How to Set Up and Run an LPG Bain Marie at Temperature
Last updated: July 2026
In 30 seconds:
- An LPG bain marie is a wet unit — fill the tank with water before you light it, every time.
- Run it on propane at 37 mbar through a low-pressure regulator. High-pressure valves are prohibited by the manual.
- Hold the tap in for 15–20 seconds after the pilot lights, or the flame failure device shuts it down.
- It holds food hot — it doesn’t cook. Load it with food that’s already piping hot and keep it at 63°C or above.
- The Infernus LPG 4-pot starts from £399 with pans, lids and tap included; the 6-pot from £499.
A pot of chilli sliding down through the danger zone is a queue of refunds waiting to happen. This guide shows you how to set up an LPG bain marie in a food van or trailer, light it properly, and run it at a safe holding temperature all day.
A propane wet bain marie, connected by a Gas Safe registered engineer and supplied at 37 mbar, is the accepted standard for hot-holding curries, gravies, beans and pulled meats in UK mobile catering. Every figure in this guide comes from the Infernus gas bain marie manual for the units we stock.
The mistake that catches most new traders? Lighting the burner with a dry tank. A wet bain marie heats a water bath, and the water is what protects your food — and the unit — from scorching. Water first, flame second, always.
What You’ll Need
- An LPG bain marie sized for your menu — the Infernus 4-pot or 6-pot for most vans
- A propane cylinder — 13 kg or 19 kg suits most setups
- A 37 mbar low-pressure propane regulator and commercial LPG hose
- A Gas Safe registered engineer to connect and commission it
- Fresh water for the tank, and Gastronorm pans with lids
- A probe thermometer for checking food temperatures
Step 1: Choose a Level, Ventilated Spot
Sit the unit level on a non-combustible surface, secured so it can’t shift in service. The manual asks for 100 mm clearance at the sides, 350 mm at the rear and 1,500 mm to any shelf or ceiling above — and if you’re using the legs, fit the supplied leg channel.
Why: combustion air enters through the base and rear of the appliance. Box it in and the burner is starved of the airflow it needs to run cleanly.
Step 2: Have the Propane Connection Made Properly
The connection is a ½” BSPT fitting at the rear of the unit, and there’s a pressure test point beside it. Have a Gas Safe registered engineer fit the hose and a 37 mbar low-pressure propane regulator, then leak-test the run with soapy water. Our LPG hose and regulator rules guide covers the standards your engineer will work to.
Why: the manual states the appliance should be fitted and tested by a registered fitter before use, and that high- or medium-pressure valves are prohibited — the unit is built for low-pressure propane supply only.
Step 3: Fill the Tank With Water
Before any lighting attempt, add water to the tank. A good working level sits just below the bottoms of the pans, so the bath wraps heat around every pot without slopping into them.
Why: the water bath is what turns a 3.3 kW burner into gentle, even holding heat. Run the unit dry and you’re scorching an empty steel tank instead of warming food.
Step 4: Light the Burner
Push the control tap in and turn it anti-clockwise to the flame position. Keep the tap held fully in, press the red ignitor button on the right side until the pilot lights, then keep holding the tap for 15–20 seconds before releasing.
Why: those seconds warm the thermocouple — the safety probe that holds the propane valve open. Let go too soon and the flame failure device drops the burner straight out. If it hasn’t lit after a minute, turn back to the off position, wait five minutes, and start again.
Step 5: Expect a Slow First Light
On a brand-new unit — or after a cylinder change — there’s air in the inlet pipe. Repeat the lighting sequence until the propane reaches the burner and the pilot holds.
Why: the manual calls this out as the most common reason a new bain marie “won’t light”. It isn’t a fault — it’s an air lock, and it purges itself with a few patient attempts.
Step 6: Bring the Bath Up, Then Load Hot Food
The flame is at its strongest with the knob at the 90 position — turn it either side of that to reduce the heat. Heat the bath before service starts, then load pans with food that’s already piping hot and put the lids on.
Why: a bain marie holds temperature; it doesn’t put heat into cold food fast enough to be safe. UK food safety guidance expects hot-held food to stay at 63°C or above — spot-check with a probe through service and keep an eye on the water level, topping up with hot water as it evaporates.
Step 7: Shut Down at Close
Turn the control knob clockwise until you hear the click, then close the valve on the propane cylinder itself. Once the unit has cooled, drain the tank and wipe it out.
Why: the manual is blunt about this one — turn off both the appliance and the cylinder supply as soon as the work is done. A closed cylinder valve is the cheapest piece of gas safety you own.
Which LPG Bain Marie Fits Your Van?
