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Why Does My LPG Fryer Keep Going Out When the Gas Bottle Is Running Low?

by Paul
(Newbury Berks UK)

Burgundy twin-axle catering trailer serving chips and burgers to a queue at a busy UK Saturday market

Burgundy twin-axle catering trailer serving chips and burgers to a queue at a busy UK Saturday market

hi
I have a catering trailer 14` x 6`6"
it is lpg equipment.
the gas bottles x2 are at the back of the trailer and the lpg fryer is right at the other end and furthest from the bottles.
there is a 3` gas griddle with 3 burners a bains marie with one burner a boiler with one burner a gas fridge with a small flame- Dometic rge 700 I think- and a pie warmer that is rarely used.
Trouble is when the gas nears the last hour or two of gas the fryer just goes out and I have to switch over to the new bottle (manual changeover) like happened yesterday.
so after work yesterday I switched back to the near empty bottle to see how long it would last on Saturday as I don't use the fryer on Saturday.
So the gas fridge was on all night and for a good hour this morning I was able to use the gas equipment before the bottle actually ran out.
Can you advise me as I need to sort this out as sometimes I don't realise (most of the time)! the fryer has gone out until I go to fry an order and the iol has gone luke warm due to this problem!
It is a standard manual changover set up with a common regulator and 15mm pipework.
There is no room for bigger bottles as they are in a cupboard at the back of the
trailer and the pipework splits to either side of the trailer as it comes into the inside of the trailer.
on the side with fryer there is the fridge then the lpg boiler 20 litre, then the fryer.
on the other side is the griddle, the Bains Marie and another griddle which is never really used.
Can you help please!!!
Paul

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Oct 29, 2026
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by: MobCater

Paul, that is a frustrating one, because the first you know about it is a basket of lukewarm oil with a customer waiting. The good news is that what you are describing is a very common pattern, and the fryer is actually behaving exactly as it should.

Your fryer has a flame failure device, a small thermocouple that shuts off the gas the moment the pilot goes out. As a propane cylinder gets close to empty, it cannot turn liquid into vapour fast enough to keep up with a heavy demand. The pressure drops, and it drops most at the far end of the pipework. With the griddle, the bain marie, the boiler and the fridge all drawing from the same bottle, the fryer at the end of the run gets whatever is left. Its pilot flickers out, the safety device does its job and the fryer shuts down. That is why your Saturday test worked. Without the fryer pulling gas, the same nearly empty bottle carried the lighter load for another hour.

The fix most traders go for is an automatic changeover regulator in place of your manual one. It draws from the duty cylinder and switches to the reserve on its own when the pressure falls, and most have a small indicator that turns red so you know to swap the empty bottle at a quiet moment. The valve itself is usually somewhere around £50 to £100, plus the engineer's time to fit it.

I would also ask the engineer to do a pressure check with every appliance lit at once. Propane catering appliances in the UK are set up to run at 37 mbar, and the engineer can measure what is actually arriving at the fryer under full load. If it is low even on a full bottle, the 15mm pipe may be undersized for the length of the run and the total load, or the regulator may not be rated for the amount of gas you use. Both are quick for a qualified engineer to diagnose and put right.

One tip from experience. On a cold day a cylinder working hard will frost up on the outside, and that is a sure sign it is struggling to keep up. Keep the low level vents in that rear cupboard clear too, because they matter for safety as much as performance.

Please do not swap the regulator or alter the pipework yourself. Any change to the gas system has to be done by a Gas Safe registered engineer, who will test it and update your gas safety certificate. Until then, changing to the full bottle a little early on busy days will save you a few cold orders.

Best wishes

David

Disclaimer: Gas installation and maintenance must be carried out by a Gas Safe registered engineer. Never attempt gas work yourself. Check gassaferegister.co.uk for qualified engineers in your area.

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