Flame failure

How to keep a propane heater lit

It goes out because a safety device noticed the pilot was disturbed and shut the gas off. That is the system working. Here is how to stop it having to.

Every gas patio heater has the same safety interlock, and understanding it makes the whole problem legible.

A small probe called a thermocouple sits in the pilot flame. When it is hot it generates a tiny voltage — a few tens of millivolts — and that voltage is what holds an electromagnetic gas valve open. It is why you have to hold the control knob down for twenty seconds when lighting: you are holding the valve open manually until the thermocouple is hot enough to take over.

The consequence is direct. Anything that cools the thermocouple closes the valve. A gust that lifts the pilot flame away for two seconds is enough. The heater does not fail gracefully and it is not supposed to: the alternative is unburnt propane flowing out of an unlit burner, which is exactly what the interlock exists to prevent.

1. 1Shelter the windward side. By far the largest effect. A wall, a fence, a corner, or a screen. The flame does not need still air, it needs air that is not being torn past it.
2. 2Point the access panel away from the wind. Most towers have an opening in the housing for lighting and for the cylinder. That gap is the route the wind takes to the pilot. Turning the unit 180 degrees is free and often solves it entirely.
3. 3Clean the pilot assembly. A partly blocked pilot burns a smaller, weaker flame that is easier to disturb and heats the thermocouple less. Spiders build nests in gas orifices — this is a well-documented failure in outdoor gas appliances, not folklore.
4. 4Check the thermocouple tip is in the flame. It gets knocked out of position during cleaning, moving, or a fall. It should sit in the upper part of the pilot flame. If it is beside it rather than in it, it will hold at full flame and drop out at the slightest disturbance.
5. 5Run it a little higher for the first few minutes. A larger flame is harder to disturb. Once it is properly hot the whole assembly is more tolerant, and you can turn it back down.

Then wind is not your problem, and this is the wrong page. A heater that will not hold on a calm night has a fault, and the symptom tells you which one.

• Dies the instant you release the knob — the thermocouple is not generating enough voltage. The fault tree.
• Runs for a few minutes then stops — often a thermocouple that is marginal rather than dead, or a control valve going.
• Will not light at all since it fell — the tip-over switch has latched. How to reset it.
• Burns yellow and sooty rather than blue at the pilot — a combustion or airflow problem, and worth taking seriously rather than persevering with.

Tabletop heaters are much worse at this and it is not a quality issue. A small burner at table height, with a screen guard rather than a deep housing, has far less protection than a tower's shielded assembly. On an exposed balcony a tabletop unit will go out repeatedly, and there is not much to be done about it beyond blocking the wind.

If a balcony is the space and it is windy, an electric infrared heater is the honest recommendation — there is no flame to disturb, and the radiant heat is unaffected by the air movement that is defeating the flame.

There is a wind speed beyond which no amount of shelter keeps a patio heater useful, and it is lower than people expect. At that point the manual's own advice applies: shut it down, secure it, and go inside. Relighting a heater six times in an evening is not persistence, it is a sign the patio needed a windbreak or a different kind of heater.