Quick answer
A gas appliance is not approved in general. It is approved for a declared gas family and a declared supply pressure, and that declaration is what the category marking states. Change the destination and you change the gas, which means a different injector, a different nominal pressure and a different type-examination. Injector size is not a workshop preference; it is part of the approved design.
What does the appliance category actually declare?
European gas safety law is built around a simple admission: gas supply conditions differ between countries and have never been harmonised. Regulation (EU) 2016/426 handles that by making the manufacturer declare what the appliance can burn.
Article 2 defines the vocabulary. A gas family is a group of gaseous fuels with similar burning behaviour linked together by a range of Wobbe indices. A gas group is a specified range of Wobbe indices within that of the family. The Wobbe index is described as an indicator of the interchangeability of fuel gases, used to compare the combustion energy output of different composition fuel gases in an appliance. The appliance category is the identification of gas families and gas groups that an appliance is designed to burn safely and at the desired performance level, as indicated by the category marking.
That chain matters commercially. A buyer asking “can this range run on our gas” is asking whether the unit’s category includes the local family and group. “Yes, we can adjust it”, without stating the resulting category, is not an answer.
| Term | What it means in the regulation | What it means on a purchase order |
|---|---|---|
| Gas family | Fuels with similar burning behaviour, linked by a range of Wobbe indices | The broad gas type the site receives |
| Gas group | A specified Wobbe range inside that family | The quality band the local network actually delivers |
| Wobbe index | Indicator of interchangeability, comparing combustion energy output | The number that decides whether an injector can stay |
| Appliance category | The families and groups the unit is designed to burn safely | What the data plate and certificate must state |
Why does changing the gas change the injector?
Because the burner is a fixed-geometry device being asked to deliver a specified heat input from a fuel whose energy content per cubic metre varies.
Heat input is the product of volumetric gas flow and calorific value. For a given injector and a given supply pressure, the flow is roughly fixed by the orifice area and the pressure drop across it. If the gas arriving at the site carries less energy per cubic metre, the same orifice delivers less heat; if it carries more, the burner is over-fired, with consequences for flame stability, carbon monoxide and the life of the heat exchanger. The Wobbe index exists precisely to compress that comparison into a single number, which is why the regulation defines gas families and groups by Wobbe ranges rather than by chemical composition.
In practice, three things move together when the destination changes: the injector diameter, the declared nominal supply pressure, and the primary aeration set at commissioning. Changing only the injector produces a machine that is neither the old type nor a compliant new one.
Where do the pressure numbers come from?
They are published, not negotiated. Article 4 of the EU regulation requires Member States to communicate to the Commission and to other Member States the types of gas and corresponding supply pressures used on their territory, and the Commission publishes that information in the Official Journal. In the version of the same regulation that applies in Great Britain, that article is replaced by a duty on the Secretary of State to publish equivalent information for the United Kingdom.
Annex II fixes what those communications contain, and it is a useful checklist for a buyer writing a specification:
| Parameter in the national communication | Why it matters to the appliance |
|---|---|
| Gross calorific value, MJ/m³, minimum and maximum | Converts gas flow into delivered heat input |
| Wobbe index, MJ/m³, minimum and maximum | Sets the family and group boundaries the appliance must tolerate |
| Composition by volume: C1 to C5, N2 plus CO2, CO, unsaturated hydrocarbons, hydrogen | Affects flame speed, aeration and combustion products |
| Information on toxic components | Relevant to flue and ventilation design |
| Supply pressure at the appliance inlet, mbar, nominal, minimum and maximum | The pressure the injector is sized against |
The reference conditions are also fixed: a combustion reference temperature of 15 °C, a volume measurement reference temperature of 15 °C, and a volume measurement reference pressure of 1,013.25 mbar. Quoting a heat input without those conditions is quoting half a number.
Article 1 sets the boundary. The regulation covers appliances used for cooking, refrigeration, air-conditioning, space heating, hot water production, lighting and washing, but not appliances specifically designed for industrial processes carried out on industrial premises. A commercial kitchen range is covered; a bespoke process burner for a factory line is not.
What has to be marked and documented?
The declarations are itemised, which makes them easy to audit. Annex IV lists what the appliance or data plate must carry; Annex I point 1.6.3 adds the warning notices, which must clearly state the type of gas to be used, the gas supply pressure, the appliance category and any restrictions on use, including any restriction to install only where ventilation is sufficient. Point 1.6.1 requires the installer’s instructions to give the technical specifications of the interface with the installation environment — gas supply, auxiliary energy, combustion air and flue.
| Document | Required content that concerns gas type | Clause |
|---|---|---|
| Data plate | Appliance category marking and nominal supply pressure | Annex IV |
| Warning notices, appliance and packaging | Type of gas, supply pressure, category, restrictions on use | Annex I, 1.6.3 |
| Installation instructions | Interface specification for gas, air and flue connection | Annex I, 1.6.1 |
| EU type-examination certificate | Type of gas, appliance category, gas supply pressure | Annex III, Module B |
Does a different injector require a new certificate?
