Frequently asked questions

Answers to questions our customers frequently ask, from how to service a boiler to the best type of wood pellet to use.

Oil condensing boilers

Oil-Fired Condensing Boilers

What is a Condensing Boiler?

In standard boilers up to 20% of the energy produced is lost to the atmosphere through the flue system. Condensing boilers are designed to capture part of this lost energy (latent heat) and can therefore maintain extremely high efficiency levels. See our article What are Condensing Oil Boilers? for more details.

Can condensing oil boilers be used on gas oil?

No, condensing oil boilers can only run on kerosene.

What’s the difference between the Euroflame and Vortex Boilers?

The Award Winning Vortex boiler was launched in 2001, 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 Euroflame range to meet this growing consumer demand.

Both the Vortex and Euroflame are high efficiency boilers, the major difference being the efficiency, the Vortex efficiency is from 92.6% to 97%, whereas the Euroflame efficiency is 92.1% to 93% and both are ‘A’ rated boilers, there would be a difference in price with the Vortex being slightly more expensive.

The Vortex has a larger heat exchanger area which gives it a higher efficiency than the Euroflame, the Vortex module has a frost stat and a service switch inbuilt.

There are 28 model variants in the Vortex range and 9 model variants in the Euroflame range, there is a Grant NI boiler suitable for every domestic application.

Features and characteristics of both Vortex and Euroflame are:

  • The award winning Vortex stainless steel heat exchanger and turbulator baffle system for ultra high efficiency
  • All models are SEBDUK Band ‘A’ rating
  • Factory fitted internal condensate traps to make sitting the appliance straight forward
  • The unique heat exchanger is covered by a 5-year guarantee.

All Vortex and Euroflame boilers are compatible with Grant’s EZ-fit flue systems, which include low-level, high-level, rigid and flexi vertical balanced kits and also flexible and external conventional flue packs.

What’s the difference between Seasonal efficiency vs 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 or 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.

Should I have a Frost Stat fitted to my Boiler?

We recommend that Outdoor Boilers should have a Frost Stat fitted.  The Grant Vortex Module range is factory fitted with a Frost Stat set at 5ºC plus or minus 1ºC.  A permanent live is required with a frost stat.

For added frost protection on Grant Vortex Modules, 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 boilers have Frost Stats fitted and what are they set to?

Frost stats come as standard on all Grant Vortex Outdoor Modules. They are set at 2°C plus/minus 1°C and require a permanent live to the boiler.

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 there anything I can do to help prevent freezing of a condensate trap?

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

If I change my Boiler for a new Condensing Boiler can I use the existing Flue?

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.

I‘ve heard 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’sproperty, we recommend you install a high level, vertical or a plume kit flue.

Grant EZ-Fit Flue System

EZ-Fit Flue System

What is a flue?

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 EZ-Fit Flue options

Grant has a range of unique EZ-Fit Flues. These are available as low level, high level or vertical kits, for internal and external applications, and even as unique EZ-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.

Flue Terminals

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.

See our article on clearance for balanced flues for clearance distances in accordance with Building Regulations.

What is ‘Pluming’?

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’sproperty, we recommend you install a high level, vertical or a plume kit flue.

If I change my Boiler for a new Condensing Boiler can I use the existing Flue?

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.

wood pellets

Wood Pellet Boilers

What are wood pellets?

Wood pellets are cylindrical in shape and generally made from compressed sawdust, which is often the waste product from industries (e.g sawmills). They are fused by the natural lignin present in dry wood. It strengthens the wood as well as having water proofing properties.

All pellets used must meet ENplus standard EN14961-2 and be bark and sand free and must be approved by GRANT before being used in the current Spira boilers. Failure to use approved pellets will invalidate the product warranty.

  • Moisture content below 10%
  • Calorific value of 4.8 – 5.2kWh/kg
  • Ash content of <1% (Low)
  • Bulk density of 650kg/m³ or less
  • Chlorine content of 0.03% or less
  • No additives

Using pellets which are not approved by GRANT will void your boiler warranty. If you are in any doubt, please contact GRANT before purchasing your pellets.

