How Gas Patio Heaters Work
Patio heaters that are fuelled by LPG produce radiant heat. LPG (liquid petroleum gas) cylinders are connected via an approved LPG gas regulator. The regulator is specifically designed to control the flow of gas from the LPG cylinder to the burner. Regulators in the UK are available to fit propane cylinders operating at 37mbar and butane cylinders operating at 28mbar. The regulator maintains the correct flow entering the burner chamber. The regulator will be connected from the cylinder via a LPG high pressure hose which in turn is connected to the gas burner.
Older gas patio heaters operate by lighting a pilot light fired via the piezo ignitor before firing the main gas chamber. Newer patio heater gas valves operate on a continuous pilot system called a 'pulse pilot'. Both system require the thermocouple to reach the required temperature before firing the gas chamber. Thermocouples control the level of heat and allow patio heaters to turn up the heat or lower. A thermocouple is connected to the back of the gas control valve and linked to an electromagnetic valve that sends a signal to open or close the gas control valve. The seating within the gas control valve will open sufficiently for the pilot to light and heat the thermocouple. Providing the thermocouple is working OK the gas control valve seating will open to allow the full chambers to light in the burner.
The gas control valve will be connected to a flame failure device and if fitted a tilt switch. The tilt switch is designed to shut the gas supply off should the heater tilt or fall over by more than 30 degrees.
Gas burners are measured in BTU/h - British Thermal Unit. Radiant heat produced by the burner is reflected towards the ground via the reflector.
The height and size of the reflector is designed to force radiant heat downwards heating a large area below, typically around 6 metres. To work efficiently the height of patio heaters will be a minimum 2 metres with a reflector size of 80cm minimum. Radiant heat is a form of energy that heats objects through a process called conversion without having to heat the air between. Radiant heat is also called infrared energy or IR. The electromagnetic spectrum is divided into three segments by wavelength, measured in microns or micrometers (a micron = 1/1,000,000 of a meter): 0.076 to 1.5 microns = near or close; 1.5 to 5.6 = middle or intermediate; 5.6 to 1000 = far or long wave infrared. Patio heaters produce the same natural heating effect of the sun.
Most of the energy produced by the sun is within the infrared segment of the spectrum. The atmosphere allows infrared rays within 7 to 14 micron ranges to safely reach the surface of the earth. When the earth is warmed it radiates infrared rays within 7 to 14 micron bands.
Gas patio heaters feel just like the sun, warming people and objects, while not wasting valuable energy trying to heat air. The infrared heat will provide warmth much like the sun’s gentle waves but without the harmful UV rays.
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