Yes, as a rule, because the certificate is tied to the configuration it examined. Under Annex III, Module B, the EU type-examination certificate must contain the necessary data for identification of the approved type, such as the type of gas, appliance category and gas supply pressure, and it has a maximum validity of ten years. Point 1.7 of the same module requires the manufacturer to inform the notified body of all modifications to the approved type that may affect conformity or the conditions for validity, and states that such modifications require additional approval in the form of an addition to the original certificate.
That is the structural reason why a “nozzle kit” shipped loose is not a compliance solution. A kit that converts a certified unit to another gas family changes the type. If the change is covered by the original certificate — some appliances are certified for more than one family and shipped with the corresponding injectors — the paperwork already anticipates it. If it is not, the addition has to be obtained before the converted unit is placed on the market.
Two adjacent obligations are worth checking at the same time. Manufacturers keep the technical documentation and the declaration of conformity for ten years after the appliance is placed on the market, and importers must satisfy themselves that the assessment was carried out, the marking is applied and the instructions accompany the appliance.
What does this look like in Great Britain?
After the UK left the EU, the same regulation was retained with targeted amendments rather than replaced. The GB version keeps the definitions, the essential requirements and the conformity assessment modules, substitutes the UK marking for the CE marking, refers to approved bodies rather than notified bodies, and refers to designated standards published by the Secretary of State. Enforcement runs through the Gas Appliances (Enforcement) and Miscellaneous Amendments Regulations 2018, which designate market surveillance authorities and set out enforcement powers, offences, penalties and compliance, withdrawal and recall notices.
The consequence for a supplier outside the UK is that a unit built for an EU member state is not automatically a unit for Great Britain: the marking differs, the issuing body may differ, and the gas supply information to design against is the UK publication rather than the EU communication.
What should the purchase order specify?
A gas specification that survives delivery contains five lines, and none of them is “natural gas”.
- Destination country and the gas family and group supplied to the site, taken from the published national communication.
- Nominal supply pressure at the appliance inlet, with permitted minimum and maximum, in mbar.
- Appliance category marking required, matching the certificate.
- Whether the unit must be certified for more than one family, and which injector set travels with which configuration.
- Documents to be supplied: declaration of conformity, type-examination certificate or addition, data plate content, and installation instructions in the destination language.
Zhongji Metal has manufactured stainless steel commercial kitchen and cold storage equipment in Shandong, China since 2010 and exports to more than 130 countries. Gas-fired items are configured against the destination rather than against a catalogue default: the western kitchen cooking equipment range is built to the gas family and inlet pressure confirmed for the project, with the category marking and nominal pressure stated on the data plate, and the buffet holding stove is specified the same way where a gas version is ordered. Where a unit has to work on more than one gas, the injector set and the corresponding certificate coverage are agreed before production rather than at commissioning. The full range is on our Alibaba.com storefront.
Frequently asked questions
Can a gas appliance be converted on site to a different gas?
Only within what its certification covers. The type-examination certificate identifies the gas type, appliance category and supply pressure, and modifications that may affect conformity require an addition to that certificate. A conversion that moves the unit outside its approved category is a change of type, not a maintenance task, however simple the injector swap looks.
How is the correct injector size determined?
From the declared heat input, the calorific value of the gas and the supply pressure, with the Wobbe index used to compare fuels. Because gas families and groups are defined by Wobbe ranges, the injector and the declared nominal pressure are set together for each family. The result is part of the approved design and appears in the technical file, not on a workshop note.
What must the data plate show for a gas unit?
Under the EU regulation’s Annex IV, the appliance or its data plate must carry the CE marking, the manufacturer’s name or trade mark, the type and batch or serial number, the electrical supply where applicable, the appliance category marking, the nominal supply pressure, and the information needed for correct and safe installation.
Where are national gas pressures published?
Article 4 of Regulation (EU) 2016/426 requires Member States to communicate gas types and corresponding supply pressures to the Commission and other Member States, and the Commission publishes that information in the Official Journal. In Great Britain, the retained version places an equivalent duty on the Secretary of State to publish UK information.
Does the gas regulation apply to a commercial kitchen range?
Yes. The regulation covers appliances burning gaseous fuels used for cooking, refrigeration, air-conditioning, space heating, hot water production, lighting and washing, and it applies to domestic and non-domestic appliances. The exclusion for appliances specifically designed for industrial processes on industrial premises is narrow and does not cover standard catering equipment.
What happens to the certificate over time?
An EU type-examination certificate has a maximum validity of ten years from issue. The manufacturer must keep the technical documentation and the declaration of conformity for ten years after the appliance is placed on the market, and must notify the notified body of modifications affecting conformity. Check the certificate date, not just its existence.
Local codes vary; verify requirements with your authority having jurisdiction.
Sources
- Regulation (EU) 2016/426 on appliances burning gaseous fuels — definitions of gas family, group, Wobbe index and appliance category; Article 4 gas supply conditions; Annex I warning notices and instructions; Annex II content of national communications; Annex III Module B; Annex IV inscriptions.
- Regulation (EU) 2016/426 as it applies in Great Britain — retained version with UK marking, approved bodies, designated standards and the Secretary of State’s publication duty.
- The Gas Appliances (Enforcement) and Miscellaneous Amendments Regulations 2018 — enforcement authorities, powers, offences and penalties, and compliance, withdrawal and recall notices in Great Britain.
Author: China Zhongji Metal
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Website: https://zhongjimetal.com
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