Are wood pellets from a sustainable source?

As the sawdust used to make wood pellets is a by-product e.g. from sawmill industries, or has been sourced from a managed forest where trees are planted to replace the ones cut down, they are classed a sustainable ‘carbon neutral’ source of fuel.

Are wood pellets readily available in Northern Ireland?

Yes. Wood pellets are available from a number of manufacturers and specialist suppliers. Also, some of the larger Plumbing and Heating merchants are now stocking wood pellets.

How are wood pellets supplied?

Pellets are available in both bagged quantities – usually in 10kg bags – or in bulk. The minimum bulk pellet delivery is typically 3 tonnes but this needs to be checked with the supplier concerned, as smaller deliveries may be possible.

Do GRANT NI recommend which type of wood pellet to use?

There are a wide range of wood pellets, of differing qualities, available on the market. Only 6mm diameter pellets should be used in GRANT wood pellet boilers. These pellets must first conform to EN plus standard EN14961-2.

Currently, GRANT have tested and approved Balcas ‘Brites’ and Verdo pellets for use with the GRANT Spira wood pellet boilers. The use of pellets not conforming to the foregoing EN standard, may cause operating problems with the boiler and would invalidate the product warranty.

See also our article ‘What makes a good quality Wood Pellet

Will I need to manually fill the boiler with wood pellets?

If the indoor pellet hopper (supplied with the boiler) is the only form of storage used then this will need to be filled manually with pellets supplied in bags. The hopper has a maximum capacity of 110kg or, eleven 10 kg bags of pellets.

If a bulk pellet store is used to feed the pellet hopper, the hopper will be filled automatically from the bulk store. Of course, it is important to regularly check the bulk store and to order a bulk delivery before it is empty.

How will I know that the hopper requires refilling and how often will it need to be done?

If the indoor hopper only is used, then the boiler will automatically stop when the pellet level in the hopper reaches minimum. There is a facility to have a warning light to indicate when this minimum level of pellets is reached. Topping up the hopper with pellets will automatically re-start the boiler. However, to avoid this happening, the pellet level in the hopper should be regularly checked and topped up as required –usually once to twice a week.

If a bulk pellet store is used, then this will automatically top up the indoor pellet hopper. However, the pellet level in the bulk pellet store must be regularly checked and a delivery of pellets ordered before it becomes empty. The time between deliveries will depend on the size of the bulk store, the size of the boiler and how it is used. Typically, for a 26kW boiler around 3 tonne of pellets should last for about a year, based on a heating demand of 14,400kW input.

How are wood pellets stored?

Wood pellets should always be stored in a damp free environment. Care must be taken to ensure that stored wood pellets never come into contact with water. Any external stores must be sealed and protected against rainwater entry. Grant market a range of internal and external pellet storage solutions, but advice on the type and location of bulk pellet storage is also available from the pellet suppliers.

How does a wood pellet boiler work?

On start up the auger feeds the wood pellets from the hopper into the burner where it is lit by an ignition element. The burner output is adjusted automatically (modulates) to achieve the set temperature by controlling the feed rate of pellets. The fan in the burner propels hot gas generated from the fuel into the Spira’s primary heat exchanger. The heat energy is then transferred to water from the central heating system, before being circulated around the house to either radiators and/or underfloor heating.

Watch our guide to the GRANT Spira Biomass boiler here »

Is the Grant Spira wood pellet boiler noisy in operation?

The noise from Grant wood pellet boiler comes from the following main sources; the flue fan, burner fan, self-cleaning process and the pellets themselves dropping into the burner. Whilst the combination of these is not excessively noisy, the Spira would be unsuitable for installation within ‘habitable’ rooms of a house, e.g. kitchen, utility room etc. which are more commonly used for locating conventional oil and gas boilers.

How much space is required to install the boiler and hopper?

