Oregon Energy Coordinators Association | WarmandSafeNow.com

By Kurt Torgerson

Clackamas County Weatherization 

This article outlines common maintenance tips to keep your stove at it best.

Pellet stoves have become tremendously popular as a cost-effective home heating source. Pellet stoves appeared in the early ‘70s following the oil embargo of 1973. Early designs were rather simple in appearance and operation. Stoves have evolved over time to become complex combustion devices requiring regular maintenance to work safely and efficiently. Some models are capable of burning a multitude of fuels including such things as corn, olive pits, soybeans, and even processed silage!

The graphic shows a diagram of how a typical pellet stove operates. Air for combustion, heat transfer, and exhaust is supplied by fans. Fuel from the hopper is fed to the burn pot via an auger arrangement. The stove illustrated is a top-fed model. Some stoves feed fuel pellets into the burn pot through the bottom. The fire is started initially with an igniter, which is a glowing coil of wire similar to a car cigarette lighter. Older stoves may need to be started manually.

The fire burns very hot and clean as it is supplied with combustion air under pressure. The heated gases from the fire heat incoming room air through a heat exchanger, so there is no direct contact between the fire and the room air. The exhaust, after passing through the heat exchanger, is relatively cool, and can be vented to the outside through a double-wall pipe. Stoves typically burn from 2 to 7 pounds per hour of fuel, depending on the size and the heating demand of the home.

Most new models are designed to be used with a remote thermostat, and will automatically turn on and off as heat is called for. Modern stoves have a number of safety and control devices to shut down the stove if something goes wrong. It is important to note that pellet stoves will not work in an electrical outage, unless the home has a back up system to supply electricity to the unit.

Fuel quality is important to the operation and maintenance of the pellet stove. Most pellets are made of wood products and / or corn as mentioned above. The quality of the pellets has a direct influence on how often cleaning has to be performed. Top fed models are generally more sensitive to fuel quality than bottom-fed models. Pellets are generally made in 1/4 or 5/16 inch diameter. If your pellets are longer than 1-1/2 inches they may not feed correctly.

Fuels containing ash and minerals can form a clinker in the firepot, restricting airflow and fuel distribution. Some fuels produce more clinkers than others. Clinkers are a glassy slag material formed when ash melts above 2000ºF in the firepot. Most manufacturers of top fed units recommend using fuels with less than 1% ash. Some pellets may contain up to 4% ash. Most of the time, clinkers are easily removed from the firepot with a small tool provided with the stove.

Be aware that wet fuel burns and feeds inconsistently. It also has a lower heating value than dry fuel.

Care of pellet stoves typically consists of daily, weekly, and periodic (as needed) maintenance tasks.

Daily Checks

The burn pot needs to be checked every day for clinkers and plugging of the air ports. Some stoves have an integral ash tool or a firepot cleaning rod. Clinkers interfere with combustion and need to be cleared away. The stove must be shutdown and cool to perform this operation. Check the owner’s manual for specific instructions for your model stove.

Weekly Checks

As mentioned above, some fuels produce more ash than others. As the heating season progresses, the amount of ash made will increase. It is important to keep the ash drawer clean. The stove must be cool to perform this operation. Remember to place the ash and debris into a noncombustible container.

The heat exchanger chambers may need to be cleaned weekly during the heart of the heating season. Many stoves have rods that are pulled out to clean the exchangers. Dirty heat exchangers reduce the stove’s efficiency. Again, this is best performed on a cool stove.

Periodic Checks

Some manufacturers recommend cleaning the back of the heat exchangers after each ton of fuel is burned. This may require removing a panel or baffle for access. Consult your owner’s manual for the specifics for your model.

The glass should be periodically cleaned of soot. Dark soot absorbs heat, and may make the glass very hot to the touch. The glass must be cleaned with a soft, damp cloth while cold. Do not use an abrasive cleaner that can scratch the glass.

The nature of the pellet stove fuel makes it inevitable that sawdust will build up in the hopper and auger assembly. The sawdust can cause the auger to turn slowly or even bind. After each ton of fuel is burned, empty the hopper of pellets and vacuum out the accumulated sawdust.

The exhaust system may need to be cleaned once each heating season. This is particularly true if there are frequent cold stove start-ups and / or a lot of soot and ash accumulated in the ash drawer. A dirty exhaust system may cause poor combustion and a reduced heat output in extreme cases. There are often access covers that need to be removed to get at the exhaust blowers and venting system. Check your owner’s manual for the instructions for your stove.

Pellet stoves are a popular way to provide heat for a large number of households. By following some simple maintenance procedures, your pellet stove can provide your home with heat for many years.