Most gas combi ovens can be converted between LPG and natural gas, but it is a job for a Gas Safe registered engineer with commercial catering qualifications, never a DIY swap. A gas combi leaves the factory set for one gas type. Run it on the wrong one and you risk poor combustion, carbon monoxide, flame failure and a burner that won't light at all.
This guide is for chefs, kitchen managers and owners who are moving premises, getting mains gas connected, or buying a second-hand gas combi that was set up for a different supply. It covers what changes between the two gases, what a conversion involves, the legal requirements in the UK, and what to ask before you buy.
LPG vs natural gas: what actually changes
LPG carries well over twice the energy of natural gas per cubic metre and is supplied at a higher pressure, so a burner set for one will over-fire or under-fire on the other. That is why the burner, gas valve and combustion settings must match the supply.
|
|
Natural gas (G20) |
LPG propane (G31) |
|---|---|---|
|
Typical UK supply pressure |
20 mbar |
37 mbar |
|
Energy content (approx.) |
~38 MJ/m³ |
~95 MJ/m³ |
|
Weight vs air |
Lighter, disperses upwards |
Heavier, pools at floor level |
|
Supply |
Mains pipeline |
Bulk tank or cylinders |
|
Common in |
Towns and cities |
Rural sites, mobile units, sites off the grid |
The weight difference matters for siting too. Because LPG sinks, it is restricted in cellars and basements, so check your kitchen layout before choosing it.
When kitchens need to convert
Conversion usually comes up when the oven stays put but the gas supply changes, or the oven moves to a site with a different supply. The common cases:
- Mains gas arrives. A rural pub or farm shop cafe on bulk LPG gets connected to the grid and wants cheaper mains gas.
- Moving premises. A restaurant relocates from a mains site to an off-grid one, or the other way round.
- Buying second-hand. A used oven was set up for its last owner's supply, not yours.
- Mobile and event catering. A unit that runs on cylinders on the road moves into a permanent kitchen.
If your site has a choice, compare running costs per kWh before you commit. Mains gas is usually cheaper to run, while LPG trades higher fuel cost for independence from the grid.
Can every gas combi be converted?
Most modern gas combis from the major manufacturers (Rational, Electrolux, Convotherm, Eloma) are approved for both gases and can be converted, but only if the manufacturer supports it for that model. The data plate is where you start. Look for:
- Gas category. A multi-gas category (for example one listing both 2H and 3P) shows the appliance is approved for natural gas and propane.
- Gas type currently set. The plate or a label beside it states which gas the oven is set for, often with the G20 or G31 code and supply pressure.
- Model and serial number. Your engineer needs these to source the correct conversion parts and settings.
If the plate lists only one gas, or the manufacturer offers no conversion kit for that model, treat the oven as single-fuel. Older or grey-import units can also fall outside UK approval, so check before you buy rather than after.
What the conversion involves
The exact procedure varies by make and model, but a qualified engineer will typically work through these stages:
- Isolate and inspect. Shut off gas and power, then check the burners, seals, flue and gas train are in good condition before changing anything.
- Fit the conversion parts. Depending on the model, this means swapping injectors, orifices or a gas restrictor to suit the new gas.
- Change the control settings. Many modern combis also need the gas type changed in the service menu so the ignition and modulation match.
- Set the gas pressure. The engineer sets the appliance for the correct working pressure of the new supply.
- Run a combustion analysis. A flue gas analyser checks CO and CO2 across the burner range and the settings are adjusted until they sit within the manufacturer's limits.
- Test safety devices. Flame failure, ignition and any interlock are tested under real operation.
- Relabel and record. The data plate is updated or a conversion label fitted, and the work is written up.
Skipping the combustion analysis is the most common shortcut and the most dangerous. An oven can light and cook while still producing unsafe levels of carbon monoxide.
The legal side
In the UK, converting a gas appliance is gas work under the Gas Safety (Installation and Use) Regulations 1998, so only a Gas Safe registered engineer can do it. For a commercial kitchen, the engineer's Gas Safe ID card must also show the right commercial catering categories, not just domestic ones.
Before the engineer leaves, make sure you have:
- A check on their Gas Safe card for commercial catering appliances, which you can verify on the Gas Safe Register website.
- A written record of the conversion, including combustion readings.
- An up-to-date commercial catering gas safety certificate for the kitchen, often called a CP42, covering the converted oven.
- A working interlock. Commercial kitchens should have the gas supply interlocked with the extraction, so gas cuts off if the canopy fan stops.
Your insurer and environmental health officer may ask to see these documents, so keep them with your other kitchen safety records.
Costs and downtime
A straightforward conversion on a supported model is usually a few hours' work, so plan it for a quiet day or before opening. The total cost depends on:
- The conversion kit or parts for your specific make and model.
- Engineer labour, including travel and the combustion analysis.
- Pipework changes if the new supply needs a different connection, regulator or isolation valve.
- Certification if the kitchen's gas safety certificate needs reissuing at the same time.
Ask for a fixed quote that names the parts and includes the combustion test and paperwork, so nothing is added on the day.
Buying a refurbished gas combi? Say your gas type first
The easiest conversion is the one sorted before the oven arrives. When you enquire about a refurbished gas combi, tell the supplier whether your site runs on natural gas or LPG, and ask:
- Which gas is this oven currently set for?
- Is this model approved for both gases?
- Can it be supplied set up for my gas, and is that included in the price?
- Will it come with a record of the settings and combustion check?
If you're still deciding on fuel, it is also worth weighing up an electric combi. Electric models need no gas supply, interlock or conversion, which can simplify installation in kitchens where gas is awkward or expensive to bring in.
FAQs
Can I run an LPG combi on natural gas without converting it? No. The burner will under-fire, may fail to light or keep going out, and combustion will not be safe. It must be converted first.
Can I convert it myself? No. It is illegal in the UK for anyone who is not Gas Safe registered for commercial catering to carry out the work.
Does converting affect the warranty? It shouldn't if a qualified engineer uses the manufacturer's approved parts and procedure. Using non-approved parts, or unqualified fitters, can void it.
Will my oven cook differently after conversion? A correctly converted oven should perform to the same specification on either gas, because it is set to deliver its rated output.
Can it be converted back later? Yes, on supported models the same process works in reverse, again by a qualified engineer.
Looking for a combi oven that suits your supply?
CaterCombi supplies fully refurbished combi ovens from Rational, Electrolux, Convotherm and Eloma, in gas and electric. Tell us your gas type and kitchen setup when you get in touch, and we'll help you find the right oven for your site. You can also sell or part-exchange your current oven through our Sell Your Oven page.