Suitable space must be allowed around the boiler for servicing and maintenance. Full details of the precise minimum clearances are to be found in the Installation and Servicing instructions provided with the boiler, or read our Trade article on ‘Wood Pellet Boiler Siting & Maintenance‘ for more details.

Typically, an overall floor area of 1700mm wide x 1500mm deep will be required to locate the boiler/hopper and provide the clearances required.

Can the Grant Spira wood pellet boiler be installed outside?

No. Grant Spira wood pellet boilers must be installed in a damp free environment along with the accompanying pellet hopper. The boiler can be located in an outbuilding, etc. but must not, under any circumstances be exposed to the elements (e.g. located under a car port or lean to canopy).

Are there any special requirements for the base on which the boiler and hopper are installed?

Yes. The base must conform to the requirements of Building Regulations. Full details are given in the Installation and servicing instructions supplied with the boilers. Read our Trade article on ‘Wood Pellet Boiler Siting & Maintenance‘ for more details.

What type of heating system can a Grant Spira wood pellet boiler be used with?

Grant Spira wood pellet boilers can be used with 2-pipe, fully pumped hot water heating systems – either open-vented or sealed system – using radiators and/or underfloor heating.

Sealed heating systems must incorporate a suitably sized expansion vessel, a pressure gauge and approved filling loop. The 2.5 bar pressure relief valve required is supplied with the boiler.

What type of heating system controls can be used with a Grant Spira wood pellet boiler?

Grant Spira wood pellet boilers can be used with most commonly installed domestic heating control systems, e.g. Y-plan and S-plan type control systems, where a programmer and room thermostat will control the operation of the boiler to the requirements of the householder.

Can a Grant Spira wood pellet boiler be fitted as a replacement boiler on an existing heating system?

Yes, provided that the existing system is chemically cleaned and flushed, and complies with current Building Regulations. The existing control system may also be used providing that it also complies with these regulations. If not the system and/or controls will need to brought in line with these requirements.

How should a Grant Spira wood pellet boiler be sized?

As with all boilers, a full heat loss calculation for the property should be made to determine the heat load that the boiler will be required to meet, under design conditions. If the heating system includes a circuit to a hot water cylinder then an allowance for water heating should normally be included in determining the final heat load to be met by the boiler.

What does condensing mean?

During combustion a proportion of the heat produced is locked up in the flue gas. A conventional boiler cannot recover any of this heat and this energy is lost to the atmosphere through the flue.

The Grant SPIRA Condensing wood pellet boiler contains an extra heat exchanger which is designed to recover this heat normally lost by a conventional boiler. It does this by cooling the flue gases to below 90°C (Typically conventional boiler flue gases are 200°C plus) thus extracting more heat. This is achieved by cooling the flue gases to their dew point.

How efficient are the Grant Spira wood pellet boilers?

The Grant Spira is a condensing wood pellet boiler with a modulating burner and has exceptionally high efficiency levels. The 6-26kW model has a tested and approved full load efficiency of 97.4% and the 9-36kW model 93.1%.

This is comparable with high efficiency condensing domestic oil fired boilers (and better than many high efficiency gasfired boilers), making the Grant Spira both an energy efficient and ‘Green‘ alternative to fossil fuel burning boilers.

What is unique about the Grant Spira wood pellet boiler?

Grant Spira wood pellet boilers benefit from the use of award winning condensing technology, originally developed for Grant’s market leading Vortex oil-fired boiler range. This, in conjunction with the all-new fully modulating pellet burner, has resulted in an extremely efficient range of renewable home heating appliances. Higher efficiencies, coupled with lower and more stable fuel costs, creates a very environmentally and consumer friendly heating solution.

Who can install, commission and service a Grant Spira wood pellet boiler?

Only Grant trained and accredited wood pellet boiler installers (registered on the G-One Scheme) can install the Grant Spira wood pellet boiler. Courses are available via the Grant Training Academy and can be booked by calling FREEPHONE 0800 279 4796.

