installer is not a guarantee that the installation will be eligible for an RHI payment.
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.

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.
Is UFH restricted to the ground floor?
No. UFH can be installed both upstairs and downstairs in a property. Speak to our renewables team for specifications.
How long does installation of an UFH 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 the system be added to my existing heating system?
UFH is suitable for gas, oil, and LPG boilers as well as heat pumps and biomass boilers. For more information, speak to our Renewables Team.
Does underfloor heating work the same way as a radiator?
Radiators rely on air circulation to enable the hot air to move around the room, this is called thermal currents and involves the hot air moving from the radiator to the ceiling, cooling and falling to create an air cycle. This can leave colder areas and takes time to heat the room. An underfloor heating system heats the room by hot air rising from the floor surface upwards, this uses considerably less energy and also creates a more even dispersion of heat.
Do I need to dig up the floors?

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 incredibly quickly and with minimal disruption to a property’s existing floor and door arrangements.

I have carpets. Will this stop the Underfloor heating from working?
Not all types of floor finishes are compatible with underfloor heating systems. The objective of underfloor heating is to transfer heat from the system into the room and some floor coverings can restrict this movement of heat. Flooring materials such as tiles and vinyl floor coverings are low resistance and are therefore ideal for underfloor. Meanwhile, thicker finishes such as certain types of wood and thin carpets have medium resistance which means that some of the heat is retained. Any carpets and overlay which are over 2.5tog are not suitable for an underfloor heating system.
Is underfloor 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?
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 a manifold?
The manifold is the system hub for the underfloor, the pipes are connected to it at installation stage and it then controls the distribution of the water from the heating systems 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 be situated?
The manifold should be located in a central point where the pipework is most evenly distributed.
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.
Its 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.
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.
How quickly should heat from an ASHP be introduced to a Grant Uflex underfloor heating system?

Upon commissioning a Grant Uflex screeded underfloor heating system connected to a Grant Aerona³ R32 Heat Pump, the initial temperature increase rate of the system should be gradual, so to avoid a situation where the heat pump ices up as a result of trying to heat up the fabric of the underfloor system too quickly. 

This can be achieved by first ensuring that the screed has been allowed to dry and cure normally (the underfloor heating must not be used to speed up this process) before initial heating. The initial temperature increase rate of the underfloor system can be controlled to be gradual by setting the thermostatic mixing valve to setting 3 and leaving the system to run for two weeks upon initial start-up. Once the underfloor system has reached operating temperature, the system can be set to operate to the householder’s requirements.

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