Possible causes and solutions:

1- The moisture content of your wood is too high.

Solution: Make sure you use good, seasoned cord wood. The wood you burn plays an important role in the overall performance of your heater. Your wood should have been properly dried for approximately one year. Storage is also key. Wood that has been cut for one, two or even more years, will not necessarily be dry if it has been stored in poor conditions. Under extreme conditions, it may have rotten instead of drying. Smaller pieces of wood will dry faster. The wood should be stored in a place where the grass is not too long, and where the wind will be able to circulate between the logs. A 12-inch gap should be kept between the cords. The wood should be placed in the sunniest area and should be protected from the rain and snow on top, but not on the sides. Use a moisture reader to measure the moisture content of your wood. Ideally, it should be below 25%.

2- The logs are positioned too close to the glass and are obstructing the air flow that is necessary to keep the glass clean.

Solution: Make sure to keep a minimum gap of 2 inches between the logs and the glass.

3- The chimney draft is too weak.

Solution #1: In many cases, a weak draft is simply due to insufficient heat in the exhaust system. Build a small, intense fire, and leave the door ajar (never leave the heater unattended). Before inserting larger logs, use dry kindling to obtain a good bed of red embers. Gradually increase the size of the logs. Close the unit’s door when you reach a flue temperature of approximately 475 °F on the chimney thermometer. Leave the air intake fully open for approximately 15 minutes. Then, gradually close the air intake control. Note that there is no danger in letting the temperature inside the flue reach approximately 700 °F during the start-up. This is even favorable in order to properly start your heater. You must, however, avoid maintaining excessive temperatures (above the comfort zone on your thermometer) during a long period of time. Your chimney thermometer should be positioned on the exhaust pipe, approximately 18 inches above the unit.

Solution #2: Your heater may not have all the oxygen it needs to allow for a sufficient draft. You first need to insure that the room where the heater is located is sufficiently large and well ventilated. Open the nearest window by approximately 2 inches. If you notice a significant improvement, it is a sign that the unit needs more oxygen. The room may be too insulated or too small. Without an additional source of oxygen, the draft will remain weak and cause the glass stay dirty.

Solution #3: The chimney may be too short. In order to obtain a sufficient draft, your chimney must have a minimum height. Twelve feet (from the heater to the chimney cap outside the house) is a minimum. A height of 15 feet or higher is ideal.

Solution #4: Your exhaust system may be too tortuous or may lack a sufficiently steep slope. Ideally, your exhaust system should not have more than one 90° elbow. Furthermore, all horizontal sections should be as short as possible and have a minimum slope of ¼" per foot.

Solution #5: Your exhaust system may be oversized. When your chimney is oversized, the volume of air that needs to be warmed-up is larger. It is therefore difficult to reach temperatures that will allow for a sufficient draft. Most advanced combustion systems (those certified to EPA/CSAB415.1-10) have a 6" flue outlet (152 mm). If your exhaust system does not have a 6" diameter, a solution is to insert a stainless liner with a 6" diameter inside the exhaust system.

Appliances that are EPA or CSAB415.1 certified tend to create larger coal beds due to their higher efficiency. This can be controlled by the way you burn your appliance. After an overnight burn, you may have a more significant coal bed. Simply rake the coal bed forward and add a smaller piece of wood on top. Burn the appliance on a higher setting (air control fully open). This will pull more primary air into the firebox and will increase draft. The coal bed will burn down with the log. You may have to repeat this operation a couple of times before the coals are reduced. You are then ready to load your appliance with a larger fuel load.

EPA refers to the CSAB415.1-10 standard for the calculation of the appliance’s efficiency. The efficiency reported as per EPA’s directives consists of an average between four different burn rates, ranging from the lowest burn rate (air intake completely closed) to the highest burn rate (air intake completely open). The optimum efficiency that we publicize is the efficiency obtained according to the same test data, but for the low burn rate only. This efficiency is more realistic for a majority of users whose heating needs require that the unit be used to maximize burn times.

You will notice a difference between the BTU output as per the EPA’s test data and what is advertised on our web site and/or product literature. The maximum BTU output we advertise is what will be obtained with a full load of seasoned cordwood inserted inside the firebox. The EPA output, on the other hand, is what has been obtained during emissions testing. The EPA test procedure requires that a special type of wood is used and positioned inside the firebox in a manner that does not represent the way the firebox volume would normally be utilized using seasoned cordwood. The EPA test load is typically much smaller. Hence, the BTU as per the EPA’s test data is reduced. The BTU output that should be considered by a normal user is the one we advertise for seasoned cordwood.

EPA or CSAB415.1-10 certified heaters function best on a 6-inch chimney (interior diameter). The problem with an 8-inch chimney is that the appliance may struggle to heat-up the air volume contained inside the chimney. A hot chimney is required to create enough draft. Poor draft will inevitably lead to poor combustion, which will cause smoke roll backs, a dirty glass, lack of heat, and a large quantity of unburned fuel inside the firebox. It is therefore highly recommended installing a 6-inch liner inside the 8-inch chimney. This liner may be rigid or flexible.