We stock two Infernus wet LPG units, and both run the same 3.3 kW single-burner spec — the difference is capacity and counter space.
| Model | Pots | Size (w×d×h) | Heat input | Price |
|---|---|---|---|---|
| Infernus LPG 4-pot | 4 × GN 1/4 (6″ deep), pans, lids and tap included | 590 × 430 × 350 mm | 3.3 kW propane | from £399 |
| Infernus LPG 6-pot | 6 × GN 1/4 (6″ deep) with pans | 870 × 430 × 350 mm | 3.3 kW propane | from £499 |
The Infernus LPG 4-pot bain marie suits burger vans and smaller menus — four sauces or sides in a 590 mm footprint. The Infernus LPG 6-pot bain marie earns its extra 280 mm on curry, carvery and rice-and-three menus. Both have piezo spark ignition and a flame failure device as standard. If you’d rather compare the full range — including the Parry LPG wet units (from £653) — browse the bain marie category page.
Staying Safe and Compliant
Flame failure device. Fitted to every model in the range. If a gust through the hatch kills the flame, the propane shuts off automatically instead of pooling in the van.
Ventilation. The burner needs a steady flow of fresh air, and the vents on the appliance should never be altered or blocked. Your engineer should confirm the van’s ventilation suits the total heat input of everything fitted.
The annual certificate. Councils and event organisers typically expect an annual gas safety certificate for the van’s whole propane system — the CP44, the commercial catering equivalent of a landlord’s certificate. Sizing your cylinders to feed the bain marie alongside the rest of your kit is covered in our LPG cylinder sizes guide, and the off-grid mobile catering setup guide walks the whole propane-power-water picture.
Common Mistakes to Avoid
- Lighting a dry tank. Water first, every time — the bath is the whole point of a wet unit.
- Releasing the tap straight after ignition. Hold it 15–20 seconds or the flame failure device wins.
- Using it to cook. A bain marie holds hot food hot. Bring food up to temperature on the hob, then transfer.
- Letting the bath boil dry mid-service. Top up with hot water as it evaporates.
- Fitting a high-pressure valve. The manual prohibits it — 37 mbar low-pressure propane regulator only.
- Blocking the vents. Combustion air comes through the base and rear; never box the unit in tight.
Frequently Asked Questions
Do I need to put water in an LPG bain marie?
Yes — the Infernus LPG units are wet bain maries, and the manual says to add water to the tank before use. Fill to just below the bottoms of the pans, and top up with hot water through service as the bath evaporates. Running the unit dry scorches the tank and gives uneven, unsafe holding.
Can I run a bain marie on butane instead?
No — use propane. Butane stops vaporising below about 2°C, so it can leave you with no heat on a cold UK morning. Commercial mobile catering runs on propane at 37 mbar, and the LPG bain maries we stock are set up for exactly that supply. Butane belongs on patio heaters, not in a working van.
What temperature should a bain marie hold food at?
63°C or above — that’s the hot-holding figure UK food safety guidance works to. Load the bain marie with food that’s already piping hot, keep the lids on, and spot-check pans with a probe thermometer through service. If a pan drifts below 63°C, reheat it fully before it goes back on display.
Can a bain marie cook food from raw?
No. A bain marie is a hot-holding appliance — a gentle water bath, not a cooker. It can’t drive heat into cold or raw food fast enough to pass through the temperature danger zone safely. Cook on the hob or griddle first, get the food piping hot, then transfer it to the bain marie to hold.
Why does my bain marie go out when I release the knob?
You’re releasing too soon. Hold the tap fully in for 15–20 seconds after the pilot lights so the thermocouple warms up — that’s the probe that tells the propane valve the flame is real. If it still drops out after a proper hold, the thermocouple may have shifted and needs a professional’s attention.
What propane pressure does an LPG bain marie run at?
UK mobile catering supplies propane at 37 mbar through a low-pressure regulator. The Infernus manual lists the units under LPG category I3+ (28–30/37 mbar) with a 0.88 mm injector, and it prohibits high- or medium-pressure valves outright. Your engineer sets and leak-tests the supply at commissioning.
How much does an LPG bain marie cost?
The Infernus LPG 4-pot starts from £399 with GN 1/4 pans, lids and a drain tap included, and the 6-pot from £499. The British-made Parry LPG wet units run from £653 for the 4-pot and from £918 for the 6-pot. Budget separately for the engineer’s connection visit and a propane cylinder.
Do I need a Gas Safe engineer to install an LPG bain marie?
The manual states the appliance should be fitted and tested by a registered fitter before use, in line with the Gas Safety (Installation and Use) Regulations. In practice that means a Gas Safe registered engineer connects the ½” BSPT inlet, fits the 37 mbar regulator and hose, and leak-tests the run — typically alongside your annual CP44 certificate.