Pellet heaters have been around since the 1980s (history of pellet heaters from Wikipedia) and to answer the question how do pellet heaters work we need to look inside them. Pellet heaters create heat by burning wood pellets. A fan blows heat out of the heater into the room it is in. The main parts of a pellet heater are the hopper where pellets are stored, an auger which takes pellets from the hopper and feeds them into the burn pot where a fire burns and two fans, one for the fire and one for heating. Pellet heaters start automatically using an igniter which lights pellets in the burn pot, so there’s no need to manually light a fire.
Unlike most wood heaters, pellet heaters need electricity to run. They use very little power and you’ll most likely notice no increase in your power bill. However, this is a difference between a wood heater and pellet heater that many people are not aware of and comes as a surprise. Many people don’t realize this and it’s one of a few reasons why some people shouldn’t buy a pellet heater. However, like anything nowadays, if you look after and service and clean your pellet heater it will operate trouble free and heat your house for many years to come.
Below I go into detail about each of the major parts in a pellet heater to help you understand how they work.
Hopper: Storing Wood Pellets
The hopper in a pellet heater holds the wood pellets before they are burned. The hopper eliminates the need to constantly load pellets into the heater every few hours, like you have to do with a wood heater and firewood. It offers an easier and more convenient method to heat your home because the hopper can typically hold a day or two worth of pellets. The hopper is located at the top of the pellet heater and accessed via a lid . Most hoppers can hold between 15kg to 30kg of pellets, which is about one to two bags of pellets. Pellets stored in the hopper are slowly fed into the burn pot by an auger.
Depending on how big your house is, how well insulated it is, how cold the climate it is where you live and how often you run your pellet heater, a hopper will hold anywhere from one to three days worth of pellets. The smaller a hopper the more often you’ll have to fill it with pellets. This is why I consider hoppers very important when buying a pellet heater. Since hoppers are just a metal box, nothing really needs to be serviced or maintained. However, once a year it’s a good idea to empty pellets out and just give it a quick vacuum out to ensure no pellet fines or dust is building up inside of it.
Auger: Feeding the Fire
Probably the most important part in a pellet heater is the auger, which feeds pellets from the hopper into the burn pot to keep the fire going. How fast the auger turns is directly related to the heat output of the pellet heater, and its speed can be controlled to maintain the desired temperature in the room. During startup, the auger turns quickly so it feeds a lot of pellets into the burn pot to create a big fire and quickly heat up the room to the desired temperature. The faster the auger turns, the more pellets are fed into the burn pot and the bigger the fire is.
Once the room has reached your set temperature, the auger slows down, and fewer pellets are fed into the burn pot. This results in a smaller fire, reducing the heat output of the pellet heater and maintaining the room temperature. One of the biggest benefits of pellet heaters is they offer greater control over heat output compared to wood heaters. By controlling the speed of the auger you control heat output, much like a heat pump. This means you can heat a room to a set temperature and then maintain that temperature, making it more comfortable and saving pellets by not burning more than you need. You have more control over heat output in a pellet heater than wood heater.
Burn Pot: Where the Fire Burns
The burn pot in a pellet heater contains the fire which heats your house. At startup when you switch a pellet heater on, the auger drops wood pellets into the burn pot in preparation for the fire to start. The fire is automatically started by an igniter. The igniter sits behind the burn pot and heats air to such a high temperature that as that hot air blows over pellets in the burn pot they catch fire. Unlike a wood heater, there’s no need to manually light a fire in a pellet heater. It’s worth pointing out here that the igniter doesn’t actually touch the pellets. It’s the hot air which starts the fire.
Once the fire has started, the igniter switches off, and the auger continues to feed pellets into the burn pot, keeping the fire going. As long as the auger continues to feed pellets into the burn pot, the fire will continue to burn. Because of the hopper, the auger and the burn pot, pellet heaters are much easier to use than wood heaters. There’s no need to manually light a fire. There’s no need to add more “fuel” to keep the fire burning and you can control how big or small the fire is in the burn pot by setting a temperature, which adjusts how heat output by how fast or slow the auger spins.