How often should a Grant Spira wood pellet boiler be serviced?

In order to ensure efficient and safe operation, Grant Spira wood pellet boilers must be serviced annually when amongst other things, the primary and condensing heat exchangers, combustion chamber, flue fan box and burner, must all be cleaned of any ash deposits and the burner re-set for a further year’s operation. The boiler will indicate when this is due, by displaying a ‘SERVICE’ message on the burner control panel. This service interval is based on the actual running time of the burner and thus may vary in length depending on the degree of use of the boiler.

How often does a Grant Spira wood pellet boiler require cleaning out?

The efficient combustion of the Grant Spira burner, coupled with the consistently high quality of the wood pellets approved for use with the appliance, results in a relatively small amount of fine ash being produced within the boiler. The majority of this will be collected within the easily accessible ash pan located inside the combustion chamber.

Furthermore, as the Spira incorporates automatic cleaning of both the primary and condensing heat exchangers, and the burner brazier, at pre-set intervals to remove any ash deposits, they generally only require manually cleaning out around once per year i.e. the ash pan requires emptying, or after about 3 tonnes of pellets have been burnt.

Is the Grant Spira MCS approved?

Yes, all boilers within the Grant Spira Wood Pellet Range are MCS approved.

Solar Thermal system

Solar Thermal System

5 Things you should know about Grant Solar Panels

  1. The lifetime of Grant Flat Plate Solar Panels can be up to 40 years compared to 12 years for tubular solar collectors
  2. In comparison to the high costs of other energy sources solar energy provides a saving of up to 70% in hot water or 30% of the total heating and hot water costs in a year.
  3. The Grant Sahara Flat Plate has an efficiency of 79% and is NSAI Agrement approved.
  4. Grant NI offer a 5 year warranty on all solar panels

Advantages of GRANT Solar Panel

  • Grant Solar Panels can provide up to 70% of your hot water needs FREE for the year.
  • Grant Solar Panels are NSAI Agreement Approved for on roof and in roof systems.
  • The lifetime of Grant Solar Panels can be up to 50 years compared to tubular solar collectors whose lifetime is greatly shorter.
  • The Grant Solar Panel is comprised of 3.2mm low iron glass which makes it  more robust and shock resistant than the tubes.
  • The Grant Solar Panels are the most affordable efficient panel on the market with an efficiency rating of 79.1% with a heat loss co-efficient of 3.307.
  • The Grant Solar Panel is aesthetically pleasing with its dark frame and glass and it means you don’t see the pipes in the panels and it blends in better with your typical Northern Irish roof slates or tiles.
  • The Grant Panels can be used in many situations, on roof, in roof, flat roof, portrait or landscape and can be used with slate tile or corrugated roofs.
  • Our Solar Systems are designed to be plumbed with ½ inch pipe which is quicker to heat and cheaper to plumb.
  • The Grant Solar Panels are made in Germany.
  • GRANT NI provide FREE training both in the factory and on site for our Solar Panels.
  • GRANT NI can provide a full range of Solar Cylinders in both copper and stainless steel to suit all applications.
Grant Triple Pass Back Boiler

Triple Pass Back Boilers

Who can install a GRANT boiler?

Any gas installation work should only be carried out by a qualified installer. You can check here for our qualified back boiler installers.

How long does it take to install?

Each case is different and your installer will be able to advise more specifically on the amount of time your installation should take.


How many radiators can I run with this?

You can heat up to 10 radiators with our triple pass back boiler.


Is the Queenstar Fire, grate and ashpan included with the back boiler?

No these are separate items and must be purchased separately.

What type of fuel can be used?

Briquettes, coal, logs and turf.

Can a back boiler be fitted onto a sealed system?

No, it must be fitted to an open vented system only.

Can this boiler be used as part of a dual heating system ie. Oil or gas?

Yes, once it is piped correctly and fitted according to manufacturers instructions.

Does my boiler need regular cleaning?

Yes about once a fortnight.

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