All you need to know about Gas Geysers

Join us as we cover the most important details about gas geysers and a bit more.

What is a gas geyser

How do gas geysers work

Types of gas geysers

How much it costs


A gas geyser is a water heating system that runs of gas. The traditional south African gas geyser does not have a reservoir to store hot water, instead, it heats the water instantly. The gas geyser will be only activate when there is a demand. For example if someone opens up the hot tap the gas geyser will activate and send hot water to the tap. When the tap is closed the gas geyser will deactivate and stop producing hot water.

How do gas geysers work



Gas geysers have a sensor to detect water flowing through them, either via a pressure drop or flow detection through a dynamo.



Once gas geysers detect that there is flow, they will ignite. They will send gas into the combustion chamber and ignite the gas via alternating current electric spark. This is normally done through a much smaller pilot flame. The electric spark never actually stops, it simply becomes inaudible, more on this later.



Gas geysers detect that they have ignition either through a Thermocouple or in most cases through Flame Rectification where the sparker sends AC current through the flame, where it is converted into DC current which is detected elsewhere in the combustion chamber. This is how gas geysers know if there is combustion, by detecting the DC current. From there Gas geysers will allow more gas to flow into there combustion chambers and fill the rest of the burners.

More on Flame Rectification here:



Once gas geysers have combustion the heat produced rises or is forced through a copper or aluminum heat exchanger. This is where the water is heated up. The heat from the combusting gas gets transferred through the aluminum or copper, where the water is flowing, and finally into the water.

More on Heat transfer here:


Types of gas geysers

Natural Draft:

Natural Draft gas geysers make use of the natural principle of hot air rising. The hot gasses produced from combustion rise up through the heat exchanger and then, in most cases, through a chimney, which normally assists in the draft.

How chimneys work:

Why Hot air rises:

Fan Force Driven:

Fan Force Driven gas geysers make use of a fan to assist in the complete combustion of of the gasses and then to force the combustion gasses through the heat exchanger. Fan Force Driven gas geysers are generally more efficient than Natural Draft and can supply a lot more hot water per minute.

HOW MUCH do gas geysers cost

Gas geysers can cost from +/- R3000 up to as much as R20000.

As with most things in life, you get what you pay for and in general, the more expensive gas geysers have a much higher quality.

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