Exhaust Fan: Keeping the Fire Going
Pellet heaters are much more efficient and environmentally friendly than wood heaters. One of the ways this is achieved is by using an exhaust fan to keep the pellets in the burn pot burning and vent emissions out the flue. The exhaust fan in a pellet heater creates a much more efficient and cleaner burn than wood heaters. Smoke is only visible for a few minutes during start-up, and for the rest of the time, there is no visible smoke coming from the flue.
The igniter behind the burn pot heats the air blown in by the exhaust fan to ignite the pellets, and once the fire has started, the igniter switches off, and the exhaust fan keeps the fire going. By adjusting the speed of the exhaust fan and auger, the rate of burn can be controlled to adjust how much heat is put out by the pellet heater. This feature provides greater control over the temperature and heat output in the room, which can save energy and reduce heating costs.
Room Fan: Heating the Room
The heat generated by the pellet heater is blown out of the heater using a room fan. The room fan blows air through a heat exchange chamber that is heated by the fire in the burn pot, and the hot air is then blown out into the room. Adjusting the speed of the room fan allows you to control how much heat is blown out of the heater. When the heater is running in high mode, the fan runs faster, blowing out more hot air than when the heater is running in low mode. This enables you to adjust the heat output of the pellet heater based on the rate at which pellets are being fed into the burn pot.
The fan’s speed can be controlled in two ways. First, if you set a desired room temperature, then the temperature sensor tells the pellet heater what the current temperature is. If the room is colder than your desired temperature, the pellet heater automatically goes into high heat mode, which increase feed rate of pellets into the burn pot, creating a bigger fire, and then increases the room fan speed to blow more hot air out of the heater to heat the room. Once the room temperature reaches your desired setting, it switches back into low. The speed of the room fan can also be adjusted manually, allowing you to set high, medium or low speeds, depending on your personal preference.
Igniter: Automatic Fire Starting
An igniter in a pellet heater starts the fire in the burn pot automatically. The igniter, typically a 300 to 400 watt heating element, sits just behind the burn pot close to the pellets but doesn’t actually come into contact with the pellets in the burn pot. Air is blown over the igniter and heated by it which gets so hot during start-up it causes the pellets to combust and catch fire. Once the pellet heater has detected a fire is burning, the igniter switches off and the auger continues to feed pellets into the burn pot keeping the fire going.
The igniter uses the most electricity in a pellet heater, the equivalent of a three or four old fashioned light bulbs, which isn’t much. However, the igniter is only switched on and drawing power for around 5 minutes during pellet heater startup, which is why you’ll most likely not notice an increase in your power bill. While modern day pellet heaters start the fire automatically, older models had to be lit manually. Most people achieved this by using metho or something similar. Luckily, all pellet heaters sold in Australia today have automatic ignition, so you just sit back and let the pellet heater do the hard work.
European Heaters: Special Features
The above describes how pellet heaters work, regardless of when they were made or brand. However, it’s worth pointing out that some European models, such as Piazzetta pellet heaters, include some unique and interesting features. These features primarily increase efficiency by sealing the heater better so air to heat your house is drawn from the outside, not inside and also augers that control and regulate the amount of pellets fed into the burn pot more precisely. These features usually come at a premium cost and European pellet heaters, especially the high end luxury models, can be very expensive.
Whether or not these features are worth the cost depends on your personal preferences. However, European pellet heaters typically score very high in pellet heater reviews due to unique designs and advanced features. I strongly recommend visiting retailers to see the different brands and models in person and ask a lot of questions. Check out my top 5 pellet heaters in Tasmania article if you live in Tassie or if you live elsewhere then I do recommend the my best pellet heater article covers other states and brands around Australia.
Hopefully the above gave you a good idea on what and how pellet heaters work, especially if you are considering buying a pellet heater. If the idea of moving parts in a heater has you worried, maybe you’ve only ever used wood heaters, then there’s also a good post I wrote on how reliable pellet heaters are which goes into detail about how reliable pellet heaters are. How do pellet heaters work is such a common question I also made the video below. If you’d like to learn more then please considering watching the video below.
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